[Elecraft] Dummy loads for dummies

[Mel Farrer]

Yes, and you should test the dummy load at the highest frequency you will be using it.  Even leaded non-inductive resistors will have a reactive component at higher frequencies.
Frankly, I usually test them above the max frequency I intend to use it to not have any concern about error.

Mel,  K6KBE


      From: Ryan Noguchi via Elecraft <elecraft at mailman.qth.net>
 To: Paul C <paulc22 at sbcglobal.net>; "elecraft at mailman.qth.net" <elecraft at mailman.qth.net> 
 Sent: Tuesday, December 27, 2016 8:16 AM
 Subject: Re: [Elecraft] Dummy loads for dummies
   
>I made my own dummy load last night from two 100 ohm resistors wired in parallel.  They are rated for 10 watts each and look like little bricks.  I measured the resistance at 51 ohms.  Do you think this is close enough or should I reduce it to 50?



>Paul KG5KXG


If your impedance is really 51 ohms, that's an SWR of 1.02. If your antenna had an SWR of 1.02, would you trim it to get to 1.00, fire up your tuner, or just start operating?

However, some of those resistors that look like bricks are really coils (inductors) inside, which produce a higher impedance than the DC resistance. Under RF excitation, that dummy load may be well above 51 ohms impedance. 

73, Ryan AI6DO  
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