[Elecraft] K3 RF Power Meter Accuracy

[Edward R Cole]

I would trust a Bird43 meter to be more accurate (but even they only 
claim 5% of full range).  I have compared my 1976 era Bird43 with one 
that is only a couple years old using the same element and had 10% 
disagreement in readings using a Bird dummy load.  My old meter read 
lower in power.

On another note I have measured the output of my K3 in TEST mode and 
1.0mw is pretty close when measured with a HP432A mw power meter.  I 
trust the K3 meter is as accurate as my Bird43.

Power readings into an antenna are relative and will vary with 
reactance of the load.  Not uncommon to see more output than the 
radio can deliver when into a reactive load.  All SWR meters are 
reading RF voltage on the line and that depends where on the line you 
look unless the load is perfectly resistive 50-ohms.

I spent about six weeks making coax line loss and matching 
measurements on my eme array in 2010.  Load variations drove me crazy 
with non repeatable measurements.  Only after carefully using the 
same test leads and loads was I able to get a satisfactory set of 
measurements (on all 8 antennas).  IN the end my line loss came out 
to 1.7 dB +/- 0.1 dB.  I did determine that I improved loss by about 
0.2 dB by replacement of bad cables.  That represents 5% of my power 
or 65w.  1.7 dB line loss means I get 68% of my 144-MHz transmit 
power to the antenna  (1000w for 1500w output).  The rest is warming 
my cables (LMR600 and 1-5/8 inch Heliax).

73, Ed - KL7UW