[Amps] Bandswitch arcing

f1fly f1fly at orange.fr
Fri Mar 6 13:18:33 EST 2015



I just finished a homebrew amplifier with 2 X 3-500ZG.


It works fine but I have some arcing problems in the bandswitch when working
at full power on 80 m.


The antenna is a shorted dipole so I suspect it.


The bandswitch is a non-shorting one I found on Ebay (ceramic cheap russian
NOS - 4 wafers, 2 poles, 5 positions).


So I have 3 questions :


- Do I have to change to a shorting switch in order to short the unused
parts of the tank coil and also to avoid parasitic resonances ?  


- Do I have to buy a more heavy duty switch (shorting or non-shorting) ?


- An om told me that if I use several tank coils at right angles instead
only one, the auto induction is less and I decrease the arcing in the


In this amplifier I have 3 coils, the 10 m Pi coil that is mounted right
angle from the 15 to 80 Pi coil, the 15 to 80 m Pi coil and the L coil for
all bands


I think it's the same that in several commercials amplifiers.


What is the good solution to avoid bandswitch arcing ?


Both ?




Eric - F1FLY



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