Got MMDS eBook

of 73
Written by SSG Buenavista, Joash - United States Army Public Affairs . 20APR2011 . AFN-Iraq
GOT MMDS?
by SSG Buenavista, Joash
United States Army Public Affairs
25R Broadcast Technologist
20APR2011

of 73
Numbers in image 1 are referenced with the Table of Contents - Chapters 1 & 2

of 73
Table of Contents
Chapter 1: Basic & Advanced Concepts
1. Basic Setup of MMDS …………………………………………………………………………………………..………………… Pg 6
a.) Understanding Basic setup of signal flow with MMDS ……………………………………………….. Pg 6
b.) Parts, Accessories, and Tools that may be needed to setup MMDS ……………………………. Pg 6
2. Advanced Setup of MMDS ………………………………………………………………………………………..……………. Pg 7
a.) Understanding Advanced setup of cable distribution …………………………………………………. Pg 7
b.) Parts, Accessories, and Tools that may be needed to setup Cable Distribution ………….. Pg 7
Chapter 2: What you need to know about MMDS
1. MMDS Transmitter ………………………………………………………………………………………………………..………. Pg 9
a.) Meaning of MMDS …………………………………………………………………………………………………….. Pg 9
b.) Channels Transmitted ………………………………………………………………………………………………… Pg 9
c.) Finding the MMDS Transmitter ………………………………………………………………………………….. Pg 10
2. Understanding the Downconverter Concept ………………………………………….……………………………… Pg 10
a.) Purpose of the Downconverter ………………………………………………………………………………….. Pg 10
b.) Receiving the signal ……………………………………………………………………………………………………. Pg 11
3. MMDS Grill Dishes ………………………………………………………………..……………………………………………….. Pg 11
a.) Types of MMDS Grill Dishes ……………………………………………………………………………………….. Pg 11
b.) Assembling & Mounting the Grill Dish ……………………………………………………………………….. Pg 12
4. Power Inserter ……………………………………………………………………………………………………………………….. Pg 13
a.) Types of Power Inserter & internal parts ……………………………………………………………………. Pg 13
b.) Types of Power Supply ……………………………………………………………………………………………….. Pg 13
5. Coaxial Cable & the MMDS Signal Flow ………..……………………………………………………………………….. Pg 14
a.) Coaxial Cable and its parts …………………………………………………………………………………………. Pg 14
b.) Basic MMDS Signal Flow …………………………………………………………….………………………………. Pg 14
c.) Electrical Theory ………………………………………………………………………..………………………………. Pg 15
d.) Detailed MMDS Signal Flow ……………….………………………………………………………………………. Pg 19
e.) Things to be aware of before distributing the signal from basic to complex ….…………... Pg 32
f.) What to do to prevent signal loss and signal noise …….………….…………………………………… Pg 33
g.) FAQs ………………………………………………………………………………………………………………………….. Pg 34
h.) How to connect an F-Type Compression Connector to an RG6 Coaxial Cable …………….. Pg 35
6. Types of Splitters …………………………………………………………………………………………………………………… Pg 37
a.) Types of splitters ……………………………………………………………………………………………………….. Pg 37
b.) Understanding the symbols ………………………………………………………………………………………. Pg 37
c.) Which one is the two way splitter? ……………………………………………………………………………. Pg 37
d.) Differentiating the two ………………………………………………………………………………………………. Pg 38
e.) Will satellite splitters work with MMDS cable distribution? ………………………………………. Pg 39

of 73
7. Types of Connectors and their uses ………………………………………………………………………………………. Pg 40
a.) Distinguishing the F-Type Connector …………………………………………………………………………. Pg 40
b.) Types of Connectors and Adapters ……………………………………………………………………………. Pg 40
8. Signal Amplifiers …………………………………………………………………………………………………………………... Pg 41
a.) Amplifier Description …..…………………………………………………………..………………………………. Pg 42
b.) When to use Amplifiers ……………………………………………………………..…………………………….. Pg 42
9. Understanding TV settings and workarounds ………………………………………………………………………. Pg 43
a.) A snippet of television history …………………………………………………………………………………… Pg 43
b.) Compatible TV Systems with AFN-Iraq MMDS Transmission Channels (NTSC) ………….. Pg 44
c.) Bought a non-NTSC TV? No problem. Got a Laptop? No problem ……………………………… Pg 44
Chapter 3: Tools, Tricks, and Tips
1. Tools ……………………………………………………………………………………………………………………………………… Pg 47
a.) Types of Tools …………………………………………………………………………………………………………… Pg 47
b.) Basic Tools for MMDS Setup …………………………………………………………………………………….. Pg 47
c.) Tools to consider for a major setup ………………………………………………………………………….. Pg 47
2. How to use a Test Equipment ………………………………………………………………………………………………. Pg 48
a.) Basic use of a ProMax Spectrum Analyzer ………………………………………………………………… Pg 48
b.) Basic use of a Stealth Digital Analyzer ………………………………………………………………………. Pg 50
c.) Suggested test points within the MMDS cable distribution setup …………………………….. Pg 50
d.) Basic use of a Multimeter …………………………………………………………………………………………. Pg 51
3. Creative ways to test equipment without test equipment ………………………………………………….. Pg 53
a.) How to build a Promax …………………………………………………………………………………………….. Pg 53
b.) How to build a Multimeter ………………………………………………………………………………………. Pg 55
Chapter 4: Conclusion
1. Troubleshooting ....................................................................................................................... Pg 67
2. Summary ……………………………………………………………………………………………………………………………… Pg 69
3. Exam ……………………………………………………………………………………………………………………………………. Pg 70
4. References …………………………………………………………………………………………………………………………… Pg 73
5. MMDS Certificate ………………………………………………………………………………………………………………… LOCKED

of 73
Chapter 1
Basic & Advanced
Concepts

of 73
Section 1:
a.) Understanding Basic setup of signal flow with MMDS
Basic Setup of MMDS
Here’s the quick rundown how to setup an MMDS. Assemble the MMDS Grill dish (#3a, image 1) with an
attached downconverter (#2, image 1). Make sure to lock it down to the pole or mount of choice (#3b,
image 1). Point it directly to the MMDS Transmitting Tower (#1, image 1) within the base. Run an RG6
Coaxial Cable (#5a, image 1) from the downconverter to the “ANT” tap of a power inserter (#4a, image
1). Secure the Power inserter closest to an electric outlet to plug in the power adapter (#4b, image 1).
From there, attach an RG6 Coaxial Cable (#5b, image 1) from the Power Inserter’s “TV” tap (#4a, image
1). Since each dish can support up to 10 TVs, depending on how long the cable runs are and how far
apart the TVs will be, it is possible to add a splitter (#6a, image 1) to share the signal. From the splitter
(#6a, image 1), run a cable (#5i, image 1) from the Tap to the TV’s (#9a, image 1) RF input. Setup the TV’s
Auto Scan and it should automatically rearrange the AFN Channels in order. Mission Complete.
***Please note that AFN only works with NTSC TVs and MultiSystem TVs. Good signal strength to the TVs
are from 0dB to 10dB without damaging the TV’s tuner card. Although it’s ok to have 15dB at the TV,
10dB to 15dB are mainly reserved for the cable run from the tap to the TV. Some TVs may not have an
auto dB corrector to attenuate the acceptable signal to the TVs before damaging the tuner and possibly
the pixels. Here’s a tip: If it looks too bright, there’s too much power – this typically applies to CRT TVs
(Tube Version TVs). But don’t worry, with the basic setup and no amplifiers involved, MMDS
Transmissions are typically received at 17dB-20dB. By the time the signal gets to the TV, it’s already at
15dB or less due to the attenuation from the cable length, connectors, and splitters.
b.) Parts, Accessories, and Tools that may be needed to setup MMDS
- MMDS Grill Dish (Small/Large), Antenna Bracket, Downconverter, Power Inserter
- RG6 Coaxial Cable, Snap&Seal F Connectors (RG6 cable ends)
- Splitters, IEC PAL Connectors (Multi System/PAL TVs)
- Snap&Seal cable stripper/compression tool (tool to make cable end connectors)
- Pliers, Hammer, Screw Driver, and a Drill
- Pole, Screws, Nails, Zip Ties, other means of tie downs
- NTSC TV Tuner (Needed if the TV is only PAL and not an NTSC/Multisystem TV)
Ex: Kworld KW-SA230WP 1920ex PlusTV Gamer's Ed TVBox (For PAL TVs, Monitors) $68.99
KWorld Hybrid TV Stick UB445-U USB 2.0 Interface (For Computers) $39.99
Any NTSC VCR with RF input that converts video to PAL/SECAM Composite
TIP:
To ensure
quality
distribution, the
dish alignment
has to be at its
peak. See “How
to build a
ProMax” for
more details on
how to utilize a
TV to align the
dish Chapter 3,
Section 3a.
NOTICE:
Please note that
two of the
suggested
products have
not been tested
for quality and
compatibility.
Therefore, I
suggest learning
more about the
product by
reading reviews
and making
comparisons
with other
brands. Purchase
of these items is
at your own risk.

of 73
Section 2:
a.) Understanding Advanced setup of cable distribution
Advanced Setup of MMDS
In addition to the Basic Setup as explained above, here’s a quick rundown how to setup a Cable
Distribution System. With only 1 MMDS Dish, it is possible to expand the signal strength to several TVs
utilizing a distribution amp (#8, image 1). Depending how hot the signal strength is, it may require an
attenuator (#7a, image 1) to decrease signal strength before it’s plugged into the Distribution Amp. Read
the amplifier’s manual for acceptable dB input. Another reason for attenuation is due to the safety of
the TVs. Splitters (#6c-f, image 1), especially the first, may not have enough dB attenuation to decrease
the signal strength at acceptable ranges (0dB to 10dB, 15dB max) before damaging the tuner card in the
TV. So, keep that in mind when working with amplifiers. From the amplifier, running an RG6 coaxial
cable, known as the trunk line, (#5d-g, image 1) will need special attention to dB loss (signal loss) as each
is connected between each splitter. As a general rule of thumb, every 100 ft of cable loses 3dB of signal
strength but at higher frequencies, the losses are higher of up to 3.8dB loss (CH 54 - 408Mhz). When
running a trunk line between splitters, it is highly recommended to attach the cable at the Pass Thru
Port (typically a 1dB drop or less). Doing this eliminates the degradation of signal quality as the
expansion of cable distribution increases. Finally, at the end of the trunk line is the last splitter (#6f,
image 1) which would need a 75 ohm terminator (#7b, image 1) if the last splitter has a Pass Thru.
Otherwise, there’s no need for terminators. Doing this maintains impedance matching, which results in
better signal quality because it prevents causes of reflections. A reflection sends the signal back to the
original source due to a change to the signal path causing an effect called STANDING WAVES. The
terminator simply fools the signal that more cable rated at 75ohms is still connected. If 75 ohm
terminators are not available, replace the last splitter with a splitter that doesn’t have a Pass Thru.
b.) Parts, Accessories, and Tools that may be needed to setup Cable Distribution
- MMDS Grill Dish (Small/Large), Antenna Bracket, Downconverter, Power Inserter
- RG6 Coaxial Cable, Snap&Seal F Connectors (RG6 cable ends)
- Splitters, IEC PAL Connectors (Multi System/PAL TVs), 75 Ohm Terminators
- Snap&Seal cable stripper/compression tool (tool to make cable end connectors)
- Pliers, Hammer, Screw Driver, and a Drill
- ProMax Spectrum Analyzer
- Pole, Screws, Nails, Zip Ties, other means of tie downs
- NTSC TV Tuner (Needed if the TV is only PAL and not an NTSC/Multisystem TV)
Ex: Kworld KW-SA230WP 1920ex PlusTV Gamer's Ed TVBox (For PAL TVs, Monitors) $68.99
KWorld Hybrid TV Stick UB445-U USB 2.0 Interface (For Computers) $49.99
Any NTSC VCR with RF input that converts video to PAL/SECAM Composite
TIP:
For advanced
cable
distribution, a
ProMax
Spectrum
Analyzer is
highly
recommended
to monitor dB
losses between
drops.
NOTICE:
Please note that
two of the
suggested
products have
not been tested
for quality and
compatibility.
Therefore, I
suggest learning
more about the
product by
reading reviews
and making
comparisons
with other
brands. Purchase
of these items is
at your own risk.

of 73
Chapter 2
What you need to
know about MMDS

of 73
Section 1: MMDS Transmitter
a.) Meaning of MMDS
MMDS Acronym: MultiChannel MultiPoint Distribution
Service. MMDS is more than just video transmission, which
operates in the 2.0 to 2.9 Ghz frequency range (within the
same range as WiFi at 2.4 Ghz). But since AFN uses MMDS
transmitters for TV Broadcast, the frequency ranges are
from 2.5-2.7Ghz range. This range is at the UHF range.
Anywhere above 3.0Ghz is at the microwave range. To
avoid any conflicts, the transmission frequencies were
approved by the base frequency manager in order to avoid
any frequency conflicts.
MMDS has a variety of uses, from telecommunication to
wireless networking. But it’s commonly used for cable tv
transmissions which renders the nickname: wireless cable.
MMDS is transmitted in direct line of sight at an omni-
directional transmission (360 around the transmitting
antenna). Therefore, aligning the receiving dish properly is
very important. But, in certain instances, intermittent
interferences such as unmonitored WIFI or certain military
radio frequencies around the base may interfere with signal quality to the consumer’s TV reception. Of
course, other unknown causes at the consumer’s end are also variables.
b.) Channels Transmitted
The standard channel setup for MMDS Transmissions are set to 10 channels (AFN Prime Pacific, AFN
Prime Freedom, AFN News, AFN Sports, AFN Spectrum, AFN Family, AFN Movie, AFN Xtra, TPC – The
Pentagon Channel, AFN Program Guide – Freedom Radio). In some situations, an extra channel is added
to a maximum of 11 channels, AFN Prime Atlantic. However, even at its maximum provided channels,
desires to add more channels are still being asked. Here are the reasons why NO more than 11 channels
are transmitted:
1. All the remaining channels are either repetitive Video Programs or Program Guides
embedded with FM Radio that are set to play at specific regions and time zones. For
Example, in Iraq, the Program Guide is set to play Freedom Radio and Italy plays Video
Programs for Vicenza specific.
2. Every channel requires 1 dedicated satellite decoder to transmit via MMDS. But before it is
transmitted, every channel requires a dedicated modulator. From there, it is inserted into a
combiner to combine all the other channels then transmitted via MMDS Transmitter.
Although, it is possible to add more modulators, more decoders, more combiners to a
maximum of 31 channels to the transmitter, it’s pointless to broadcast Program Guides after
DID U KNOW?
FOBs such as
VBC can watch
AFN through the
NIPR network.
Simply look for
VBRICK in the
start menu.

of 73
Program Guides. Not to mention, it will cost more money for parts and accessories. See
image 2 for a visual setup of an MMDS transmitter.
3. The main reason why no more than 11 channels are transmitted is due to transmitted
content. Only the listed channels above are authorized for AFN Broadcast via Air Waves in
specific regions since they are provided for free to US Military as a gesture of gratitude by
the US National Networks. This is another reason why US Commercials are not broadcasted
at all in the AFN Channels, especially during the Super Bowl. So, let’s say we added third
party decoders aside from AFN decoders to watch FOX, CNN, BBC, Sports, Aljazeera, MTV,
VH1, etc., since there are 20 remaining channels out of 31 that can be filled. The question
comes to mind of, who’s paying for the service? Who’s willing to authorize the broadcast of
paid content? At this point, legal concerns become an issue including the maintenance of
the paid service for the additional decoders. Only through controlled communication
mediums, such as networking, have a higher chance of achieving approval. But through the
air waves, aside from US Military, Local Nationals are capable of accessing the broadcasted
channels which is completely out of our hands.
c.) Finding the MMDS Transmitter
1. MMDS Transmitters are typically located at the central and highest point in the FOB. The
transmitting antenna are also installed at the highest point of a MAST (A lego looking/oil
rigging piece of metal erected up to over 100 feet with guide wires that hold it down).
2. Another way to find the transmitter within the FOB is by looking at other MMDS Grill Dishes
around the area for a general direction.
3. This may be the last resort but without properly aligning the MMDS Dish, assemble the
MMDS equipment to its basic setup including the TV. By traversing the dish in either
clockwise or counterclockwise, using a TV to find the MMDS Transmitting signal is possible.
Let’s just hope the TV is NTSC compatible and that the channel is set at a known AFN
Channel. If the transmitting channel is not known, simply put the TV at AUTO Scan until it
tunes to some sort of an AFN distorted video signal. At that time, peak the dish to its best
alignment. See “How to build a ProMax” for more details on how to utilize a TV to align the
dish Chapter 3, Section 3a
Section 2: Understanding the Downconverter Concept
a.) Purpose of the Downconverter
In layman’s terms, the purpose of the
downconverter is to break the transmitted
MMDS signal apart to their own individually
modulated AFN channels that entered before the
combiner phase as explained on Chapter 2,
DID U KNOW?
US National
Networks make
their bulk of the
money through
advertisements.
Shows, Sitcoms,
and Movies are
methods to keep
viewers
watching TV.
The more
viewers watch,
the more the
advertising.
Same concept
applies with
AFN. The reason
for AFN’s
existence is
more than just
boosting morale;
it’s intended to
advertise
COMMAND
INFORMATION.
How else do you
think the
Generals get to
reach out to
their troops?
Does that
answer your
concern about
Super Bowl
commercials?

of 73
Section 1-b2. From the downconverter, the signal is then passed through the Power Inserter to the TV.
The TV will then demodulate each channel with its built in NTSC Tuner to its individual baseband
channels (Video, Left audio and Right audio). Only then is
it possible to watch the broadcasted channels.
Taking the MMDS concept a little farther, as mentioned in Chapter 2, Section 1-
a, MMDS can be used for several purposes from telecommunications to
wireless networking. And because telecommunications and networking send
and receive data, it would be necessary to use a transceiver antenna which is
typically shaped like a 10” x 10” squared box. Although there are different
types of transceivers, the picture to the right (image 4) are the types commonly
used. But because AFN only transmits wireless Cable TV, it’s called a
downconverter, not a transceiver.
b.) Receiving the signal
The radiated signal from the transmitter is captured by using the grill dish to bounce off the signal to the
downconverter’s deflector, which is located at the tip of the LNB as shown on image 3. The signal is then
downconverted and amplified before it leaves the LNB. And since amplifiers and conversions need
power, a power inserter (image 7) is necessary to accomplish this process. Power inserters are located
after the downconverter; see (#4a, image 1).
Section 3: MMDS Grill Dishes
a.) Types of MMDS Grill Dishes
There are two types of grill dishes – Small (#3, image 5) and Large (#4, image 5). The difference between
the two is obviously their size but mainly their purpose. The smaller dish is used for closer ranges to the
transmitter with direct line of sight to the transmitter. The bigger dish is used for farther ranges to the
transmitter. As explained in Chapter 2, Section 2-b, the concept of the radiated signal being bounced off
DID U KNOW?
Downconverters
are short names
for LNB? LNB is
an acronym for:
Low Noise Block-
downconverter.
DID U KNOW?
Increase of
Signal to Noise
ratio means that
there’s an
increase in
quality signal
over noise.

of 73
by the grill to the downconverter’s deflector improves a signal to noise ratio. When installing the larger
dish it will require an extender (#2, image 5) to the downconverter for the deflector to funnel more of
the signal. The higher the signal to noise ratio, the cleaner the video. #1, image 5 is the mounting
accessory kit that universally works with both Small and Large dishes along with the extender.
b.) Assembling & Mounting the Grill Dish
Assembling the dish is quite simple. By simply looking at these pictures (image 6), the assembly is self
explanatory. However, for documentation purposes, it will be explained in detail here.
1.) From the front, there are two plates (#1, image 6) that clamp the downconverter in place. Simply
insert one of the plates with the bent lip facing towards the left or right slit. Pull the plate toward
the center and it should stop at a right angle facing outward. Do the same for the other side then
hold the two in place.
2.) Insert the downconverter between the two plates as the notches of the downconverter are aligned
with one of the holes on the plate. Insert the only fine screw (#2, image 6) that came with the
mounting accessory package. Firmly secure the assembly in place with its matching nut. The
downconverter should not move and can only be assembled either upward or downward. It doesn’t
really matter as long as it attaches to the grill.
3.) Depending how the grill will be mounted, vertically or horizontally, two sets of 4 small punched off
squares are available for this option. From the front, insert the two U brackets either up and down
or side to side as depicted on the picture above (front, image 6).
4.) From the back, insert one of the jagged half circular clamps (#3, image 6) with the flat side facing the
back of the dish. Insert the second jagged half circular clamp facing inward as though assembling a
set of dentures together. Thread in the two matching nuts for the first assembly. Do the same for
the bottom set. The completed setup is clamped to a pole as depicted on the picture above (back,
image 6).
5.) The common mistake with the assembly is flawed not by the grill assembly but by the mounted
pole. Poles need to be tightly secured in place, preventing from rotating clockwise or
counterclockwise after the alignment is complete. Because when rainy or windy days come, the dish
TIP:
When installing
a new dish,
assemble the
dish at one of
the endpoints
of the pole first,
then raise the
pole and secure
it in place but
allow it to
rotate
clockwise or
counter-
clockwise. Peak
the dish
alignment by
rotating the
pole then lock
the pole in
place with a
screw, a bolt,
550 cord, duct
tape, or other
means of
securing.

of 73
easily moves out of alignment, causing a series of distorted signal quality to no video. As a general
rule, all screws and mounting brackets need to be firmly tightened to prevent future misalignments.
Section 4:
a.) Types of Power Inserters & Internal Parts
Power Inserter
There are several types of power inserters.
It’s easy to confuse them with splitters.
But as long as the label says Power
Inserter with supporting frequencies of 5-
1000 Mhz and above, then it should work.
As illustrated on image 7, the internal
parts of a power inserter has electronics
that are susceptible to voltage damages.
The first to go is the capacitor as this holds
a charge of current. If the current
tolerances are exceeded, it will blow. And
because they are sealed inside the power
inserter, it may not be heard when it blows. Main causes for power inserters to fail are due to power
surges that come from the electrical sources such as instances of generators being turned on or off.
When the power inserter goes out, the entire cable distribution system goes out. Realigning the dish will
not do anything. Therefore, this is the first equipment to check to make sure it’s still works. The only
way to test these is by checking the voltage with a multi-meter set to DC at the “ANT” port, see (outside,
image 7). The voltage reading should be at the power supply’s DC output (#1, image 8), sometimes a
little higher by 5 volts or less.
b.) Types of Power Supply
There are several types of power adapters. In this picture (image 8), is the standard power adapter
supplied with our MMDS Grill dishes. Any power supply that outputs a 12VDC at 1A (#1, image 8) with a
polarity the same as the picture (#2, image 8) above (center conductor is +, outer ring is -) will work.
Typically, Iraqi versioned MMDS receivers require more power of up to 24VDC making this power
inserter’s power supply incompatible. Also, with this type of power supply, the voltage input is dual
DID U KNOW?
Majority of the
known cause to
signal
interruption is
due to someone
unplugging the
power inserter’s
power supply.

of 73
voltage. In other words, it will work with either 110 volts or 220 volts (#3, image 8). So be careful when
plugging in the power supply to an electrical outlet and be sure that power supply on hand is plugged in
to its rated voltage input (#3, image 8).
Section 5: Coaxial Cable & the MMDS Signal Flow
a.) Coaxial Cable and its parts
Coaxial cables have two wires. The inner conductor, known as simply
copper, found at the center of the cable is where the main RF signal travels
through. The outer conductor, called the woven wire shield, surrounds the
center wire at an evenly tubular space around it. The short name for it is
“shield”. The space between the two wires is filled with a non-conductive
material known as a dielectric insulator. The outer shell of the coaxial cable
is the outer plastic sheath, providing both internal and external protection
from external damages and to prevent its own magnetic fields from having
to cause external interferences. The thin foil surrounding the insulator in an
option that not all coaxial cable have. This foil creates a perfect waveguide
for the RF signal travelling through the copper wire to minimize loss of RF power.
A general understanding about coaxial cable is that it is the medium that conducts an RF signal from
point A to point B without induced magnetic fields being felt outside the cable, making it a safe
conductor near storage devices such as hard drives, flash drives, cassette tapes, etc. Coaxial cable can be
used in its simplest application yet become extremely complicated when major cable distribution is
applied.
b.) Basic MMDS Signal Flow
When an MMDS Antenna receives the signal from the transmitter, it is downconverted back to the
original frequency band of VHF & UHF – the standard frequencies for broadcast television that TV
Tuners are compatible to. From the downconverter, the signal travels through the center wire of a
coaxial cable as it passes through the power inserter and back through another coaxial cable that runs to
the TV. The signal is then routed into two ways after reaching the TV Tuner. The first half of the signal
goes through a series of electronic components for it to be broken down into viewable signal, which is
the Video and Audio. This signal is what’s being seen and heard by the viewer. The second half of the
signal is routed through the TV tuner’s outer connection as it travels back through the woven wire shield
of the coaxial cable. From there, the signal gets shorted from the outer shield of the power inserter
travelling to the negative line of the power supply. The power supply converts this signal into useable
voltage and is routed back into the MMDS downconverter for power consumption. Power is used to
make the MMDS work as it’s also dissipated into heat. The process continues to repeat itself in a cycle.
Although it may seem as though the signal really starts from the Antenna, the flow really starts from the
power supply. The moment the power supply is plugged in, the DC Voltage travels through the positive
wire entering the power inserter’s center connection. The voltage is then routed to the “ANT” port but is
DID U KNOW?
Not all coaxial
cables will have
an extra foil as
part of the
shield. The foil is
there for added
protection and
to keep the
signal trapped
inside the coax.

of 73
blocked from the “TV” port by a series of electronic components called capacitors. The voltage provides
power to the downconverter and only then would the transmitted signal be received, demodulated, and
amplified as it shoots out to the coaxial cable as described on the first paragraph. The voltage however,
returns from the downconverter’s chassis, into the coaxial cable’s woven wire shield, through the power
inserter’s chassis, and shorted to the negative conductor of the power supply, and is cycled back into the
downconverter for power. Keep in mind that when voltage exists, it is because electrons were moving.
To better understand this concept, electrical theory needs to be explained.
c.) Electrical Theory
To better understand how to properly distribute RF signal through a sophisticated distribution system
such as Image 31 on Chapter 2, Section 8b, it is important to understand the complexities of RF signal
flowing through coaxial cable. However, explaining the signal flow into detail would require an
understanding of basic electricity theory as the signal travels through
the copper wire. In this discussion we will discover how conductors,
more specifically copper, can be used to generate electricity. But first,
we need to learn the atomic composition of copper and its elements.
Copper atom is composed of 29 protons, 34 neutrons, and at a
minimum 29 electrons. Protons are positively charged, Neutrons has no
charge, and Electrons are negatively charged. The copper atom has
layers of 4 shells that surround the protons and neutrons together in the
center. In each shell holds a specific number of electrons: 1st
shell = 2
electrons, 2nd
shell = 8 electrons, 3rd
shell = 18 electrons, 4th
shell = at least 1 electron but wants 32

of 73
electrons. In copper, the fourth shell is the key factor that makes the atom conductive. Although it
wants 32 electrons, all 31 electrons normally found on the 4th
shell can easily break free. This happens
because the 1 electron found on the 4th
shell add up with the rest of the electrons in the 1st
, 2nd
, and 3rd
shell to an equal amount of protons, keeping the copper atom stable. Each proton and electron within
the copper atomic composition is naturally charged.
Copper wire is created through melting techniques, fusing copper atoms together. The 31 excess
electrons in each atom that normally revolve around the fourth shell would leave their parent atom.
When they leave, they surround the entire wire as though the wire is one big atom. And since there are
at most 31 free electrons that can leave their parent atom, they all add up to a sea of electrons around
the wire. Scientists call this “electron sea.” Electrons are negatively charged and protons are positively
charged. Both have the ability to induce electromagnetic fields when they move. But since protons are
located at the center of each atom, they can’t move because each atom is fused together that makeup a
copper wire.
Before I move forward, I need to explain what potential difference is because this is tied to the driving
force of electricity. Hence the phrase: “driving force”. Potential difference is the difference in electrical
charge between two points in a circuit expressed in volts. What does this mean? To better grasp this
concept, look at the image below (image 12). Imagine having two cylinders side by side and a pipe that
connects the two. When water flows from the left cylinder (full of water) to the right cylinder (least
water), a force of current will come pushing out of the pipe filling up to a level that is balanced with the
left cylinder (see BEFORE). Once it’s balanced the flow of current stops (see AFTER). If the cylinders were
in outer space, this concept would not be true. But because there is an external force on earth, called
“gravity”, the water on the left cylinder is drawn down to a level with the right cylinder. The same
concept applies to voltage as voltage is the external force or pressure that makes the electrons move
either forward or backward. Potential difference occurs when one line is at a higher voltage so that
electrons would flow to the much lesser voltage as though trying to relieve pressure. To eliminate
confusion, voltage should not be described as either just positive or negative but rather electrical
pressure. Keep in mind that voltage is not the only force that makes electrons move but also would a
difference in charge attract electrons to move. A good example would be the heavy dark clouds with
excessive amounts of electrons as they are attracted to the positive charges in the ground creating
lighting.
DID U KNOW?
The basic
operation of an
atomic bomb is
to simply return
back to its
neutral state.
Scientists would
separate the
electrons from
the atoms and
keep the protons
at the nucleus in
two confined
cylinders. When
the trigger is
pushed, the
immediate surge
of the electrons
attracted by the
protons would
cause a major
electrical
implosion in a
highly
compressed and
confined
container that it
explodes in great
magnitude.

of 73
As mentioned earlier, the only free element that can move around the wire is the electron. Any moving
bodies of elements such as electrons are called current. In electricity, moving electrons are called
electric current. And just to eliminate future confusion, in different forms of matter such as air, ground,
or human flesh, protons would move in order to neutralize the potential difference between charges.
The only difference between electrons and protons are, protons have to take the entire atom along with
it since protons are found at the center of an atom. This means that ground is both positively and
negatively charged. This is why any difference in charge can be shorted directly to ground without any
problem. Lightning, for example, strikes the ground due to the excess electrons in the clouds as it is
attracted by the positive charges of the ground in an effort to neutralize the difference in charges.
Because electrons hold a charge, when they move, they create an electromagnetic field around it as it
moves away from the electron like a rippling effect. The reason why electromagnetic fields travel faster
than electrons is due to resistance as it causes electrons to generate heat and when heat exists, power
exists. Resistance exists because of the different elements that were added in a copper wire as well as
the atom’s pull to retrieve the 31 excess electrons. Resistance is measured in ohms and every copper
wire has its own rating of resistance. If resistance did not exist, a piece of copper would remain
electromagnetically charged because electrons would move freely in the wire without external forces. It
would be like holding a lightning rod without batteries.
Here are a some need-to-know info about electricity:
1.) It will always take the path of least resistance. This is why it is always recommended not to touch
electrical lines while standing barefooted on the ground as human flesh would be the lesser
resistive conductive material.
2.) To get an idea of how fast electricity can travel, imagine travelling around the earth at 7.5 times
per second. That’s about 186,000 miles per second, assuming impeding factors do not interfere. In
other words, it’s about the same as the speed of light.
3.) AC stands for Alternating Current and DC stands for Direct Current. To simply explain it, direct
current is electric current that travels only in one direction from sources like batteries. Alternating
current travels forward and back because of the way that electrical plants generate voltage. They
generate voltage by inducing electromagnetic fields through the movement of electrons because
electrons are attracted to magnets. They simply have a thick copper wire at about 20 feet thick by
100 feet long. Around it are magnets that rotate at 60 times per second (United States = 60 Hz)
and 50 times per second (other countries = 50 Hz), making electrons move around the copper as it
generates electromagnetic fields. Because these electromagnetic fields surround an electron,
when they move, voltage is produced. This voltage is routed through massive amounts of
transformers that make the electromotive force (EMF) or “VOLTAGE” excites electrons beyond the
transformers to move forward and back at either 60 or 50 cycles per sec. They move forward and
back because of the constant change of polarities in the electromagnetic wave as electrons move
around the thick copper wire. In other words, the electrons would wiggle back and forth 60 or 50
times per second in the wire as it induces voltage across the wire. To simply put it, electricity can
be generated by simply rotating magnets around a piece of copper.
4.) Transformers are methods of changing the amount of output voltage from the source. It is done
by creating two separate coil windings that are opposite of each other. For example, if one side
has a winding 50% lesser than the other winding, then the voltage is dropped by 50%, assuming
DID U KNOW?
EMP stands for
Electro Magnetic
Pulse. The
reason why it
disrupts any
electronic device
is because it
practically
disturbs the
electrons from
its normal flow
in an active
device causing
electrical surges
within the circuit
blowing
components
beyond their
tolerance levels.
EMPs are similar
to the creation
of FM or AM
radio but in
greater
magnitudes
without the
music.

of 73
the source was at 100%. But if the source needed to be stepped up in conversion twice its voltage,
then 200% of the source’s coil winding needs to be in the other side. The conversion takes place
through the amount of electromagnetic flux that can radiate into a set number of coils without
touching each other.
5.) Around the world, even in the United States, the standard electrical voltage before it is supplied to
the house is 240 Volts. They come in 2 wires both having opposite phases or should I say 180
degrees apart. Each wire has 120 Volts. But in the United States, they added a third wire called the
Neutral wire. This neutral wire originates at the center of the transformer before it enters the
house. Just like the source at the power plant, they take all the fluctuating voltage from the
generator and run it through a transformer for a uniform amount of voltage which basically
creates a pressured voltage called Electromotive Force (EMF) that may be higher than 1000 Volts.
The power lines by the highway carry so much voltage causing large magnetic fields, of which they
needed to be raised above reach to prevent any electromagnetic interference. As power is routed
through the city, the power is routed to a step down transformer to another step down
transformer before it reaches the consumer’s house. By the time power is provided to the
consumer, the voltage from 1000 Volts has been down converted to consumer grade voltage of an
average 120 Volts per line but in pairs of two out of phased lines. Again, like I said earlier, in the
United States, they added a third line, being neutral to help maintain a stable source of electrical
voltage. But if 240 Volts is needed to power equipment, simply replace the neutral wire with the
second hot wire. Seldom do we use 240 Volts in the United States because they are really meant
for power hungry equipment such as certain dryers, central AC units, furnaces, etc. Besides,
consuming voltage at 120 volts means we use less fuel to run those power plants. But unlike other
countries outside the United States, they use 240 volts as standard consumer grade voltage. The
problem with this is, voltage could easily fluctuate, exceeding tolerances of appliances.
6.) In AC (Alternating Current), Voltage is created by simply making electrons move in a copper wire
through magnetic influences. Electrons would detract and attract to magnets because of their
positive and negative poles. As mentioned earlier, when electrons move, they create an
electromagnetic field around the electron. And as electrons move this induced electromagnetic
field is what we call “voltage”. Although this is one way to create voltage, there are other methods
to produce voltage such as chemicals in batteries producing DC (Direct Current).
7.) When it comes to measurements, Current is measured in amperes (I=Inductance), Power is
measured in watts (W=Watts), Potential Difference is measured in volts (V=Volts), and Resistance
is measured in ohms (R=Resistance). The pie chart of
formulas when calculating electrical measurements
illustrate the behaviors of electricity (image 13).
8.) Let’s verify the theory by choosing one of the formulas
from each section of the pie chart.
• Power (W) = Volts (V) x Amps (I)
Earlier, I mentioned that Power is produced based
on the amount of voltage that pushes or pulls
electrons. If that were true then it means that if I
increase my voltage, the more wattage I should get.
However, if I increased my voltage, this also means
DID U KNOW?
Power can be
generated
through many
different means
without relying
on electrical
companies.
However,
because we
consume so
much power to
supply power to
our phones, tvs,
and other
electronic
devices, it’s
difficult to
sustain
renewable
energy if we
don’t change the
way we
consume power.
Electric
companies
consume fuel o
use nuclear
energy to keep
power plants
generate power
just like the way
portable
generators do.

of 73
that my current flow (amperage) would also increase. When applied through a circuit breaker,
if my voltage increases then this means that the amperage would increase to a point where it
would surpass the tolerance of the circuit breaker, causing the switch to trip. This means the
theory is true since it’s already being applied in our day to day electrical use.
• Volts (V) = Ohms (R) x Amps (I)
I mentioned that the voltage is in the form of the induced electromagnetic fields. If this were
true then let’s go back to the cause of electromagnetic fields in a wire. Here’s a fact in
electronics:
When a piece of wire has a constant voltage that goes from the source to
the destination, it can be decreased at the destination by adding a piece
of resistor in between the wire. When that happens, a term called
“voltage drop” would have a higher voltage reading at the resistor, lesser
at the destination, but constant at the source.
I mentioned earlier in theory that electromagnetic field exists due to resistance in the wire as
the current continues to flow. Since a known fact about voltage drops increasing at the
resistor; it must be true that induced electromagnetic field is the voltage because resistance
has increased. This is also the reason why Ohms x Amps = Voltage & not Ohms x Voltage =
More Voltage.
• Ohms (R) = Volts (V) / Amperage (I)
Based on the fact about voltage drops as mentioned above, it only makes sense to that if a
voltage has a certain amount, it is because the resistance level has changed yet the current is
still being forced to move forward. Therefore, if we divide the amount of voltage by current,
we should get the amount of resistance applied that induced the voltage drop. Once again,
the theory is true about resistance causing electromagnetic fields as depicted on the formula.
• Amperage (I) = Power (W) / Volts (V)
In the overall explanation of electrical theory, I basically mentioned that: Heat is the result of
Power, Power is the result of Amperage, Amperage is the result of Voltage, Voltage is the
result of Resistance, and Resistance is the result of Atomic Composition. If my statement were
true then it means it should match every formula that engineers came up with to illustrate the
behavior of electricity. So far Power, Voltage, and Resistance are true. As for Amperage, I
mentioned that Amperage is the result of Voltage. So, if I had 120 volts and my amperage was
10 Amps, to get my wattage, I would simply multiply the two, which equals 1200 Watts. I
multiply the two because as I am feeding 120 Volts through the line, electrons would move at
a rate of 10 Amps. And because Power is the result of Amperage, I multiply both Voltage and
Amperage together to get a product of Power. Since now we know what our Wattage is, how
do I get the amount of Amperage if all I know is 120 volts? The answer is to divide 1200 Watts
by 120 Volts and that should give us 10 Amps, making the theory true and the formula true.
Confusing enough?
d.) Detailed MMDS Signal Flow
Radio Frequencies (RF) are pulsing electromagnetic waves that hold properties of intelligence signal
such as music, video, and data as they travel through air. In its basic form, RF is simply the same induced
RADIO FREQUENCY CHARACTERISTICS
TIP:
When plugging
electronic
devices into a
multiple power
strip, always
check the
rating of the
power strip
making sure
that the
amperage it
can handle are
within
tolerance. All
that needs to
happen is
simply add up
all the
annotated
amperage
rating listed at
each electronic
device and
make sure it
adds up to a
much lesser
amperage
rating than the
power strip’s
tolerance
levels.

of 73
electromagnetic field caused by moving electrons. One way to make them radiate off the wire is by
making the electrons change in charge (charge/discharge) by turning the power on and off. In advanced
engineering, the pulsing effect is called Pulse Modulation, where they are able to create a circuit that
mimics the on and off switch of radiation without turning off the power. It’s like the ripple effect on
water. Keep the ball afloat, no ripples occur. Drop the ball on water, and ripples occur. In a sense, it’s
the sudden on and off of the radiated signal but it’s engineered to keep the transmission at a constant
radiation. In addition to that, what boosts the signal outward from the antenna is through the amount
of heat that the transmitted output power is producing.
Unlike electricity where the electromagnetic fields travel along the wire due to its low oscillating
frequency of either 50Hz or 60Hz, RF has a minimum oscillating rate of about 3 kHz (3000 cycles per sec)
to 300 GHz (300,000,000 cycles per sec). This fast frequency oscillation make the signal radiate off the
wire. Zooming closer into the atomic view, the frequency is so fast, there is no room to bend or weave
around bumps and pot holes caused by impure copper elements in a wire, making the signal deflect
outward. This simple explanation is called “radiation” as frequencies travel into space. They similarly
oscillate like Alternating Current but not like Direct Current where the signal is flat lined. To better
describe it, they look like Hills and Valleys in a daisy chain or a moving snake. Without the intelligence
signal, RF would not be called RF but rather static interference caused by electromagnetic fields. But
because we are able to inject information in the signal, we are able to receive the broadcasted signal
through a receiver such as cell phones, walkie-talkie, WiFi, radios, MMDS, you name it. Every electronic
device that consumes power radiates a certain level of electromagnetic field. And because of that,
interference between electronic devices can disrupt proper functions of other devices. That’s when
governing the spectrum of radio frequencies was necessary to develop some type of rules which
required every inventor and engineer to abide by. A common rule required for every transmitting
electronic device is shield in order to control the electromagnetic radiating interference between
devices; hence the creation of coaxial cable.
Other known facts about RF:
a.) The lower the frequencies, the longer the wave length.
b.) The higher the frequencies, the shorter the wave length.
c.) The lower the power, the smaller the sine wave in amplitude.
d.) The higher the power, the bigger the sine wave in amplitude.
The beauty about RF is that it can travel through air and through conductive materials. In the process of
MMDS, the transmitters would carry intelligence signals through injected modulated signals.
Modulation is the process of converting the intelligence signal to be injected into the carrier signal of
the UHF band (300Mhz-3Ghz). In our modulators, however, we are only able to modulate the baseband
signal (Video & Audio) to the low end of UHF spectrum of Channels 24 to 54 (222Mhz to 408Mhz). At
that point, the modulated signal is routed to the transmitter for an up conversion to the higher end of
UHF spectrum of 2.5Ghz to 2.7Ghz to broadcast as MMDS transmission. But because MMDS has a higher
frequency than the modulated low UHF signal, it has to go through a cable called a waveguide. This
waveguide is then connected to a dipole antenna that would radiate the signal in a donut shape within
its radiating capabilities. And because MMDS is transmitted at high frequencies, the receiving antennas
MMDS TRANSMITTER
DID U KNOW?
Creating a radio
signal can be as
easy as simply
using a 9V
battery and a
penny. Every
time the penny
touches both the
positive and
negative
terminals, the
penny generates
an induced
electromagnetic
field around it.
The moment the
penny is
released from
touching one of
the terminals,
the
electromagnetic
field around the
penny is
released into the
air as 1
frequency pulse.
This is essentially
the way radio
frequencies are
based off from.

of 73
need to have a direct line of site to the transmitting antenna. Otherwise, the signal would not be
received.
RECEIVING ANTENNA
Looking at the diagram of the MMDS signal flow in Chapter 2, Section 5b – Basic MMDS Signal Flow, the
radiated MMDS signal is deflected by the grill dish into the downconverter’s deflector shield, which is
radiated into a plate of copper inside the downconverter. From there, the signal doesn’t go anywhere
until the downconverter is supplied with its proper voltage.
Downconverter Specs from Loma Scientific:
Model: 2278-030
Input RF: 2500 to 2686MHz
Output IF*: 222 to 408MHz
Gain: 30dB +/- 3dB
RF output level: +35dBmV
Output Connector: “F” Type Female, 75 Ohms
DC Supply Voltage: +16 to +24 VDC through output connector
Current: 235mA Max
Operating Temp: -40C to +65C
*IF stands for Intermediate Frequency which is basically the downconverted output product of the MMDS downconverter. It has
to take the high frequencies and convert it to lower frequencies and is mixed with a frequency that was created locally through
an internal oscillator. It’s not the original up converted signal from the transmitter but rather intermediate version of it. It is,
however, still considered an RF signal.
POWER SUPPLY part 1
Assuming the Basic MMDS Setup is put in place as described on Chapter 1, Section 1a, once the power
supply is plugged into the Alternating Current of either 120VAC or 240VAC, the power supply converts
the voltage into 18VDC. The conversion is an important aspect to remember as this is where the signal
ends and is recycled into useable voltage. But before we get ahead of ourselves, let me explain that
when a power supply converts AC to DC, it has to go through a series of components. The first step is the
step-down transformer from 120VAC/240VAC to 18VAC. As explained in the electrical theory regarding
transformers (Chapter 2, Section 5c, #4), the input conversion is through a transfer of electromagnetic
flux that radiates to a set number of coils. This concept is practically the same in the RF Antenna concept
radiating the signal to be downconverted at the receiving antenna. Realize that the concept of both RF
and Electricity are both electromagnetically influenced.
The second step is through a component called rectifier. This step converts the 18VAC to a 18VDC,
where the signal is no longer alternating in hills and valleys but in a flat smooth line, directing the
electrons forward and not in a wiggling motion like AC does. To avoid future confusion, when reading
the label as indicated on image 8, the output voltage may say it’s 12VDC @ .35A but when measuring
the voltage, the actual voltage comes out to 18VDC. The reason for this is due to tolerances, there will
always be a +/- voltage on any output source as resistance and amperage are considered for voltage
drop compensation (this will be explained in “Coaxial Cable part 1”).
DID U KNOW?
CATV, or Cable
TV frequencies
are called Super
Band and Hyper
Band. Super
Band are
channels: 23-36
(216 – 300 Mhz).
Hyper Band are
channels: 37-62
(300 – 456 Mhz).
And yet, they fall
under the
spectrum of
UHF.

of 73
Power Supply Specs from Loma Scientific
Model: LSI-TESA
Input Voltage: 100/240VAC +/- 10%
Input Freq: 50/60Hz
Input Connector: 2 prong (no ground)
Output Connector: “F” type male
Output Voltage: +18VDC @ 350mA (.35A)
Output Power: 9 Watts Max
POWER INSERTER part 1
From the rectifier of the power supply, current flows out through the positive wire and in through the
center conductor of the Power Inserter’s input line. Once it reaches the power inserter, the voltage goes
through a series of components called filters made up of transistors, capacitors, and diodes. This
circuitry basically directs 2 separate frequencies in their own rightful path, where the RF frequency can
pass through both the “ANT” & “TV” tap, while electrical frequencies could only pass through the “ANT”
tap. Remember that electricity is either in 50Hz or 60Hz while RF can range from 3kHz to 300Ghz. But in
MMDS, once the signal is downconverted to the lower UHF signal, we’re only concerned about the
channels from 24 to 54 (222Mhz to 408Mhz). The power inserter’s acceptable radio frequencies are
from 5Mhz to 1000Mhz allowing a range of VHF & UHF channels to pass. The inserted voltage of 12VDC
simply enters the “INPUT” tap and out through the “ANT” tap.
Power Inserter Specs from Loma Scientific
Model: LSI-TESA
Operating Freqs: 5-1000MHz
Insertion Loss: 1dB
Connectors: “F” type female (x3)
DC Voltage Drop @ 300mA, 1VDC max
COAXIAL CABLE – ELECTRICITY part 1 “PWRINSTR to DWNCVTR”
When deciding how long the wire needs to be from the power inserter to the antenna, there are a few
things that need to be considered. Let’s say I’ve setup my MMDS system to its basic setup where I have
my TV setup, my power inserter setup, my dish aligned, and cables installed. With that setup, however, I
decided to run 1000 feet of coaxial cable from the power inserter to the downconverter. I turn on the TV
and I get my MMDS signal. Although it works on the first TV, what is not realized is that the RF signal is
actually weaker than it should’ve been if the cable from the power inserter to the antenna were a lot
shorter. Therefore, sharing the signal to others through a splitter may start causing major issues with
signal loss. Here’s the reason why:
At this point the coaxial cable acts just like a regular electrical wire. Neither the shield nor the insulator
matters. The electrical current of 18VDC would travel out of “ANT” tap, through the center copper wire,
and into the downconverter without a problem. And because electricity has a low frequency of 50 or 60
Hz, it can travel through the wire at long distances.

of 73
Understand that the impedance rating (resistance/ohms) printed on a coaxial cable is different
compared to the actual impedance measurement of the center copper wire of a coaxial cable. The
reason for that is simple, the 75 ohms is measured for RF, while the copper wire’s impedance is
measured for electricity. It also means that electricity travels along the copper wire while the RF
travels along the inner insulator as it slides through outer skin of the copper wire called “skin effect”.
Therefore, if we pinch or flattened a coaxial cable, the impedance rating of a coaxial cable regarding RF
would increase while the impedance rating of the copper wire regarding electricity remains the same.
For example, a 1000 ft of RG6 coaxial cable is rated to have a constant 75 ohms of impedance. As a
matter of fact, we could have a million feet of RG6 and the impedance rating would still remain at 75
ohms. However, when measuring a 1000 ft of coaxial cable with an ohm meter, it’s center copper wire
from tip to tip would probably get a reading of +/- 28 ohms. And when measuring a million feet of RG6’s
center copper wire from tip to tip, it would get an average of 28,000 ohms.
So how does this affect the length of the cable? The answer is voltage drop. Just as how engineers
named it, the voltage drops at the destination due to the total amount of impedance on a cable, which
is determined mainly by length (although this is mainly true, realize that impedance could be caused by
many different factors such as purity of the wire, size or gauge of the wire, a cut in the wire, etc.). Why
by length? Because the longer the wire the higher the impedance because it acts like a long resistor.
The formula for voltage drop is the same formula for voltage which is V=R (impedance) x I (current). On
image 9, the coaxial cable from Belden Manufacturer states that the center conductor is an 18AWG,
that’s .040 inches thick. According to its specs, the center conductor’s impedance is 91.9 ohms/km =
.028 ohms/ft = 2.8 ohms/100ft = 28 ohms/1000ft. The second piece to the formula is amperage. The
question here is, which amperage reading do we take? Is it from the power supply or the
downconverter’s operating current? The answer is the downconverter. We take it from the
downconverter because it’s the load that demands that amount of power. Therefore, we are only
interested in its operating current which, according to Loma Scientific, it operates in 235mA (.235A)
MAX. Now that we have all the pertinent information we can simply do the math.
Based on 1000 ft of coaxial cable
Voltage drop = Ohms (cable) x Amperes (downconverter)
V = 28 ohms x .235 Amps
V = 6.58 volts (in the wire)
To know what the voltage would be at the load (downconverter), we simply subtract the voltage drop
from the output voltage of 18VDC, which comes out to be 11.42VDC. This means that if we ran 1000 ft
of cable from the power inserter, we wouldn’t have enough power to supply the downconverter. At this
point we either cut the cable shorter or change the power supply that outputs a voltage of at least
25VDC to compensate for the power loss. To prevent this from happening, I highly suggest not
extending the cable any longer than 300 ft. 300ft of cable would provide a minimum of +16VDC at the
downconverter. Although this is the minimum requirement for the downconverter to operate, expect it
not to provide an optimal amount of signal gain, making it susceptible to noise and all sorts of issues.
Coaxial Cable Specs from Belden Cables
Model: RG6 Series 6-18AWG
DID U KNOW?
Most of the
tolerances in
coaxial cable are
based of 1000
feet of cable.
This why they
only supply 1000
feet spools to
guarantee their
specifications.
Any longer than
1000 feet
requires a few
technical know-
how on Cable
Television since
cable
distribution can
become
extremely
complicated.

of 73
Center Conductor: 18AWG (solid) .040”, 28.0 ohms/1000ft, 91.9 ohms/km
Shielding Material: Duobond II (Aluminum Foil) + 60% Aluminum Braid, 9 ohms/1000ft
Nominal RF Impedance:75 ohms
Nominal Capacitance: 16.2 pF/ft (picoFarads/foot)
RF Attenuation/100ft: @ 5Mhz = .54dB NOMINAL, .67dB MAX
@ 55Mhz = 1.45dB NOMINAL, 1.60dB MAX
@ 1000Mhz = 5.99db NOMINAL, 6.54dB MAX
@3000Mhz = 11.30dB NOMINAL, 11.90dB MAX
COAXIAL CABLE – ELECTRICITY part 2 “DWNCVTR to PWRINSTR”
From the downconverter, the voltage travels back through the shield reaching the power inserter’s
chassis. It then travels down to the power supply and gets recycled back through the power supply for
DC Voltage. If the Power Inserter is grounded, then chances are, the voltage gets grounded too.
However, there will still be some voltage recycling through the power supply since it maintains
potential difference within the circuit.
MMDS DOWNCONVERTER
Once the downconverter receives the 18VDC, it is powered up to receive the MMDS signal at 2.5Ghz to
2.7Ghz. This signal is downconverted back to the CATV channels 24 to 54 (222Mhz to 408Mhz). Before
leaving the MMDS downconverter, the signal is amplified and is shot out of the downconverter and back
through the coaxial cable, ready for distribution.
DID U KNOW?
Decibels (dB) is
widely used to
represent the
amount of
power to RF,
acoustics, and
others and yet
electric power
is in watts. dB
came after the
discovery of
phone lines,
which is why
electrical power
is still in watts
because it
originates to
the first
discovery of
electricity.

of 73
When the RF signal leaves the downconverter, the signal travels through the same center conductor as
the 18VDC came through. Because the electric current is at the frequency range of either 50Hz or 60Hz,
the RF signal of 530 MHz to 710 MHz would ride or cross the electric current in the same conductor
without colliding with each other. Although I’ve use the term RF signal to describe the MMDS signal, the
actual term for RF signal in a wire is called “RF current”. But for the sake preventing confusion, we’ll use
“RF signal” to follow the signal path.
Coaxial Cables are like waveguide conductors used in transmitter systems. Waveguides are hollow
inside, rigid, and doesn’t have a center conductor. They look like poles, bent at angles that don’t
compromise the integrity of the internal circumference. Waveguides are ideal for transmitted high
powered frequencies. Because these frequencies are excessively powerful, they don’t bend but rather
bounce off the wall inside the waveguide. It’s like a flat piece of rock; toss it into a lake and it simply
sinks. Throw it as fast as pitching a fast ball and expect to see it skip a few times above the surface of
the lake before it sinks. Now take this concept and apply it to frequencies. The flatter the rock = higher
frequencies. The fatter the rock = lower frequencies. The faster the throw = higher power. The slower
the throw = lesser power. So what does that tell you about coaxial cables? It basically means that the
frequencies it can handle are frequencies of lower power but high enough in frequency to be travelling
through the inner insulator but at the surface of the copper wire. The coaxial cable then acts just like a
waveguide except it can follow through the wire. Too much power (+30dB or more) and it will start to
cause noise on the signal. Just as I have mentioned earlier, RF travels through inner insulator and only
in the surface of the copper wire. It basically slides along the skin of the copper wire. Engineers have
named this, “skin effect”, where the signal does not have the ability to penetrate the copper wire due
to frequency properties. Again, like I’ve mentioned earlier, the higher the frequency, the flatter the
rock, making it skip even more over the surface of the water. When the input signal changes to higher
frequencies, impedance to the RF signal would start to increase because it is not able to latch on to the
copper wire… like a skipping rock out of control.
There are many different types of coaxial cables. But in MMDS, we will focus on three of the commonly
used cables: RG59, RG6, and RG11.
COAXIAL CABLE – RADIO FREQUENCY part 1 “DWNCVTR to PWRINSTR”
• RG59 has a thinner center conductor of 20AWG (.032” in diameter) with a higher attenuation
on RF compared to RG6. The operating frequencies for RG59 are from 5Mhz to 1000 Mhz.
Although it works with the MMDS signal, it is impractical to use it for cable distribution because
of its high attenuation over long cable runs. Its best use is for short cable runs from the tap
directly to the TV or in professional broadcasting, we only use them for the baseband video
signals without the RF. Its impedance characteristics is 75 ohms.
• RG6 on the other hand, is the most common and preferred CATV distribution cable. This type
of cable is great for basic cable distribution of +/- 15 TVs. Its center copper wire is an 18AWG
(.040” in diameter); can handle frequencies from 5 MHz to 3 GHz; provides lesser RF
attenuation compared to RG59; and is considered to be the most practical and commonly used
in CATV (Cable TV). Its impedance characteristics is 75 ohms.
DID U KNOW?
Some companies
like Belden
exceed the exact
sizing charts of
wire gauges
even if the label
states its gauge
value. So, in
addition to the
gauge
designator, they
include in the
actual thickness
of the copper
wire in the
specs. They
increase the
thickness to
decrease the
amount of skin
effect to the
signal so that
lesser dB losses
do not affect the
signal.

of 73
• RG11 is the better cable amongst the three. It is popularly used for trunk lines because it can
handle high powered frequencies. And when I mean high powered, I mean the same MMDS
signal but amplified to carry the signal farther. Its center conductor is at 14AWG (.064” in
diameter) and has the least amount of RF attenuation. The operating frequencies for RG11 are
also from 5 MHz to 3 GHz. Although it can handle RF perfectly, it is fairly rigid and is not
popularly used at consumer level. The connector is also fairly thick that it becomes difficult to
fit in most common TVs. Not to mention, it’s impractical to use for common CATV distribution
since the cable itself is also more expensive. Like I said earlier, it’s best use is for distribution
trunk lines. Its impedance characteristics is 75 ohms.
If there is anything common about these three cables, it’s the fact that they can all carry RF signals and
that they have an impedance rating of 75 ohms. So what’s so significant about impedance? There is a
term in broadcast engineering called, “impedance matching”. Impedance matching is self-explanatory. It
means that the impedance rating from the source needs to be the same all the way through to its
destination in order to maintain good signal flow. Sounds simple, right? Not quite. To understand
impedance matching, we first need to know how impedance is measured and what it takes to maintain
that impedance.
• The impedance of a coaxial cable is not measured by its copper resistive properties. Instead, it’s
determined through a formula calculation utilizing the size, spacing between both conductors,
and the type of insulator used. It is dependent mainly on the dimensions of the inner and outer
conductor. Although this impedance is calculated to describe the physical properties of the
coaxial cable, the actual impedance to the signal is still dependent on the frequency and power
that is being pushed through the wire. The results would vary based on the effects of
capacitance and inductance.
• The formula used to characterize the physical impedance of a coaxial cable is : Z (impedance) =
138 log b/a. “b” represents the inner diameter of the outer conductor (shield), and “a”
represents the outside diameter of the inner conductor (center copper wire). However, the
formula to calculate the signal’s impeded signal is Z=SqRoot[L/C] according to Caltech University
where “L” is the calculated inductance produced and “C” is the calculated capacitance effect
measured in picoFarads. The signal’s impedance will be explained in greater detail at the
description of the shield (return path).
• Because the impedance rating is based on the space between two conductors, it is safe to
assume that the RF signal travels within the space but is latched to the outer rim of the center
conductor called “skin effect”. In order to maintain this precise space between both conductors,
engineers have thought of filling the gap with a Gas-injected Foam Polyethylene Insulation.
Although this holds true for Belden products, not all coaxial cable are filled with this type of
insulation. The type of insulation would also affect the impedance rating. Although not added in
the formula, the spacing has been compensated to meet the 75 ohm standard.

of 73
• Now that we know that RF travels through the insulation, maintaining its perfect cylindrical
shape is imperative to maintaining impedance. If we pinch the coaxial cable to a flat, the
impedance rating would increase tremendously, causing an effect called “reflections” and
“standing waves”. Imagine a water hose that has water flowing through it. Pinch that hose and
the water pressure at the open end will decrease but the pressure will increase at the pinch,
practically sending the water back to the source. When this happens, it could potentially
damage the equipment as it would react as VSWR. In RF terms… it’s considered bad juju.
• Another aspect to consider regarding maintaining impedance is to ensure that any bends
causing kinks, twists, and cuts, should be avoided at all times. If any signs of cuts or abrasions on
the outer surface, or worse, if the copper is exposed, fix the damaged section by simply cutting
the bad section, terminate both ends with an F connector, and barrel the two together.
Since we have a better understanding on impedance matching, the types of cables we use, and how
frequencies travel through the coaxial cable, we can now move forward to the next path of the RF
signal, which is the Power Inserter.
POWER INSERTER part 2
As the RF current travels down the coaxial cable it simply enters the power inserter through the “ANT”
tap, enters the gateway filter, and then exits towards the “TV” tap. The RF current is blocked from
having to exit through the power inserter’s “INPUT” tap through certain components. As far as the “TV”
tap, however, it is comprised of a capacitor. Capacitors allow AC to pass and not DC. And since RF acts
like an AC, the frequencies would simply pass through the capacitor and out through the “TV” tap.
The skin effect causes a few things to the copper wire… heat and inductance. Again, if we think about
this, heat is caused by moving electrons. The faster they move, the hotter it gets. And because they
COAXIAL CABLE – RADIO FREQUENCY part 2 “PWRINSTR to TV TUNER”
The moment the RF signal leaves the Power Inserter’s “TV” tap, there are no other existing signal but
the RF signal. The signal travels along the inner insulator as it latches itself to the outer rim of the center
conductor. This so called phenomenon is what engineers named it as “skin effect”. The reason why they
call it skin effect is because the RF signal would not and could not penetrate the copper wire but rather
slide along the outer surface of the wire. If we think about this clearly and apply our basic electrical
theory and RF theory, it makes absolute sense why the phenomenon occurs. First of all, we know that RF
is created by electromagnetic fields that were released from an actively induced copper wire by simply
turning it inactive. When scientists learned that the induced electromagnetic fields would leave the
copper wire the moment power was turned off, they must’ve realized that creating a pulsing effect
would be able to translate into intelligence signal. Over time, they’ve manipulated this basic finding into
something so sophisticated called Radio Frequency. And because we are able to inject harmonic
frequencies to form the intelligence signal, we could technically consider Radio Frequencies as a
“PIMPED OUT VEHICLE” that carries the baseband signal in style. RF is nothing but a manipulated version
of the natural cause of induced electromagnetic fields from electrons. And since we know that electrons
exist only in the outer surface of the copper wire called, “ELECTRON SEA”, it’s only natural that RF would
return to its rightful place where electrons exist; hence the reason for “skin effect”.

of 73
move, they induce a certain amount of electromagnetic fields. The question is, how are they moving and
why? Well, because RF acts like an Alternating Current, the electrons would push and pull, creating a
wiggly motion. However, because the MMDS RF signal has an Ultra High Frequency rate, the push and
pull effect happens so fast that it doesn’t really wiggle but rather constantly turning in place of clockwise
and counterclockwise. And because this happens, it only induces a little amount of electromagnetic
fields. And when it moves in place so fast, it also causes a certain amount of heat. When the RF signal is
amplified at greater decibels, RF burns may happen when human skin comes in contact with the copper
wire. Not only because of the generated heat but also because the human flesh acts the closest route to
ground. Remember that current travels to the least amount of resistance. The only way to decrease the
amount of generated heat and inductance is to decrease the amount of resistance on the wire, which is
why trunk lines use RG11 cables to compensate for the effects of amplified signals. Here’s the key note
when amplifying signal: The thicker the wire; the more electron sea; the lesser the resistance; the lesser
the heat; and the lesser the inductance effect.
As the RF signal travels through the coaxial cable, the signal is then received by the TV tuner’s center
conductor.
TV TUNER
As the RF signal enters the TV tuner, the signal is split in two ways. The first half of the signal is used to
be projected into the TV. Any channel selected by the remote control will basically tell the TV Tuner to
dissect the input RF signal and pull out the channel. The channel is then dissected again to pull out the
base band signal of Video and Audio. Once it’s found, it simply displays it on the screen at the viewer’s
demand. This process is what we like to call demodulation.
The second half goes through a series of components within the TV Tuner is and routed out to the outer
conductor called the shield. The TV Tuner doesn’t do any pushing or pulling of the signal but rather
routes the signal to where the signal needs to be. What pulls the signal to the outer conductor is the
power supply’s negative potential, which is attached to the power inserter’s shield. All signals are pulled
back to the power inserter’s shield through this negative potential.
COAXIAL CABLE – RADIO FREQUENCY part 3 “TV TUNER to PWRINSTR”
Now that we know the secret to the Power Inserter, the signal being pulled back across the shield wire
creates an effect to the signal flow such as: dB attenuation (impedance), inductance, capacitance, heat,
noise protection, electromagnetic field, and a few others not needed mentioned here. Most of these
effects occur with long cable runs of lengths over 100 feet.
Believe it or not, it is the shield wire that makes all the difference in a coaxial cable. Some folks believe
the shield is simply there to protect the inner conductor from external damages and that it’s woven for
flexibility purposes. Although that may be true, it’s only 1/10 of what the shield is really designed for. It’s
through the shield where most of both electrical and RF theory comes in play. As much of an important
role it plays with the signal flow, it’s also the most neglected piece. Below are the following effects in a
coaxial cable that needs special attention to.

of 73
• Capacitance – capacitance effects are apparent due to the
opposing signal flow as seen on the right (image 15). The
forward path acts as the positive charge and the return path
acts as the negative charge as seen on image 16. The arrows
originating from the center to the shield simply illustrates
that the distance between both wires are equidistantly
spaced around the center wire. To better understand this
concept, let’s take a look at how a standard capacitor works.
To simply put it, capacitors are two plates of opposing charges. They hold this charge until the
wire that charges each plate is shorted together, discharging the
both plates. The discharge process results in electricity. Keep in
mind, that both plates are separated at a precise distance to
generate this effect. Looking at image 17, a simple illustration of
how capacitors keep a charge is shown here. On the flip side of
capacitors, however, when voltages exceed the capacitor’s
tolerance, the capacitor does not discharge between shorted
wires but instead, between both plates. When this happens, an
arc that originates from the negative charge to the positive
charge occurs and BOOM!!! , the capacitor blows up. In any
electronic device, these are typically the first to blow up since they are mainly found in power
supplies. And when voltages exceed the tolerances, it blows. Capacitors are measured in
picoFarads (pF). This measurement tells us how much
charge it can hold based on the capacitor’s construction.
Keep in mind that there are different types of capacitors
that can hold different levels of voltages. Obviously the
larger the capacitor, the higher the voltage it stores. This
also means that bigger capacitors have a wider gap
between plates to prevent higher voltages from causing an
electrical arc (miniature lightning).
With that said, the concept also applies to coaxial cables. As I have mentioned once before,
every RG6 is created differently. The construction of the insulator and the spacing between the
inner and outer wire typically determines the different tolerances and effects of capacitance.
But, for the most part, RG6 has an average of 16.2 pF/ft. So, the longer the cable, the more the
capacitance effect is likely to exist resulting in higher attenuation to the signal. The attenuation
happens because instead of the RF current having to flow flawlessly; it slightly slows down as it’s
also trying to keep a charge on both plates (center wire & shield). The end result is also a loss in
power. And as this happens, realize that the both charges exist in the outer layer of the center
conductor and the inner layer of the outer conductor. Knowing that fact means that when
anyone touches the center and the outer conductors together, expect an immediate jolt of
shock also called RF burn. Why? Well, it’s because they have just completed the circuit, creating
a short for the capacitance effect to discharge through their skin. And unlike regular capacitors,
the discharge will not stop because a continuous supply of RF is being pushed through the wire
DID U KNOW?
Camera flashes
are mostly
comprised of
capacitors to
hold a charge.
The bright flash
of light requires
so much power
that a capacitor
would
discharge a
surge of
electricity to
the bulb. This is
why after a few
flashes have
been taken; it
takes a while
for the camera
to release
another flash
since it has to
recharge its
plates. And yes,
it will also
consume more
of the battery
power.

of 73
from the down converter. Again, to fully experience the effects of capacitance effects, the cable
has to be longer than 100 feet.
Another issue that happens with capacitance effects in RG6 is the similar arc effect found in
capacitors when voltages exceed the tolerances. In coaxial cable, however, the cable doesn’t
blow up. Instead, it causes a major distortion to the signal when viewed onto the TV. This
happens when the signal is amplified above 30dB. The picture would display white sparks onto
the screen like little fireworks. Also, instead of voltage causing the effects, it’s actually the
amount of power being pushed to amplify the signal. So, the higher the signal gain, the higher
the chances of causing this sparkling effect. So how do we alleviate the issue? Create a wider
gap between both wires while maintaining a 75 ohm impedance because the wider the gap, the
lesser chances of capacitance effects. This is why Engineers developed the RG11 for trunk lines
because first, trunk lines need to carry higher amounts of dB to support long distances that are
being pushed through by large amplifiers. Second, RG11 has a wider gap between wires causing
a lesser effect of capacitance buildup which allows the signal to flow less attenuated. If RG11 is
not available, add an attenuator at the output of the source, amplifier or power inserter,
ensuring that no more than 30 dB is being outputted. If the power is not enough to feed the
desired amount of TVs, add another amplifier at the farthest end of the trunk line. Make sure
that the input is at the very least 1dB without noise and amplify again at an output of no more
than 30dB. In situations where only 1 amplifier is available, I highly suggest adding the amplifier
towards the end of the cable trunk line where 1dB of clean signal is still available. After all, the
downconverter itself is already amplifying the signal at +30 dB. Keep in mind though that the
input to the downconverter is never going to be exactly 0dB but rather in the negative levels.
The result would range below 30dB at the output level when the MMDS Dish is fully peaked.
In summary, dB levels ranging around 0 to 30 dB would be ok with RG6. Levels higher than 30dB
and up will likely start to see distortions and the sparkling effects on the TV screen as explained
earlier. Therefore, when dealing with higher levels of dB ranging from 30dB and up, I highly
suggest using an RG11.
• Inductance – The occurrence of electromagnetic flux that exists in a wire as current flows
through it. When coupled with two coiled wires, the circuit creates a transformer of either step
up or step down. With that said, because there are two wires (center & shield) that induce a flux
within the coaxial cable as RF current travels through, inductance exist for every unit/length.
Inductance can be calculated by the amount of electromagnetic flux produced based on the
amount of RF current that travels through the wire (Ampere’s Law). Once that’s found, the
formula for inductance is as follows: L=Flux/I, where “L” is the inductance, “Flux” is the
electromagnetic flux, and “I”, is the amount of RF current.
One of the characteristics of inductance that pertain to us is the known fact that it delays and
reshapes alternating currents. And since RF acts like alternating currents, the RF signal gets
delayed. This is one of the known factors that result in an impeded signal.

of 73
• Impedance – Impedance to the signal is a known effect that occurs due mainly to two known
factors: Inductance and Capacitance. A coaxial cable’s physical impedance rating is calculated
differently from the signal’s impeded levels. The levels will always vary based on the input
frequency, the amount of power being pushed through the cable, the dielectric properties of
the insulator, the purity of the copper, the type of shield being used, the thickness of the center
wire, effects of skin effect, and a few others. All that I’ve mentioned play a big role in the
resulting impedance based on two known factors, capacitance and inductance, occurring only as
the RF signal travels through the wire. This signal loss can be calculated by using Caltech
University’s derived formula expression of Z=Sqrt[L/C]. Where Z=impedance, L=Inductance, and
C=Capacitance.
• Shielding – The whole reason behind the outer conductor is to provide shielding from
introducing external electromagnetic interferences from having to bleed over to the signal. Of
course, there is also a limit as to how much shielding can actually be effective. A good example
would be electromagnetic fields caused by major electrical lines resulting in interference to the
signal. In reality, shielding to the coaxial cable is mainly focused on consumer level for
distribution. As far as I know, it serves two main purposes: First, to shield the consumer and
other magnetic media materials (tapes, hard drives, etc.) from the induced electromagnetic
fields that occur within the center copper wire. The second is to shield the main signal from
negligible interferences caused by consumers such as running the cable next to electrical wires.
AFN uses Belden DuoBond II RG6 coaxial cable. We select the dual shielded cable for a couple of
reasons, of which, I only know of one… more shielding. The new Belden Duobond II RG6 is made
up of two different types of shields. The first is a thin foil wrapped around the insulator. The
second shield is the original design in the form of a woven form. Here’s how it works: the thin
foil acts as a waveguide for the signal, where no RF leaks through the foil, keeping the signal
inside the insulator as it minimizes the amount of dB loss within the cable. Unlike the first
coaxial cables, they don’t have a thin foil around wrapped around the insulator. Because of that,
the signal would leak through the gaps of the woven wire. The woven wire is weaved for a
specific engineering reason. It’s woven because any electromagnetic field that comes in contact
with the shield immediately induces an electric current, causing the electrons to move. As the
electrons move, current flows through the wire,
and then gets cancelled when they both meet at
any of the cross section of the wire. It cancels
because one wire acts as positive and the other
acts as negative. When they meet, it neutralizes
the signal. The diagram to the right (image 18)
provides a visual understanding.
Although the shielding works, this alone is not
effective enough from continuous interferences as
it would induce higher levels of inductance causing
interference to the signal. This is why engineers
require the signal to have a return path back through the power inserter and into the power
TIP:
When dealing
with trunk lines
and major
distribution
lines, a ProMax
Spectrum
Analyzer is
highly
recommended
to monitor
signal strength.

of 73
supply so that it can carry and short any unwanted signal either to ground or be recycled back
into the power supply. If the power inserter is grounded, then the return path shorts to the
ground yet some would still return to the power supply due to the maintained potential
difference. When the signal reaches the power supply, the signal gets converted to DC through a
rectifier because the RF current acts like an Alternating Current.
e.) Things to be aware of before distributing the signal from basic to complex
• Basic Cable TV distribution utilizes RG6 Coaxial Cable. RG stands for “Radio, General”. Looking at
the image above (#2, image 19), Series 6 is the identifier that the cable is an RG6 cable. The
cable has to be 75 ohms (#1, image 19) with a center conductor of apprx 18AWG in size or 1/25
of an inch thick (.040”). If the center conductor is thinner than 18AWG, it’s not RG6. Not all RG6
will have an 18AWG at a thickness of .040”. Some will be precisely at 18AWG and the more
expensive versions will have a thicker wire. Thicker means lesser attenuation and better SNR
(Signal to Noise Ratio).
• A good indicator whether the cable is RG6 or not is through its malleable properties (the
flexibility of the center conductor - copper). As a general rule, if it’s easy to bend the center
conductor, it’s too thin. Long runs with a thin center conductor will cause major attenuation to
the signal strength. An RG59, thinner than RG6, has an attenuation of almost twice the dB loss
of RG6. Therefore, short lengths with this type of cable are ok to run from the splitter to the TV
input (see #5h or #5i, image 1).
• It is not recommended to mix both RG6 and RG59 together for extended runs. Doing this will
distort the signal to a pulsing effect. As for major cable distributions, however, it is
recommended to use an RG11 (2x thicker than RG6) as the trunk line when dealing with large
amplifiers that outputs more than 20dB. The reason why I say more than 20dB is because the
input may be as low as 10dB and the overall output may add up higher than 30dB. Doing this will
exceed the tolerance levels of RG6 causing major distortions to the signal.
• When running long cable runs, depending on the frequency and the type of RG6 coaxial cable
being used, the signal tends to have a signal loss of approximately 2.70dB per 100 feet @
Channel 24 – 222Mhz and even higher 3.80dB loss per 100 feet @ Channel 54 – 408Mhz.
Typically, short cable runs of less than 100 feet may experience only lesser loss due to lesser
capacitance and inductance effects. dB losses are explained in greater detail in the “Detailed
MMDS Signal Flow” (Chapter 2, Section 5d).
TIP:
The thinner the
copper, the
higher the
attenuation to
the signal.
When
purchasing
cable from the
local market,
keep an eye out
for cheap
cables to
prevent future
issues with
signal quality.
Be sure not to
mix RG6 with
thinner cable
when
expanding
cable
distribution.

of 73
• When running complicated distribution lines, always terminate the last pass through, otherwise,
the signal will cause standing waves and reflections that it will cause a rippling effect of
distortions along the path. Terminating the pass thru port allows the signal to have a return path
through the shield. This in turn will protect the signal from external interferences because the
shield will be more effective.
• When running long cable runs (500 ft or more), from pass thru after pass thru of every splitter,
make sure that if ground is being integrated, put the ground only at the power inserter. The
splitters and the amplifier should not even be connected to ground. The reason for this to
ensure that the return path is going back to the source because the power supply is already
providing a potential difference for the return path. Anywhere else and it will cause problems of
distortions. Another alternative, however, is to cut the RG6’s Shield located at the power
inserter’s “TV” tap. This ensures that no potential difference is being pulled back by the power
supply and instead, the ground is. Since ground is common everywhere, it would be much easier
if the ground was the return path for every splitter. The whole point is to eliminate different
potential differences and have only 1 along the path of the signal.
• RG6 can be used as the trunk line for simple and complex cable distribution projects. Trunk lines
are the main lines that originate from the amplifier to the last splitter. These lines are connected
at the splitter’s pass thru ports to avoid major dB drops between splitters. Keep in mind that
each pass thru has a dB drop of approximately 1dB or less. It is important to understand that
when dealing with trunk lines that originate from an amplifier, the first splitter will always have
the highest amplified signal. This means that the splitter should have a rating dB drop that
outputs the signal strength between 3dB to 15dB before it reaches the TV. The reason for no
less than 3dB is to compensate for the cable that extends to the TV. The useable signal strength
at the end of the cable that plugs into the TV should be around 0dB to 10dB, 15dB max.
Sometimes even at negative 9dB, the signal still looks good. See #5d-g, image 1 for a visual
understanding of a trunk line. And one important reminder… if RG6 is being used as the TRUNK
LINE, the dB levels should not exceed 30dB otherwise, capacitance and inductance effects would
make things worse. Not to mention the skin effect where the frequencies would no longer have
the ability to latch on to the surface of the copper wire because of higher amplitudes. This in
turn will cause the signal to attenuate even more. Many other issues not mentioned will
happen. But if the trunk line will be longer than 100 feet with many splitters tapped into the
trunk line, I suggest using RG11. I believe the dB levels can be as high as 45dB on the RG11
without distortion. Not to mention, lesser dB attenuation and lesser amounts of amplifiers
needed to maintain at 30dB.
f.) What to do to prevent signal loss and signal noise
After reading Chapter 2, Section 5e, there should be an understanding of how coaxial cable works. With
that are a few tips to prevent possible degradation with the signal quality:
1. Do not bend the cable at an abrupt 90 degree angle. This causes the signal levels to drop
even more. The more 90 degree bends, the more the signal drops. This happens because the

Got MMDS eBook

Recomendados

Recomendados

Más contenido relacionado

La actualidad más candente

La actualidad más candente (10)

Similar a Got MMDS eBook

Similar a Got MMDS eBook (20)

Got MMDS eBook