John, One must be careful not to zap the diode in the RF Probe - so measuring directly across the dummy load is good only up to 20 watts or so. A 'scope with a proper probe will handle the full 100 watts of the KPA100 easily. Builders may not have a known good 'scope, and the RF Probe method must be used with some intelligence - many folks do not know the accuracy of their dummy load at the frequency of operation - and both the 'scope and RF Probe methods are highly dependent on knowing the accuracy of the dummy load - it must be entirely resistive for accurate results.
Yes, I feel that my 'scope and 1% 50 ohm dummy load (checked for both R and X on several antenna analyzers) will provide better than 5% accuracy for any wattmeter that I calibrate by that method. Of course, I can do a more accurate job at 30 watts or lower because I can read the voltage differences on my 'scope face with greater precision (the 10 volts per division scale) and at higher power, I end up at the 20 or 50 volts per division scale and the interpolation becomes more coarse. 73, Don W3FPR > > I think this speaks somewhat to assumptions about what the k2 builder > will already have or purchase for the project. I already had a good > DMM which agrees in the areas we checked with a really good Fluke - no > fluke apparently. The manual for the KPA100 suggest you may have > problems if you callibrate with a bad wattmeter. Soooooo, if you can > use the rf probe which you build with the k2 kit and a DMM, why not > suggest this as an alternative method to anyone who suspects his > wattmeter is not good or (gasp) doesn't have one? Or am I all confused. > > Incidently 5087 works so well, I can't believe the range I get both in > and out on ssb 20, 40 & 80- meters with just the 23 foot whip. 73, > John KI4NGH > > _______________________________________________ > Elecraft mailing list > Post to: Elecraft@mailman.qth.net > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.1.375 / Virus Database: 267.15.12/266 - Release Date: 2/21/2006 > > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
