Monitor Distortion (MONI)
PROBLEM: Ever since my MkV was new, I have
noticed that after I transmit for a while, the monitor gets
rough, whether on CW or voice. It's been back > to Yaesu once,
for this and other issues, but they found nothing wrong, and the
problem continues. Voice signals sound rough, and CW signals
less than T9. Today I was operating in the ARRL DX contest, and
I noticed that if I was hearing the rough sound in the monitor
and switched the IPO button on, the monitor sound cleaned up
dramatically. Have other people noticed the same thing? And if
so, what does this tell you about the possible origin of the
problem and how to fix it?
SOLUTION: I used to think that my transmitted audio quality was poor because it sounded horrible in the monitor. Many reassurances that it was actually nice and crisp caused me to decide that the monitor was a piece of crap and not to be trusted. One day, bored out of my tree while listening to my 40th consecutive contest CQ without an answer, my idle fingers clicked a ferrite around the earphone line plugged into the front panel. No particular reason, just something to do. Say what? The monitor audio sounded better. Hmm . . . wrap a bunch of turns of the earphone line around the ferrite. Monitor audio roughness has pretty well disappeared.
I do have quite a bit of RF in the shack. I have found that ANYTHING plugged into the jacks on the front panel can introduce RF into the rig. So, nothing is. I have also found that a way of testing for RF getting into the MkV is to turn the MONI knob fully CCW so you shouldn't hear anything from the monitor. If you hear weird stuff it's probably due to RF feedback. Now, I can't think of any mechanism by which RF introduced into the MkV is going to cause increasingly severe problems simply due to the passage of time since power-up so this may not be relevant to your situation.
IPO button? Can't make an informed comment. Can say that if RF is running around in there I suppose that it is possible that anything you do might make it sound different. How to find out if it's RF? Temporarily disconnect everything you can from the back and absolutely everything from the front panel. Wrap all remaining lines several times around ferrites. The monitor should now sound nice and clean. Let some time go by and see if it sounds any different.
An easier way of reducing the RF
level is, of course, to simply turn the RF PWR knob fully CCW.
Hope this is of some help. Jim Smith VE7FO
This site was last updated 08/27/07