On Nov 17, 9:36 am, Tony Giacometti wrote:
My neighborhood is loaded with some kind of electrical noise which makes
working 160 & 75 meters difficult. I have tried to locate the source but
have come up empty at this point. It appears to be something other than
power line noise which may mean its coming from someones house.

I was hoping the solution to the problem was to build a low noise receiving
loop antenna.

Well, the noise is mostly gone..........but so are the signals.....even when
I use a preamp.

I have tried an ICE 75 meter preamp and a KD9SV 160/75 meter preamp.

Still the noise is gone but the signals are really weak, if I hear anything
at all.

Not sure what if anything I did is wrong or if I am expecting too much from
this loop or the preamps don't have enough gain to make this work.

Anyone familiar enough with receiving loops to be able to assist me in
figuring out whats wrong here?

TIA

Tony

Hi Tony,

I haven't bothered to wade through ALL the responses so far, but I am
left wondering just what you did build. Could you explain it in more
detail? Diameter, number of turns, how you're feeding it, how it's
"shielded," exactly where the gap is, ... All the details.

A loop can be effective in decreasing noise in two ways. If the noise
is electromagnetic radiation it can only work if that radiation is
coming from one direction, and in that case, you orient the loop to
reject radiation from that direction. You better not want to be
receiving a signal from the same direction, of course. The second way
it can help is by rejecting locally generated electric field noise--
where you are in the near field of the source, and the electric field
is considerably stronger in relationship to the magnetic field than it
is in electromagnetic radiation. But the electric and magnetic fields
fall off with distance rather quickly, so this only works if the noise
source is on the order of a wavelength or less away.

In order to build a loop that's effective in not responding to an
electric-only field, it must be small compared with a wavelength. I'd
think you'd want something around a foot in diameter for 80 meters,
possibly slightly larger. You won't pick up much signal, but more
importantly, it will be a high Q loop that you need to tune, and the
resulting bandwidth will not be great. I have a suspicion that's
where your problem lies. Reg Edwards supplied us with a very decent
loop analysis program that might give you some insights. Look for
rjeloop3.exe under http://www.we0h.us/G4FGQ-index.html.

Cheers,
Tom