Don: I've purchased several surplus 75 watt high quality terminations from Ridge Equipment. These are cell site pulls, and are flat from DC up to 1 GHz plus and sell for $11.95. For a small amount more, Ridge will give you a return loss sweep.
https://www.ridgeequipment.com/store/dummyloads.html is the URL for their loads page. Sometimes they will have Decibel Products 100 watt loads that, for ham purposes, are really 150 or 200 watt loads, but I don't see any listed at the moment. The 75 watt loads are OK at 75 watts but I would not push them past 100 or so watts for long periods. As I say, I have a couple of these and recommend them. Sure a lot better than the Heath Cantenna I built 40 years ago--and they don't leak. Jack K8ZOA Don Wilhelm wrote: > Steve, > > Your "confession" should be preserved in bold type for others to heed > and lessons to be learned. > > Attempting to do calibrations with 'almost good enough' dummy loads (or > other equipment too) will result in 'funny behavior' - one cannot obtain > precision results with 'almost good enough' equipment. > > An accurate dummy load is the basis for many amateur measurements and > calibrations. 1% 50 ohm dummy loads are not difficult to come by. A > 100 watt dummy load can be built from a thick film power resistor > (Caddock MP9100-50), a heat sink and a BNC, UHF, or N connector. These > 50 ohm 1% resistors, when mounted on a heat sink with zero length leads > to the connector, will be flat up to 200 MHz or more depending on the > construction techniques. That kind of dummy load and a precision > voltage reference (along with some basic math) have become the basis for > calibrating other equipment on my workbench. I practice the "trust no > measurement tool until it has proven its accuracy" rule. > > Good calibrated equipment does not need to be expensive, nor of > laboratory quality, but it must be used intelligently with respect for > its shortcomings. > > 73, > Don W3FPR > > > list1 wrote: > >> Hi Everyone, >> >> OK I seemed to have "removed" the problem. >> >> I added 11 small resistors in parallel to my MFJ 949E dummy load to change >> its resistance from about 56.5 Ohms to close to 50.0 Ohms. I then ran the >> "Calibrate Transmitter Gain" procedure from the configuration Menu of the K3 >> utility. Now I can talk with 100 Watts and 6 bars of ALC all the time >> regardless of the temperature of the radio. No more fiddling with the Mic >> gain. Changing the Mic gain affects the power out and ALC reading now as >> expected. >> >> I think when I built my K3 I skipped the "TX Gain Calibration" step. I may >> have thought that it was optional like the Wattmeter calibration, but with >> my dummy load being off I think I was afraid that I would do more harm then >> good. >> >> I can now see how some people have problems with the K3 by not following >> instructions. I am a bit amazed the radio worked as well as it did in spite >> of the "loose nut in operator's chair" syndrome I was experiencing. >> >> OK, now to have even more fun with the radio, now that is it perfect. >> >> Steve, W2MY >> >> _______________________________________________ >> Elecraft mailing list >> Post to: [email protected] >> 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 - http://www.avg.com >> Version: 8.0.176 / Virus Database: 270.10.9/1900 - Release Date: 1/18/2009 >> 12:11 PM >> >> >> > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > 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 > > _______________________________________________ Elecraft mailing list Post to: [email protected] 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
