After 30 years of no activity, I am still learning CW with a straight key which I shall continue to use for the time being.
I recently completed the building of the 80m of the QCX and it is functioning reasonably well except for a few tweaks such as?possibly adding a few turns to T1 transformer.
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After completing the assembly, I connected 50R dummy load, headphones, and straight key (Kent) with mono jack and was ready for alignment.
When I powered up with a LiFe battery (9.5V) I was rewarded with a loud tone in headphones and after some agonising?time I established that the transmitter was in fact being keyed (measured power at RF BNC output with DVM)?even though I was not keying.
Removal of key jack stopped the keying and I was able to proceed with the alignment.
I also have a Palm Radio PPK straight key which has a stereo jack but this also caused the transmitter to turn on without keying and I removed this.
The microswitch keyed the transmitter normally as did shorting the two offboard connections at the front of the PCB.
My first thought was that there was a fault with the key stereo socket but on closer inspection of this and the circuit diagram it seem that the transmitter is keyed when the
either a mono jack or a "standard stereo jack" is inserted in the socket causing a connecting between the ground and either (or both of the contacts in the socket).
In fact partially inserting either jack into the socket did not key the transmitter until I started using the key. This is obviously unsatisfactory and I wonder whether there is a "suitable" jack which should be used (unfortunately, and embarrassingly so, I am not yet?up to speed with Iambic keys etc).
In fact, I have a short?extension lead with tip, 2 intermediate sections plus the bore which did not set off the transmitter when inserted.Apart from using the microswitch, obviously a quick fix would be to connect a suitable mono (?)?socket to the front 2 key pins?on the PCB?but this is?also not an ideal as the wires could easily break.
Have I made a basic mistake or is this to be expected ?
If it is to be expected, then I believe a caution is required in the assembly manual stating that "..mono jacks (and simple stereo jacks??)?cannot be used in the key socket or should be of a specific length otherwise the transmitter will be keyed".
This would be extremely useful for the inexperienced operator to make it "idiot proof".
I have had a lot of pleasure building this kit so please allow this old man a little indulgence as I can't wait to order the 17m version (I have a MTR-3B for 20/30/40m).
Comments are invited.
Best 73s
Robin
G4DNP
