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I want to build a Radio Propagation Beacon but I would like to find an integrated circuit that does most or all of the work of the transmitter.

  1. Transmit to 28Mhz (Ham 10-meter band)
  2. Allow me to feed it Morse code audio and for it to transmit that.
  3. As cheap and simple as possible, such as a single-chip solution.

I'll write some code on an Arduino to produce the Morse code. It doesn't have to be high power, 200mw range is perfectly fine.

I do have an radio amateur license.

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  • \$\begingroup\$ Do you have an amateur radio license? What you propose is illegal, otherwise. 73 from G1HSM. \$\endgroup\$ – Leon Heller Feb 10 '11 at 18:50
  • \$\begingroup\$ Yes, actually as I was editing my question I must have accidentally removed that info. I'll re-edit the question to include it =) \$\endgroup\$ – Brad Hein Feb 10 '11 at 19:25
  • \$\begingroup\$ When you say "feed it Morse Code audio" are you talking about Modulated CW (e.g. an audio side-tone) or a binary on/off signal? How many external components are acceptable? Would a 7MHz/14MHz/28MHz oscillator outside the chip be acceptable? Is it on all three bands simultaneously, or is each band selectable, or does it just have to be for one band? How tunable do you need it to be? \$\endgroup\$ – W5VO Feb 11 '11 at 2:32
  • \$\begingroup\$ One band at a time, Tunability not critical, for example swapping crystals is fine. Once I find a good frequency I'll stick to it. I'd like to feed it a sine wave at most, so the CW modulation needs to happen in the circuit. I also would be happy feeding it an "on off" to modulate its own tone etc. \$\endgroup\$ – Brad Hein Feb 11 '11 at 13:45
  • \$\begingroup\$ You'll need different filters on the output for each band, if nothing else, to ensure a clean signal. \$\endgroup\$ – Leon Heller Feb 11 '11 at 13:59
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Honestly, there isn't a lot of work to sending Morse Code. All you need is a frequency-stable oscillator that you can turn on and off.

The closest I can find to a "single chip" solution is one of these oscillators. Add in some low-pass filtering and you're there...

The way I'd expect to make a circuit is to use a discrete crystal oscillator (like something you'd find in the ARRL handbook) and add another transistor to be able to switch the oscillator on and off. A simple Morse Code radio is a good place to start.

A straight key can be replaced with a transistor, and that transistor can be driven by your Arduino.

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Don't know if this helps but here, have a look at this: http://www.sparkfun.com/categories/16

and this more specifically: http://www.sparkfun.com/products/9411 (This unit is legal without a licence in some countries !!!

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I found a ten meter beacon kit which got a writeup in CQ Magazine (PDF) a while back. It's 30 bucks, and looks like a quality product. Should be a fun build!

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