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Re: 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 the 
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 to 
hear all stations and even the strong ones were headache producers.  The 2' 
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 optimistic 
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 all 
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 is 
slightly worse than barely acceptable.

I'm sorry if I've caused people to "lose faith" in AMSAT.  But I'm trying to 
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, but 
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 it 
had issues...

IF we are not able to debate a technical subject, and I'm sorry the numbers 
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 is 
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


>From: Jon Ogden <na9d-2@speakeasy.net>
>To: Doug Faunt N6TQS +1-510-655-8604 <faunt@panix.com>, 
><amsat-bb@AMSAT.Org>
>Subject: Re: [amsat-bb] receiving system design tradeoffs
>Date: Wed, 05 Feb 2003 23:06:08 -0600
>
>on 2/5/03 7:54 PM, Doug Faunt N6TQS +1-510-655-8604 at faunt@panix.com
>wrote:
>
> > I believe that a 3' aluminum dish that was perforated properly would
> > give just as much gain as a solid dish of that size, but would be much
> > lighter in both weight and windload.  Now, if we could easily locate
> > such.
>
>It's a question I've thought of and with living in a warm climate, you are
>OK.  But for those of us who live where we have snow and ice, a perforated
>dish isn't going to offer much help during the winter...
>
>One interesting thing though about BBQ grill type dishes I've heard is that
>with snow and ice on them their windloading is actually GREATER than a 
>solid
>dish.  I had the systems engineering manager for a cellular telephone
>company tell me that once.  Can anyone back up his claim?
>
>73,
>
>Jon
>NA9D
>-------------------------------------
>Jon Ogden
>NA9D (ex: KE9NA)
>
>Citizen of the People's Democratic Republik of Illinois
>
>Life Member: ARRL, NRA
>Member:  AMSAT, DXCC
>
>http://www.qsl.net/na9d   <- Updated on 1/22/03!!!
>
>"A life lived in fear is a life half lived."
>
>
>----
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