[TriLUG] OT: I promise, I'll take this off-line, but I wanted to make sure I shared all the beans ; -)

sjackson at radarfind.com sjackson at radarfind.com
Thu Feb 24 13:14:10 EST 2005


Rick wrote:

"I'm not sure that a directional loop is what I'm looking for. I'm not
really wanting to do AM DXing, just get the local AM stations clearly by
locating the antenna away from the equipment which is colocated with the
receiver."

OK.  If I recall correctly, you are besieged by noise, and when the noise
overcomes the weak signal, you are unable to hear your desired station.

Happens to me, too, all the time!  And, there are several ways to solve the
problem.  

First, though: the propagation of (HF) 'AM' broadcast band signals (530-1710
kHz) is radically different than those in the (VHF) 'FM' band at 88-108 MHz.
So, putting the antenna in the roof won't help pick up stronger signals,
because there aren't any more HF signals in your attic than in your living
room, unlike at VHF.  At best, it *might* move the antenna away from some
potential noise sources as you surmise, but at worst, you'll couple even
more noise in, via the feedline.

If you build a simple, cheap directional antenna (loop), you can reject
in-band noise that comes from any direction other than the direction of the
station you want.  And, you'll boost the desired signal, at the same time.
When receiving amplitude modulation, increasing the signal-to-noise ratio is
*the* whole game.

You are correct that the loop antenna would be useful for receiving distant
stations, but, it's even MORE useful for NOT picking up noise, which is the
#1 enemy of AM radios.  Since noise IS 'AM' - you can only get rid of noise
by rejecting it in the first place.

I hope this helps.

Steve Jackson, KZ1X/4
RadarFind Corp., RTP, NC








More information about the TriLUG mailing list