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QMX+ RX and TX problems
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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 |
开云体育Greg
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Your quote:-?? """On some bands there is a continuous low level audio tone of 700 to 800Hz """"
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Would you be talking about 24 through 50 MHz bands? If so, My self and one other?have seen this problem
but no resolution has been put forward. It is very distracting in CW mode. Maybe this tone is peculiar to our rigs only?
As no other reports have been aired on here.
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73
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Ian G4GIR
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I’m hearing the continuous tone (or data type tone/pulsing) to various levels on some bands, plus so many “birdies” across all bands - one particularly ear splitting one ?around 14.143.00, when listening on digi caught me out just now! Another 18.068.96 CW even louder3/4 scale on S meter…
Plus some increases of noise over a few 10s of kHz tuning back and forth. The background tones are just barely audible on 18MHz, none on 21, data noise on 24, same on 28, same on 50. |
开云体育"Plus some increases of noise over a few 10s of kHz tuning back and forth"
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Yes I have highlighted that too.
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Glad it isn't just mine!
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73 Ian G4GIR
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