[1000mp] feedback from rf or speaker in MH31 mike

[Mike Schatzberg]

Hello Bill:

You may be bringing RF into the shack on the shield of your coax cable.  The
first easy thing to try is a couple of the snap on ferrite blocks on the mic
cable, and see if the problem is eliminated.  Radio Shack usually has a few
snap ons in stock.  The proximity of your station to your antenna, and the
routing of the coax away from your station may be the root cause of the
issue.

You can also try a line isolator, which is really a number of ferrite beads
on a piece of coax, just outside your shack.  See Radio Works for more
information.

Of course, if you test your radio with a dummy load, and the problem
persists, then something else is at fault.  But if the problem clears up,
you might first consider re-routing your coax so that it is at right angles
to a wire antenna for example.  Or raise the antenna higher above ground.

So there you go, a few things to investigate.

73 and Happy DXing,

Mike
W2AJI


----- Original Message ----- 
From: "Bill D" <capers at toast.net>
To: <1000mp at mailman.qth.net>
Sent: Friday, February 09, 2007 11:48 AM
Subject: [1000mp] feedback from rf or speaker in MH31 mike


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> ______________________________________________________________
>
> Hello; I've exhausted my capability to correct the problem of  feedback
> through the mike on 80meters when using more than 50 watts of power. I
have
> tried adjustments on mike and can overcome feedback when positioning the
> mike gain at about 9 o'clock or less and alc meter shows little or nothing
> and PO meter is no longer accurate. I tried by passing (disable) tuner and
> still able to transmit with 1:0 or less SWR. Still the effect on the
> microphone and unable to increase power beyond 60 watts. Tried manual
tuner
> and no difference. Tunes OK but mike feedback still a problem. Re-grounded
> unit and new balun. All looks OK, but not on 80 meters. Problem does not
> occur on other bands except when using the Ameritron 811H amp with manual
> tuner (3k Roller Inductor) I cannot get the power to the antenna from the
> amplifier and load and plate adjustments must be retuned each time I use
> amplifier.
> Too much text, I apologize. But I've studied help sites on internet for
> 1000mp mk V owners as well as read the manual  many times and still have
the
> mike problem on 80 meters with more than 50 or 60 watts . Wonder if anyone
> has had this problem and how it was solved? Thanks much
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