Most power meters display the average power unless a peak reading circuit is switched in.
An analoge meter cannot follow the RF waveform at an audio rate and display anything but an average of that 'complex' waveform.
A analoge meter's balistics has to be dampened to limit 'over swing' so becomes an average reading meter by nessitity, then every meter design used in a power meter may be different yet for displayed average value.
In peak reading mode if the meter design has it, it reads about 90% +/- of the real peak and holds that reading for some 'designed in' or sleightly adjustable time period. Again using the same 'dampened ' display meter.
As the articale by R.L. said, RMS is not a usefull value unless you use it to calculate the average or peak value.
Otherwise the meter would have to be designed to display RMS which would only be some other value on the meter face.
How much use or advantage would it be as opposed to the convention of average and peak power?
On SSB the peak and average is the most usefull.
.
On AM the peak power 'unmodulated' is the same as the 'carrier' value.
With modulation the average and peak goes upward at the audio rate so your back to average and peak reading again.
If the carrier were modulated 100%, this is the same as the carrier power x 4.
Or a 4 watt carrier modulated 100% is 4 x 4 = 16 watts peak envolope power.
RMS has little value.
Here is a little curve you may not know about.
On AM, if the meter circuit were to read both the positive and negitive AM swing values equally, there would be no carrier power movement indication on the power meter because the positive upswing = the negitive down swing leaving the average movement 'zero' as far as the 'meter rsponse' would be.
But because the meter circuit is built to respond to the positive swing, the circuit cuts off the negitive swing so the meter will move in one direction as far display goes.
.
SSB CB actually has a 12 watt peak limit that is 4 watts less then AM to be legal with both modes.
Now throw in a digital display and you quickly see that bar graph type displays are almost always used because using a number display would result in an unreadable value because of the fast number changes 'unless' it were slowed down intentionally, then it would still be an undesirable way to look at the varying signal.
With a bar graph, the total length of the indicating line against a calibrated face plate is the fastest way for a human to interpet the display value.
Here again of what value would an RMS value be, just for observation?
.
It's very much the same deal with horse power reading of a gas engine. It a calculated value using engine torque and rpm divided by 5252.
People got used to evaluating engine performance by seeing the HP figure when engine torque is the better indicator of performance.
Example of this is the engine of about the same displacement that has the higher torque output will pull weight faster and a heavier load than one just based on a HP figures alone.
An analoge meter cannot follow the RF waveform at an audio rate and display anything but an average of that 'complex' waveform.
A analoge meter's balistics has to be dampened to limit 'over swing' so becomes an average reading meter by nessitity, then every meter design used in a power meter may be different yet for displayed average value.
In peak reading mode if the meter design has it, it reads about 90% +/- of the real peak and holds that reading for some 'designed in' or sleightly adjustable time period. Again using the same 'dampened ' display meter.
As the articale by R.L. said, RMS is not a usefull value unless you use it to calculate the average or peak value.
Otherwise the meter would have to be designed to display RMS which would only be some other value on the meter face.
How much use or advantage would it be as opposed to the convention of average and peak power?
On SSB the peak and average is the most usefull.
.
On AM the peak power 'unmodulated' is the same as the 'carrier' value.
With modulation the average and peak goes upward at the audio rate so your back to average and peak reading again.
If the carrier were modulated 100%, this is the same as the carrier power x 4.
Or a 4 watt carrier modulated 100% is 4 x 4 = 16 watts peak envolope power.
RMS has little value.
Here is a little curve you may not know about.
On AM, if the meter circuit were to read both the positive and negitive AM swing values equally, there would be no carrier power movement indication on the power meter because the positive upswing = the negitive down swing leaving the average movement 'zero' as far as the 'meter rsponse' would be.
But because the meter circuit is built to respond to the positive swing, the circuit cuts off the negitive swing so the meter will move in one direction as far display goes.
.
SSB CB actually has a 12 watt peak limit that is 4 watts less then AM to be legal with both modes.
Now throw in a digital display and you quickly see that bar graph type displays are almost always used because using a number display would result in an unreadable value because of the fast number changes 'unless' it were slowed down intentionally, then it would still be an undesirable way to look at the varying signal.
With a bar graph, the total length of the indicating line against a calibrated face plate is the fastest way for a human to interpet the display value.
Here again of what value would an RMS value be, just for observation?
.
It's very much the same deal with horse power reading of a gas engine. It a calculated value using engine torque and rpm divided by 5252.
People got used to evaluating engine performance by seeing the HP figure when engine torque is the better indicator of performance.
Example of this is the engine of about the same displacement that has the higher torque output will pull weight faster and a heavier load than one just based on a HP figures alone.
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