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[RFI] RFI into Rig

To: <rfi@contesting.com>
Subject: [RFI] RFI into Rig
From: w6jzu@rf.net (Dr. Robert C. Smithwick) (Dr. Robert C. Smithwick)
Date: Mon, 8 Feb 1999 09:55:56 -0800

I 'enjoyed' (is that the right word?) the summary on your problen and its
ultimate solution. You demonstrated the correct way to go about solving
such a problem. The changes you made in your grounding system, altho it may
not have contributed a great deal to the solution of  your particular
problem as it turned out, shows good engineering practice. (I don't mean to
talk down to you!)

This comment obviously does not apply to your case as it turns out, but the
one aspect or dimension that you did not address, is the/your antenna. If a
beam, how far away from the amp? The farther away, the better. On low bands
most hams don't use a beam but if a dipole, the distance from the shack and
orientation may be significant or - worse case - a long wire that some
less-experienced ops attempt to feed directly from the output on the
ampifier or external tuner is trouble. Big trouble.

"Smitty", W6JZU

At 10:12 AM 2/6/99, MICHAEL W. ELLIOTT wrote:
>I hope this is ok to post on this reflector  if not accept my apology.
>Wanted to share this with the group and ask for any further suggestions.
>Wanted to thank my mentor and friend  NI0G for guiding in the right
>Station description:
>I have two rigs
>IC 765
>Linear Amp
>I am using a KAM dual port tic with hookup to hf radio and vhf radio for
>Using a Astron Power Supply
>2 meter radio
>Both rigs have experienced rf feedback into the speakers as well as the
>Did not get this problem on cw.
>Did not happen on low pwr but running amp and working SSB/RTTY I  got
>feedback into the speakers while transmitting..
>I have  tried using some toriods but saw no help.
>I thought my problem was the cause of  old grounding so I ran new
>grounds to a new ground setup described below:
>Placed 4 -  10 foot ground rods outside the basement wall.
>purchased #4 copper wire from my local Home Depot store.
>Connected #4 wire to all 4 ground rods and ran inside to shack.
>Copper cold water pipe is too far from the shack.
>Bought 1 inch copper strap and grounded tuner to amplifier then to #4
>wire. Next.
>Ran a copper strap from the rig to the ground.
>Problem did not go away with the new ground arrangement  so I started a
>hunt for the cause.
>Next moved the Astron power supply and disconnect the vhf radio.
>Problem appeared to clean up in 80meters on low and with liner but when
>I went to 20 meters to chat with a friend in Brazil I used the linear
>and the problem was back.
>Well I cured one problem but now the problem moved.
>Could not under stand what was going on but the lightbulb came on.
>Only thing I had not done was remove the KAM cable from the back of the
>FT1000mp. This cable provides the digital mode and the 25din cable from
>the back of the KAM  goes to computer.
>Could it be the db25.. No.
>I removed it from the Kam and prob was still there.
>What's next?
>Light bulb went on again and then Success:
>The cable from the KAM to Ft100mp was still connect.
>By removing the cable from the Kam to radio cleared up all feedback and
>Next work today will be to run grounds to all equipment
>Astron Power Supply
>Ameritron Ant switch box
>and anything else I can my hands on in the shack
>While what I have said  is not unique it does pay to use good grounding
>methods on everything.
>.Next thing my friend suggested is to try a ferrite on the Kam cable to
>the FT1000mp.
>Has anyone else experience this prob??? with the Kam to the radio ???
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>Questions:                owner-rfi@contesting.com

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