transmit power measurement
transmit power measurement:
Measuring low power transmissions requires special equipment, and measuring short burst transmissions creates
its own problems.
A power level of 0 dBm corresponds to a power of 1 milliwatt. dB are logarithmic and additive, so an increase
of 3 db doubles power, and an increase of 10 dB is 10x the power. See chart below for 0-36 dBm watt values.
Radios often are capable of more than the max power allowed in your region. USA unlicensed limit is 30dBm.
After flashing meshtastic firmware you may find the default power has been reduced to something like 22dBm.
(some regions also have duty cycle and other limits)
A an example, many of the inexpensive Heltec radios are capable of a maximum of 21dBm (125-150mw)
It appears that I'm getting a consistent 75mW on my radios here. I may not always see 75 on the meter, but
it's trtying to report on a 100ms burst when its sample window is closer to 250ms so it may require several
transmissions for the meter to capture the full extent of the power in a burst.
I've found that most radios do two bursts on power-on, at about the +20 and +30 second points. The first
burst seems to be shorter and tends to measure low, while the second burst is more likely to get a good
capture. But this is a very cheap power meter so I'll take what I can get out of it.
My frequency counter measured 906.876 MHz, expected 906.875 (definitely close enough)
/wattmeter/athumb/Taidacent%20HP363%20Power%20Meter.jpg)
