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Date: | Thu, 7 Apr 2011 16:22:02 -0700 |
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The 468 comes in to play as dipoles have what is called an end effect of
around 5 percent.
I'm not sure where the formula for the loop comes from but if you're
figuring say a quarter or half wave stub, you use 300 meters which is a
full wave length and the speed of light. To convert this, take meters
times 3.28 so 984 over frequency gives youa full wave length. for a
quarter wave stub, for example, divide this by 4 and then that number
times the volocity factor of your coax.
Way back when I was selling a lot of cb rigs, and people were running
quarter wave whips, 102 inches long. These ghings would pick up enough
static here in a dirt storm, you could lay the pl259 on the dash and
sparks would jump from the center pin to ground. Needless to say, this
was hard on fet transister front ends, so her was my fix. I would divide
984 by 27 mhz, which comes out 36.444 and 36.44 divided by 4 for a quarter
wave in feet is 9.111. The coax I used which was rg58 had a volocity
factor of around .7 as I recall, so 9.111 times .7 is 6.377 feet. I'd
make this stub, short one end and put it on a t connector on the radio
with the antenna to the other leg. It was a dc short, but as a quarter
wave looks open at its frequency, the radio didn't know it was there.
Worked like a champ!!
73
Butch
WA0VJR
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