RF susceptibility

Technical Support
1

This is really more an FYI than anything.
There are some notes on radio frequency interference in the microwave region (WiFi frequencies), but depending upon the power density, it looks like other frequencies can cause interference too.

My S/B is located inside a metal building (pole barn), on the concrete floor.
I have an amateur radio antenna (80m dipole), one end attached at the roof of this building, probably 30’ (~10m) from the S/B. This being the end of the dipole, it has zero current, high voltage signal at this end.

I noticed spike when I transmit (3.96MHz). I have since added a UPS which filters the power, and added a ferrite core to the power cable of the S/B. I was expecting that the problem would be RF picked up on the power wiring and getting in that way. However, there was no difference.

Looking a bit closer, I noticed that the infrasound channel showed no sign at all of any interference.
Only the Z channel.

I now suspect that it is the transducer that is picking up the RF.

This is what it looks like:

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2

Hello Philip,

Yes, this is indeed a possibility. Another ham radio enthusiast has detected similar events when transmitting with his equipment, and he even created a shielded vault to minimise them and enjoy both passions in full.

3

I was wondering about trying out various shielding ideas. Not sure that an underground vault is the best solution for a shake/boom, it would probably not help the “boom” part very much.

In my case the peak RF is more like 1kW. I can probably drop that to more like 100w in the summer months (80m after dark is not ideal for local-ish communications).

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