Posted on Feb 6, 2014

What do you do with those old 2-Meter FM rigs that don`t have any CTCSS tone capability Well, you add it of course! While big knob` tone encoders have been available from several sources, their downside has been having to know the tone of the repeater you would like to use and the need to turn the knob every time you change repeaters. Wouldn`t it be nice to have an add-on tone encoder, and decoder, that

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sniffs  the PL from the repeater just like those fancy new rigs Plus as an added convenience, and safety feature, remember what the tone was for each repeater! Imagine, not having to take your eyes off the road to rotate a knob just to change the PL! Now you can have all this and, as the man on the late night infomercials says, more with the Uncoder! The details of a Universal Encoder/Decoder, or Uncoder for short, really started to gel when I decided to resurrect a couple of 2 meter rigs that had been laying around the shop, unused, for quite a while. One of the rigs was a Kenwood TS-700A all-mode base station transceiver and the other was a TR-7400A mobile that I wanted to be able to use with some of the local PL required repeaters. I wanted a device that was intuitive to use; just tune the transceiver to the repeater and let the Uncoder worry about the tone setup. The best solution would be a tone encoder / decoder that could detect the frequency that I was operating on and set the tone frequencies appropriately. Once I had given the Uncoder the CTCSS tone information for a particular frequency, it should be able to remember the setting and automatically set up the tone info as I tuned my radio to various repeaters. To accomplish this task, the Uncoder needed to incorporate a frequency counter, along with the tone encoding / decoding and the appropriate microcontroller circuitry. The selection of a microcontroller chip...

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