[AMRadio] Receive Preamp question


sbjohnston at aol.com sbjohnston at aol.com
Sun Nov 4 11:07:41 EST 2007


>Does anyone have a good recommendation for a preamp to
>help my radio receive better.

It depends to some degree on what receiver you're using, and the bands 
of interest.  On the lower shortwave frequencies, almost all receivers 
already have enough gain (if they are working OK), but as you go higher 
in frequency, say 14 MHz on up, many receivers can benefit from another 
stage of RF amplification.

For example, I built an extra preamp into my Heath HR-1680 receiver and 
rigged it to be in-line when the bandswitch was on the 21 and 28 MHz 
band positions.  Let's see if I can recall what preamp board that 
was... hmmmm... OK I had to get my notes on that project... it was a 
Hamtronics LNY preamp.

See  http://www.hamtronics.com/pdf/Manuals/LNY-WB.pdf

One way you can know if you have enough gain is to note the background 
noise your receiver picks up with the antenna connected, versus not 
connected.  If the background hiss (not lightning crashes or the 
various buzzes from local noise sources, but just the steady even 
background hiss) is louder with the antenna connected, then you already 
have enough RF gain.  If it doesn't jump up with the antenna connected, 
then you need more gain, either thru repair of the receiver or an extra 
stage.

Steve WD8DAS

sbjohnston at aol.com
http://www.wd8das.net/
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