hello all,

as the title suggests, this inquiry is about the opentx telemetry page. please seeic below:



what is the RSSI low alarm (50) and critical alarm (35) measured against? i have already set the osd_rssi_dbm = -95 as a reference threshold for my use case. i have encountered twice during flight an audible warning from my transmitter “RF SIGNAL LOW” where the quad was ironically within only a hundred meters away from me with perfect LQ and RSSI in the ~70dBm only. 

what values must i put on said alarms to closely match that of my OSD settings?

The RSSI value is effectively useless for ExpressLRS and Crossfire receivers. Just tick the box to disable the RSSI alarms and manually set up audible warnings for LQ and RSSI dBm instead using special functions and logical switches if you haven't already done so.

(03-Apr-2023, 08:56 AM)SnowLeopardFPV Wrote: The RSSI value is effectively useless for ExpressLRS and Crossfire receivers. Just tick the box to disable the RSSI alarms and manually set up audible warnings for LQ and RSSI dBm instead using special functions and logical switches if you haven't already done so.

good to know this audible warning from the TX is irrelevant to ELRS as it only caused confusion on my part hearing it despite the healthy LQ and RSSI via OSD. although i will lose the ever familiar “TELEMETRY LOST” and “TELEMETRY RECOVERED” audible advisories whenever i unplug/plug the lipo pack once i tick the disbale alarm box. 

(03-Apr-2023, 09:22 AM)hawk01 Wrote: good to know this audible warning from the TX is irrelevant to ELRS as it only caused confusion on my part hearing it despite the healthy LQ and RSSI via OSD. although i will lose the ever familiar “TELEMETRY LOST” and “TELEMETRY RECOVERED” audible advisories whenever i unplug/plug the lipo pack once i tick the disbale alarm box. 

In that case leave the alarms enabled but just set the Low and Critical RSSI values to ZERO, then the RSSI warnings will never sound but the telemetry recovered/lost warnings will

(03-Apr-2023, 10:24 AM)SnowLeopardFPV Wrote: In that case leave the alarms enabled but just set the Low and Critical RSSI values to ZERO, then the RSSI warnings will never sound but the telemetry recovered/lost warnings will

as a follow up to this RSSI portion on the telemetry settings, i was able to get some valuable info from the folks as radiomaster. while they did not mention much about the significance of these alarms, they did explain the nature of how RSSI values behave relative to range! see their response below:

now i have a much better appreciation on how to appraise this OSD metric and the way it will behave with range.

Yes, as previously mentioned, raw RSSI values are completely useless and unreliable / unpredictable with TBS Crossfire and ExpressLRS which is why they should just be switched off / disabled to avoid causing you any unnecessary stress while flying. RSSI dBm, LQ, and SNR are the only meaningful values when using Crossfire/ExpressLRS.