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Re: AO-40, K-band Tx Test Successful!



>From: "Stacey E. Mills" <w4sm@cstone.net>
>On Orbit 396, MA=118 to 138, the K-band (24.048 GHz) transmitter was active 
>and connected to the same inputs as the S2 transmitter.  The passband and 
>beacon were first detected by Petra G4KGC (radio op) and Charlie Suckling 
>G3WDG (dish op) at 1930 utc,  MA=122.  Shortly thereafter the beacon and 
>passband were also detected by Michael Fletcher, OH2AUE.  The Suckling's 
>used a 22 cm offset dish and reported signals 6 dB above the noise 
>floor.  Michael used a 60 cm dish and reported that the beacon was 7 db 
>above the noise floor under less than ideal conditions with overcast skies 
>and occasional rain.  Both used linear feeds and reported good, stable 
>signals except for cyclic deep fades due to the linear polarization of the 
>K-Tx antenna,  the linear polarization of their feeds, and the rotation of 
>AO-40.  A circularly polarized feed should eliminate these spin fades.
>
>The command team is delighted to report this additional functional 
>transmitter on AO-40!!!
>
>---W4SM for the AO-40 Command Team

Thanks for the report, Stacy.

I wonder what equipment was used, specifically NF of the 24G front-ends.
I'm hoping Charlie or Michael are subscribers to the Amsat-bb and can
respond.  It is nice to have a second downlink band, though I suspect only
a few microwave experimenters will utilize it.  

I have a surplus 22 GHz harmonic down converter by P-COM that is
convertible to 24,192 using 10,368 as an LO and 3456 as an IF.  The NF is
~9.5 dB with 19 dB conversion gain per tests by W5LUA [published in the
proceedings of MW Update-2000].  I will consider trying to set this up for
use with my 86 cm offset-feed dish.  Making a circular feedhorn will be
another thing?  The down converter uses wr-42 rectangular w/g and a
pyramidal horn would not be difficult to make.

I have the LO source: my DEM 10,368/144 xvtr, but haven't constructed the
DEM 3456/144 xvtr I bought at CSVHF as yet.  Then the little detail of
generating 144 MHz for the the LO xvtr input while receiving 144 and
transmitting on 435 a the same time!  Guess that is why I have both the
FT-847 and FT-817 ;-)

It looked like a 10 Ghz test was done a few days ago as I saw the IF matrix
connected for that mode...any news?

Ed


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