I'm looking at various switches for an HF PA. What's the highest
anode voltage the model 80 and 86? Anyone know what switch
type number Alpha used in the higher anode voltage amplifiers?
Here's what I've found on sample switches.
Measuring voltage breakdown of a modified JV-9000 series
compared to RSC (multitech) samples of the model 80 and 86:
9000
contact to contact 7.8
open contact to rotor 11.7
open contact to adjacent rotor 6.3
rotor to shaft 9
80
contact to contact 7.6
contact to rotor 6.1
open contact to adjacent rotor 6
rotor to shaft 8
86
contact to contact 9.85
contact to rotor 6.8
open contact to adjacent rotor 6.8
rotor to shaft 10.8
It looks like the model 80 is ruled out because it has less voltage
breakdown than the 9000 series, and voltage is the primary failure
mode of switches.
The bulk of voltage appears from the ten meter contact to the rotor,
where peak voltage exceeds the voltage applied to the tank
because the input and output are almost out-of-phase when the
load is open. I have to watch the contact to rotor or open contact to
adjacent rotor the most, since that is the spot where maximum
voltage can appear.
Between the 86 and the 9000, I'll lose 1 kV of breakdown in the
best case situation if I use a 86. I'll gain a lot of current handling
with the 86, but that is not often a problem. I'm torn here. Does
anyone know of a reasonable priced switch that handles more
voltage? Anything bigger than the 86 isn't feasible cost-wise, since
it is almost three times the price of the 9000.
73, Tom W8JI
w8ji@contesting.com
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