On Thu,9/17/2015 6:37 PM, Don Wilhelm wrote:
While a dummy load that has a power rating greater than your maximum transmit power is a worthwhile addition to any hamshack - at higher power levels, I do not see them being used as precision measurement devices, but only as a temporary load for the purposes of "tuning up" or operating into a dummy load for test purposes.
Remember also that dummy load ratings include a duty cycle. The cheap stuff has a very short duty cycle -- one might be rated 100W for 1 minute. :) It's all about heat -- do you get hot enough to damage it?
Duty cycle can be interpreted two ways. One is to use a series of dits to tune up, which gets you to full power but half the time. That's what I do. I just sold a nice little keyer-pulser that W2VJN used to make. Its duty cycle could be adjusted as low as 20%.
Another way to interpret it is how LONG you transmit into it. My big professional oil filled dummy load is rated 500W for a long time (don't remember the spec). I transmit dits (and even RTTY) into it at legal limit for a minute or so, and it doesn't overheat. And then I let it cool off.
73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
