[k3] Wattmeter calibration

Posted by GW0ETF on Jun 27, 2008; 1:30pm
URL: http://elecraft.85.s1.nabble.com/k3-Wattmeter-calibration-tp365927.html

Finally I got round to checking the wattmeter calibration as I've felt it's been giving out power levels below what the wattmeter on the front panel reports ever since I've had it.

First alerted when my Acom 1000 seemed to giving low output until I saw the amp's input reporting a significantly lower driving power eg 35w as against a K3 setting of 45w into a dummy load. Also 2 independant power meters seemed to agree even though admittedly they weren't lab standard.

So I did the configuration while measuring voltage across a dummy load with my 40MHz 'scope and found I needed to wind the <WMTR HP> setting way down to minimum (010) to get the power up to 50 watts on the 'scope (and yes I did remember the RMS to peak conversion ;-). Seeing that the default setting is 100 I thought I might ask others what setting seems to be the norm.

Needless to say I've not noticed anything odd about running 80 or 85 watts instead of 100 these past few months but (wrong) numbers do have a habit of bugging you eventually....

73, Stewart Rolfe, GW0ETF (K3 145)