RF interference from amateur radio

I’m a ham operator and have a HF antenna about 50 feet from a Shake RS4D. Transmissions on 10 or 14 MHz strongly affect the geophone. Accelerometers are unaffected. Transmitter is only running about five watts. Has anyone else seen this? I haven’t tried to mitigate yet, thinking of trying ferrite chokes on ethernet and power cables. This is a digital protocol (FT-8) with continuous transmissions of 15 seconds duration followed by 15-second listening periods. Interference seems to be a spike at beginning and end of the transmission.

Hello Jay,

yes, another user of our Shakes reported a similar phenomenon, and this is what he did to solve the issue caused by RF interference: https://raspberryshake.org/amateur-radio-my-rf-shielded-raspberry-shake-vault-experiment/

This is the same article, but here on the community: My RF shielded in-ground vault experiment. Maybe you can get in touch with him (and possibly others) and you can exchange your ideas on the subject.

FWIW - I put my Rshake in one of those diecast metal boxes and used a feedthrough capacitor for the DC and ferrite core on the ethernet cable and DC. I have also used a 24-12/5 volt DC-DC converter. In the case of the RBoom device I added an ethernet isolator device in line with the ethernet cable. You can see the RBoom setup here

the photo itself is here:

https://community.raspberryshake.org/uploads/default/original/1X/c6736427d6fa23a08d7d271efae6f5840f51c2fc.jpeg

Ken

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I should add one more thing - the diecast box looks shiny, but in fact is made of materials that will react quite strongly in contact with concrete and moisture - or just continuous heavy moisture. If you are locating it in a wet area (as most outdoor locations are) you should lightly sand and thoroughly paint the exterior of the box before setting it out.

What is the beige box in the upper right of the photo that looks kind of like an old-school baseboard mount telephone jack? The Ethernet cable plugs in to it.

That is the ethernet isolator.

It provides galvanic isolation (no DC path) and >5000 volts breakdown voltage. It is rated for Gigabit speed. I suspect it offers some help at the lower RF frequencies (160 meter band for example) and, of course, at power line frequencies 50/60 Hz.

Here is one: https://baaske-medical.com/isolation/ethernet-isolation/

You can find these for not too much money if you hunt around. The ones rated for medical usage (patient care facilities) and tested to IEC60601-1 can be quite expensive, however.

Note that this is not a surge protector as such. If you expect lightning surges you should also use a surge protection device (gas discharge tube type).

My RBoom device includes a cable run along the forest floor between tall trees and I know, if one of those trees gets hit, it will put a lot of voltage into any cable running along the surface nearby. So, ahead of the ethernet equipment at the RB location, I use a Ubiquiti SP-G2. These are cheap and actually contain 8 gas-discharge protectors.

good luck

Ken

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I have to add more. Not stated, but implied, is that for RS:

  • the metal enclosure should be non-ferrous material

  • electrical connection to the chassis should be at only one point - both the geophone and RPI should be floating from ground. No currents flowing in the chassis.

  • Ideally the enclosure should be big enough to allow some space between the geophone and the metal walls. Mine is a little small from the point of view.

Ken

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