The SDR1000 displays power from one of two sources. Calculated and measured.
'Peak power' is calculated from the audio. You can verify this by disconnecting the SDR hardware and watching the meter with only the s'ware running. 'Fwd' and 'Rev' are measured on the 100W PA board. If you own the 1W SDR there is no Fwd/Rev display. On the 100W radios a rectified sample of the Fwd/Rev voltage is captured by a single analog to digital converter. A sample is taken when the software asks for one. For SSB it may happen while the output is zero or at a peak, but statistically most likely somewhere in between. This is why readings are usually lower than expected. On CW key down all samples are at the peak due to the constant output and the reading is what you expect. Also, because the ADC makes a fwd measurement reports the results and then makes a rev measurement, the results can only be used to calculate SWR for a constant envelope signal. I'm sure the calculated 'Peak Pow' was an attempt to overcome the limitation of the hardware sampling ADC power detection. Since I own a 1W SDR without power measurement hardware, I homebrewed Gerald's circuit onto a small board and added a few components to allow hardware peak detection. Now I can read actual peak fwd and rev power from my linear amp during SSB and AM. Plus SWR. I can provide the schematic and Eagle artwork for those interested. On the 100W radios I'm pretty sure peak detection can easily be accomplished by adding a resistor and capacitor for both fwd and rev paths. 73, John k2ox -------------------------------------------------------------------------- Now, would someone please explain to me why I still see 100+ watts on the peak power meter of the SDR while the external wattmeter peak power reads about half that? Also, please tell me why I should be happy with half the power I used to put out. I assume the answer will be something like "you were overdriving and distorted before, now you are not". The signal reports I got were nothing like that, I might add. Sorry to pose questions which may be obvious to most, but I really would like to know. Gary
