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23/13cm dual helix feeds - response




Rafal,
I have just completed building a dual 23/13cm Helix feed for a 60cm dish. I
will use same as a portable rig. So far I have tested the 13cm downlink
portion with very good results. I am comparing it with my 1.2m dish. As
expected I see about 3db drop in levels.
To date I have been unable to test the 23cm uplink portion since the two
feeds colocated result in massive desensing of the SSB-3000 downconverter. I
have a 50db and 100db filter coming which will take care of that problem. I
will then report the Tx results. The 60cm dish on 23cm will only give me
15db gain. It is a small fish for that frequency, but we will give it a try.
I have not yet placed pictures on the web site (maybe this weekend) but the
short story is that both helix feeds are made of 1/4" 3m copper tape wound
on plastic tubes, 13cm inside the 23cm tube. The reflector is full size for
the 13cm and spokes from there out to 10 inches for the 23cm. I did not want
to over block the dish with a big reflector.
I have attached a picture ( not very good one) for your inspection. (This is
on the personal e-mail only)
A week or so and I'll have the full story on the results of this work.
73
Gunther Meisse
W8GSM
AMSAT LM: 594


-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On Behalf Of
Rafal Grygorowicz
Sent: Tuesday, October 30, 2001 7:02 PM
To: amsat-bb@AMSAT.Org
Subject: [amsat-bb] 23cm/13cm dual band feed dish


Hello!


            I`m looking for a 23cm/13cm dualband feed dish
documentation. Have you some experience in dualband feed for 23cm/13cm
dish? I was spent some time in the Internet but I didnt find anything
about 23cm/13cm dualband feed. There are some dual feed project for
5,6Ghz/10Ghz but not for lowest microwave band.



Best Regards

Rafal SP9VFD



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