[1000mp] RE: Mark V resetting while running an amp on 10M

[Ian White G3SEK]

Jim Smith wrote:
>
>I've found that items plugged into the front panel jacks of the MkV 
>will enable any RF floating around the shack to get into the MkV.  Does 
>your monitor sound horrible on SSB?  Do you hear a growling sound when 
>talking even with the Moni button on and the Moni knob turned all the 
>way down?  Unplug or put ferrites on all the leads plugged into the 
>front and, in my experience, the RF problems go away.

I don't know the Mk V in detail, but many modern rigs have similar 
problems. In many cases the cause is a design error: no ground 
connections at the audio jacks.

The designers have followed the method of grounding shielded audio 
cables at the internal circuit board only, deliberately leaving the 
jacks on the front or rear panel "floating". The reason for not 
grounding the jacks to the chassis is presumably to reduce the risk of 
ground loops inside the rig, in other words to avoid cross-connecting 
"audio ground", "RF ground" and "power ground".

Theoretically, this is good design practice - but in the real world it's 
a disaster for RFI! If there is any stray RF floating around, the 
ungrounded jacks let it right into the box, and then the coax shields 
act like little antennas, radiating RF all around the inside of the rig.

Very often the cure is simply to ground the jack to the chassis, with a 
short wire jumper to a solder tag under the nearest available grounded 
screw.

One of the main offenders is the microphone lead. Very often the "mic 
gnd" shield is not connected to the front panel, so it carries any stray 
RF all the way to the audio input stage! The Heil website has an easy 
fix that you can apply to the mic *plug* without having to open up the 
rig.

Try it - it's often the complete solution.


-- 
73 from Ian G3SEK         'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek