Re: [amsat-bb] Re: Re: was TS-2000X, now AO-40 lids

["Frederick M. Spinner" <fspinner@xxxxxxxxxxx>]

Egads.. what a political debate.  Let me state this a little more 
practically...

All I can say is I've tried both, and yes I use crappy "surplus" 
downconverters.  I also drive a
1988 vehicle because at present I can't afford or need better.  And it works 
75% as well as a new $35,000 one.

I'll bet you my <$100 cheap downconverter/surplus dish combo side by side 
with your $300 UEK and high priced Hyperlink BBQ
I'd do better.  Would it be bigger?  Yes.  In my case I'm on 36 acres, I can 
care less.

I don't think anyone is saying your system is a problem.  But there are many 
people out there trying to use a Drake with a BBQ.  It works only well 
enough to hear the beacon.

But I have to strongly disagree with the following comment:

>I can't tell you the number of people I work using surplus D/C's that can't
>hear worth a darn when connected to moderate receiving antennas. Connect
>them to a 3 meter TVRO dish and they "seem to work really well", but it is
>an illusion. They still don't work worth a darn, but the massive antenna in
>front of them lets the "system" work well.

ITS NOT AN ILLUSION.  AS A SYSTEM, THEY HEAR VERY WELL.  This is an 
acceptable set of trade offs.  I am getting a
bit tired of you UEK-3000 people saying that spending $300+ dollars on a D/C 
is the only way to get good signals on AO-40.
(And I've heard plenty of that, and you are certainly implying that here, 
and its BS).

As you yourself said, put the numbers into the spreadsheet.  If the final 
S/N ratio is good it really doesn't matter how you get there.
Yeah, your beamwidth is smaller with the larger dish.  Unless it's too 
small, who cares?  Gain, noise pickup, efficiency all are better.
These are tradeoffs.

My point is that if you have a BBQ and can't hear well (and it is obvious if 
this is the case) try getting a *FREE* Primestar or other VSAT, MUZAK or 
similar dish-- they are all over the place.   Or a larger prime focus.  If 
it's a offset, use a 5.25 turn helix, if it is a prime focus, a
patch.  G3RUH patches are expensive.  W0LMD designs are almost as good and 
are free with a weekend of effort.  The difference between my BBQ and even 
my 2 foot prime focus w/patch is about an S-unit.  An S-unit is a lot on 
AO-40.  For me that was the difference between
struggling to hear the bird and having enjoyable copy.

Could I make that up by getting myself a sub 1dB converter?  Yes.  It is 
worth $300 to me to do this?  No.

The logic of spending $300 for a D/C and then going minimal on the antenna 
is like spending $300 on a stereo system and then hooking 3" speakers to it! 
  It could work, but is this an optimal setup?

If you don't have an AO-40 setup already, skip the $%#$ BBQ's altogether.  
Or don't listen to the (radio engineers in the) group and waste $75+ on 
something that is marginal.

The BBQ's would have worked GREAT if $hit didn't happen with AO-40.  It did. 
  What is you system going to be like if the transponder loses another 3-6 
dB over the years?  This is a common occurance with commercial sats....

>
>I really can't emphasize strongly enough sitting down with Gene's
>spreadsheet and "playing" with all the variables, especially the "front 
>end"
>ones like antenna gain, circularity, coax losses, D/C NF and Gain, etc.
>

>(Much snipped and attribution removed to protect the guilty.)
>

I agree.  Try more dish gain versus NF improvement.  Things move the same 
way...

I'm probably one of the leaders in the "try and use what you have" camp in 
ham radio.   But even in the AO-13 days, hearing the transponder noise floor 
was a goal of a good system.

It frankly scares me that so many people think its actually good to have a 
system with no overhead margin.  And for that matter
how do you know you are not hearing the noise floor by only 0.5 dB if you've 
never heard it?  A spreadsheet and models are very good
and necessary engineering tools, but are only approximations of reality.  It 
ain't gospel until its actually measured.

Fred W0FMS


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