[Elecraft] OT: Now Balun effectiveness

[Stuart Rohre]

Darrell,
When the coax is coiled as an RF choke, it does not have significant losses
as the inductance comes from the SHIELD acting as a coil.  The choking
action is all outside the coax shield.

There will be some effect between the turns, of the dielectric outer jacket,
but nothing it can't tolerate.
The added capacitance may make the coax coil mostly effective over a given
set of bands, but you can alter that by varying the number of turns of coax
used.

Do use good quality coax, that will not have the center lead migrate thru
the dielectric by being coiled.  Foam coax may suffer that if too tight.
Poly insulation as on old styles of RG 8 and RG 58 is preferred.  Check the
diameter suggested for winding a coil of a given coax.  IE check the minimum
bend radius.  The same problem affects jumpers around rotating masts and
rotors below beams.

Coax is sometimes used to fashion traps for antennas but that is a different
set of loss considerations, where the center conductor and shield perform
both a capacitor and inductor role.
-Stuart
K5KVH