Re: {Collins} KWM-2



richard pumphrey wrote:
I have a query regarding 40 meter night time reception. I appear to be getting an image at night. Careful turning of the exciter turning gets rid of most of it, but it still is in the background. Is this normal? If not, how can I fix it? Otherwise, good receiver and transmitter. Richard wn9ddv


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Hello Richard,

My 75S3 receiver also has a low level heterodyne on 40 meters. I have tracked it to a short wave station in Florida. The frequency is 9505 khz, and this is passing through the receiver and mixing with the 40 meter crystal output to the first mixer. From here it passes through the rest of the receiver and is heard as a faint note.

Go to http://en.wikipedia.org/wiki/WYFR and scroll down to frequencies. Look for 9505 khz and check the time schedule.

Tuning the pto has no effect on the heterodyne, in fact you can pull the 6AU6 and the heterodyne is still present. This station has a 100,000 watt output. It goes off the air at 11:45 pm CTD and presto the heterodyne is gone.

Detuning the preselect reduces the level but it also reduces the desired signal. With the narrow cw filter, 200 cps, it is very noticeable so I try to stay in the wider passband. Try listening just as they are going off 9505 khz and see if your problem also goes away.

I don't know how S Line users near them can operate on 40 meters if the signal is so strong in Indiana it passes through various tuned circuits.

Smith Bradford
W9HAK







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