---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
are a Ham Radio swapmeet, a Ham club news-letter'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[RFModulator]----U[LinearAmp]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)
[I] ceramic insulator (the kind with a hole at each
end)
Building The Dipole Antenna:
wire wire
[I]---------------------+[I]+----------------------[I]
| |
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 8.47 ft
3 60-66 61.25 65.75 7.64 ft
5 76-82 77.25 81.75 6.05 ft
6 82-88 83.25 87.75 5.62 ft
7 174-180 175.25 179.75 2.67 ft
8 180-186 181.25 185.75 2.58 ft
9 186-192 187.25 191.75 2.49 ft
10 192-198 193.25 197.75 2.42 ft
11 198-204 199.25 193.75 2.34 ft
12 204-210 205.25 209.75 2.28 ft
13 210-216 211.25 215.75 2.21 ft
(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.
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 manifestos. Commercials
are an opportune time to break into TV broadcasts.
Cable TV Piracy: With modifications it may be possible to feed the
power RF signal directly into a cable TV system, overriding
cablecasts or commandeering unused channels.
Mobile Operation: Using storage batteries and a 110-volt inverter
the transmitter may be modified for mobile use to avoid detection
by the FCC during long broadcasts. Battery operated mobile linear
amps and portable camcorders are also available.
article from Helter Skelter
