Hello Ed, John and everyone,
Generally speaking, Sparking sources are stronger and travel further when
received at lower frequencies. However, the noise level is determined by the
noises ability to propagate to the receiving antenna. There are allot of
things that can affect this and create many different scenarios.
The distance between the noise radiator's antenna and the receiver antenna
is the most important factor. Let me explain this, the way I have
discovered.
The source radiator is not usually the actual noise source. If the source is
close enough to the receiving site it can radiate directly to the receiving
antenna, if not the radiator might be hardware on a pole closer to the
receiving site after conducting its way down the line. The noise in this
situation would be too weak to be received if it weren't for the noise
having a means of travel to get closer to the receiving antenna.
The next contributing factor is the wave length of the receiving frequency.
If you are receiving the noise on 7 megahertz (ok you can call it megacycles
if you wish) the wave length would be 40 meters long. If the distance
between the sources antenna and the receiving antenna is exactly 40 meters
than your antenna would be at the peak of the signal and the receive level
would be maximum. If the receiving antenna were moved 10 meters closer it
would now be in the null for 40 meters and the same noise source would now
be much weaker. The same source, same antenna but now weaker. So if we were
to install several towers with multiple antennas on each we could easily
switch to another tower to null the noise and improve reception. Wow was
that my idea? LOL
This is the reason the frequency verses noise level idea isn't always true.
It all depends on the position of the noise sources antenna and the
receivers antenna.
A good example is when you are sitting at a traffic light and can move your
vehicle a couple feet to improve the radio stations signal or reduce the
power line noise.
During a few of my classes I've demonstrated this by stopping the van at the
peak of a noise signal, I mark the ground with chalk and travel to the next
peak. If I'm monitoring the noise at 145megahertz the marks will be 2 meters
apart. Guess how far apart they would be at 3 megahertz? Now I'm gonna get
100 emails with some correct and some incorrect answers!
Keep an eye on my web site, starting 2011 I'll be posting the date and times
of my presentations.
Good Night,
Michael C. Martin
RFI Services
6469 Old Solomons Island Rd
Tracys Landing, MD 20779
www.rfiservices.com
240-508-3760
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|