Topband: Antenna matching question

[HAROLD SMITH JR]

Tom, 

I have an amplifier with a pair of 3-400Zs I built in the 60s. When I built it it was for 20, 15 and 10 meters. 
I used 3 of the 5 positions of a BC375 tuning unit switch. Everything work fine. I added 160, 80 and 40 meters. 
160 was switched in and out with a RJ-1a vacuum relay. When I went to 20 and up meters the switch contacts arced. 
I added another RJ-1a to short out the unused lower band coils. I switch the RJ-1a's in and out with 2 mini toggle 
switches. One says 160---other bands, the other switch says low bands---high bands. It works fine on all bands. 
At that time 3-400Zs were new from Eimac $34.00 each. 

73 Price W0RI


>> 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??
> 

Here you go, Carl

That's the wrong way to do a bandswitch. It does not pick up and hold the lower band contacts when switched to higher bands. This allows the taps to build up high voltages on lower band taps when working higher bands.

Switches should be pick up and hold, or progressively shorting.

73 Tom 
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