Tuesday, February 07, 2012


From Textfiles.com...

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)
<I>  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.

No comments: