I am not as experienced as many of you out there but feel that some recent experiences and issues?may be?useful?for some others completing a?kit for the first time
Firstly, I managed to build the QCX 80?and got it working first time thanks to the excellent instructions in the manual.
Key Issues
As I am learning CW (now 10wpm)?I am still using a straight key (Kent and Palm Radio PPK).
Both these keys switched on the tx when the key jack was inserted in the stereo socket and I resolved these issues as follows:
1) I changed the mono jack to a stereo jack for the Kent connecting to?tip and common/ground
2) I disconnected the green wire inside the PKK which connects to middle ring of stereo?jack?(Hannes advises that this modification is required for KX3 and similar rigs)
Please note that in this configuration the keys no longer work properly?in my LNR?MTR-3B where the middle ring needs to be connected to ground for straight keying
As an alternative, a mono socket can be connected to the PCB which I have also done.
"Stray RF"
As this was my first rig construction, I decided to place all components "onboard" and use the set on the bench.
The set is connected to a Resistive Bridge, L Tuner and an random length end fed Wire (no feeder) - I know this is not ideal but it works for the MTR
The resistive bridge has 3 positions: dummy load, tune and transmit.
In dummy load position, the tx keys properly.
However,?in tune and tx positions (RF applied to the antenna) the QCX appears to become unstable?after initial keying?with loud "hissing" (feedback ?)?and RF indicated on a FS meter.
Switching back to dummy load stops the effect
After re-positioning the tuner, bridge and key away from the QCX the problem appears to be resolved and keying can?takes place normally. It may be my imagination but this phenomenon appears worse with Kent key (with all that brass).
Consequently, I have concluded that there is stray RF from antenna feeding back into the QCX etc which is causing to run out of control.
Again, I have not experienced this with the MTR.
Obviously one possible solution would be to put the QCX in an metal/metal lined enclosure but I wonder whether this phenomenon is to be expected or whether it could be indicative of something within the QCX.I would be interested in receiving your comments.
Robin
G4DNP
