On Sat,9/19/2015 11:54 PM, Rick - DJ0IP / NJ0IP wrote:
If you want to run high power (more than 800w), you will need to glue two cores
together.
You won't find the coax I used, so use RG-142.
Rick,
I hate to be a wet blanket, but off-center fed antennas produce VERY
high common mode voltage/current, enough to fry a very good ferrite
choke with as little as 100W. Running a power amp is really asking for
trouble.
I now recommend using TWO 5,000 ohm ferrite chokes on well balanced
dipoles running more than 1,000W.
The "coil of coax" chokes are simple inductors. If the length of the
feedline makes the feedline capacitive, the choke will cancel part or
all of the reactance of the feedline and the common mode current will
INCREASE. Obviously, the extent to which this occurs will be different
on every frequency. For this reason, a coil of coax makes a lousy common
mode choke.
73, Jim K9YC
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