@tridge and @Yuri_Rage and other followers -
I appears I have solved this problem well enough - and also resolved the F9P RTK problem with GPS glitches.
The resolution to the SiK radio TxBuf saturation was to increase the Max Window parameter to 280. I still have a question out to RFDesigns for advice and clarification on maximizing throughput between radios - which should keep the transmission buffer at a minimum.
Here are the SiK radio settings I used:
The resolution to the GPS glitch issue during F9P RTK turns out NOT to be saturation of the transmission buffer - limiting the transmission of RTK corrections. Instead it was a firmware issue on the F9P receiver.
When I received the Holybro F9P receiver I uploaded the latest firmware - as it came with a firmware release that was 3 versions old. I saved the original parameters - but did not reload them.
I reverted back to the original F9P firmware version and reloaded the original parameters. That resolved the problem.
As an interesting aside - the parameters file that’s created when U-Center saves a receiver’s current parameters is tied to the version of firmware. You cannot upgrade the firmware, and reload the parameters from the older firmware version.
This creates a dependency on ArduPilot. Unless ArduPilot updates the uBlox parameters necessary for RTK, it’s dependent on a version of F9P firmware. It might work well enough to upgrade the firmware and to then change the F9P parameters manually with U-Center from the firmware defaults. But there’s no way to know what parameters should change - or to what values.
Unfortunately, the parameters file saved by U-Center is coded - you can’t read it to know what the settings were.
I’m going to close out my previous post on F9P RTK gps glitches by referencing this post - to avoid duplicating what I’ve entered here.
Here’s chart from a test flight - a simple climb in LOITER to 100 meters.