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Re: Help with problems

Where is the preamp mounted? It should be as close to the feed as possible.
The noise figure of the DEMI preamp is appx. 0.6 dB so 0.6 dB of coax and/or
connector loss halves the SNR.



----- Original Message -----
From: "Gerald Payton" <n5gpc@earthlink.net>
To: "AMSAT-BB" <amsat-bb@AMSAT.Org>
Sent: Wednesday, 05 September 2001 03:36 UTC
Subject: [amsat-bb] Help with problems

> Last time I was admonished for saying it was a "stupid question."
> I should rephrase it and say, "a question from a stupid person."  I REALLY
> feel inapt for having to ask these questions.
> Yes, I know that everyone on the BB has had to start sometime, but these
> problems seem like they "should" be relatively easy to overcome.
> (Setup= IC-820 H, Andrew 26T-2400 Grill antenna, DEM 13ULNA Pre Amp,
> Millicon MC-251 d/c and LMR-400 coax.)
> Problem One:   The signal to noise ratio seems that it should be better.
> >From my previous post, I'm told that my setup is nominal.
> I receive the MB very well, but the QSO's are very weak and down near the
> noise level.
> Adjusting my SHIFT helps some, but the majority are still not good enough
> for contact.  I believe that if I cannot hear the audio, I should not try
> contact!  Therefore, I'm still unable to attempt a contact.
> I am just wondering if a newer radio with DSP and better filtering and
> adjustment might be the cure.  Of course, I'm sooooo
> frustrated now, I'm about ready to throw in the towel and sell everything!
> Problem Two:   I have been able to adjust my uplink signal (70cm) and hear
> it returned.  However, it too was very weak on return.  And, then with
> additional tests, I no longer hear my downlink signal.  I don't know if I
> have an "tracking" problem with the IC-820 or not.  It appears to be
> operating OK when looking at the radio (LSB up, USB down and reversed
> transponder).
> Analyzing all this in my mind, I can't help but believe that some sort of
> selectivity (DSP, Shift or something) would help reduce the noise to a
> which I could hear well.  I realize that preamps and such amplify BOTH
> and noise and separating the two is difficult.
> I hate to be so close and have spend money that I can't really afford and
> then give up.  I'm not an experienced SSB operator and am not familiar
> operating SSB and adjusting for same.
> Sorry for the "crying towel", but I am really frustrated............
> 73 to ALL,
> Jerry  N5GPC
> ----
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