buy a real rf power meter from HP / agilent.
When i was working in the fab we had a Bird meter and a huge dummy load to check the 13.56MHz RF amplifiers for the plasma etchers. there was procedure to align those , check that the automatic matching network was doing its thing. Those things cranked out 1500 to 2000 watts. The control voltage was 0 to 10 volts and you needed to do a gain setting so the etcher could commandeer the right power. it also had an on-board power meter so you had to align that as well.
We had issues getting the etchers aligned to each other. Throw out the Bird crap and get a real power meter. You can't read that analog meter properly. is it 1.5 ? 1.6 ? 1.55 ? with a digital power meter you know what you are looking at.
Are figures power, or VSWR? if the former, they are all less than 0.5 dB different, if the latter, they represent 1.33% difference in reflected power, or 1.24 dB difference in Return loss.
Digital meters? Bird makes one, too, but it all depends on the resolution of the ADC.
A better solution would be a Spectrum analyser, & a cable probe.
Some Transmitters used in an ISM had a bunch of amplifiers all paralleled through combiners, with the resulting higher powered output in turn combined with another similar group of amplifiers.
The designers (in the PRC) had "scrimped" a bit on the "imbalance loads", which which would "cook up" if there was sufficient imbalance between the amps, this in turn, would increase the imbalance between the groups, probably cooking more loads, & often, the LDMOS devices.
The power output control would try to make for the drop in power, by increasing the drive to all of them, ultimately destroying at least one LDMOS device.
Turns out, the "rent an EEs" in the dear old People's Republic had made no attempt to match the freq response ofthe individual amps, so it was left to us.
With a SA, a tracking generator, a directional coupler saved from landfill at my previous work, & a nice big test load, we got them tuned to within 0.5dB---no more blown up devices!