[Milsurplus] Shade-Tree Scope Calibration

[Kenneth G. Gordon]

On 10 Oct 2020 at 6:53, David Stinson wrote:

> I have three or four Wattmeters around here
> and none of them agree with each other.
> One Drake is connected to a Johnson Viking II
> with AM 270 V PTP output and the meter says
> the carrier is only 45 Watts.... Uhhh, no...

Lessee.....if your load on the Viking II is exactly 50 ohms, then that 270 V PTP pencils out to 
1458 PTP-watts, which is a tad high.

I am using P=IE and I=E/R, so P=E^2/R = 270*270/50=1458.

But PTP is 1.414*Avg, so dividing 1458/1.414 we get 1031 watts average power, which, 
again, is a tad high for a pair of either 4D32s or 6146s. ;-)

Now admittedly, the forumlae above are for DC, yet they have served me for many years to 
get a fairly close approximation of what is being measured.

At this point, I would trust the Drake wattmeter.

You might connect all three of your wattmeters in series and compare their readings, but I'll 
bet they aren't all that different from one another.

Seems to me that your PTP reading is off by a large factor, but others here are far more 
knowledgeable about these matters than I am, so I gladly defer to them.

Ken W7EKB