> Does anyone use directional couplers and HP Power meters
> such as a 432A?
Yes, at VHF and above I use DC's and HP power meters and sensors
(E4418/4419) to check the accuracy of other meters. HP (er, Keysight) has
spreadsheets for calculating error/uncertainty given all of the parameters
(meter, sensor, power level, frequency, etc.). DC's and power meters are
pretty much the norm for measuring power in a transmission line in the
high-power TV broadcast world.
I also have a 1000 watt oil-cooled 30 dB attenuator (Electro Impulse) that
I've characterized on the VNA and can use that ahead of the HP
meters/sensors, particularly on HF. The attenuator has better than 20 dB
return loss from DC to about 900 MHz.
Arguably the most-accurate methods for measuring high-power RF are those
based on calorimetry.
I've played around with stacking Bird 43's in a line via barrel adapters to
look at the meter-to-meter variation (using the same slug in each). What I
found is that the dominant source of error is the slug, not the meter
itself. At full scale, checking each meter one at a time using the same
slug (and a 'blank' slug in all of the unused meters to try to keep the
thru-line Z constant), they were all very close. Note that this doesn't
confirm accuracy, only relative precision, and in that regard, I was
pleasantly suprised. When comparing multiple slugs of the same model in a
single meter, it was a different story...
--- Jeff WN3A
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