Re: Pixie 2....The Bad News?....

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From: Robert J. Gobrick (rgobrick@public.compusult.nf.ca)
Date: Wed May 17 1995 - 09:25:12 EDT


Jim,

I will admit that I have not put my scope on the output of my 300 mw Pixie.
And also it's been a while since I calibrated my OHR QRP wattmeter.

I won't comment on the circuit as much to say that yous get what yous pay for.

Finally if you want to read a real "rain on the parade" article check out
Doug Demaws W1FB column in the latest issue of CQ magazine. He really gets
on the QRP designers about the inadequacy of the final tank circuit design
in their designs. It appears spectrally that the single and double stage
output networks are not so clean on second and third harmonic suppression -
look what this new design software is doing to our hobby....

Geez I wonder if my Pixie will chirp is the battery voltage gets low on the
two transistor design??

73/72 Bob VO1DRB/WA6ERB

PS: Keep us informed on your transistor selection experiments for the Pixie.
 
>I hate to rain on this nice Pixie 2 parade, but for those of you who have
>built this puppy up AND have oscilloscopes, check the power output. I
>knocked one together dead bug style last nite, and into a dummy load the
>waveform is Ugly. Even with the low pass filter, the waveform is still
>pretty gross.
>
>I wondered about the 300 mW claims, and tried all manner of PA (2N3053,
>2N3866, MRF 472, 2N3019) and could only get 300 mW out if running 24 volts on
>the supply. I will try a 2N2222A as the PA tonite. (Will also play with the
>oscillator, trying a metal can '2222A, and an MPS 6521 to replace the plastic
>'2222 that is there now).
>
>So my guess is either all my transistors are junque (they did come from the
>junque boxe), or those ugly waveforms are giving the usual 'ugly waveform
>enhancement' to the wattmeter reading.
>
>Ah, Devil's Advocate! Comes from too many readings of Morrison and Boyd in
>college! Let's get some scopes on those pixies and see how they perform.
>
>
>73, Jim N0OCT
>


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