[TowerTalk] top loading vertical question

[Dinsterdog@aol.com]

Greetings all,

After loosing my 80 meter 4SQR in 1 in 50 year ice storm in SE Wyoming this 
past month, I'm rebuilding things. Because of some damage to the aluminum, 
I'm having to modify the verticals from 52 footers top loaded with three 14 
foot top hat wires to 45.8 footers with longer top hats.

Heres my question:  How long do the top hats have to be the verticals to 
achieve individual resonant points of 3.620MHz??  Here's some past data for 
making a good guess or plugging into an antenna model program, which 
unfortunately, I don't have:  

With my first set of verticals used last year, I had 44 footers with 20 foot 
top hats attached at the 39.6 foot mark.  My resonant point of each of the 
individual vertical was 3.700MHz. 

With my second set of verticals used this year, I had 52 footers with 13.5 
foot top hats placed at the 49 foot mark.  My resonant point of each 
individual vertical was 3.470MHz.

My goal with the new set of antennas is to have each of the individual 
verticals tuned at around 3.620Mhz.  With the antennas now at 45 feet 8 
inches, with the 13.5 foot top hats in place at the 42 foot 8 inch mark, I'm 
resonant at 3.775MHz.  I need to bring this resonant point down 160KHz.  
Leaving the tophats where they are, my guess is to add two feet to the top 
hats making them 15.5 feet long.

Any one with a model program that can help me figure this out would be a big 
help.  

(Dont plug in mutual coupling as the resonant point of the individual 
antennas is not effected by the proximity of the other verticals.  The 
resonant point of this array, with my experience with it, only jumps up due 
to this effect when plugged in through the coupler- I just need a good guess 
on the individual antennas.  The aray has awlays jumped up around 180KHz.  So 
as you can see, I'm going for tuning the array for the SSB window-)

73 Paul  N0AH

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