Transmit power option

Is there any option to adjust the transmit power manually for ham licensed operators? I know that the web interface provides this, but I cannot change it to more than 13dBm even if I set the HAM option.
I did measure the power output and it was indeed 22mW (~13dBm).
The Lora modules (Tbeams) are able to provide 100mW as far as I know.


Limits are also potentially in place on the LoRa module and in the RadioLib library we use, I don’t think it is possible to increase the tx power of a tbeam beyond 22mW

For sure, the SX1276 chip has 20dBm output power. I’m pretty sure that the output was higher in 1.2 although I haven’t measure it (yet).

I worked with LoRa’s SX1276 many years ago testing possible links at many kilometers away, interfacing directly on SPI. I can confirm that they are able to output 100mW.
We also have a Ham CW (similar to OOK modulation) beacon running on a communication tower, using a hack on the SX1276 that transmits morse telemetry 24/7 and outputs 100mW of RF power.


Yes, the tx_power figure represents a dbm value in the firmware.
So as you noted, a T-Beam with an SX1276 radio would max out at 20dbm (100mw), and an SX1262 radio based one would be 22dbm (160mw).

If possible, please expose the tx_power variable to the user through an option setting. And of course, available only for licensed operators :smiling_face:

Thank you.

It actually already should be available to set manually via the python cli. For instance:

meshtastic --set lora.tx_power 22

One note, we automatically set this to the maximum power for the region when lora.region is first set, for instance 30(dbm) in the US. Beyond that, we also limit based on the hardware capabilities detected on the device so as not to allow an inexperienced use to set the power to beyond the radio module’s limitations. So the SX1276 gets limited to 20, and the SX1262 gets limited to 22 for instance.

It works. I can reach maximum power, but check out my measurements:
Set value - Measured power
20 - 105mW(20.2dBm)
17 - 105mW(20.2dBm)
15 - 105mW(20.2dBm)
13 - 105mW(20.2dBm)
12 - 105mW(20.2dBm)
11 - 84mW(19.2dBm)
10 - 68mW(18.3dBm)
9 - 54mW(17.3dBm)
8 - 44mW(16.4dBm)
6 - 29mW(14.6dBm)
4 - 20mW(13.0dBm)
2 - 13mW(11.1dBm)

Looks like there’s an offset ~8dB between the set value and the actual power. For sure there’s something to be fixed here :slight_smile:

Thanx again for the help!

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Hmmm, Interesting. Can you run a meshtastic --noproto and hunt down this line in the output?

That should be the final transmit power for the radio. Other than that, it’s possible there is a bug in RadioLib which we use for interfacing with all of the various radios, but I doubt that.

If I run a 10dBm set power command I get this in the output log:

But if I run a 17dBm command, I’m getting this:

I measured the output again just to be sure and it really is 20dBm for any given value above 12.

Hey, I’ve got the same problems here, with my LILYGO T-Beam v1.1.
Also tried all the steps above. Can’t set the TX Power to above 12dBm.

I’ve got the opposite problem. I’ve set the power to 22 yet the actual output seems to be 12.

Range is severely impacted for now.

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Well, for my T-Beams, in 1.2 version, the max. measured power is ~60mW and in 1.3/2.0 is ~100mW.
The LoRa chip is clearly capable of outputting 100mW. Indeed, setting the power in its registers is a little ambiguous I must admit. Possibly the library used in Meshtastic is not perfect…
There’s also an extra feature built in the chip to protect the final RF stage from overloading called “current limiter”. Problems might be related to that as well…

I have a Tbeam and Heltec which should both support 20dbm. When testing different power levels in the web client via serial it looks like maximum power (measured with an analog rssi meter) is reached with a setting of 17 on the Heltec and 18 on the tbeam. Setting power higher than this doesn’t appear to increase signal strength.

I understand there is a limit set in the library which can override the main TX power setting. How can I check these values?

Also, is there any hardware available for meshtastic capable of running closer to the 1 watt maximum (US) ? Performance would be amazing with a device pushing 30dbm.

Not closer to 1W, but exceeding 1W with HAM license :grinning:
Station G1 could touch 35dBm@915MHz

Very interesting. So a non-Ham could run this hardware as long as power into the antenna doesn’t exceed 30dbm correct? So you could dial in the pre-amp power to 8dbm (with no coax) and increase from there to compensate for any coax loss.

Yes, according to FCC’s regulations, your description is exactly correct.

From a hardware perspective, it is indeed possible to set higher than 30dBm and still use encrypted transmission, but this will violate FCC rules.