[TenTec] RF in SSB on my Omni VI

[George Skoubis]

Hi everyone,

  I hope one of you guys can help me fix an RF feedback problem I've been
having with my Omni VI Opt 3 upgrade rig.

  I had been using a vertical antenna but I found myself frustrated with my
inability to hear many stations so I decided to buy a 3-element beam and a
tower.

  In early July I bought a 50 foot crankup tower and ordered a Fluidmotion 3
element beam.

  I did the negotiating with my wife for my tower placement and the approved
spot puts the beam 35 feet over my 2nd floor ham shack.  I realize this is
not optimal, but this is what I
have...

  I pounded 4 ground rods in a 8' semicircle around my tower and ran #6 bare
copper up to my shack coming in through the deck and wall in grey plastic
electrical conduit.  I ran a ground wire separately from each piece of shack
equipment to the ground wire at the entrance (425 amp, 238 tuner, Omni VI,
425 power supply, 12V power supply) to avoid ground loops.

  After firing up the equipment I immediately started recieving poor audio
reports whenever I run the Titan amp.

  I wrapped the microphone cord around two ferrite toroids.  I put ferrite
and audio isolation transformers on the audio in and out rca patch cords.  I
disconnected the audio in and out rca cords.  I put an isolation transformer
in the microphone signal path (Heil headset with the DX element).  I twisted
the microphone cord so it spirals like ladder line or twisted pair.  I
wrapped the power cord around some ferrite.  I moved the amp, amp power
supply, and 12V power supply farther away from the radio.

  The station interconnects are 1/2 Andrew Superflex with LMR-400 coming
down the tower and into the shack. I put an extra 3 feet of Superflex
between the amp and rig and that had no effect either...

  I have a 19 inch Viewsonic monitor on a shelf a few inches above the rig
so I unplugged it to ensure there wasn't a magnetic field problem with the
rig (this should have showed up at 100 watts also, but I figured I would
give it a try).  I took apart an old computer case and put steel side panels
above and below the radio to partially block any magnetic fields caused by
the 425 Titan power supply.

  I have hot water baseboard heat (copper pipes) so I tried connecting the
water pipe to the ground system (no improvement).

  I made a 10 turn 6" diameter coax choke and taped it to the antenna boom
and that didn't help either...

  My Omni VI is an earlier one, not one of the later SMT ones...

  I'm going to call the factory tomorrow, but if any of you spot something
you think I missed, let me know.

Replies are welcome direct or through the reflector!

Thanks,

George / KF9YR