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Re: AMSAT-BB-digest V2000 #566



>
>MMDS antennas are very tempting to try for Mode-S and are linear.
>
>Hey, has anyone else ever tried a MMDS converter other than a Drake
>2880?  It'd be good to find a cheap replacement.
>
>Fred W0FMS

Ok I'll bite the bullet.. I used a bog standard "Conifer" MMDS antenna and
downconverter for AO-13.  And I made several CW and SSB contacts, and could
hear the beacon OK.  I used a Yaesu FRG-9600 as the IF Rx (not the best for
the job!) with a standard power injector (couple of dB loss there), the IF
cable was RG-6 quad.  The LO used for Australian MMDS was 1951 MHz to match
the hyper-band TV channels (ie cable ready or s-band tv), so the FRG-9600
was tuned to 449 MHz and considering the uplink was 435 MHz I didn't get any
desense problems.  This antenna was the BBQ grill type passed off as a 24dBi
and came in two parts with a RG-213 tail ending in a N-type crimp.  The feed
was a dipole formed from 2 strips of copper soldered onto the end of the
RG-213.  The downconverter was external and was fed with an "f" connector.
The LO was not the best for narrow band Rxing and it moved around a bit and
had a lot of phase noise on it but being used to doppler and fades and the
like it was OK to deal with.  I didn't have much success with a "Pacific
Monalithic" antenna and downconverter and AO-13 was gone before I could get
testing with other antennas.  I got a 24 ele disc antenna with hi-gain
downconverter from "Pac-mon" to test yet.
So If I get the time I'll try the arsonal of MMDS antennas/downconverters I
got laying around (about 15 or 20 with 5 different LOs and antenna feeds!)
on AO-40 and report back later.  If any VKs want info on the "Galaxy" or
"TARBS" antennas they see around town please e-mail me direct.

See-ya
Matt - VK2DAG-
vk2dag@bigpond.com


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