Topband: A word from the master W1BB

[Tom Rauch]

> Although W1BB nominated a quarter-wave vertical tower with a LARGE
> system of radials as the most effective single-element transmitting
> antenna, Stew added the rider that the antenna should be located over
> marshy ground/very close to the seashore and by "large number of
> radials" he meant at least 200.

It is well known and documented (like in the Brown Lewis and 
Epstein study at RCA) with 1/4 wl radials, efficiency is nearly 
100% with only 50-60 radials. Once efficiency is near 100%, very  
little can be gained by any changes! I'm afraid it is a total waste of 
time and wire to go beyond 50 or 60 radials, unless you make 
them very long!

You can pick up another fraction of a dB by using radials near 1/2 
wl long and 100 or so of them, but it is hardly worth it.
 
> However, if Stew was limited to just one antenna, his first choice was
> an 165 - 170' inverted-L, fed with coaxial cable via a series
> capacitor over as many radials as possible, giving both horizontal and
> vertical polarised radiation. 

That was a common though, and still is, but unfortunately that 
system does not transmit two independent polarizations. The result 
is actually a skewed polarization or tilted polarization that is neither 
all vertical or all horizontal.

You could use a 90-degree shift and rotate the wave with circular, 
but you would gain nothing.

Broadcast stations actually avoid stuff like that because it 
increases fading.

VK3ZL is a good example of how a short (40-50 ft) vertical works, 
even over poor ground, when 30 or 40 radials are used compared to 
a 100 foot high Inverted V. While there are times his V is better, by 
far mostly his short vertical is best.

The best I see, with a "droopy dipole" at 300 feet over earth, is the 
high dipole at very best just ties my omni-vertical. There are days 
that are exceptions, but all in all the vertical is best.



73, Tom W8JI
W8JI@contesting.com