[Elecraft] KPA1500 Linearity

[Don Wilhelm]

John,

You are exactly right for bring that factor to attention.  Typically 
wattmeters use diodes in their detectors, and the response will vary by 
frequency and by the power level.

I would trust only something that has been calibrated to NIST traceable 
standards.  The Telepost LP-100 is one example (and those are used on 
many Elecraft test benches).

While 10% is an OK deviation for amateur purposes, two wattmeters each 
with 10% accuracy can lead to a 20% error in the final measurements.

It is too easy to jump to conclusions by not considering the potential 
errors in measurement accuracy.  If you want 5% accuracy in your 
conclusions, your measurement tools should be accurate to 0.5% - a far 
stretch for wattmeters as we know them.

73,
Don W3FPR

On 6/19/2018 6:25 PM, John Oppenheimer wrote:
> Hi Scott,
> 
> I wonder how the linearity of the two power meters was evaluated?
> 
> Some years ago I checked the K3 and KX3 power meter against two other
> meters. They were just within 10%
> http://www.kn5l.net/Elecraft/Power.html