[Elecraft] K3 RF Power Meter Accuracy

[Don Wilhelm]

Jim,

What is the comparison power measurement into a 50 ohm dummy load. If 
your dummy load is not rated for upwards of 50 MHz, test it with an 
antenna analyzer.  Measurements made into an antenna are always suspect.

A variation of 20% between power meters are common, and 20 percent of 25 
watts is 5 watts - which would be 20 to 30 watts.  Your reported 39-40 
watts is outside that range, but since you are operating into an 
antenna, I would suspect that you are "within the ballpark".

If you have not calibrated the K3 wattmeter (see the manual calibration 
section, that could explain the difference.  Again I say that the 
calibration must be done with a 50 ohm non-reactive load to be valid.

73,
Don W3FPR

On 1/6/2013 10:30 PM, Jim Bennett wrote:
> I've been using my K3 #4359 now for several years w/o any issues. Just this past week I acquired an LDG AT-600ProII auto tuner and the matching M-600 analog meter. I calibrated the M-600 per the instructions. What I'm seeing is that the M-600 meter is showing me higher RF output than the K3's bar graph on most bands. As an example, after setting the KAT3 to Bypass, using the AT-600 to bring an antenna to a match (close to 1:1) with 5 watts out of the K3, I turn the K3 power output to 25 watts. A key-down on the K3 shows 25 watts on the K3 bar graph, but the M-600 tells me that the power is about 39-40 watts. It is like this on nearly all the bands, 160-10 meters. On 6 meters, the M-600 reads about 20% LOWER than the K3.
>
> I sent an email to LDG and asked them what's up - which is correct - the K3, or the LDG unit? Their response is that the K3 most likely is incorrect, as they calibrate their equipment with an Alpha 4500. That's a tad of an expensive meter, to say the least. Are the LDG folks tweaking me on this, or is that M-600 really more accurate than the RF bar graph on the K3?
>