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How to Make Your Own Underground TV Transmitter
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How to Build Your Own Underground Television Transmitter
Using Commercially Available Parts.
Yes, for some time now it has been possible to construct a
clandestine television station, which you can operate from your
Telecommando Lair, or modify for Mobile Media Guerrilla
campaigns.
We have named this device the Snow Box, due to its cool nature,
and the snow seen on blank television channels waiting to be
commandeered.
To put together a TV station you will need this stuff:
A VCR or Camcorder with video or RF outputs
A Ham Radio 6-meter Band Linear amplifier
(This boosts the RF signal from the VCR for broadcasting)
(The Linear Amp should have a bandwidth of 6 MHz for best results)
A cable television RF distribution amplifier may also be used.
Coaxial cable with UHF connectors
(Connects the Linear Amp to the Antenna)
A cable-TV patch cable with an F-connector and a UHF connector
(To connect the RF signal to the Linear Amp)
(F-connectors are the small ones used with cable TV)
(UHF connectors are the large ones used for Ham Radio)
If your VCR does not have RF outputs:
An external RF modulator (converts video to channel 3,6,12 etc.)
a cable with RCA connectors (a standard stereo cord is ok) A 6-
meter Ham radio antenna.
If you do not have a pre-made 6-meter antenna:
About 20 feet of strong wire 3 ceramic antenna insulators
another UHF connector
Likely places to get the linear amplifier, connectors and cables is a
Ham Radio swapmeet, a Ham club newsletter's classified ads, a
Buy-Sell-Trade paper like The Recycler, or at a store specializing
in Ham gear. RF modulators are available at specialty video stores,
or major VCR dealers.
Setting Up the Transmitter:
Using a VCR with RF out:
[VCR/RF]F----------------------------U[Linear Amp]U------------
U[Antenna]
weak RF Power RF
Using an External RF Modulator:
[VCR]R-------R[RF Modulator]---------U[Linear Amp]U------------
U[Antenna]
video weak RF Power RF
Diagram Symbols:
U UHF-connectors (Ham radio)
F F-connectors (cable TV)
R RCA connectors (stereos)
--- coax, cables, wires
[] devices (name of device in brackets)
ceramic insulator (the kind with a hole at each end)
Building The Dipole Antenna:
wire wire
---------------------++----------------------
| |
Short coax | |
[U] UHF connector
The antenna is set up much like a clothesline with the wires
tethered straight out horizontally. The outer insulators are used to
isolate the antenna from the tether lines, which should be rope or
nylon cords for good results. The inner insulator isolates a gap
between the two long wires of the antenna.
The length of the wires used for the antenna is critical. Look up the
length in feet for the channel you want to use in the table below &
make each of the two long wires that length. As a rule of thumb, a
wire half-wave antenna's length in feet is equal to 468 divided by
the frequency in MHz.
VHF Television Channel Data
----------------------------------------
TV MHz ---carrier--- antenna
channel range video sound lengths
------- ----- ----- ----- -------
2 54-60 55.25 59.75 8.47ft
3 60-66 61.25 65.75 7.64ft
4 66-72 67.25 71.75 6.95ft
5 76-82 77.25 81.75 6.05ft
6 82-88 83.25 87.75 5.62ft
7 174-180 175.25 179.75 2.67ft
8 180-186 181.25 185.75 2.58ft
9 186-192 187.25 191.75 2.49ft
10 192-198 193.25 197.75 2.42ft
11 198-204 199.25 193.75 2.34ft
12 204-210 205.25 209.75 2.28ft
13 210-216 211.25 215.75 2.21ft
(All frequencies in MHz)
(Lengths are for half-wave antennas)
For Further information: Look in the ARRL Handbook published
by the American Radio Relay League for detailed plans & theory
for antennas, transmitters & linear amplifiers. The info in that book
can be used for setting up an underground AM or FM radio station.
Uses for a TV Clandestine Station:
Public Education: Make a videotape of each step in the process of
constructing your transmitter. Show this tape in your broadcasts,
"For informational purposes only", of course.
Short-burst zipping: From a fixed or mobile base of operation show
short snippets of graffiti-like computer graphics, quick subliminal
messages, images & suggestions, or brief phreaker manifestos.
Commercials are an opportune time to break into TV broadcasts.
Live call-in shows: Using a Cheese Box, or other device for
receiving untraceable phone calls and a video camera do a live call-
in show. Encourage people to call in using Red, Blue, and other
phreaking boxes.
One way to do call ins to your station is to give a phone # of a
frend and use AT&T call forwarding to forward to your phone, then
use a radio shack phone recorder to send the signal to the input of a
tape deck and then run the output of the tape deck to the input of
your mixer.
Another way is to give the number of a local phone booth and use
CB or other means of transmission to get it back to your booth.
Both of these methods can give away your city of origin if someone
looks up the are code.
To avoid this you can find a business that has an answering
machine on an 800 number and play with your phone, trying
different numbers until you crack their playback code, (this is
usually two numbers) then have your audience call and leave your
messages or a number for you to call them back. Then you call the
machine, enter the code number, and get your messages.
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