HL2 and the Neptune PA

[Heiko Amft]

I use a HL2 in combination with the Neptune PA 100W. There are issues with this PA in mode SSB and FT8, in this cases sometimes the frequency detection for the automatic switch of the LPF failed and the PA switched off. That is the short version, we had a longer discussion at the HL2 Facebook group I won't repeat here again all.

As my solution I replaced the original PA control with my own ESP32 and add or better replace the LPF switching based at the bandvoltage option of HL2.

I publish all here: https://github.com/dl1bz/NepControl100W

This all fixed the issues with the Neptune in SSB and/or digimodes like FT8.
The Neptune works perfect now after my mod, no more issues are detected.

73 Heiko, DL1BZ

[Jürgen Weißmann (7ii)]

Do you use SparkSDR? 

[Heiko Amft]

No, I use only Thetis.
But anyway, my issue is fixed and gone (and it won't come back after my mod).
The second reason for this mod was an implementation for remote work, which I need. Two things - one solution.

[Pascal PBY]

I’ve never experienced this fault with my Neptune 50W, which I bought in March 2026.
SSB, FT8, VarAC, etc. – no problems at all.
73

[Ron Lewkowicz]

I believe this issue was fixed by the manufacturer at some point after this thread was started.  

[Claude]

I also run both 50 and 100 neptune amps and there is a firmware update, you will require a st-link v2 programmer over usb and the owner will be able to push the update to your amp by having a remote session on your computer, he has done both amps and all is good with mines.