[Elecraft] Need to select a dummy load for K3 TX calibration...(advice?)

[WILLIS COOKE]

Jeff, I would consider an ohm meter reading of a non-inductive resistor to be a better indicator of low SWR than any available SWR meter including the famous Bird (available since about 1940 or before).  My MFJ-989C tuner includes a dummy load rated at 300 watts.  It appears identical to the 50 ohm resistor in my 35 year old Heath Cantenna but without the can of cooling oil.  I also have a 15 watt dummy load that I bought from Radio Shack about 20 years ago that measures 50 or 51 ohms.  I would consider any of these good enough to calibrate a watt meter or an SWR meter.  Rectifying and measuring the RF voltage will probably induce more error than the resistor.
 Willis 'Cookie' Cooke 
K5EWJ 




________________________________
From: "Jeff Hall, W6EZY" <w6ezy at arrl.net>
To: elecraft at mailman.qth.net
Sent: Tue, February 23, 2010 12:13:39 PM
Subject: [Elecraft] Need to select a dummy load for K3 TX calibration...(advice?)

Hello all,

I need help picking out a proper dummy load to use for calibrating my new
K3.  HRO is just up the road and they carry some of the less expensive MFJ
dummy loads -- would these be sufficient? Not looking to spend a lot of
money, but don't want to buy junk either.  What factors should I consider?
I'm assuming oil-cooled dummy loads are more robust, while air-cooled loads
are more compact, but you have to be more careful when operating or they can
burn up more easily.  The K3 manual says this is just a 5W test and I need a
load with low VSWR from 160 to 6.  What is considered "low" SWR? Anything
under 1:5?

If I can get by with the MFJ-260 for just $40, that sounds reasonable to me.

73 de Jeff, W6EZY
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