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.
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.
You could attempt to shield it. Rat Shack has some clamp-on ferrites,
you could put one of these on your power cord close to the end that
plugs into the power supply. You could also make sure that the PC case
is well shielded.
--
Tim Wescott
Wescott Design Services
http://www.wescottdesign.com