[Elecraft] increasing receive gain

[Rod N0RC]

Ron,

----- Original Message -----
From: "Ron D'Eau Claire" <rondec@easystreet.com>
To: "'Elecraft'" <elecraft@mailman.qth.net>
Sent: Monday, September 23, 2002 9:30 AM
Subject: RE: [Elecraft] increasing receive gain


> It's hard to beat the "disconnect the antenna and see if the
background
> noise drops" test. No laboratory equipment can do better to tell you
if
> you have enough "preamp" gain and a low enough receiver noise figure.
If

Done that. ;-) Preamp on/Preamp off background noise drops in both cases
with antenna disconnected.


>
> I've never found a case in which the preamp was desirable on 40, from
> the standpoint of adequate sensitivity. I can understand wanting it on
> if the K2 receiver, overall, is anemic, but if the noise level drops
> when you disconnect the antenna with the preamp off, turning the
preamp
> ON will compromise the overall dynamic range of the receiver.
>

It's all a balancing act at my QTH. Attic antenna, in the middle of a
small city, LARGE apartment complex to one side, commercial buildings
less that 1/2 mile away.... Having the Preamp on helps me hear those
weaker signals, but at the price of more noise...like I said in my case
it is a balancing at. (That's why I like the Icom 746pro, the DSP
functions give me some advantage at times)

Now before anybody says move to a quieter location....I'll be happy to
if you pay the freight! ;-) real estate commissions, bonus for inflated
housing prices, perhaps provide a chauffeured limo to compensate for
time lost commuting... ;-)


> The "RF Gain" on the K2 does not control the level of signals at the
RF
> input. It is simply a manual control of IF amplifier gain. So  turning
> it down to compensate for having the Preamp On still exposes the
Preamp
> and receiver "front end" to overload from strong signals that you
cannot
> hear  because they are outside of the IF filter passband.

Understood, fortunately the K2 has wonderful close-in signal
characteristics that I am exploiting. The only time it is a big problem,
is during BIG contests with high power ops, such as field day, NOV
sweeps., NA sprints...etc. During those time you will find me hiking,
biking or on the WARC bands. Not much of a contester, but do enjoy a few
short sprints now and then, that are at QRM levels.

73, Rod N0RC