[time-nuts] electronics question or how not to fry my raspberry pi

[folkert]

Hi,

I bought a GPSDO. It outputs somewhere around 3V. This is connected to a
picdiv and then to a raspberry pi. The picdiv is happy with 3.3v, the rpi
as well. All good.

Now I bought a "Square Wave Amplifier" by BG7TBL ( https://www.aliexpress.com/item/4000192799858.html?gatewayAdapt=glo2nld&spm=a2g0o.9042311.0.0.3d764c4dMZPAX8 ). Documentation I could find was a bit vague about the
output voltage but I measured 5v with a scope (see
https://vanheusden.com/permshare/scope.png - the scope software says
2MHz but output is really 10MHz).

I did not study electronics, am only a electronics-hobbyist so bare with
me when this is a dumb question.

The RPI doesn't like 5v on its GPIO pins.
So I wonder:
- can I feed the picdiv 5v on its GPIO pin while giving it a 3.3v
  voltage so that it outputs 3.3v as well to the rpi pins?
- or should I use a voltage divider? I was thinking of a 4.7k ohm and
  8.2k ohm resistor giving slightly less than 3.2v - will that work? or
  will that attenuate the signal too much? The 50 ohm bnc cable between
  the amplifier and the rpi is 3m long. Anything else I should be aware
  of?


Regards,

Folkert van Heusden
PD9FVH