DOUGLAS ZWIEBEL wrote:
>
> Hi...
>
> The following request for information is not specific to the K3 (or
> even to Elecraft). Please craft your response to be generic.
>
> Despite being an active ham/contester for over 40 continuous years
> (but not being an ee), I just do not understand how a "preamp" works.
> It is not a "smart" device, so how does it "know" to amplify the
> signal and not the noise? I first used a preamp way back when
> (1960's) when I was a teenager...it was an Ameco job. It was more
> "fun" than useful, because I could give out "big" S meter reports.
>
> Later, when listening in the noise became more important to my style
> of operation, I never could notice a difference between putting the
> preamp "on" and just turning up the volume (many rigs with built-in
> preamps too). Sometimes, turning up the AF gain worked better.
>
> So...HOW does a preamp help to "bring a signal out of the noise"
> without the use of some fancy computer algorithms backed by lots of
> computing power? Further, does a preamp really "improve" sensitivity?
> I have yet to find a signal that I could not copy (or hear) with any
> preamp "on" vs increasing the AF gain. PS...I am talking about HF. I
> know that lots of guys use a preamp on 160m with their beverages, so
> the effect must be real...right? HOW does a "dumb" device do it?
>
> de Doug KR2Q
>
>
There is residual noise within the receiver. By amplifying the signal, a
preamp can improve the signal to noise ratio, if the noise being received by
the antenna is close to the amount of noise that is generated in the
receiver. Therefore preamps are most often needed on VHF and up where the
atmospheric noise level is low and greater gain is needed to raise it to the
point where it swamps internally generated noise.
If, as I do, you live in an electrically noisy location, then a preamp may
seem to make no difference at all. I do not find the K3 preamp has any
benefit at all, since the S meter is always reading a couple of S points
(often a lot more!) even on a dead band. Perhaps when the higher frequency
bands become workable again the preamp might show some benefits. It is
probably also useful on 6m.
-----
Julian, G4ILO. K2 #392 K3 #222.
http://www.g4ilo.com/ G4ILO's Shack http://www.ham-directory.com/ Ham
Directory http://www.g4ilo.com/kcomm.html KComm for Elecraft K2 and K3
--
View this message in context:
http://n2.nabble.com/K3-sensitivity-%2B-preamp%3A-looking-for-wisdom-tp1658815p1658925.html
Sent from the Elecraft mailing list archive at Nabble.com.
_______________________________________________
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
