Topband: Automatic Switching on 80/160 Vertical

[Chortek, Robert L]

Hello Topbanders,
 
I am trying to design an automatic bandswitching system for a linear
loaded vertical I am building. The antenna will be a full 1/4 wave on
80, and will have linear loading for 160.  The vertical will be
insulated at one section of the antenna, about 1/3 of the way up, and
the linear loading wires will be attached to each side of that insulated
gap and run down in an upside down "V".  
 
I need a way to short out the linear loading wires to use it on 80
meters.  Clearly a relay can be used to accomplish this task, but I
would prefer automatic band switching if possible. Can anyone tell me if
I put a 400 pf capacitor (or some other value) across the insulated gap,
will that cap effectively short out the linear loading wires at 3.5 MHz
and be "open" at 1.8 MHz?  This is similar to the Butternut HF2V L/C
network concept (or the 160 mtr L/C option) except that the L is
replaced by the linear loading wires.  I would like to avoid coil
loading with its inherent losses.
 
I would appreciate any help you can provide.
 
73 es thanks,
 
Bob/AA6VB   
 

Robert Chortek 
Berliner Cohen
Ten Almaden Boulevard, Eleventh Floor
San Jose, CA 95113
ph.: 408-286-5800
fax: 408-998-5388
e-mail: robert.chortek at berliner.com  


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