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Re: MMDS downconverters to 1691 mhz WxSAT?



    A couple of months ago a Brazilian Ham asked me if the Cal.Amp. MMDS
downconverter shown on my web page could work at 1691MHz. I had never tested
an MMDS converter at such low freqs and as I had one of those open over my
bench I decided to make some tests.
    The unit was a Cal.Amp. model 130645 - QLP downconverter. It is a long
metallic box with a plastic-encapsulated antenna on one extreme and holes to
mount to a mesh parabolic reflector on the other side.
    Without changing the 8.898MHz crystal I bypassed the input filters after
the first RF amplifier and also the output filters right after the mixer
with long-lead 220pF ceramic caps. The untit showed more than 10dB gain
across 1691-2110MHz, frequency was inverted in this range (increasing signal
freq decreased IF). IF slew from 587 to 168MHz on this test!. Another useful
range started at 2315MHz with over 20dB gain, IF increased when signal freq
increased on this range. My signal generator tops at 2418MHz so upper
extreme of this useful range could not be measured. Conv.gain was around
29dB at 2418MHz.
   Take into account that these measurements do not include antenna
gain -which was removed-, and would probably introduce a decrease in gain at
such low freqs.
    I have some pics if you are interested...

    73 de Nando, CX6DD


----- Original Message -----
From: "ATSB" <tiung@po.jaring.my>
To: <RogerKola@aol.com>; <amsat-bb@AMSAT.Org>
Sent: Monday, February 04, 2002 1:52 PM
Subject: Re: [amsat-bb] MMDS downconverters to 1691 mhz WxSAT?


>
> Hi All,
>
> This topic has  also been on my mind and shall be grateful for any ideas
to
> convert/tune  MMDS to 1691 MHz.
>
> Sangat, 9M2SS
>
>
> At 15:28 03/02/02 EST, RogerKola@aol.com wrote:
> >Hi All...
> >
> >I know this is stretching being off topic...heck, it probably is off
> topic....
> >
> >But, has anyone experimented putting one of the S-Band TV downconverters
on
> >the GOES 1691 MHz WX satellite band?  I know some of the d/c's were for
MMDS
> >CH1 and CH2 which were originally around 2150 MHz....
> >
> >>From commercial FM conversion days I know everything has to be
> "lengthened",
> >moving down in frequency is much harder then moving up...just thought I'd
> >ask..
> >
> >As the topic wanders...please answer off list to keep down the
bandwidth...
> >
> >Thanks es 73
> >
> >Roger
> >WA1KAT
> >Rogerkola@aol.com
> >WA1KAT@amsat.org
> >----
> >Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> >To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> >
> >
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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