View Single Post
  #57   Report Post  
Old January 25th 09, 09:31 AM posted to rec.radio.amateur.antenna
[email protected] nm5k@wt.net is offline
external usenet poster
 
First recorded activity by RadioBanter: Jul 2006
Posts: 757
Default improve S/N for AM car radio by a factor of 2...5...10?

On Jan 23, 7:37*am, Cecil Moore wrote:

I'm not saying that a coaxial loop is a "magnetic" antenna.
I am saying that antennas do exist which respond primarily
to the magnetic field and a ferrite rod antenna is one
obvious example proven by rotating the ferrite rod in the
presence of a vertically polarized signal. Note the
polarization of a radiated plane wave is referenced to
the E-field, not the H-field.
--
73, Cecil *http://www.w5dxp.com


I had to ponder the loop for a while. Something kept
bugging me, and it was mainly wondering about the
pattern of say a small 1/10 wave loop, vs a large 1 wave
loop. Both are diamonds.
I was pretty sure I remembered them as having a
different pattern, and I decided to model them to
see.
Well. I found out that even when I'm feeding the
small diamond at the bottom corner, I'm still
getting mostly all vertical polarization.
So with the small vertical loop, I'm getting almost
all vertical polarization, no matter where it is fed.
With it fed on a side corner, which most would
consider vertically fed, I have almost the same
pattern, except it's even cleaner, with very little
horizontal.
Totally unlike the large loop which if I feed at the
bottom, it's almost all horizontally polarized.
So it seems my MW loops are still pretty
much vertically polarized, even when fed at
the bottom corner.
So anyway, as far as the small loops, I'm
not receiving cross polarized after all.
I generally don't see much difference in operation
between a ferrite loop antenna, and a wound
solenoid loop with many turns for MW.
And I did make a "PVC Tube" solenoid loop
antenna once when I was messing around
with them. But don't have it together now.
But I seem to remember it acting basically
the same as all the other versions.
IE: the directivity was off it's ends.
I'd have to make another one to compare
tilting it vertical, vs horizontal.