VK3AQZ RF power meter (RFPM1) – filter response example

This article shows use of Lou Destefano’s (VK3AQZ) VK3AQZ RF power meter (RFPM1) to plot the response of a 144MHz filter.


Above, the RFPM1 as used.

Screenshot - 24_11_2014 , 10_29_43

Above, the test setup. The filter (DUT) is connected between a standard signal generator (SSG), and the RFPM1 connected to the filter output. A DVM recorded the DC voltage on the ‘CAL’ terminals of the RFPM1. A series of measurements was made from 140 to 148MHz and the results calculated and plotted in Excel.

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Above, the results of the measurements.

In this case, three measurements at each frequency were averaged, and measurements made every 100kHz from 140 to 148MHz, 81*3 or 243 measurements in all using automation, but the same outcome can be achieved by careful manual measurement and recording.

The filter has a midband attenuation of 0.8dB, a  3dB bandwidth of 920kHz, and thefore Q of 156.

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