On a sunny day (5 Sep 2006 16:24:13 -0700) it happened "Telstar Electronics"
wrote in
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Jan Panteltje wrote:
On a sunny day (4 Sep 2006 16:51:16 -0700) it happened "Telstar Electronics"
wrote in
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Slow Code wrote:
(avj 1) wrote in
:

what's a good recieve pre amp? the Dosy or the Maco.


It's amazing the things people buy just to hear CB'ers better.

Sc

The real problem is that the pre-amps don't accomplish anything. They
are just a gimmick since they are unable to improve the signal-to-noise
ratio. All they do is boost everything... noise and all... LOL

www.telstar-electronics.com

This is actually not correct.
A good pre-amp would have bit better s/n ratio then the set it is used
with.
I have experiemented a lot in the long ago past with different configurations
for pre-amps, like transistor, MOSFET, FET, cascode etc...
Best I could come up with was 2 junction FETS in cascode.....
Maybe these days there are better solutions.
But I received the world on a little wire with SSB.
So, your next project: A good low S/N ratio pre-amp?
Probably not.
Maybe you were using your power amp as pre-amp?

Don't think a pre-amp like that is worth anything without some type of
additional circuitry to discern noise from signal... and that's not
easy to do. All you're doing there is compensating for a poor receiver.

Well, the purpose of a pre-amp _______ I S _______ fixing a poor receiver.
If your receiver already has a top noise figure, and the pre-amp the same,
it will not help , see what I wrote above:
self quote
A good pre-amp would have bit better s/n ratio then the set it is used with.
end self quote

If you are sucked up in the ignition noise of your hair dryer or whatever,
then it will not help either.
Ad Dr Death already pointed out, it DOES help if the band is sort of clean.

I had all stages tunable, (tried both with varicaps and real rotary caps),
you need a high Q (I used heavy silver plated coils), very good antenna
matching, so you get maximum input signal (I used an input transformer),
and lowest noise figure FETS or whatever you can get.
The cost is practically nothing (maybe less then 50$ parts).
There are some more tricks like feedback you can use to get better Q.
You only need 3.5kHz bandwidth at 27MHz for SSB, and, as B = f0 / Q, a
Q of 27000000 / 3500 = 7714 should be the limit.
Not easy to get there !, but with feedback.......
Tuning it becomes a problem.... lots of knobs....
Did not use _that_ much feedback, basically keep the loading on the input
LC minimal.

A next project for you?
That was 1970 ties. What one could do with modern tech.