> The material in the ARRL Handbook is woefully out of date and quite
I'm not sure if "out of date" is exactly right in this context (neither the
coax nor the theory changed, did they?), but I believe you are right that
air would coax chokes are inadequate for HF. OK for VHF, maybe for the
upper HF bands too, but not as a general HF band choke. Not nearly enough
impedance to choke off common-mode currents.
There was an email thread about this on one of the many other email lists I
subscribe to, saying pretty much the same thing. To be effective at HF, one
must use some ferrite core(s) to make an effective choke.
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