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Old November 1st 04, 11:13 PM
Ken Bessler
 
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Default Help designing trap dipole - ARRL Antenna book no help!

The ARRL antenna book describes the inductive effect
of traps on lower freqs and how this physically shortens
the antenna. They talk about L/C ratio and give two
examples.

Problem is they don't give the formula! #$%#%$!

Here's my antenna - it's a 75/160 trap dipole. The traps
were designed with W8VVM's software. Cutting the
75m portion of the antenna is easy - I need to know how
long (as a starting point) to cut the 160 m end pieces!

Help!

Details: the traps are 8-1/3 turns of rg58 coax wound
around a 3-1/2" form. L is 7.211 uH, C is 232.15 pF.
X is 176.24 ohms. Design freq on 75 is 3.890. Target
freq for 160 is 1.925. I plan on cutting the 75m wires
60.5 feet to start and work up from there but what do
I cut the 160m ends to start?

Ken KG0WX



 
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