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Re: receiving system design tradeoffs



Sorry I've been really busy selling a house and at work, and not checked my 
email in days.

I have a HF dipole at about 30' right now!  It's better than I've had with 
my deed restricted house before.  But I'm putting up a tower eventually.

Understand that the problem with using a marginal system on a satellite is 
this:

If MB -10db is suggested max power level, than a good assumption is that -20 
dB to -10 db (10 dB range) is a reasonable power range.

If you can hear the stations at -10dB, but weakly, yes you can work them.   
The stations at -20 dB you will not hear at all.  Not only
will you miss them-- you risk stomping right on top of them in QSO.  And 
they are really not wrong to work at -20 dB under the beacon, and I'd 
personally not consider that QRP level.

It's like having the HF antenna at 20 feet, but running legal limit through 
it all the time.  That's the HF analogy.

It gets worse though, because on a satellite you are expected to be able to 
hear everything in the passband since it is possible to do this.  On HF it 
is not possible due to propagation.  So on HF, it's normal to get stomped on 
(but in many cases still not right), but it's not normal
on satellites.

So this is why an "alligator" is defined as: "not hearing well before 
talking" and not "running too much power".

If you run the BBQ you better be aware that you could kill ongoing QSO's by 
people that are running at legimate power levels.
If you don't tha'ts fine, but how could you know if you can't hear them?  I 
guess by people complaining on an "acronmonious" amsat-bb thread... :O(

This has been my logic all along, and is my final comment on this subject.  
I've simply tried to get this point across to you and the others in the 
group.

Good Luck,

Fred W0FMS






>From: Jon Ogden <na9d-2@speakeasy.net>
>To: "Frederick M. Spinner" <fspinner@hotmail.com>, <amsat-bb@AMSAT.Org>
>Subject: Re: [amsat-bb] receiving system design tradeoffs
>Date: Thu, 06 Feb 2003 16:36:07 -0600
>
>on 2/6/03 3:28 PM, Frederick M. Spinner at fspinner@hotmail.com wrote:
>
> > 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 guess Fred that "adequate" means different things to different people.  I
>don't consider a dipole at 20 feet adequate for HF.  A lot of guys do.
>
>Again, if one can hear themselves at a level 10 dB below the beacon and be
>comfortable with it and how well they hear others then who the heck cares
>what antenna you use.  I've never argued they are optimal. And I have 
>stated
>numerous times that my setup is a start and not an end.  I plan on 
>improving
>it, but it's a start.
>
>You compare guys putting up 20 foot yagis and not big dishes.  Consider 
>that
>the large 22 element KLM 2m yagi and the large 40 element KLM 432 yagi have
>a combined wind loading of about 3 feet.  A 3 foot dish has over 7 feet!
>Yes, like you said, you can avoid some of that by pointing it straight up.
>But then there's the time that you forget to park it and leave for the
>weekend and along comes a windstorm.
>
>Again, I encourage ANYONE to get on and try with whatever they have.  Not
>everyone on HF has 4 stacked 20 meter monobanders on a rotating tower.  Not
>everyone has to have a 4 or 5 foot dish to have FUN on AO-40.  This is a
>hobby, the purpose of which is to have FUN no matter how you define it.
>
>Jon
>
>-------------------------------------
>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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