[amsat-bb] Re: S band diagnostics (was Re: AMSAT-BB Digest, Vol 1, Issue 112)

Michael Tondee mat_62 at netcommander.com
Mon Sep 18 13:54:19 PDT 2006

Hi Bruce,
My "rf source" is actually the mode V/S adapter described by Tony, AA2TX 
in the Sept./Oct. 2005 AMSAT  journal. It's actual purpose is to convert 
the 123Mhz IF of the downconverter to 6 meters thereby freeing up my two 
meter antenna jack for mode V/S. On a suggestion from Tony, I hooked the 
downconverter up to my HT and then powered up the V/S adapter seperately 
and listened for  a 2415 Ghz. harmonic from it. I found it  at about 
137.025 Mhz. on the HT as Tony said I would.
 I have no idea as to the signal strength of this harmonic. There was no 
antenna attached to the V/S adapter. Of course you said there was no 
antenna to speak of on your signal source either so it's puzzling. One 
thing is certain, I've got a bum right arm right now and I'm tired of 
raising and lowering the dang mast! Everything sits atop a 30 ft. mast. 
I t gives my antennas a better "view" above the tree line and also gets 
them above a dogwood tree that my XYL refuses to let me cut down. They 
won't rotate otherwise.
Michael, W4HIJ
Bruce Robertson wrote:
> Quoting Michael Tondee <mat_62 at netcommander.com>:
>> I have tried all week to be able to hear the S-band downlink with a BBQ
>> grill dish and AIDC 3731 converter. I checked aim of my antennas and can
>> receive a signal when a signal source is hanging off the dish but no joy
>> as far as hearing the bird itself. I don't have an antenna for L band 
>> yet so I can't transmit.
>>  I'm very discouraged and about ready to yank the dish/downconverter off
>> the mast and give up.
>> 73,
>> Michael, W4HIJ
> I would yank them off the mast, but not give up. Others have suggested that
> the beam width of the setup you describe is quite narrow and might be
> requiring better pointing than you have right now. Here's a procedure to
> see what's what.
> I have one of the self-modified CalAmp $6 units It works much better
> hand-held than on the mast, and I have just a 8 dBi gain patch antenna on
> it. On future S-band opportunities, I would try pointing the d/c by hand
> with its feed alone, no dish, and see if that works. If you can hear
> something, then I'd say there's a pointing issue. (For the sake of
> comparison, I can hear part of a 20-30 deg. max el. pass through a window.
> Not good copy, but enough to prove things are tickety-boo while the snow is
> flying.)
> If you can't hear anything at all by this means, I wonder if your d/c is
> sensitive enough. It worries me that your rf source has to be 'hanging off
> the dish'.  I have an rf source like the one described in the latest Amsat
> Journal, but with no antenna to speak of. I can still hear it as a weak
> signal indoors through a window about 15' from the antenna when the rotor
> is vaguely pointing my way. When I first was working on the d/c and hadn't
> peaked the filter, the source had to be no more than an inch or two from
> the d/c. At this point, the d/c wouldn't receive Echo.
> Steve, WI2W, gave me some excellent advice, which I think should be shared
> with others. Noting that our CalAmp $6 d/c's were a bit marginal, he
> recommended that instead of building a more narrow beamwidth antenna, I
> should get a mast-installed preamp for 2.4 gig. The plan is to keep my
> broad-beam antenna (which is better for the LEO situation) and improve my
> gain and noise floor with the preamp. SSB USA has them for $125ish. His is
> the sensible plan if one's goal is a easy-to-use LEO s band setup. I'm
> interested in building antennas and such, so I'm working on a 15 turn helix
> and adding elevation control to my rotor. But by the time P3E and ESEO fly,
> I think the preamp will be necessary.
> Maybe the next time Echo is transmitting on S band, we'll both have working
> systems!
> 73, Bruce

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