coax coil choke conductor migration

[K6JEK]

The 75M dipole is down, alas. Before putting it back up I thought I might switch from the W2DU choke to a K9YC choke, swayed by his analysis which boils down to 5000 ohms is better than 500. However, I've eschewed coiled coax, scared off by horror stories of conductor migration, inner to outer as time and heat bear down. Do you serious hams use coiled coax chokes?

The coax in question is LMR 240 to be looped through a stack of Fair-Rite mix 31 OD 2.4" cores.

Here, if you haven't seen it, is the short version of Jim Brown, K9YC's, treatise on chokes etc. He doesn't disparage Walt's design. But a few turns can boost the impedance in a hurry.

http://audiosystemsgroup.com/NCDXACoaxChokesPPT.pdf

Details here in Chapter 7: http://audiosystemsgroup.com/RFI-Ham.pdf


Jon

[W1ITT]

Times Cable specifies the MBR, minimum bend radius, as 0.75 inch for a one-time bend, and 2.5 inches for repeated bending for its LMR-240.  You're only going to build that balun once, so as long as you don't kink it, and as long as you stay within the power specification of 1.49 kilowatts at 30 mhz and below, all will be good.  Don't forget to waterproof the end of the cable.

[K6JEK]

Thanks