Topband: Antenna matching question

Tom W8JI w8ji at
Tue Mar 18 17:33:22 EDT 2014

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 

160-40 is less of an issue than 80 or 160 through 10.

73 Tom

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