Sunday, January 1, 2012

Propeller on 30m QRSS - Output Power

First - Happy New Year to Everyone, I hope all is well, or as good as it can be.

Another first - this is my first electronic measurement of the year. Julian - G4ILO ask (via comments) "what is the output power" of the Propeller 30m QRSS and low pass filter circuit.?

I do not have a power meter that measures that low, but I measured 1.1V p-p across an accurate non-inductive 50 ohm load. With P=(Epp/2x.707)^2/R, the measure power is; (1.1÷2×.707)^2÷50 = 3mW.

Scale = .5v / Div
I still need to measure the harmonic content, my friend Jeff - KO7M has a Spectrum Analyzer that I will use to report the results.

But, looking at the ragged output waveform, I am becoming less hopeful that the Propeller will be useful for RF generation for radio work. The Propeller may be relegated to just control of other oscillators and/or displays.

Note: I would have expected more measured output voltage, because the Propeller is sourcing from an active 3.3V CMOS circuit. I need to investigate more.


1 comment:

  1. Hi Eldon,
    I am doing some work to use the Propeller as an 80m transmitter:

    You might be interested to know that I got maximum power transfer from one Prop pin into a 82Ohm load. So I suspect if you redesign your lowpass filter then you will see (a little) more than 3mW RF output power.

    My ultimate goal is to be on-air without an additional PA. Just the Propeller + LPF.