Ian White GM3SEK wrote:
With the right length of coax, number of turns and method of winding,
such a simple coil resonates with its own self-capacitance and is
unbeatable as a single-band choke.

Unfortunately, at approximately double that single-band
frequency, the choke is 1/2WL self-resonant and essentially
useless. Someone on QRZ.com quoted the 2006 ARRL Handbook
as saying the following: "A flat coil (like a coil of rope)
shows a broad resonance that easily covers three octaves,
making it reasonably effective over the entire HF range."

Such a coil is certainly NOT "reasonably effective over
the entire HF range" when used on a typical ladder-line
fed all-HF-band dipole. With a 50 ohm 75m dipole, the
SWR on 450 ohm ladder-line will be 9:1. Worst case, the
choke will see 9*450 = 4050 ohms. An effective choke of
five times that value would be 20K ohms or about 850 uH
of inductance. What do you reckon would be the 1/2WL self-
resonant frequency of an 850 uH coil of coax?
--
73, Cecil http://www.w5dxp.com