My understanding is that the total radiated power of the LoRa module is a combination of
1) transmit power on the output stage (AT+TXP)
2) antenna gain (AT+ANT).
Valid values for AT+TXP are 0-20 (dB).
Valid values for AT+ANT are -128 to 127 (dBi), defaults to 3, which is the antenna that it’s certified for. The AT command document states that the AT+ANT is used to help adhere to transmit power regulation (FCC, etc..)
If you enter a really high value for antenna gain (say AT+ANT=15) and set the max AT+TXP=20, does the mDot actually dial down your transmit power (AT+TXP < 20) to meet FCC, despite your setting? In effect, the firmware is de-rating TXP based on what you enter for ANT?
I’m confused how this ANT value is useful. If we decide to save power by using a larger gain antenna, we’re going to need to go through the FCC certification anyways, in which case we’ll be tuning the TXP value down and probably don’t want the LoRa stack applying an ambiguous de-rating.
On the other hand, if we use a lower gain antenna than the certified 3dBi one, it doesn’t make a difference if we remember to modify ANT or keep it at the default, because no de-rating will occur. Is that right?