Atlantis wrote:
W dniu 2010-08-23 00:52, Dave M pisze:

$15.00 US (minimum) for shipping to countries other than Canada. If
you're interested in trying them, I have a most of a tube of them in
my parts bin. I used a few of them for 40 & 80 meter receivers a few
years ago, and still have about 20 of them left. If you wish, I'd
be glad to mail you a few to experiment with.

Thank you for your offer. I will remember it, but first I would like
to try find it in local electronic stores.
And I still prefer a little bit more complicated and challenging
constructions, with each stage on separate transistor or IC. I found
only few polish publications from early 70's amateur radio press. All
of them consist germanium transistors, manually made coils and few
transformers in AF stage.

There recevers for 40 and 80 meter band, which You mentioned... What
was that? Superheterodyne? Homodyne?


They were superhet receivers, since the LM3820 is basically a superhet
design. The chip has poor sensitivity, so I had to add an RF preamp stage
to get the performance up. I thought about trying to run it as a TRF
receiver, but ran into trouble biasing the oscillator stage so that the
mixer would work. It was more trouble than it was worth.
The final build was decent, but not great. Sensitivity was around 3uv, even
with a good FET preamp stage. I used them for about 18 months before
abandoning them for a better receiver (an old Heathkit unit), which I still
have and use occasionally.
You should be able to make a pretty good BCB receiver with these chips,
since the in-band noise will swamp the receiver if you try to make it more
sensitive. You can find good preamp designs for BCB on the web if you wish
to experiment. You might be able to get a bit more sensitivity by making
the RF tanks more selective (higher Q inductors and capacitors, high
impedance FET preamp stage, etc).

--
David
dgminala at mediacombb dot net