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1.5 Volt Tracking Transmitter: (Electronic Schematic / circuit added 4/02) |
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10W HF Linear Amplifier: (added 8/03) |
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1-transistor FM Transmitter: A truly minimalist circuit. Performance is
relatively poor and stability is a problem. Q1 modulates the signal and acts as an
oscillator. L1 and C5 determine the frequency. Decrease C5 for a higher frequency and
vice-versa. You won't get a long range transmission with this one. The author claims
50-500 feet. A lot depends on the antenna. It must be made of stiff wire or else the
frequency will change as you move the antenna. Experiment with different lengths to
get the maximum range. 50cm or less should work reliably most of the time. A longer
antenna might give even better range but if you exaggerate, the circuit will begin to
oscillate and performance will drop dramatically. A regular telescope whip should
work, too. (added 10/05) |
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2 Transistor FM Transmitters: (added 8/03) |
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2 Valve 40m CW Transmitter: (added 2/05) |
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222 MHz Transverter: (added 8/03) |
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2N2222 40 Meter CW/DSB Transceiver: (Electronic Schematic / circuit added
4/02) |
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2-transistor FM Transmitter: While there are a plethora of similar
2-transistor schematics available, this one is above average. A major improvement over
the little 1-transistor circuit that we've discussed previously, this transmitter
consist of two stages. The first transistor is used to amplify audio, which means that
the microphone is now much more sensitive to sound. The second one acts as an
oscillator. All in all, this is an interesting project for beginners and more
experienced hobbyists alike. Use any stiff wire or telescope whip antenna, just make
sure that it's not too long. Range should be about 100m or even more in the open.
Stability is still a problem, though. (added 10/05) |
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30 Meter QRP Transmitter for Morse Code: This transmitters' intended purpose
is for morse-code only in the 30 meter band (10Mhz). It is a low-power QRP type
and needs to be connected to your existing tranceiver. The harmonic rejections
on the prototype were measured at 40dB on 20Mhz and 50dB on 30Mhz... added 4/02) |
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3W HF QRP Linear Amplifier: (added 8/03) |
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4 Transistor Transmitter: (added 8/03) |
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49MHz Walkie Talkie: Lots of people are requesting walkie-talkie and RF
remote control schematics, so here is some. Building these circuits needs special
equipment and expertise in RF circuits. If you are going to experiment with these
circuits, please note that I did not build them, and I am not able to help you with
any details. If you have no experience in RF, I suggest that you choose the easy way
and buy a ready-made RF module. Otherwise you can realize you have an exact copy of a
circuit in your hand, still it doesn't work the way it should. (added 8/03) |
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4W FM Transmitter : Don't be fooled by the relative simplicity of this
transmitter. With 4W of power, it's not a toy! Since it operates in the FM band
(88-108MHz), a license is required for broadcasting. With a good and properly mounted
antenna this baby has a range of up to 50km. In mountainous terrain or in built-up
areas, this figure is smaller, of course. The circuit is fairly small. The last two
transistors dissipate quite a lot of heat. Make sure to protect them with sufficiently
large heatsinks or else you'll have a nasty meltdown. The coils are not all that
critical, but should still be winded carefully to ensure efficient operation. Use
enamel-coated wire at least 1mm thick. As with all RF circuits, work slowly and pay
attention to details. …. (added 11/05) |
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5 Watt 80 Meter QRP CW Transceiver: (Circuit / schematic design added 6/06) |
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500mW HF Linear Amplifier: (added 8/03) |
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80 Meter DSB Transmitter: (added 2/05) |
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807 and 1625 Valves: data on vacuum tubes 807 and 1625 used in ham radio
transmitters. Describes various pin voltages and different operation modes. . (Circuit
added 9/04) |
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A Basic RF Transmitter for PIR Sensors: (circuit / schematic added 6/05) |
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AM/FM/SW Active Antenna: This circuit shows an active antenna that can be
used for AM, FM, and shortwave SW. On the shortwave band this active antenna is
comparable to a20 to30 foot wire antenna. This circuit uses receivers that use untuned
wire antennas, such as inexpensive units and car radios. L1 can be selected for the
application (Electronic Schematic / circuit added 4/02) |
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Assorted RF circuits: (circuit / schematic added 6/05) |
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ATV Repeater Controllers: (Electronic Schematic / circuit added 4/02) |
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Automatic Repeater: This circuit will be of interest to the radio amateur
and anyone possessing two radios, (one of which must be able to transmit i.e. a
transceiver). It is a self powered (audio derived) repeater circuit for receiving a
signal and re-transmitting it via the other radio. (added 10/05) |
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Basic RF Oscillator #1: (Electronic Schematic / circuit added 4/02) |
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Basic RF Transmitter for PIR Sensors: (added 8/03) |
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Building a Simple LF Exciter: (added 8/03) |
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Building an RF Remote Control System: (added 04/05) |
