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Re: 2.4 GHz Helix & static type noise



G'day again Bill and others. My noise wasnt there when I first did the mods
( all known mods ) to the drake but noticed it after about the second day
and intermittantly ever since, ( more there than not ). Like you my first
antenna was a BBQ Grill type antenna with a dipole feed inside the original
plastic housing ( ex microwave TV dish / converter )and about a metre of
RG213 to the converter. Worked ok on receive except for the noise problem,
then built my current antenna ( 60cm solid dish with helix feed ) and the
noise remained but the signals improved dramatically.
Now the interesting part, I visited WC0Y's web page and it got me thinking
about static build up and the noise problem. I ordered the chip inductors he
mentioned and waited. Being the type of guy I am I couldnt any wait any
longer so installed a chip inductor ( as per WC0Y ) I had left over from
when I made my 1.2GHz ATV transmitter ( different value but was trying and
learning ). Bingo the drake has never worked so well, the static type noise
is now gone completely, the general background noise is alot lower ( to the
ear and it shows on the ao40rcv program ). The best thing is it does not
apper to have changed the sensitvity of the drake. I used to be able to
decode ( good crc ) about 20% - 30% of the blocks of telemetry I received
when the squint angle was reasonable, that figure has nearly doubled to 50%
or more. I can now receive the UO-11 beacon more consistently as it doesnt
disappear intot he noise anymore.  I am very happy with the inductor across
the input mod, it has worked wonder's for me. I dont know if it has changed
the impedance so there is now no self oscillation or it has grounded all
static build up, but it works. I hope this also fix's your problem. If you
need any clarification or more info dont hesitate to email me.

Cheers Geoff VK3JDG



> 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
>
>
>

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