On 11/12/2013 8:20 PM, Roger (K8RI) on TT wrote:
may be wrong, but I've always looked at the solenoid coil as if it
forms two resonances. The choke itself forms a parallel resonant
frequency with a rather high Q So it may work on one or two bands and
it also forms a second resonant frequency with the overall coax length
which can be worse than no choke at all.
That's a good way of looking at it, but also an optimistic one. The
resonance of the solenoid coil (no ferrite core) has a rather high Q (so
it's a narrow resonance) and is usually much higher than the band where
it needs to work, in which case the resonance is of no value. It's also
optimistic that only one resonance will form with the coax. :)
73, Jim K9YC
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