[Elecraft] K3s - 80W on 160

[Jim Brown]

On Fri,12/16/2016 9:27 PM, Gary Smith wrote:
> With the ATU in or out it gives 81W out on 160, SWR is 1.28
>
> All other bands except 6M give around 98W, 6M gives 87W
>
> Any ideas what might be causing the lower output on 160?

81W is 0.9 dB less than 100W; 87W is 0.6 dB less than 100W.  On 6M, it's 
probably a simple matter of efficiency -- power amps are slightly less 
efficient on 6M than on the lower bands.

And there may be a power calibration issue. There's a procedure in the 
manual for doing that.

Or even error in the power measurement itself. Few power meters are 
specified for better than 5%. Bird wattmeters are specified as 5% of 
full scale, and a condition of that is that the slug is in calibration. 
If, for example, you're using a 250W slug, accuracy is +/- 12.5W. I use 
an N8LP LP100A, which specifies 5% at any power level from 1W, and 
quotes 3% typical. 5% is 0.22 dB.  3% is 0.13 dB.

Low DC voltage can also be an issue, either due to the power supply 
itself or IR loss in the power cable (or even the connector(s). Use the 
built-in metering function to check DC voltage with just the RX running 
and keydown. Short, fat copper is your friend. :)

73, Jim K9YC