I have to argue with my friend Jim on this one. The coax itself can be an antenna, and can pick up RF along its path from the antenna to the radio. The best example is a vertical antenna which will use any metal it can find for return currents, which includes the coax after the antenna-mounted choke. This current will combine with the internal shield current at the first place they are connected (which very well may be the SO239 on the back of the ATU). A choke at this point will protect against the problem. This may not be common-mode currents, which is one of the reasons I hesitated in calling it that in my previous email.
Perhaps the best way to make sure there is no current flowing on the outside of coax shield would be to add ferrites along the entire path, a solution that is way to expensive to be practical. 73! Jack, W6FB > On Aug 4, 2019, at 10:29 AM, Jim Brown <[email protected]> wrote: > > On 8/4/2019 9:20 AM, Jack Brindle via Elecraft wrote: >> And, do you have chokes on the coax at the KAT500 or KPA500? > > I hope not -- to be effective, a choke must be that the antenna's feedpoint. > A choke on an antenna in the shack does nothing. > > 73, Jim K9YC > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
