A few thoughts,
Give them some distance. Then compare with and without ATC to see the difference.
As Tom/Luka stated, to really know what's going on, print out or send the radio._transmitLevel to watch it go down.
Also don't forget you need ATC on the receiving side (for feeback) and you need to send with retry or request ACKs otherwise the sender will never receive any ACK with feedback, so obviously it will not know how to dial power level.
Correct, you need 3 things:
Serial.print("My TX level:"); Serial.print(radio._transmitLevel,DEC);
This will print your level
Next thing is, your need to know RSSI on other side (node)
Serial.print(", RSSI:"); Serial.println(radio.getAckRSSI(),DEC);
This will give you your RSSI
and third thing you need is to set
This value is your target RSSI, which you want to get, by changing power level.
Also you need to keep in mind, if you are above your target RSSI and your power level is already on 0, your distance is closer than your minimal power level, you might need to think about turning of PA2, maybe even PA1 (on HW version only) and power boost register turned off and have only PA0 active
PA1 is up to 13dbm
PA1+PA2 is up to 17dBm
PA1+PA2 and boost up to 20dBm
unfortunately in default RFM69, all this things are turned on, not good for power consumption. Is there easy way to set those in sketch?