Repetitive signal showing on SWARM

I’m getting a waveform that occurs at rate of something slightly greater that 30 minutes.

I’ve noticed a similar waveform in the past, but it was much smaller. As of today, the magnitude is much larger and is now identifying as a quake as indicated by the vertical red slashes. The RS is in my garage in a quiet residential area.

Here are my logs:
RSH.RAA00.2020-03-31T23_17_12.logs.tar (2.5 MB)

Any thoughts as to what is causing this? Thanks.

I have occasional spike like this when an electrical switch is thrown or freeze/refrigerator cycles. I would suspect something in you garage is turning on every 30 minutes or so.

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My largest source of things regularly turning off and on is my furnace. You can see that start at 0530 in the morning. It is as I expect - a noisy signal with frequencies between 17 to 22 Hz. I’m surprised by the magnitude. I registered the Idaho 6.3 quake yesterday and it had a magnitude of 40,000 counts. Whereas this is about 30,000 counts. Any of the cultural signals I’ve experienced exhibit lots of ringing and noise. This is an incredibly clean signal. Even doors closing don’t look this clean. Footsteps in the vicinity are not this clean. If anything, it looks like an RC coupled signal as is explained in this tutorial:

I think I have a likely suspect. Does anyone know if RS has had any studies done with regard to radio interference?

In the past, I’ve noticed a similar waveform which is much smaller, but with a repetition of about 2 minutes. This new waveform is much larger with a repetition of about 30 minutes.

The waveform presented earlier has now stopped as of early this morning.

As a radio amateur I had setup an Amateur Packet Radio System (APRS). It required an upgrade, so I setup the new system in my garage. The old runs on about 2 minute intervals and is about 50 foot from the RS. The new one runs on about a 30 minute interval and is about 8 foot away from the RS. The frequency is 144.39 MHz. Because the new system isn’t ready for service, I turned it off this morning - at about the same time the above waveform stopped.

So, I believe the RF from the APRS system is getting into the RS Raspberry Pi Hat and putting a DC offset into the circuitry of the Analog to Digital Converter. The RS subsequently tries to remove the DC bias and that produces the exponential type curve and then when the APRS stops transmitting, the DC bias which was just removed, suddenly becomes a DC bias in the negative direction and then the RS tries to remove that and makes the exponential curve in the other direction.

I’ll continue to observe and make time notes as to when my APRS is operating and verify.

I recommend that some information be associated with the RS documentation to warn of potential RF interference.

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Perhaps you could put a Faraday cage around your shake ?