DIY SRP portable radio programming leads

[Rob_Brookes]

Another broken link reported. It's easier for me to put the files back where they were intended to be rather than try and get broken links fixed so here's the circuit back again. Any problems in future, please contact me directly.
As most of you will undoubtedly know, the programming lead for the SRP9000 family of radios is a very simple affair with just a couple of resistors providing level shifting for the voltages needed. The circuit diagram is shown here.
[Click the diagram to display all of it if you have scroll bars showing]

You can buy these leads from Simoco of course along with the inevitably out of date software that's better obtained FOC from the TMC website at http://www.tmcradio.com

Note that the TMC website is unfortunately no longer carrying all the information it used to. Some of this but not in your wildest dreams, all, has been transfered to the Simoco website. Nothing of any great use is to be found there now however.

The circuit diagram shows the lead wired to two individual jack plugs but if you do it this way you'll discover, as many have, that the spacing between the two sockets on the radio itself, isn't 'standard' and the two plugs are too close together to sit comfortably side by side. The tendency is for them to force each other away and distort the contacts inside the radio. This can result in very hit and miss performance when you're using them to program a radio.

Possibly a better way of doing it is to buy the bare-ended lead from Simoco at http://www.teamsimoco.co.uk. The item code is PA-LDST. This is a straight lead terminating in the correct connector for the SRP9120/9130 range and it will also fit the earlier SRP8000 series and can be used to program these models.

Prog Lead.png

The last time I wired up a batch of these, the Simoco lead cost around £6 and the colours exactly match those of the circuit diagram although I didn't draw it up so it's always best to buzz them through just to check.

Unfortunately some of you by now will have noticed that the leads from murdered speaker microphones can't be used for this purpose as a couple of critical wires aren't fitted.

The SRP programming leads are not only used to program SRP radios but also as a means of extracting GPS from them when operating in short-range temporary locations for example. If anyone has seem Dave or I give demos of MRMap, we usually use a portable SRP as the 'base' radio as it's far easier to set up than humping a vehicle set and power supply about the place.

If I had to make any suggested changes to the circuit as shown above, I'd insert 1000pF RF bypass capacitors between pins 2 and 5 and between pins 3 and 5. These leads are prone to letting RF into the computer if the radio transmits whilst it's connected, which it will do if being used for GPS tracking. Slipping an appropriate diameter ferrite bead onto the cable sheathing is probably good practice also. Secure it to the D-Connector end of the cable.