Hi, all - Last night, I tried the use of a PAR BCB High-Pass filter to
substantially weaken the signal of AM BCB stations coming into the
system via the antenna. This device works great - it is obvious from
listening to the MW spectrum that MW stations are attenuated
enormously; signals as high as S-7 or 8 are made unreadable without
the preamp, and even powerhouses are cut way down to size.

With this thing in line, both before and after the MFJ-1026, the
intermod products are *still there* on many frequencies from 5 MHz and
down, and even show up as high as the 31 meter band, plus one spot on
25 meters. Some of the products heard reflect stations that, with the
PAR filter, only register about S-3 or 4 on their home frequency!

I cannot believe that the 1026 is causing this weird siuation, despite
the fact that it appeared simultaneously with the use of the DeOxit on
the pots. The same problem happens on both radios that are attached
to this antenna system, so I do not think it is with radios
themselves. Moreover, it seems at worst before sunset, with gradually
diminishing severity as the evening progresses.

The only other path I can think of is that *the signals being mixed in
are coming over the 115VAC electrical lines.* I had never considered
this before, but with miles of power lines fairly close to several
high-power AM BCB transmitters, it does not seem far-fetched to think
that some resonance may be occuring in the lines. We don't get this
problem on any other equipment in the house (portable radios, TV,
etc.) so I am not yet married to this idea; but, if this is the case,
then it may be that the only way stop it is to run the whole works
from a 12v battery, which I am not quite prepared to try yet. I have
placed RF chokes (ferrites) on the power cords coming into the R75
wall wart, both the 115VAC and 13.8VDC sides, and will soon place one
or more on the MFJ-1026 power supply and more on the antenna cables as
well, especially either side of the PAR filter.

Aside from this particular annoying problem, I have already managed to
get the radio's RF background quieter than at any time in the past,
using the chokes and some coax coil "baluns." As I keep track of what
works and what does not, I will try to report my results.

73, and remember that the U.S. and the world will survive regardless
of which candidate is elected...

Bruce Jensen
************

(bpnjensen) wrote in message . com...
Hi, folks - thanks to the recommendations of the good folks here, and
having reasonably assured myself that the MFJ-1026 does not have
plastic pots inside (or any other similarly sensitive innards), I gave
a couple quick squirts of DeOxit D5 Power Booster 5% to each of the
three key pots (main antenna gain, aux antenna gain and phasing
adjust), rocked the knobs several times as prescribed on the DeOxit
can, and allowed the stuff to evaporate for about 24 hours. I was
careful to gently cover the rest of the innards with a clean cotton
terry cloth while spraying the stuff into the pot holes. Two amazing
things happened:

(1) The static of the dirty pots is GONE GONE GONE! Huzzah!
(2) The degree of AM BCB intermod, especially below 4 MHz, is
dramatically increased, almost to the point where nothing legitimately
below 4 MHz can get through. All preamps off, still get the gunk
where it wasn't before. Booo.

So, a mixed bag (it least for now)!

It could be that the DeOxit worked so well that it brought the unit
back to its normal operating status - that is, a collector of intermod
junk from lower freqs (I do live in an area where BCB powerhouses
abound, on the edge of SF Bay). Or, it could be that I did not let
the stuff evaporate enough (so it gets another 24 hours as we speak).

Or, the DeOxit had some unintended effect on the unit, either inside
or outside the pots. I think this is unlikely.

As I investigate more, I will try to fill in the gaps. I also have a
PAR BCB intermod reduction filter I will try ahead of and behind the
unit. Meanwhile, I will appreciate any other ideas folks might have.

73, and don't let the political junk get you down,
Bruce Jensen