Topband: Antenna matching question

Carl km1h at
Tue Mar 18 18:01:27 EDT 2014

----- Original Message ----- 
From: "Tom W8JI" <w8ji at>
To: "Bill Wichers" <billw at>; <topband at>
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??


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