Someone here recently stated that they had problems with howling filters.
Recently I experienced the same problem.
Notice on the schematic of the IF/AF board that the reg. voltage comming in on
connector 44 has no bypass capacitor. Putting a .01uf from reg to ground
completely took care of my problem. I tacked it on the ajacent 4.7k resistor
which is in series with that lead then to the foil on top. To find the
resistor. Remove the bottom covers. With the rig upside down and facing you,
look at the board on the right front corner. This is the IF/af board. Look
on the far right end and locate connector 44. It is should have a sticker on
it with the number 44. Look slightly to the left and you should see a 4.7k
resistor. Attach the .01 or .02uf from the right end of that resistor to the
foil.
I don't know why this was overlooked at the factory because all other boards
with the reg. voltage are bypassed and of all boards, the IF section has the
greatest gain of all and is more likely to cause unwanted coupling. I believe
most Omni's are operating on the verge of feedback and all would benefit from
this capacitor.
ANOTHER TIP
If you experience a lack of gain, broad selectivity skirts and excessive
clicking in the speaker while in the fast qsk mode. Check your filters.
Remove the 2.4kc filter in the first IF. Turn it upside down and look carefully
for minute solder traces across the crystal's solder connections. Use a knife
to scrape away any evidence of solder. Then check your connector pins. They
are pretty wimpy. I recommend resoldering them just to be sure. When you
reinsert them, apply pressure to the pins, working around the filter one pin
at a time until it is seated. Don't push on the board. Do this for all your
filters.
I'de like to hear from anyone who has tried this and about any other problems
encountered with the Omni 6.
Steve Ellington N4LQ@iglou.com
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