[TowerTalk] Vertical versus horizontal polarization on 160m

[David Gilbert]

Recent threads here have pointed out the adverse effect of poor ground 
conductivity on vertical polarization versus horizontal polarization, 
but as best I understand things there is some advantage to vertical 
polarization due to the gyro-frequency of electrons in the atmosphere.  
Bob Brown, NM7M (SK), was known worldwide for his studies on 160m 
propagation, and his tutorial on HF propagation in general, and 160m in 
particular, is noteworthy:

http://www.astrosurf.com/luxorion/Radio/nm7m-hf-propagation-tutorial.pdf

I live on a steep hillside with a wide and very deep ravine running down 
across my property, and in order to work a DXpedition to 3B9 (2003 or 
2004 or so) I ran a 2 element wire yagi across that ravine and it just 
luckily pointed to 3B9.  I had to feed it with a few hundred feet of 
RG-8X coax (thicker coax would have been too heavy) to a spot where I 
could park my car, and although I used a 400 watt solid state amp I was 
probably feeding only about half that to the antenna.  I easily worked 
the 3B9 on 160m, though, and was the furthest west station to do so.  
Most hams only heard the 3B9 for five or ten minute openings, but for 
several days I could easily copy them for periods ranging from 30 to 55 
minutes.  I posted my success here on TowerTalk, and NM7M sent me a post 
telling me that he calculated that for that path vertical polarization 
had an 11 dB advantage over horizontal polarization on 160m.

The gyro-frequency effect decreases significantly at higher frequencies, 
but for 160m it seems to be pretty important ... at least for some 
paths.  I've heard lots of hams claim that verticals rule on 160m, and I 
suspect that it isn't only because putting up a suitably high horizontal 
antenna is so difficult.

I guess my point is that maybe we shouldn't be dissuaded from putting up 
a vertical antenna on 160m just because we have poor ground 
conductivity.  Control the return loss in the near field as best we can 
(lots of great comments here recently on how to do that) and hope the 
gyro-frequency effect helps with the far field effects.

Caveat:  I don't think that the theoretical gyro-frequency advantage 
holds true for all paths.  I think east-west paths are different than 
north-south paths.

73,
Dave   AB7E