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Re: Mode-B vs Mode-J VERSUS Mode-S



Bruce,

The reason why S-band is difficult to hear unless you have decent 
antennas is that we are NOT operating on the primary S band.  We are 
operating on a helical antenna at 60,000 kM!!!!!  S1 had the dish and 
the HELAPS PA.  If the S1 transmitter still worked, you wouldn't have 
the link budget issues we now have an a BBQ dish would be more than 
adequate to hear the bird.

Still, there are many of us who have had a damn good time with BBQ 
dishes on the bird.  I'm moving up to a larger dish, but that doesn't 
change the fact that you really don't need that large of a dish even 
now to hear AO-40 just fine.

S-band is a great band for downlinking.  Personally though for the 
future,  I think it may get worse in terms of noise due to the 
proliferation of WI-FI and other 2.4 GHz wireless stuff.  Being in the 
wireless industry, I don't want to see these devices go away for the 
sake of a few dozen or even a few hundred hams.  The real solution is 
likely to be to move even higher.  A C band uplink and X band downlink 
can be done and a single 18" DSS dish used for both.  With 500 MHz 
exclusive allocation on X band, I don't think we'd have a lot of 
interference problems.

73,

Jon
NA9D

On Thursday, Jun 19, 2003, at 11:23 America/Chicago, Bruce Bostwick 
wrote:

> If it were my call .. I'd want to move the downlink to something else. 
>  I can fully understand that it's desirable in some circles to have a 
> certain level of technical expertise be the price of admission, 
> because it's well worth having something that takes a little work to 
> achieve, but the current setup on AO-40 isn't the best way to do that, 
> because it doesn't filter *out* the ops that don't quite have the 
> equipment up to speed -- like I said, most VHF/UHF all modes can hit 
> the uplink with a modest beam antenna -- but rather encourages them to 
> QRM and/or overload the U band AGC.
-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)

Citizen of the People's Democratic Republik of Illinois

Life Member: ARRL, NRA
Member:  AMSAT, DXCC

Ham Radio Webpage: http://www.qsl.net/na9d   <- Updated on 1/12/03!!!
Digital Photography Page: 
http://homepage.mac.com/jogden/Photography.html

"It takes as much stress to be a success as it does to be a failure."
                                                                         
                 - Emilio James Trujillo

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