Jim, dummy loads are invariably rated for limited periods of time before they must be allowed to cool off. So a larger dummy load allows you to feed it power longer. For example, I have a 1.5 KW dummy load that will handle 1.5 kW, but for less than 10 seconds between cool-down periods. It'll handle 100 watts for ten minutes before needing to cool down.
A practical dummy load for Ham use is not a highly-precise load. Such loads are available at a price for lab work, but not needed to check a transmitter output in the real world. That said, be careful when buying a used load. Since they require cool-down periods, many loads are sold used after they have been overheated and the resistance element has been damaged. There are many built units available. I picked up an MFJ-264 years ago. It's rated at 1.5 KW, 1-650 MHz and still available new for under $80. You can "roll your own" these days too. Resistive elements are readily available. The biggest part of the project is providing a suitable heat sink. Tom, N0SS (SK) has notes and design suggestions for building a dummy load on his web site which is still active: http://www.n0ss.net/index_general.html Ron AC7AC -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Jim Miller Sent: Tuesday, February 07, 2012 7:11 AM To: Elecraft Reflector Subject: [Elecraft] Dummy load for KPA3? I'm considering adding the amp to my k3/10. I see a 50w dummy load is reqd for setup. Any recommendations? Should I get a 100w one instead? Build vs buy? 73 jim ab3cv ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
