Heltec v4 high noise floor

[Joebobbers]

after updating from 1.17.0 to 1.17.1 the noise floor went from -108db to -86db

[GreenFruit1]

Same happened to me

[vaizki]

There were FEM LNA activation persistence fixes in 1.17.1 .. try:

set radio.fem.rxgain off

to see if your LNA was turned on and raised the noise floor. LNA also amplifies noise, the "low noise" just means it does not introduce significant noise of its own.

[XTZnig]

Can agree! Have the Same Problem with my Heltec v4. Think it is a Hardware issue.

[GreenFruit1]

There were FEM LNA activation persistence fixes in 1.17.1 .. try:

set radio.fem.rxgain off

to see if your LNA was turned on and raised the noise floor. LNA also amplifies noise, the "low noise" just means it does not introduce significant noise of its own.

Might be a stupid question but how can i run commands on a companion node

[smiller11]

Similar issue in the Heltec T096. The default for the FEM LNA in companion v1.16 seemed to be off (hence the -110 to -115 noise floor) and now hard-coded to on in companion 1.17.1 (hence the 20 dB higher figure.) The problem is, the LNA isn't necessarily a positive factor and really should only be used when the receiver is noise-limited, otherwise it can negatively impact dynamic range. Basically the LNA should be user selectable on/off, or if that can't be done then most are probably better with the prior v1.16 default of off.

[vaizki]

Might be a stupid question but how can i run commands on a companion node

It is not a stupid question at all, you can't run CLI commands on a companion. Somehow I missed the whole companion part and was talking about repeaters, sorry.

Went throught the companion source, no way to disable FEM LNA on it (now). I think your only option for now is to compile the firmware yourself after patching _prefs.radio_fem_rxgain = 0 ..

EasySkyMesh powersaving firmware has femoff variants but no companion build for v4... https://github.com/IoTThinks/EasySkyMesh/releases