[RFI] High Noise Levels on 80m

Rick Karlquist richard at karlquist.com
Tue Dec 19 20:21:28 EST 2006

Kelly Johnson wrote:
> I'm trying to figure out why my noise levels are so high on 80m, but
> not on other bands.  I'm hoping someone can provide me some clues.
>> I have a 3 element SteppIR and a 2 element 40m yagi.  My 80m antenna
> is an inverted vee with the apex at about 50 feet and the ends at
> about 10 feet.  The SWR on the inverted vee is good, with 1.1:1 at
> about 3550 or so.
> Question 1 - I know that 80m has more noise than 40m, but should it
> really be 6 or 7 S-Units higher than 40m?  That seems like a lot.

I recently put up a 30 ft high dipole for 80 meters and compared it to
an inverted vee.  It was much quieter than the inverted vee.
Not just quieter, but better signal to noise ratio.
I attribute this to the inverted vee picking up vertically polarized
noise.  I also have a transmit vertical on 80.  The vertical is
noisier than the vee which is noisier than the dipole.  The
three antennas are many hundreds of feet apart, so they do not
interact.  On 40m you have Yagi, which is quiet because, like a dipole, it
is horizontally polarized.  Have you tried your 40 meter Yagi as an
80m receive short dipole?  I suggest you use it with a preamp.

Rick N6RK

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