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Re: Problem with ft-847 & fo-20/29



Denny,

I tried to reply private with this reply, but it bounced.  I hope you read it
here:
====
First, make sure you have current keps.  I assume you have az/el control and are

tracking the birds properly.  Right now, FO29 is in digital mode, so scratch
that one.

Second, with that sort of setup, you should be able to connect with 50 watts,
and at times that will be too much.  Both of the FO birds change polarity
several times in a pass.  Sometimes the uplink and downlink will be at a
different polarity sense.

Make sure you are going up on LSB and down on USB.  Are you using tracking
software?  For the 847, I think The Station is the best for doppler control.
You only need a null modem cable to the computer. Make yourself a chart showing
the uplink and downlink frequencies on a piece of paper.  These birds have
inverting transponders, so tuning is counter-intuitive to Oscars 10 and 27.
Make it look like this:

435.800----810----820----830----840----850----860----870----880----890----900

146.000----990----980----970----960----950----940----930----920----910----145.900

Once you begin a QSO, fix the transmit and move the receive.  This is a
convention on the birds.  Tune the higher frequency.

FO-20, your only choice right now has a sensitive receiver, usually.  The trick
to any of the mode J birds is hearing your downlink.  Of course, if you're
hearing other people, you're probably OK.  I get serious desense on my 70 cm
downlink with the 847 (3rd harmonic) UNLESS I kick in my mast mounted preamp.
Another thing that might work if that is the problem is to take a duplexer (I
have a cheap MFJ one) and run the 70 cm side through the duplexer, and let the
2M one just dangle.  I think the 847 suffers some from lack of dynamic range,
because it is only dual convserion, and another tuned circuit removes the 3rd
harmonic.

If you want to make a sched, we can go up passband and I'll help you out. Let me

know!

73, Mike kf4fdj@amsat.org



Denny Jakubisin wrote:

> Slowly learning the intricacies of my new FT-847 but seem to have either
> missed something or have some sort of a problem. So far I have been
> unsuccessful at making a contact via FO-20 or 29.
>
> I do have the correct frequencies set up and have verified I am transmitting
> . The problem is that I have not been able to hear myself on the downlink on
> these two birds. I have ruled out a desense problem as I can still hear
> other stations while I transmit.
>
> Antennas consist of  a pair of homebrew yagis for 435MHz , 22 elements each
> on 14' booms, mounted and fed to give a right hand elliptical pattern. The
> 144 MHz antenna is an M sq. CP-22.  All antennas are mounted on a fiberglass
> crossboom at 65' and fed with 1" 5/8 heliax and are separated by about 7'.
> I also use a 435MHz cavity filter on the downlink.
>
> I have made a few contacts on AO-27 and AO-10 so I know the radio and
> antennas are working.
> I can hear stations on FO-20 & 29, some are very strong but they don't hear
> me ---. I can't hear me either!
>
> What is the recommended power output needed to access these birds? I would
> think 50 watts plus the gain of my antennas should be more than adequate.
>
> Any suggestions from the masses?
>
> BTW, I apologize for any unintended qrm I may have caused over the past few
> days as I was trying to get this to work.
>
> 73
>
> Denny  WB8K  ,, from not so rare EN-91
>
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