[Antennaware] Q on 3/8 WL Verticals

[Joe Subich, W4TV]

Ed, 

> I am curious if there is any benefit to be had from inscreasing 
> the number of counterpoises or (given the height) lengthening 
> them.

Lengthening the counterpoises would definitely cause a problem 
and detune the antenna.  The traps and/or top loading of these 
"3/8 wave" antennas are really designed so that the antenna acts 
like an off center fed dipole (a vertical Windom, if you prefer). 
The counterpoise length, series capacitor and radiator length 
are all chosen carefully to allow the antenna to show a reasonable 
match to 200 Ohms (and to 50 Ohms via the "step down" auto-
transformer and common mode choke).  

The best "performance enhancement" is probably to add an extra 
common mode choke at the feedpoint to prevent feedline radiation 
from effecting the antenna and prevent common mode currents from 
effecting the transceiver or any station accessories. 

73, 

   ... Joe, W4TV 
  



> -----Original Message-----
> From: antennaware-bounces at contesting.com 
> [mailto:antennaware-bounces at contesting.com] On Behalf Of 
> atrampler at att.net
> Sent: Thursday, February 28, 2008 12:39 PM
> To: antennaware at contesting.com
> Subject: [Antennaware] Q on 3/8 WL Verticals
> 
> 
> Hi
> 
> I'm new to the list and run an AV640 with its base about 18' 
> above the ground.
> 
> Has anybody modeled this or a similar 3/8 WL loaded vertical, 
> like the R8, regarding efficiency, radiation pattern, etc?  I 
> am curious if there is any benefit to be had from inscreasing 
> the number of counterpoises or (given the height) lengthening them.
> 
> I know to many of you this is probably not a "real" 
> antenna...but it fits my yard and its obstacles.
> 
> 73,
> Art, KØRO
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