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SWR meter as power meter
If it is the type where calibration varied with frequency, you could copy
what was done with some commercial instruments of the seventies, eg the Oskerblok. 1. Calibrate the sensitivity knob with a logging scale. 2. Add a power scale to the meter face. 3. Measure a set of points of sensitivity setting vs frequency where the meter scale is correctly calibrated for power. 4. Create an interpolated smooth graph as a lookup, and attach it to the instrument. Be prepared for significant linearity error at the low frequency end if you calibrated the meter for low fsd power. If it is a Bruene type sensor, the response should be reasonably flat within a frequency range which you must establish. The interesting thing with either type of sensor (and both are used in Bird elements, though the first type is frequency compensated), is that although the Pfwd and Pref power readings are of each of no value by themselves, the power in the line is Pfwd-Pref irrespective of the load impedance or line Zo. Owen |
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