Re: [amsat-bb] Preamp de-sensing, 910

[MM <ka1rrw@xxxxxxxxx>]

Hi Richard,
i had a similar problem with my 910.
i have a fully loaded version with the icom
antenna mounted preamps.

I could work ao-27,  438 up, 144 down Mode B,.
but could not work the the other way Mode J.
too much desense, eventhugh my antennas are 12 feet
apart.

I installed a DCI cavity filer on 2-meters, that did
not help. I did not have a 70cm pass band at that
time.  I assume is just front end overload no 70cm.

I found the satellite mode swith on the 910 usless
and just used the stock vfo's.

After a few months of fustration, I put the 910 back
in the box and rebuilt my lightning struck Yeasu 736R
and put it back in service.  

With the FT-736 I can work all the birds now, but need
to keep my 2-meter power limited to 50 watts to
prevent desense on 70cm.

I have ejoyed reading the Pre amp stories and my try
some of their suggestions.

Antenna, 12 foot solid fiberglass, M2-22cp, M440 44
elem cp versions, lmr-600 coax.  In-shack amp/premaps
at this time.

wf1f


--- Richard Williams <richardw@mho.com> wrote:

> I am just getting back into the satellite side of
> the hobby and recently put
> back up my antennas and pre-amps.  Radio is the Icom
> 910.  Using the KLM
> circular antennas (CP14 and CP30) on a fiber glass
> cross boom. One is mounted
> with the elements vertical/horizontal and the other
> is turned 45 degrees.  TO
> complete the system I am using SSB Electronics pre
> amps (SP-2000/SP-7000)
> mounted on the roof tower.
> 
> The problem is that I am getting a tremendous amount
> of "de-sense" and "hash"
> when either pre amp is turned on and I am
> transmitting on the other antenna.
> Problem is worst when transmitting on 144.  ON SSB
> the S meter goes up to S9
> on the 910 and I can here "hash" as I talk.   When
> using FM and the power all
> the way back to minimun (supposely 5 watts), the S
> meter shows S3 and at full
> power on 144, it shows about 40 over S9..
> 
> The problem is not near as bad when transmitting on
> 435.   No interference at
> 5 watts and only about S3 at full power.
> 
> I was on the satellites several years ago with a
> very similiar setup, except
> was using a FT736  and the larger KLM antennas;  but
> the same pre amps.  I
> don't remember having this kind of a problem then,
> but that was over 5 yrs ago
> and before I turned old and senile
> 
> Is anybody else using a similiar setup and have the
> same problem; or better
> yet, solutions.
> 
> Thanks
> 
> Dick K8ZTT
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