We were discussing about the output power of the RAK4631 and it has been improved in version 2.0.13 it seems.
That leads me to also do power measurement of the T-Beam, the 433 MHz version again.
Even with version 2.0.13 i’m getting just about 8 mW or 9 dBm. However it should be 20 dBm! Even when i set lora.tx_power 22, there is no difference.
So, at 20 dBm, i’m missing 11 dB of signal. Could this be a FW issue?
During the measurement the output was correctly terminated with 50 Ohm.
The limit for 433 is 12db
I know, but not if you enable meshtastic --set-ham ham, at least during the measurement.
The ham mode is not well tested on 433, have you verified that it does anything? Seems like you are seeing 12db over and over.
Well, first: How to set the tx power to more than 12 dBm on 433 MHz - #7 by SR7673
And then: Remote Node Administration does not work, somehow - #31 by SR7673
So, i DID measure 20 dBm today… …but just with the RAK4631 under V2.0.13. However not on the T-Beam, even with 2.0.13. What’s why i started that thread.
Is power over 12db allowed in Europe even if you are a ham? Seems like it is 12.15db max on 433 without any exclusions.
This is irrelevant when discussing the question of an eventual to low output power, here, in the above example 9 dBm instead of 20 dBm.
But, as i explained, it is not useful to limit a TX power when there is no regulation for a maximum TX power but for a maximum ERP.
As long as you transmit into a dummy-load (internal 50 Ohm of the oscilloscope) or if you have cable losses of many dB, you are still within the limits. This is why there should be no 12 dBm limit at all! This was my initial recommendation. I could have 10 dB losses and with 20 dBm instead of 12 dBm i could compensate at least 8 dB of those 10 dB.
So maybe we can now focus on the question: Why is the output of the T-Beam just 9 dBm instead of 20 dBm. People are doing a lot of effort to improve their signal, and 11 dB more or less is a big difference.
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It is limited in the firmware, and to date I have not seen anyone that was convinced by your opinion on the regulations so it remains at 12db. You have a strong opinion here, does not make it a bug.
I didn’t say it is a bug. I asked why the power is just 9 dBm instead of 20 dBm, when set to 20 dBm.
And replacing “12” by “22” in line 30 of RadioInterface.cpp and re-compiling on your own also does not make it a bug.
And there may be people beeing convinced by my argumentation who do not reply to this discussion. Actually it is the only argumentation that makes sense! Let me give an analogy: If someone says “Your car must not be stronger than 100 kW because you must not drive faster than 100 km/h” That is not useful.
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In a car, the end user can see its speed at all times. You can’t assume everyone will measure the ERP of their device and adjust the Tx power to stay within the limit.
According to its FCC report, the T-Beam’s maximum conducted power (although at 915MHz) was only 11dBm.
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That’s right. But then, just set the default value to 12 dBm and allow a maximum of 20 dBm. Then, the advanced user may decide to set it to 20 dBm, if he has 8 dB cable losses to compensate.
When coming back to the car: In the car, the end user can decide to drive faster than 100 km/h even if this is not allowed. Actually this is what you see on the streets each day. It is the drivers decision, he is responsible, not the car manufacturer.
For me it doesn’t matter at all, my FW does not have this limitation any more. But others may suffer from an unnecessary limitation that slows down the mesh, if signals are on the limit. 8 dB can make a difference from “impossible” to “easily”, you know.
BTW, on 866 MHz: If the legal limit is 27 dBm ERP (ERP, not TX power!!!) and someone uses an antenna with 8 dB gain and the node directly connected to the antenna feed point, you know, the then ERP is 35 dBm! And this is above the limit! You can’t avoid this by firmware. And people ARE using high gain antennas at the maximum power setting. Do we want to bet? Because:
But again, this is not the reason why this thread was started.
We can continue endlessly here, but actually all has been said and explained multiple times.
In the end, the output power stays unexpectedly low on the T-Beam.
That’s why I included a link to the FCC report, it seems a hardware limitation.
OK, thanks. So that’s the first on-topic reply in that thread 
Well, see: http://www.lilygo.cn/claprod_view.aspx?TypeId=62&Id=1281&FId=t28:62:28
LORA
Product Description
Working voltage: 1.8~3.7v
Acceptable current：10~14mA
Transmit current: 120mA@+20dBm
90mA@+17dBm
29mA@+13dBm
Operating frequency: 433/470MHz(433HMz version) /868M/915M(868MHz version)
Transmit power: +20dBm
Today I measured the output power as a function of the requested power for the T-Beam V1.1 at 2.0.13
Requested [dBm] | Measured [dBm]
22 | 9
20 | 9
17 | 9
13 | 6.6
10 | 3.6
7 | 0.55
6 | 0
3 | -2.8
0 = default value
In the other discussion i read about differences with V2.0.5. However on the T-Beam there is no difference with 2.0.5.
Clearly an issue lowering the performance.
BTW a TTGO Lora 2.1_1.6 produces 18.7 dBm when set to 20 dBm on V2.0.13. So this is satisfying and may be close to the precision of the measurement.
It seems to be a specific T-Beam problem!
ui thats interesting…
i am really having too low range on many devices.
its quite dissapointing, when i expect 10km range but only get 100-200m range
have you tested some more different firmwares on the t -beam?
maybe there is one 2.x version that gives better results?
Were all of these readings with ham enabled?
No, just 2.0.13 and 2.0.5. That should be enough. The error has to be found. I’m still not in the files…
Consider, there are a number of reasons why you can get just low distances!:
-Noisy environment
-No line of sight or to much shield / attenuation by walls etc. 433 MHz is less critical than 868 MHz here!
-An inefficient antenna
-False polarisation of antennas
…and more…
I have removed the power limit for non-ham settings. So it is not necessary to use the ham mode. But please, don’t start the “law and order” discussion for a 3rd time. It has been discussed above.
Ah, got it. Good luck on your adventure then.
on t-beam,
maybe you can try a 2.0.0 firmware ?
and also a 1.2.xx
i will do that later, but i can only read out the rssi on some receiving device…