On Tue, 31 Jan 2006 15:22:33 -0500, "Robert11"
wrote:

Hello:

Will be putting up a receive-only antenna (30 MHz) in my backyard.

The antenna will terminate in a Balun, and then a lightning arrestor,
immediately before the coax (8X probably)
run back to the house some 30 feet away.

Have read in one or two places a brief comment that it is a good idea to
make a few turns of the coax
right before the start of the antenna. Termed a "Choke".

If so, what is the purpose ?
Needed even if there will also be an arrestor ?

If a good idea, how many coax turns, of what diameter ?

Also a good idea at the other end, by the receiver ?

Thanks,
Bob


A choke passes DC unimpeded and blocks higher frequecy AC. Unless
your SWL antenna is mounted on an FM transmitter tower I don't see any
advantage. Lightning wouldn't notice it.

Most Baluns are actually autotransformers and all parts are at DC
ground (provided your coax outer conductor is grounded and the
termination is properly affixed). This is the best solution to
protecting you from anything other than a direct hit. A lightning
arrestor will keep your house from burning down but won't save your
radio's front-end.