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Re: Downconverter noise



With my UEK-3000 d/c (nf 0.6 dB, gain 30 dB), I see a noise increase from S0
to S 2.5 without the preamp on. With the preamp on, it goes from about S1 or
less to about S5, doing nothing more than turning the d/c on.

This makes perfectly good sense...30 dB of gain with no antenna, amplifies a
lot of noise...I'm not sure why this should be a mystery...it's a perfectly
expected effect. Keep in mind the d/c is just a big IF amplifier...it would
be amazing if you could add that much IF gain and NOT see it show up on the
S-meter.

...hasan, N0AN

----- Original Message ----- 
From: "Jon Ogden" <na9d@speakeasy.net>
To: "Howard Long" <howard@howardlong.com>
Cc: "Phil" <phil@spiderweb.com.au>; <amsat-bb@AMSAT.Org>
Sent: Tuesday, May 27, 2003 6:27 AM
Subject: Re: [amsat-bb] Downconverter noise


>
> On Tuesday, May 27, 2003, at 01:53 America/Chicago, Howard Long wrote:
>
> > I might have misunderstood the question, but of the 50 or so AIDC
> > 3731's
> > I've distributed here in the UK, all of them have produced a very
> > significant increase in noise level and S meter reading when hooked up
> > to
> > the half a dozen different radios I've used them on (and no antenna,
> > dish or
> > feed connected). S5 is about ball park but due to the vagueries of S
> > meters
> > it might be S3 or it might be S7.
>
> Well, then I guess I stand corrected.  But it just doesn't make sense.
> If the d/c is at S5 with no antenna and no signal, then you are already
> at least 10 to 15 dB above the noise floor of your radio.  Does the
> noise actually go DOWN once the antenna is mounted on the dish and put
> in place?
>
> I can tell you that form my experience you do hear an increase in noise
> with the d/c on, but it certainly isn't enough to move the s-meter more
> than a unit or less.  It's certainly not 5 units.
>
> I'm confused..
>
> 73,
>
> Jon
> NA9D
>
> ----
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