I’ve been tuning the gain on my system for a while, initially using gut feeling and seeing the impact on daily positions and aircraft reported.
More recently I’ve been using the excellent graphs1090 and during a spell of relatively flat propagation conditions I’ve more or less settled on my optimum gain setting.
In my case, at my particular location, --gain 20 gives the best results. I’m sure every other site will get a different optimum value.
However what I didn’t expect, is that a 1 db change on my gain manifests in such a noticeable CPU utilization pattern difference.
Before ~ 11.21 I was running with --gain 21 (notice the finegrain cpu utilisation up/down)
After ~ 11.21 my “optimal” --gain 20 was set (notice the much smoother CPU utilization!)…
Now I have no idea if this is just a graphing artifact or if the slightly higher messages > 3dBFS causes more processing for the CPU, but I do find this interesting nonetheless!
The graph for the message rate also appears smoother after the gain reduction and I certainly don’t suffer lower number of positions reported…
…or degraded weak ADS-B Signal Level performance:
To me it looks like the dynamic range is slightly better and cpu usage smoother.