[Elecraft] KX3 and Data modes

[Edward R. Cole]

OK, I guess I need to repeat what I said.  The 25H is SPECIAL order 
from Radiodan W7RF
<<mailto:rfpower at radiodan.com>rfpower at radiodan.com>, who has the 
ability to run NBS traceable calibration on these elements.

Any Bird element can be modified to a different power range (if you 
do a search you should find some sites that talk to this).  But most 
of us do not want to dig into one that far.

I think the wrong impression has been taken of Bird's statement of 
accuracy.  I doubt the inaccuracy is a fixed amount that is the same 
at any reading.  More likely Bird does its calibrations at full scale 
and this is the accuracy that they will warrantee.  Seem more 
reasonable that the error is relative to the level of the 
reading.  The actual adjustment is a variable cap inside the 
element.  That and a resistor determine the level the element functions at.

But that being said, I have no proof the element in question is any 
better than reading 25w +/- 1.25w.  Ideally, I would have sent the 
meter to Radiodan to be calibrated with the element.  Then he could 
have specified what the accuracy was for the calibration.

But this is a brand-new element, freshly calibrated.  Should I doubt 
it in favor of my 35 year old 100H element?  Especially since 
resolution of reading 12w is much worse on the 100 scale than on the 25 scale.

There is only one way for me to determine what the accuracy 
is.   That is by observing the waveform across the dummy load with my 
scope, calculating Vrms from the peak-peak voltage and using that to 
determine power using V^2/R, assuming the load is not reactive.  Well 
I might do that out of curiosity.   That is probably the most 
accurate way for most hams to measure power (unless you are very rich 
and own a calorimeter).  I did power measurement at 500-KHz by using 
my scope since I have no elements that work below 2-MHz.  My 100w 
500-KHz transmitter is equipped with an RF ammeter for 
measuring/monitoring power.

For normal daily ham measurements I am willing to assume that the new 
element is my most accurate.  Will it matter much if I am off 
1.25w?  BTW it could be better than that.  That is the worse-case 
specification.



73, Ed - KL7UW, WD2XSH/45
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