104 lines
3.9 KiB
Plaintext
104 lines
3.9 KiB
Plaintext
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To put together a TV station you will need this stuff:
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A VCR or Camcorder with video or RF outputs
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A Ham Radio 6-meter Band Linear amplifier
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(This boosts the RF signal from the VCR for broadcasting)
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(The Linear Amp should have a bandwidth of 6 MHz for best results)
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A cable television RF distribution amplifier may also be used.
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Coaxial cable with UHF connectors
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(Connects the Linear Amp to the Antenna)
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A cable-TV patch cable with an F-connector and a UHF connector
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(To connect the RF signal to the Linear Amp)
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(F-connectors are the small ones used with cable TV)
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(UHF connectors are the large ones used for Ham Radio)
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If your VCR does not have RF outputs:
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An external RF modulator (converts video to channel 3,6,12 etc.)
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a cable with RCA connectors (a standard stereo cord is ok)
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A 6-meter Ham radio antenna.
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If you do not have a pre-made 6-meter antenna:
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About 20 feet of strong wire
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3 ceramic antenna insulators
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another UHF connector
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Likely places to get the linear amplifier, connectors and cables is a
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Ham Radio swapmeet, a Ham club newsletter's classified ads, a Buy-Sell-Trade
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paper like The Recycler, or at a store specializing in Ham gear.
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RF modulators are available at specialty video stores, or major VCR dealers.
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Setting Up the Transmitter:
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Using a VCR with RF out:
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[VCR/RF]F----------------------------U[Linear Amp]U------------U[Antenna]
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weak RF Power RF
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Using an External RF Modulator:
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[VCR]R-------R[RF Modulator]---------U[Linear Amp]U------------U[Antenna]
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video weak RF Power RF
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Diagram Symbols:
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U UHF-connectors (Ham radio)
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F F-connectors (cable TV)
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R RCA connectors (stereos)
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--- coax, cables, wires
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[] devices (name of device in brackets)
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<I> ceramic insulator (the kind with a hole at each end)
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Building The Dipole Antenna:
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wire wire
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<I>---------------------+<I>+----------------------<I>
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| |
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Short coax | |
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[U] UHF connector
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The antenna is set up much like a clothesline with the wires tethered
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straight out horizontally. The outer insulators are used to isolate the
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antenna from the tether lines, which should be rope or nylon cords
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for good results. The inner insulator isolates a gap between the two
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long wires of the antenna.
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The length of the wires used for the antenna is critical.
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Look up the length in feet for the channel you want to use in the
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table below & make each of the two long wires that length.
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As a rule of thumb, a wire half-wave antenna's length in feet is equal to
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468 divided by the frequency in MHz.
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****************************************
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VHF Television Channel Data
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----------------------------------------
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TV MHz ---carrier--- antenna
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channel range video sound lengths
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------- ----- ----- ----- -------
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2 54-60 55.25 59.75 8.47ft
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3 60-66 61.25 65.75 7.64ft
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4 66-72 67.25 71.75 6.95ft
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5 76-82 77.25 81.75 6.05ft
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6 82-88 83.25 87.75 5.62ft
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7 174-180 175.25 179.75 2.67ft
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8 180-186 181.25 185.75 2.58ft
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9 186-192 187.25 191.75 2.49ft
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10 192-198 193.25 197.75 2.42ft
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11 198-204 199.25 193.75 2.34ft
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12 204-210 205.25 209.75 2.28ft
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13 210-216 211.25 215.75 2.21ft
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(All frequencies in MHz)
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(Lengths are for half-wave antennas)
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****************************************
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For Further information: Look in the ARRL Handbook published by the American
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Radio Relay League for detailed plans & theory for antennas, transmitters &
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linear amplifiers. The info in that book can be used for setting up an
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underground AM or FM radio station.
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