Not to belabor the issue - but some interesting new info on this matter....
The alarm company blew me off completely; said that if the alarm is working
properly, that's their only concern, there's nothing they can do about it.
This afternoon, I called the manufacturer of the alarm system, NAPCO, who
happen to be based right here on Long Island. As soon as their tech
support person determined that I was not a professional installer, but the
home owner, she immediately dismissed me saying that their tech support is
only for installers. I pressed her for some comment on the problem, and
she then grudgingly suggested that I install ferrite beads, as a number of
you had also advised. She was not at all surprised that I was experiencing
RFI from the system and was clearly not interested in helping.
Having done the previously mentioned tests of cutting off all Ac/Dc supplies
to the alarm to confirm it was the problem, I decided to go outside tonight
in my yard where my HF antenna is located. It's a Cushcraft vertical
mounted 12 feet AGL and about 20+ feet away from the house. I took with me
in the yard, my trusty FT-817 with the duckie, tuned to 75 meters. What I
found is is that my entire house is radiating this insidious alarm noise
both indoors and out; no surprise there since the sensor wires run all over
the place, especially in the attic.
But here's the kicker - the most intense levels of the RFI (like a loud
buzzsaw) are coming from - my rain gutters!! I have a vertical downspout
about 10 feet long and directly in line with - you guessed it, my Cushcraft
vertical. If I move the Ft817 to the left or right of the downspout, the
RFI remains but drops off somewhat. If I change the position of the duckie
to horizontal, the noise is much less pronounced, but still there.
Next, I walked around to the other side of my house, nowhere near the yard
and brought the FT817 in close proximity to the structure. The noise is
audible at all points, but man, when I came into contact with another
vertical downspout, I practically blew out the front end of the rig. And
of course, I then realized that all of the downspouts are fed by horizontal
gutters running completely around the perimeter of the house right at the
base of the two attics (I have a split-level home). And as already
stated, the attic is where the major (horizontal) alarm wires and junctions
No wonder some people have had success using their gutters to work DX. If
I end up getting that noise canceller, at least now I know where to position
the noise antenna - I'll just tape it vertically to the downspout!!