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Old November 7th 05, 02:11 PM
John Passaneau
 
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Default how to combat noise?

I use 2 ham stick mobile antennas phased to produce a receive antenna on 80m
that works very well.
It has a response that is close to a reasonable sized beverage. They are
spaced 1/8 wavelength apart and feed 135 deg. out of phase with a coax
phasing line. I have a relay setup that lets me change the direction, in my
case north-east / south-west. The signal levels are down from the dipole I
use for transmit but the signal to noise level are much better. A signal
that would be S-9 with S-8 of noise on my dipole becomes S-6 to S-7 on the
verticals with no noise. It makes DXing on 80m fun. Details for the design
of the phasing system are in ON4UN's book on low band dxing. One of the
advantages of using mobile antennas is the mutual coupling is very low
between them. This greatly simplifies the setup. Note that this would be a
poor transmitting antenna do to the poor ground plane I have and mobile
whips are not a good antenna on 80m.


--
John Passaneau, W3JXP
Penn State University



"andy" wrote in message
oups.com...
Here is the situation: have an inverted V for 80m and noise level is
S9.. Not good really....
I did the next logical step and tryied magnetic loop for 80, reciving
only, indoors. That antenna failed awfully.... Noise was S8 but I could
not hear stations that were 9+10 on inverted V. Did'nt matter how I
tryied to rotate the loop, all there was is noise. So, indoors is right
out..
All that is left is roof. And that makes my situation interesting. It
is a big house with new metal roof, electrically bounded. 10X60 metres,
17 metres hight, angled about 20 degrees. Big ground plane indeed. All
I could figure is to get some sort of antenna to the roof so the roof
would act as a shield from all the noise generated inside the house.
That antenna would be for receiving 80m, can be narrow band (50KHz
ok). NVIS pattern would be prefered.
So, I have huge ground plane, lots and lots of noise below it, and need
a receiving-only antenna.
What would you do in this situation? Loop, magnetic loop, dipole, short
beverage perhaps???
Any advice is welcome. Right now I cant even figure if that roof is
acting like a shield or a big noise-sucking antenna..

Andrus



 
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