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RE: dual feed problems -- REPLY --



Good stuff!

I will likely try the dual L/S circular patch feed of W0LMD on my 2.4m
center-fed dish.

I have an associated question:  I will be using a 435 MHz IF converted
Drake 2880 for downconvertor preceded by an DEM preamp.  I wonder if the
preamp will suffer any desense from my approx. 15w L-band uplink?  I can
insert a notch filter ala G3WDG between the preamp and convertor without
impacting NF, but I would guess that is not the case if the filter preceeds
the preamp.

But then I guess desense would be worse than higher NF on this big dish.

Ultimately, I would like a dual-sense circular patch feed for 1269-1296 so
that I may also operate eme with the dish...guessing that may be a second
generation feed.  It would be nice to simply change freq between AO-40 and
eme.   But perhaps running 125w on 1296 is a bit dangerous for the S-band
receiving equipment.  Interesting engineering challenge in any case.

Note: 1296-eme Tx is RHCP and Rx is LHCP (I think).  So having AO-40 Rx in
RHCP provides another configuration problem.  Oh well, swapping feeds may
be the only solution.

73, Ed - AL7EB
I will maintain my existing mode-US set up separately:
436CP42 & 33-inch helix-fed offset dish/MKU-232/unmod Drake.

At 06:34 PM 1/4/2003 -0500, Gunther Meisse wrote:
>JC
>Not a problem. Dual band S + L are common and there is even a tri-bander,
>70cm + S + L patch which I understand does a wonderful job. I personally
>just got an S + L dual patch from Dr. Robert Suding, and have run a dual S +
>L Helix for over a year with not problem. De-sensing is an issue. You must
>have down converters that have a VERY selective filter on the front end or,
>as I do, use a digital filter on the front end of the down converter. I have
>a 50db and a 100db filter and the 50 seems to be plenty.
>Regarding feeds contact Dr. Robert Suding W0LMD at:
>Dr. Robert Suding [roberts@qadas.com]
>His web site is: www.ultimatecharger.com He has all the info you will need
>and he sells the dual and triband Patch feeds.
>I use the filters from a Ham named (I Think, or close) Sudling, in England.
>I had a hard drive crash and have lost a number of my reference contacts.
>Perhaps someone on the -bb will pipe up with his call and web site.... They
>are great filters!!
>Hope some of this info is of help.
>73
>Gunther Meisse
>W8GSM
>AMSAT LM: 594


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