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Mark V QRM Fighting
Last weekend's SSB contest allowed me to discover many effective
control settings for the Mark 5 to fight SSB QRM... really tough
QRM. Being an appliance operator, here are my findings:
1. 1.9 INRAD cascade filters are a must.
2. Notch control can work to attenuate one QRMer somewhat off
your freq., but if your desired sig comes near the under desired
one, both are notched, of course. Manual notch effective this
way about 25% of time tried to use it.
3. Width control should be offset in an equal but opposite
direction from the Shift control. On Narrow (1.9 filters), these
two controls require less deviation from center detent.
4. Sometimes using more deviation from center on Width and Shift
with Normal filter setting (stock Yaesu filters) produced better
results (more voice intelligibility) than Narrow filter and less
Width and Shift usage. Both 3 and 4 are especially true with
IDBT switched on.
5. Contour controls were less helpful switched on... any of the
3 options... because of less voice readibility.
6. NR button in the top LED cut some hiss, but lower LED
settings killed too much of voices.
7. VRF worked wonders, but required too much time to adjust it
for ever-changing condx. Also, it needs to have its own
indicator on so that u can see how far from center it is tuned,
and it needs a center detent to rapidly return to center... but
that would mess up its other (dual) usage as a channel
selector... but who in the world wants to channelize a Mark 5...
not a ham, I think.
8. The real secret weapon is the IPO. Switch that thing on, turn
up the AF volume, and read even no-S-meter-signals with
startling clarity! The crud even very near ur dial freq. just
drops off to nothing and even the little sigs jump in there!
There were very few cases indeed when a very weak sig was helped
be turning the IPO off because the crud rose higher than the
weak sig. In really bad QRM, this IPO makes communication
possible!
The Mark 5 receiver is a marvel. For less than $3,000, amazing.
Where has it been all my ham life?
K4VUD Charly
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