[TenTec] Even MORE on vertical antennas!

AC5E@aol.com AC5E@aol.com
Tue, 3 Sep 2002 09:42:08 EDT

Faraday rotation causes radio signals to "rotate" from horizontally polarized 
to vertical and back, more or less continuously. Particularly over a 
multi-hop path. Therefore it's not uncommon to find a station coming in quite 
strongly on a vertical antenna and not be workable on a beam. Terman's Radio 
Engineering makes that situation quite clear for those  interested. It also 
makes it clear that those who omit a decent vertical from their antenna 
arrays are missing some easy Q's. 

And speaking of cracking a book, the 4th edition of the Radiotron Designers 
Handbook has a very revealing chapter, written by one of the real pioneers in 
radio propagation, on antennas. As he points out, a mismatched antenna 
reradiates most of the signal it intercepts. Therefore an antenna with a 
serous mismatch at the feedpoint is a poor performer on both transmit and 
recieve. While recievers commonly have more "excess gain" than transmitters 
have excess power output there are limits to everything. 

For a little more book cracking I notice the latest ARRL Handbook lists the 
SWR of a 100 foot dipole at 50 feet. The two foot difference between that and 
a G5RV is essentially trivial, as a few minutes with EZNEC or another antenna 
modeling program will show.  And even casual consideration of the data will 
show why a G5RV is not the all band wonder wire some old hams tales make it 
out to be. 

I have seen battered but servicable copies of both Terman and Radiotron 
Designers handbook (the fat red backed version, not the slimmer black 3rd 
edition) at hamfests for a few bucks each. They make invaluable additions to 
a shack. 

73 all  Pete Allen  AC5E