"Tim Wescott" wrote in message
...
W. Watson wrote:
I bought this antenna on a 30 day trial, and just got it about 12 hours
ago. So far I'm not at all impressed. I live about 150 miles from an AM
station, at 810, in the SF/SJ Bay Area, which has a marginal signal, but
usually listenable. Putting a new PSU in a PC about a month ago increased
the noise in AM radios 70-100' from the PC to an almost unacceptable
level. I had hoped the antenna would boost the signal enough to knock
down the noise. There are times when I can get a good signal from the
station, but certainly less frequently than before.

The antenna consists of three parts: a 600-1800 KHz control dial, a
ferrite antenna and something called the antenna element. The latter is
about 8" long by 3" by 1.5" (high). The idea is that one puts the ferrite
antenna very near the radio and the antenna element in some other spot,
then adjusts the control dial to the max strength. I detect zero change
in any AM signal from the (C. Crane) radio anywhere on the dial. The
antenna element can be grounded. I modestly did this by hooking a wire
(alligator clips) from the element to the ground socket of an AC outlet
(nail in the socket). No change. BTW, when I was doing the experiment
last evening, the signal was pretty decent during that period. In fact,
quite listenable. All this without the device though.

I'll continue to experiment, but so far not so good. Comments?

I'd change the power supply to a better brand.

Generally if you have atmospheric or man-made noise increasing the antenna
efficiency is just going to increase the noise along with the signal.

You could try to make a directional antenna; this would increase your
desired signal more than your noise.

The antenna would have to be big, however. The wavelength at 800kHz is
somewhere around 370 meters and you'd need to use around 1/4 of this.

The ferrite antennas are already directional. That is one of their
advantages.

You could try to feed power supply noise to the radio antenna at just the
right amplitude and phase to null it out. This would be a good subject
for an undergraduate or even a Master's thesis in EE but probably not a
good thing to do in practice.

These devices are well known and sold at least by 2 ham manufacturers- MFJ
and Timewave(?).

Dale W4OP