ATS Mini vs ATS25 RSSI measurements on SSB

[max-arnold]

I had a short conversation with Antonino Russo (one of the ATS25 firmware developers) regarding the bogus RSSI measurements on ATS Mini in SSB mode (see the comments section of this FB post). I had an assumption that the SSB patch for Si4732 simply lacks proper RSSI and SNR measurements, but Antonino said that in any ATS25 receiver this feature works as expected even in SSB modes.

I tried both patches (patch_full.h and patch_init.h) and found no differences, so my assumption that there are some hardware differences in ATS25 that make this possible.

Any insights/comments from ATS25 owners?

P.S. the confusion about the "Chinese SSB patch" is clarified here in the comments.

[G8PTN]

Hi Max,
I don’t believe that there are any major hardware differences. The ATS-25 series does have some additional circuity for RF filtering, amplification and switching.

If you poll the rx.getCurrentReceivedSignalQuality(); faster, the behaviour may look a little different. Maybe the AGC time constants could also have an effect.

For AM/FM the polling does not need to be fast, since there is a constant carrier, while for SSB the signal will be modulating, so the behaviour will depend on the AGC times and the polling speed.

Activity on the Si4732 I2C interface can cause interference, so faster polling could be an issue.

73, Dave

[max-arnold]

Could it be related to separate (?) AM/FM antenna inputs or audio sampling circuit (decoder) on ATS25?

[G8PTN]

Hi Max,
I don’t think it will be related to the switched antenna inputs.

I believe that the audio sampling is used for the spectrum and FT-8 decoding. For the CW, RTTY decoding, there is a separate audio amplifier feeding a tone decoder chip. The tone decoder output feeds the ESP32. The typical circuit diagram is shown below.

73, Dave

[max-arnold]

I looked up some ATS25 videos on YouTube and it seems that SNR is close to zero and RSSI is mostly constant (the same as on ATS Mini):

• https://youtu.be/rzsNLW7tvpU?feature=shared&t=1061