ATV transmitter for 23cm

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Front view of my fully assembled 23cm ATV transmitter.

Although I was already able to receive the local ATV repeater PI6ATV, it has been a wish for about 8 years to be able to uplink too. So I once bought a couple of modules from PE1ACB that would allow me to do so. However, due to lack of time and other priorities the modules lost my attention and ended up on some shelf. Since I started my new job I have more spare time, which I spend (among other things) on this fantastic hamradio hobby. So then I remembered those modules. I designed a front panel and bought a case, switches and connectors. — more →

Fox transmitter for 80m

Introduction

Fox hunting is one of the many aspects of ham radio. It’s some kind of game, where the “fox” is a little transmitter, and competitors have to locate it using a directional antenna and receiver. I already built a special receiver for fox hunting, and my wife (PD2W) built one too. So having 2 receivers it would be a nice idea to add a fox to these, to get a complete mini-fox-hunt-kit. One of the members at the club pointed me at the so-called “OXO transmitter”. I looked it up at the internet, and immediately liked its simplicity. So I started to build it.

Schematic

fox_80m_transmitter_schematic
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Your first transmitter

my1sttxWith just a few components, you can make your own morse code transmitter. The output is only a few miliwatts, but this is enough to receive on any radio in your home.

In fact, it is only a simple Clapp Oscillator with the output directly driven into a few meters of wire. The transmitting frequency depends on the used crystal. This may be any crystal between 1 and 15 MHz, higher frequencies may perhaps work also, therefore you may lower the 2 capacitors a little bit.

The transmitting frequency is not only the one shown on the crystal, but also “harmonics”: If you have for example a crystal of 3.56 MHz, then it transmits (of course) on 3.56 MHz, but also a bit at 7.12 MHz (2 * 3.56), 10.68 MHz (3 * 3.56), 14.24 MHz (4 * 3.56), etc.

The operating voltage is not critical, a 9 volt battery will do the job.

Components:

  • C1 – 100 picofarad
  • C2 – 100 picofarad
  • R1 – 10 kilo-ohm
  • R2 – 1 kilo-ohm
  • S1 – Morse key or switch
  • T1 – BC547 or any other universal NPN transistor
  • X1 – Any crystal you like between 1-15 MHz