----- Original Message -----
From: "Tom W8JI" <w8ji@w8ji.com>
To: "Bill Wichers" <billw@waveform.net>; <topband@contesting.com>
Sent: Tuesday, March 18, 2014 5:33 PM
Subject: Re: Topband: Antenna matching question
You mention keeping the highest impedance part "clean" electrically, which
would make me think putting the small coil nearest the anteanna would be
best. Whichever part of the inductor is shunted out is essentially just
adding stray capacitance, that keeps the shorted turns part of the
inductors towards the feedline. Since most or all of the large inductor
will be shorted out when on 40M, it will act essentially as extra
capacitance in the matching network on that band.>>>>>
That's why tank systems in amplifiers have the ten meter coil near the
high impedance end.
If this is only 160-40 you probably won't have a series resonance issue
with unused turns, but if you cover a wide range you will want to
progressively short the large coil taps. This is why band switches that do
not short (like the old National amp) and why large roller inductors mess
up on higher bands.
If you mean the NCL-2000 I suggest looking at the schematic again. Or did
National make another ham amp that Ive missed??
Carl
KM1H
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