I completed assembling my QMX+ kit last week.? What a neat kit and apart from having to use strong glasses and a magnifier it was successfully put together.? Hans should be very proud of his quality products.?
So far testing has shown that I have some shortcomings with both the TX and RX which I hope someone may help with.?
After assembly, checking & rechecking soldering and parts placement I switched on and loaded the firmware, everthing appeared ok.? Voltages and current flow all good.? Noise in the headphones and power into the dummy load. After initial testing at 8V the voltage was increased to 11.5V with no ill effects.
I documented my findings below:
All filter sweeps (RF filter, LP filter) appear acceptable and similar to those published. (Using PUtty).
Receiver
The MDS ( minimum discernible signal) is 5uV which is not great and this is consistent across all bands 160m - 6m.? It is quite deaf.? Tested with my HP8656A Signal Generator.
There is a huge difference in audio output at the same volume setting between the CW and Digital modes taking about 3 complete turns of the audio gain to get around the same level of noise in the headphones.
On some bands there is a continuous low level audio tone of 700 to 800Hz which can mask the beat signal from the Signal Generator.
On switch on the unit defaults to 1.8382 MHz, which is fine but on turning the tuning knob in either direction the frequency jumps to 3.2000 MHz.? On pressing the band change switch it then performs normally and goes to the 80m frequency and so on.?
I have resoldered all the toroid leads and measured continuity to their pads.
Transmitter
Power output was measured with an oscilloscope across the dummy load and with PUtty.? They didn't differ much.
Band????????? Power????? Total current (@ 11.5V)
160m????????? 5.8W??????? .93A
80m??????????? 4.6W??????? .63A
60m??????????? 3.3W??????? .47A
40m???????????? .75W?????? .25A
30m???????????? .36W?????? .23A
20m???????????? .2W???????? .22A
17m??????????? <.1W??????? .19A
15m???????????? .1W????????? .16A
12m???????????? <.1W?????? .15A
11m??????????? <.1W??????? .14A
10m??????????????? 0?????????? .12A
I was unsure if I had wound T507 correctly so rewound it but it made no difference to the measurements.
The two main items that puzzle me are - 1. the decreasing output from the tx with increasing frequency and 2. the constant level of deafness of the receiver.? It appears it must be something common to all bands.
But if anyone can give me some tips on all the above items about how to proceed, I would appreciate it.
Regards
Greg, ZL4GW
