Sorry for the confusion - some clarifications below:
There is a lot wrong in that post.
1. HFTA doesn't model vertically polarized antennas, so if the
conclusion is to go with a 4-square you aren't going to learn a thing
Agree - I was referring to modeling the beam using HFTA and then comparing
to the expectation of the 4 square.
2. Radials, no matter how extensive, will not do a thing to affect the
vertical radiation pattern of a vertically polarized antenna. The
conductivity of the land beyond any practical radial field rules the day
... and night. Radials affect efficiency, not pattern.
Agree - But the losses in the efficiency are the number one thing that
disappoints vertical users. The conductivity of the near field - within 5
wavelengths - will have a big impact on performance for sure. However - if
the model assumes poor ground conductivity and the losses are minimized with
proper ground screen/radials - then a good conservative decision can be
made. If high conductivity beyond the radial field is necessary for the 4
sq to be the right choice - then it needs to be verified. My point is that
if its already winning over poor ground with good radials then the rest of
the conductivity data does not affect the decision.
3. Elevated radials make sense versus using an extensive ground screen
over really poor ground, but again ... that only affects efficiency and
not pattern, and doing both makes little sense. The elevated radials
mostly shield the ground screen from providing any useful benefit unless
the ground screen is a lot larger than the area of the elevated radials.
Try listening to K3LR running EU on 80M and think again. Ohio/Penn soil is
not salt water and a 4 sq is a 4 sq. So if the extensive ground screen over
elevated radials is so useless - what is your explanation of the
performance.
Dave AB7E
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|