DC Receiver Help


From: os2user@vmdoug.utsd.att.com (dquagliana@attmail.com)
Date: Fri Dec 10 1993 - 10:34:13 EST

   Time to tap into some of that QRP expertise out there on the net.....

   I need some help with a simple 20 meter NE602/LM386 direct conversion CW
receiver that I built. The receiver seems to receive only a few
strong signals and many weak signals. I can easily zero beat the strong
ones, but not the weak ones.
   The weaker signals all seem to have the same very high audio frequency
( I guess about 1500-2000Hz ). I assume that the weaker signals
are real twenty meter CW signals. They sound real. I'd just like
to be able to hear them at a much lower audio frequency. (No, I don't
have an audio filter, I haven't built that yet!) When I try to tune
them in, they just disappear. They're just at that one spot on the dial,
and very high pitched.
   Is this a common DC receiver problem? What might cause the receiver
to do this? What should I "attack" to try and solve this?
A bigger, better, higher antenna? Different headphones? A speaker
instead of headphones? Some bad component in the receiver? Change the tuning
method (from varactor diode to air capacitor)? What thing is most
likely to be the problem? I don't really know where to start.

Douglas Quagliana KA2UPW

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