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.
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| Scale = .5v / Div |
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.
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Hi Eldon,
ReplyDeleteI am doing some work to use the Propeller as an 80m transmitter:
http://forums.parallax.com/showthread.php?142364-Maximum-current-draw-per-I-O-pins
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.
Cheers,
ul5255.