Recalibration every 5 minutes

1

Hello All,

I have the KerberosSDR (not kraken) from the first batch.

I had tested the first versions of the demo software, before kraken, with no success. I guess I did something wrong.

When the kraken software was released, I purchased four cheap external coax switches and controlled them with the GPIO pin of the Pi. All worked very well.

Now I have tried to connect the kerberos directly to the laptop computer, which is less RF noisy than the Pi. Because of it I bought a Raspberry Pi Pico and connected it to the laptop, so I had GPIO pins on the laptop. It was needed a light modification of the heimdall code, but it was OK for me.

Unfortunately, something was wrong and three of the four coax switches are broken.

I was wondering if it is a good idea to buy a new set of external switches. Perhaps it is time to manually connect and disconnect the coax cables? Cheap coax switches need two weeks to arrive from China, then I would need to solder, test and take care of them. They apperar to be a bit sensitive.

Let’s suppose that I am interested only in one single centre frequency, and I do not change the RF gains. How often would I need to recalibrate the kerberos? Every 5 minutes, as proposed in kraken demo software? Or perhaps most of the times it would be unnecesary? Have you performed any tests about this?

Even disconnecting and reconnecting by hand when changing the frequency, the new calibration system looks easier than the first days. In my view is a good step forward.

Thank you in advance.
Ger EA4GJA

2

Once calibrated, it should stay calibrated indefinitely forever, in theory.

But there are USB glitches possible that can rarely make the kerberos/kraken lose calibration, which is why we check calibration on the Kraken every 5 minutes, just as a watchdog. The USB glitches in my experience, on a Pi 4 happen only every few days to weeks of continuous operation, so it’s not a huge deal.

Sometimes phases can also shift with ambient temperature changes, but the skewing effect is minor. Recalibration helps with this too, but it’s not critical.

3

Thank you for your fast answer!