PTP products not broadcasting at full power

PTP650 BHs won't use the maximum transmit power, even on links that struggling.  They always seem to be 3 dBm below what the max is set to, and this was the case with previous PTP products as well.  I have asked a bunch of folks at Cambium what causes this, but it's always been a secondary question as part of a larger issue and I never got an answer.  Because of an increase in noise in our area, I now find myself really needing those extra few dBm on some of our links.

As an example, I'm looking at a PTP650 link which is right on the cusp between 16 QAM 0.87 and 64 QAM 0.75.  I'm hoping an extra dBm or two will be enough to stabilize it.  The max, mean, min, current transmit power is  25.0, 23.9, 23.0, 24.0 on one side and 27.0, 24.0, 24.0, 24.0 on the other.

What causes the BHs to not broadcast at a full 27 dBm, and what can I do to remedy that?


The maximum transmitter power depends on the modulation mode, changing from 27 dBm in BPSK to 23 dBm in 256QAM. Power is reduced in the higher efficiency modulation modes to minimise saturation in the RF power amplifiers, and to minimise vector error. This is a common technique used in licensed and unlicensed microwave radios.

When you configure 27 dBm, you're setting the maximum that the radio will use.

The power for each mode is listed in the User Guide under "System threshold, output power and link loss."

The only way you can guarantee 27 dBm all the time is to set maximum modulation mode to BPSK, which is probably not something you want to do.


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Gotcha.  Thanks for the reply!