[Amps] Time for New Power Meter

[Jeff DePolo]

>   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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