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Re: receiving system design tradeoffs

Fred, well said and agreed. Thanks for applying some of the hard logic that
I may not have.

73, Drew

----- Original Message -----
From: "Frederick M. Spinner" <fspinner@hotmail.com>
To: <amsat-bb@AMSAT.Org>
Sent: Thursday, February 06, 2003 4:28 PM
Subject: Re: [amsat-bb] receiving system design tradeoffs

> First of all, I should apologize if people thought I was being rude with
> respect to what is required to hear a good signal on AO-40.
> I have *several* BBQ dishes, they should have worked just fine, down to
> xpnd noise floor.  They don't.   This is because of
> factual physical problems due to the unexpected condition and orbit of the
> satellite.  Ouch, it hurts that I spent money on them too...
> My observations showed that I could hear on my BBQ.  But not well enough
> hear all stations and even the strong ones were headache producers.  The
> prime focus with homebrew patch made all stations appear, strong ones OK.
> The 3' offset and/or the 4' prime focus dishes made just about everything
> armchair copy.
> Looking at the numbers in the spreadsheet, which I find a little
> in practice, show the same things almost exactly to the dB as
> what was observed, by me and others.
> I cannot change physics.  I personally do not care what you operate, but
> I can say is that the facts show exactly what I said originally
> about the BBQ's:  They are marginal.  Jon saying he observed the beacon at
> +20, therefore +10dB is the best SSB he can do if the other
> station is following the rules at good squint, just shows that the system
> slightly worse than barely acceptable.
> I'm sorry if I've caused people to "lose faith" in AMSAT.  But I'm trying
> preach physics here.  Reality.  I'm truly sorry that we've all
> bought so many of the BBQ's for AO-40 and they are not adequate.  But
> physics say they are not really adequate.
> I'm sorry that many of you can put up multiple 20 foot long boom yagis,
> 3 foot dishes are "not allowable" to the wife/HOA's or whatever.  I don't
> get it, but I do feel for you.
> IF AO-40 would have not had issues, even a helix could have worked.  But
> had issues...
> IF we are not able to debate a technical subject, and I'm sorry the
> prove me right, on this list-- what should we talk about?
> Having said that I replied to this e-mail to tell Jon, that if your dish
> pointed upwards and gets snow on it the two solutions are to
> brush it off, or to point it at 0 degrees elevation to knock it off.  Yeah
> if you have several feet of snow on the upward pointed dish
> it might be a problem pointing at 0 deg, but for an inch or two?
> Alternatively, if its snowing alot and it's not windy point the dish down
> and the snow won't accumulate on it.
> Fred, W0FMS

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