[Elecraft] Dummy load for KPA3?

[Ron D'Eau Claire]

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: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] 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