>
>Jim says:
>
>> >I am pondering ways of actually measuring the efficiencies of these
>> tuners, >but am not sure how to proceed.
>>
>>
>measure the load impedance, measure the current with a thermo ammeter.
>Calibrate the thermoammeter with DC: measure its RF resistance (not easy!)
>at the frequency in question, ,measure the DC resistance and calculate a
>correction factor. Taking into account the inaccuracies, and the fact that
>the tuner should hopefully be 98% efficient or better, you may well find
>that the measurements tell you that the tuner is really an amplifier!
>
>Seriously, I think the best way to get an idea of tuner efficiency is
>temperature rise after ten minutes of key down at full power. And if the
>Delrin catches fire before then, you know it ain't that efficient..........
>
Unsubstantiated rumour has it that in the ARRL lab test of the MFJ "3kW"
tuner Delrin ignition occurred at c. 30% of the mfg.-rated power level.
>
- later, Peter
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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