In article ,
"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 ?

You are looking at the Ham stuff, which is geared for transmitting. The
transmitting situation needs to take a few more things in account that
are not as important in receiving. The main idea here is to prevent
common mode RF current on the outer shield coupling to/from the antenna
as you may end up with a hot radio and shack. If you are burrowing the
coax on the way to the BALUN there is no need for this and the BALUN
already performs this function.

Needed even if there will also be an arrestor ?

Not needed in your situation.

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

As an example if you were to do this for a dipole up a mast 3 to 10
turns about a foot diameter depending on the frequency.

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

If the coax has a run through the walls of your place and 30 feet
through the air instead of 30 feet through the ground then yes both ends
and also spaced at intervals along the run.

This is easier done with a ferrite clamp on choke as opposed to coiling
the coax.

--
Telamon
Ventura, California