The Kenwood TM-742E

Kenwood TM-742E
A while back I bought a second hand radio: the Kenwood TM-742E. A great radio with 2m, 70cm and 23cm module!
The man who sold it is a heavy smoker, so I had to clean the rig intensively. But after doing a good job the radio is like brand new. No scratch on it.
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weather station PA1JIMThe new Peet Bros. weather station Ultimeter 2100 runs for a few weeks now. First results where very disappointing. All kind of weird data was logged on Even data for rain (which the weather station has no sensor for). The weather station itself logs fine and readings are okay. So I figured it has to be the serial connection between the Ultimeter 2100 and my Kenwood TM-D710. I tried several things but nothing seems to work. Then PA1EDL informed me about the fact that this is a very common problem between two devices, connected via serial port, but with separate power supplies. It can result in “floating” serial signals which the devices can’t process. Solution for this problem is galvanic separation.
I ordered some 3N44 optocouplers and start building a galvanic separation. It wasn’t very successful, there was no connection at all. I removed the optocoupler and hit a dead end.
I looked around in my shack and suddenly realize I still have a solar powered battery! Maybe it would work when I connect the weather station to the battery. It would still be floating serial signals, but maybe less floating then with 2 AC power supplies.
After a few hours of running on battery the data on starts to make sense. The weather station uses a few hundred milli amps, the battery is around 12Ah so it should be able to run 24/7.
The big data collection starts now. I’m still thinking about buying the extra sensor combo with rain gauge and humidity meter some day.
And I still want to make the optocoupler work because thats the only guarantee for a proper operation regardless of what power supply is used.
Antenna with wind meter

WSPRnetLast 24 hours I let WSPR running on 20 meters with my new FD3-antenna. It seems I hear the whole world including west Canada, Venezuela and Australia. More important: some of these stations hear me too! So I’m very happy with the results until now. Made some cw-QSO’s last night which also went fine.