[Elecraft] KPA1500 Linearity

[K9MA]

Yes, the linearity of the two power meters is suspect. However, the 
compression of interest is near the high end for that of both the 
KPA1500 and the K3, so I wouldn't expect their nonlinearity there to 
make much difference. Note that absolute accuracy isn't critical.

73,
Scott K9MA

On 6/19/2018 17:42, Don Wilhelm wrote:
> 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
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-- 
Scott  K9MA

k9ma at sdellington.us