The objective is to get a sufficiently high value of impedance. It
doesn't matter whether the impedance is inductive, capacitive, or
resistive. You'll get the highest impedance at resonance, so that's the
best choice for a single band and there's no point in modifying the
design to "be sure it is on the inductive side". Typically, the
impedance is higher even considerably above resonance than it would be
with an inductive choke of fewer turns. With HF air-core coax chokes,
the impedance is very high at resonance and on the bands immediately
above and below the resonant band -- and adequately high for some or
most applications at frequencies above and below that, since the
resonance is quite broad.
Roy Lewallen, W7EL
John Smith wrote:
Actually, Tom, my GDO measures about 440 with two tight turns. Add a couple
of inches for leads and it goes lower. So, I figured I needed something
slightly higher in resonance to be sure it is on the inductive side of 440.
No?
John
|