Digital Wattmeter Measurements


Accuracy in input signal level:


Date: 21 nov 2001, OZ2CPU Thomas
Generator: Boonton 102D
Aditional info: latest compensation, with good SWR
The Wattmeter goes up to +30dBm (1W), but my generator does not, so this is not a complete verify test.


The same test but in 1dB step. using special 1dB external step attenuator.


Information from the AD8307 Datasheet


The input signal level with no attenuation at all.
and the dB error shown at the voltage output of the AD8307.
This +1 dB error will only be readable if the input level is over +15 dBm at UHF.


The input signal level with no attenuation at all.
and the dB error shown at the voltage output of the AD8307.


The uncompensated frequency response is not so good.


Linarity -40 to -60 dBm input


Measured by OZ9MO, at 10Mhz.


The same measurement as a curve, thin line is what it shuld have been
Blue curve is the measured value, max error at -60 dBm is 2.5 dB !!


Freq. input compensation:


This is the final result, as discribed in the latest schematic
The input signal level is 0.0 dBm, Freq is changed and the dBm readout is recorded.
The Wattmeter was calibrated to show 0.0 at 10Mhz
Generator used: BOONTON 102D


Here is the same measurement, using a marconi generator.


Input impedance measurements:


Input return loss vs freq.


Input S-Plot