[hpsdr] ALEX - Input protection

[Graham Haddock]

All:
I am looking for ideas for input protection for ALEX.

Lyle has recommended a gas-discharge tube device, which I will use
on any port that could be hooked to an antenna to limit large voltage
surges. (Digikey 495-1475-ND)

But, I have a concern, that the gas-discharge tube limits in the 70 volt
range, and the Hittite electronic switches and electronic attenuators
on Mercury will probably break down at lower voltages, I am
guessing in the 25 volt range.

Frank Carcia has recommended using low capacitance diodes
(1N4148 or similar) biased at around +/- 10 volts, so that they would
clamp the input at that voltage.

Does anyone else have any other ideas that they would suggest?

I am looking for something that would present a fairly low capacitive
load to the input lines, and clamp at a voltage that must be higher than
about +/- 2.5 volts, but lower than +/- 12 volts.

Thanks,
--- Graham / KE9H

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