Category Archives: Projects

Pixie with 5-pole Axial Filter Passes

Posted on March 14, 2017 by robert

Willy, W1LY, decided to try using the standard unshielded 1 uH axial inductor that the Pixie uses for it’s current 3-pole filter (C5=47o pf, L2=1 uH, C6=470 pF) as the starting point for a 5-pole filter that could easily fit … Continue reading →

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Elsie Plot of QRP-Labs 7-pole 40-m LPF

Posted on March 5, 2017 by robert

This is the schematic of the 7-pole LPF used in the QRP Labs 40-meter LPF: The plot from Elsie 2.77 for the above filter looks like this: The actual SA response curve looks like this: The curves are remarkably similar. … Continue reading →

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A “Better” QRP Transceiver?

Posted on March 4, 2017 by robert

NCRC had several reasons for building the Pixie as a club project, and getting it on the air is probably at the bottom of the list.  Fixing flaws in the Pixie design provides learning opportunities.  But by the time you … Continue reading →

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Pixie Perfection

Posted on March 4, 2017 by robert

As has been noted in several posts, the stock Pixie 3-pole filter is hopelessly inadequate to suppress harmonics.  A typical Pixie will have a 2nd Harmonic that is only about -21 dB down from the carrier.  An external 5-pole filter … Continue reading →

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P2N2222A for the Pixie

Posted on February 27, 2017 by robert

On Semiconductor has a variant of the old 2N2222A in a plastic case called the P2N2222A and characterizes it as a small signal RF amplifier.  I picked up a few samples and ran three of them through the Pixie.  In … Continue reading →

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7-Pole Filter + Pixie

Posted on February 26, 2017 by robert

A friend of mine, Paul K1YBE, gave me a QRP Labs 40-meter Low Pass Filter Kit.  The kit came with three T37-6 cores, some #28 wire, 4 caps, a tiny PCB, and a couple of headers. Normally used with one … Continue reading →

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Better Q == Better Response

Posted on February 26, 2017 by robert

Yesterday I replaced the inductors in my original 40-meter LPS with larger cores that wound up having about twice the Q.  This morning I replaced the ceramic caps with silver mica caps.  The old caps had a Q around 80.  The … Continue reading →

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Does Size Matter?

Posted on February 25, 2017 by robert

There’s a joke in there somewhere… Yes, size does matter when it comes to Toroid diameter (which also has an impact on winding geometry), maximum wire size, etc.  All things which impact the Q of the circuit. I went back … Continue reading →

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A New Transistor for the Pixie

Posted on February 21, 2017 by robert

Of course the Pixie final transistor, Q2 S8050, gets darned hot, and I’ve blown one out in the past just holding the key down more than a few seconds.  With my Pixie + Red Core Filter, I was seeing about … Continue reading →

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Passing Pixie!

Posted on February 21, 2017 by robert

After experimenting with T37-6 yellow core inductors, it was time to change to the T37-2 red core.  These have a lower operating frequency, up to 10 MHz, and it is possible that they might have a higher attenuation on 14 MHz … Continue reading →

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