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Re: 2.4 GHz Helix & static type noise



It sort of sounds like the front end may be going into oscillation at a
parasitic frequency. I suspect that when the feed is touched with moisture,
it lowers the feed impedance and quenches the oscillation. Are both units
modified?

Just a guess....
Howie
AB2S
----- Original Message -----
From: "Bill Hurlock" <bill@hurlock.net>
To: "Geoff Taurins" <geofft@bigpond.net.au>
Cc: <amsat-bb@AMSAT.Org>
Sent: Tuesday, February 27, 2001 10:38 AM
Subject: Re: [amsat-bb] 2.4 GHz Helix & static type noise


> I have the exact same problem with mine and I use a Bar-B-Q grill dish on
mine
> which uses a dipole feed. My problem started a couple month's ago. It is
winter
> here and it is cold and very dry at times. problem is intermitant. Dipole
is in
> a plastic cover with a 1.5 foot pigtail going right into the Drake. Drake
has
> all the lastest modes in it.
>
> bill WA2TQI
>
> Geoff Taurins wrote:
>
> > G'day people. I am using a 2 1/4 turn helix feed on my 60cm dish feeding
a
> > modified drake 2880 for 2.4 GHz rx. You can see pictures of at
> > http://www.geocities.com/vk3jdg When I dont have the noise problem the
> > system works very well. I am having problems with noise ( sounds like
static
> > or at times a loose connection ) on rx. Sometimes the setup works fine,
> > sometimes usually within 10 seconds of switching the converter on I get
> > lots of noise on the rx and the S meter goes from S3 ( base line when
the
> > converter is on and everything is working as it should ) up to over S9.
The
> > amount of noise is dependant on the time of day ( night is generally
less
> > than day time ). Now this doesnt happen all the time and if I spray the
feed
> > with moisture ( only very small amount needed ) the problem disappears
until
> > the water dries. We are having hot weather here and it is very dry. The
feed
> > point on the connectors is sealed ( resealed / resolder numerous times -
> > with the same result ). I have rechecked / resoldered all the mods
inside
> > the drake with no change. Is the problem static build up on the
ungrounded
> > feed or something else ? Any ideas appreciated. I dont have any test
> > equipment for these frequencies so all tests are done with sats as the
> > signal source.
> >
> > Cheers Geoff VK3JDG
> >
> > ----
> > Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>
> --
> Bill
> WA2TQI
>
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

----
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