[1000mp] Fw: audio distortion with amplifier.

[Mike Schatzberg]

Hello Peter:

Some things need to be checked first, before you go further with your MP
changes.

Carefully check your signal with another station rather than thru your
monitor.  Very often RF is picked up on the headphone cables themselves, or
the speaker leads coming to the speaker, such as the SP-8 console, and you
will think that your radio is distorted.

In fact, your signal is not distorted, just your monitoring of the signal
internally is overloaded with RF.

Sometimes wrapping the headphone cable four or five times thru a larger
ferrite block will remove most of the distortion, or likewise for the
speaker leads.  Sometimes an inline RF choke may be necessary, depending on
the problem's severity.

Check that the problem isn't the monitor system itself.

Good luck, and happy DXing,

Mike Schatzberg
WB2AJI
----- Original Message ----- 
From: "Peter" <deypet at pandora.be>
To: <1000mp at mailman.qth.net>
Sent: Friday, October 29, 2004 11:42 AM
Subject: [1000mp] Fw: audio distortion with amplifier.




Hi there,

my setup is a FT-1000mp DC (from 1996) with an Ameritron AL-80B.
In a special occasion i'm using my amplifier,perhaps once or twice in year
mostly in a contest.....

I'm still suffering from probably RF feedback in to 1000mp.
When monitoring in SSB the audio is distorted.
it's difficult to explain,it's like sqeezing my audio with ups and downs.
Even in CW there's a raw tone on my signal.

Running my 1000mp barefoot everething is excellent,but with the amplfier
on,it's increasing as the output power increases,the higher ALC level the
more
distorted,even on 200w out it occurs.
I'm not overdriving the amplifier mostly the rig output is around 30-50w
controlled with the ALC on the amp.

I grounded amp and radio seperately,so no ground loops.
I put the 12V-dc cable several times through a large Amidon core.
The ALC and PTT cable,also several times through a Ami. core.
Ferrite clip on beads at the back with my cw key input.
Coax feed used also several ferrite clamps and also a line isolator,
between my coax doesn't helped at all.
Every bead en and core is closest  placed to my chassisrig.

Has somebody any idea or experience through which way the RF
is getting in my rig.(coax,12V-dc cable,ALC-PTT calbe....??).
So in can focus my self  on one item......???

Any suggestions or experencies very mutch welcome.


Kind regards,73's Peter ON7BJ.




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