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Input protection


J. chang 2022/01/05 07:29

Hello All,

Can anybody recommend a protection device that could be put across the input connector to discharge any voltages, like static that could build up on a lead that might be plugged into the input of either the Nano, or the Tiny SA like a low capacitance  Schottky device or something faster?

Thank you,

--jeff

Dave Johnson 2022/01/05 20:20

Common sense should do it, but the info here should either show you how not to need protection, or how to build one:

https://youtu.be/totwu4IbavE

-=dave - AI4ME

Kit 2022/01/05 21:01

Hi Jeff,

The only 2 practical devices you can install to drain off feeder static charges (neglecting gas discharge & semi-conductor devices) are a wideband RF choke - not as easy as it sounds if left in place permanently - and the antenna used for transmitting - or a 0.5 to 1w resistor, typically 47k, with either device placed in parallel on the feeder's inner & outer braid.   Not sure whether either would survive a nearby (induced) lightning surge or strike though.

In the Antarctic where open-wire feeders (600 ohm) to the antennas were once used from the HF transmitters, drift snow would impose static charges of kilovolts. Caused all sorts of problems on unused (and thus open-circuit) antennas  !

Cheers,

Kit

J. chang 2022/01/05 22:33

Thank you, however, in writing my question, I was actually looking for a part number for a low voltage low capacitance bidirectional TVS in a sot package perhaps… I usually always have at least a 6 to 10 db attenuator on the inputs of either the nano or the tinySA, but I could install a 0 to 69db step attenuator inline if needed, but it is bulky. I’d just like something that I could solder in place and forget about incase I misplace the inline pads. I’d like to use the nano to around 3.4ghz or so.



--jeff

Galvin Franks 2022/01/06 07:50

There is a very low capacitance protection diode series just for this application. See the following discussion:

https://groups.io/g/nanovna-users/message/20445?p=%2C%2C%2C50%2C0%2C0%2C0%3A%3ACreated%2C%2CInfineon%2C50%2C2%2C0%2C80361897 ( https://groups.io/g/nanovna-users/message/20445?p=%2C%2C%2C50%2C0%2C0%2C0%3A%3ACreated%2C%2CInfineon%2C50%2C2%2C0%2C80361897 )

Uses a Infineon ESD101B102ELE6327XTMA1 diode.

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