[Amps] Bird Element Calibration?

[G3rzp@aol.com]

For real fun, how do you measure the power (with what accuracy?) into a  load 
such as marine antenna at 2MHz? The dummy load is typically 10 ohms in  
series with 250pF: a DC calorimetric method might do to calibrate the resistive  
part, but the RF and DC resistances are probably slightly different. How much  
loss is there in the capacitor? If you put it on a network analyser, how good 
is  the answer at this return loss? How accurate is a thermocouple meter? The 
books  say that you can calibrate a thermocouple with DC, but that ignores skin 
 effects, which tend to make it read slightly high at RF. I believe 
manufacturers  actually compensated for this by putting a slightly higher figure on the 
scale  for applications where it mattered - which most of the time, it 
doesn't.
 
I have a very hard time with people who insist on quoting numbers to  
emaningless digits - like 2 decimal places of dBs, when most of the time,  they'll be 
lucky to have measurements to better than 1 dB anyway. But they wil  do it, 
because the digital readout gives them great resolution!
 
73
 
Peter G3RZP