Configure TX power = 30 dbm?

[K4KDR]

With a working 1W custom ESP32/LoRa board now (thanks to you & Bob-N6RFM!), I noticed that the default tinyGS "Power" parameter (5 dbm) did not take advantage of this device's power output capability.

Using the "Configure Parameters" screen on the tinyGS web GUI (direct LAN IP connection to the device), I entered a value of "30" on the Modem Startup line.
. .

.

However, after applying it, an error appears on the serial monitor:

failed, code 4294967283

... reviewing the tinyGS code (including libraries), I see the following comment in "lib/RadioLib/src/modules/SX126x/SX1268.h":

\brief Sets output power. Allowed values are in range from -9 to 22 dBm.

... indeed, the largest value that I can enter (with no error) on the 'Modem Startup' line in the web GUI is "22"

What steps are required to allow for a value of 30 dbm (i.e., 1W) to be used in this context?

Thanks!

[jgromes]

You can't enter 30 dBm directly into RadioLib configuration methods, since those are limited by the SX1268 limitations, in this case by the maximum output of the internal PA, which is 22 dBm.

Ebyte 400M30S has an external PA, labeled as H0606E - some Chinese wunderwaffe. Googling a bit yields this datasheet: https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/156/RELL-_2D00_-LDMOS.pdf

According to that, it should have a 19 dB gain (up until 13 dBm input), so to set 30 dBm on the output of the module, you have to set 11 dBm as the output from SX1268. I'm still trying to verify those numbers with an actual RF power meter, since this sort of parts always makes me suspicious.

[K4KDR]

Hello!

Any update on the proper way to use full TX power?

I see that the limits can be changed in /lib/RadioLib/src/modules/SX126x/SX1268.h ... but I don't have a watt meter to verify the device's output if it's set to '30' after adjusting that upper limit setting.

Thanks!

[jgromes]

As per my previous message, you don't set the SX1268 power output to 30 dBm when using the ebyte module. Instead, you have to set to the SX1268 power output in such a way that the external PA will output 30 dBm. The PA gain is 19 dB, so to get 30 dBm total power, you have to set SX1268 power to 11 dBm by calling setOutputPower(11);.

[K4KDR]

Ah, thanks so much! You had mentioned doing a verification to see if that really resulted in the desired max output, so I didn't know if that had been possible to check on yet.

Appreciate everything!

[jgromes]

Unfortunately not yet, I don't have access to a good RF power meter at the moment due to lockdown-induced logistics issues.

[farmaceuta777]

what is the smallest gain of these modules? (max is 30db (set 11) and min?

[ghost]

You can't enter 30 dBm directly into RadioLib configuration methods, since those are limited by the SX1268 limitations, in this case by the maximum output of the internal PA, which is 22 dBm.

Ebyte 400M30S has an external PA, labeled as H0606E - some Chinese wunderwaffe. Googling a bit yields this datasheet: https://e2e.ti.com/cfs-file/__key/communityserver-discussions-components-files/156/RELL-_2D00_-LDMOS.pdf

According to that, it should have a 19 dB gain (up until 13 dBm input), so to set 30 dBm on the output of the module, you have to set 11 dBm as the output from SX1268. I'm still trying to verify those numbers with an actual RF power meter, since this sort of parts always makes me suspicious.

If you set SX1268 output greater than 11dBm does it fry the board?

[jgromes]

@SlitheringMule it shouldn't, you just won't get much extra gain. You're also risking compromising the signal integrity, since you're out of the linear region of the gain curve.