DSDPlus and an IC-208h 2m/70cm radio :)

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Jul 17, 2011
Well, I know that SDR is the flavor of the month, but I thought I would share this with you as well.

Many newer V/UHF ham radios and some receivers incorporate a 9600bd 'Packet radio' port. Typically, this is located on the rear of the radio somewhere. To pass 9600bd Packet, the audio output on this port needs to be relatively un-processed and filtered and it turns out that this is just what we need for DSDPlus to decode D/V formats too.

The 'Packet' port on the Icom IC-208h is a 6 pin, mini-DIN socket that just happens to be the same as the old style PC keyboard and mice plugs. I happened to have an old, faulty keyboard lying around and so chopped the lead off at the keyboard end. This gave me a nice 4ft long lead that plugged straight into the rear 'Packet' port on the IC-208h.

After working out which of the 6 conductors was the receive audio (I cheated and used a cro), I connected this to the line input on the DSDPlus PC and tuned to a nearby P25 trunking control channel. Immediately, I had perfect decode on the control channel data stream.

Then I went off in search of P25 voice traffic - again, perfect decode.

A couple of hints:

* The IC-208h must be left in wide/standard FM mode. If you switch to 'Narrow' FM, you will get a lot of errors on P25 voice traffic as the received audio on the Packet port becomes too narrow to pass all required audio frequencies.

* The IC-208h can be set to do a VFO scan across a preset portion of trunking spectrum, thereby stopping on any active voice channels. This doesn't work so well if there are Control channels within the search band as the radio does not have a 'Lockout/Avoid' function in this search mode and will lock onto any control channel it finds. An alternative (better?) option is just to program all your local voice channels into memories and do a memory scan instead.

* Installing a surplus laptop into your car and connecting it to your V/UHF radio, could give it a new lease on life, picking up all those Digital Voice modes that you were previously missing out on :)

Have fun.. :)
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