Category Archives: Projects

Using a Diplexer (Duplexer) as a 2-meter LPF

First off, to be clear, I’m talking about a Diplexer, the small device that will fit in your pocket and costs < $60, that is used to combine 2-meter and 70-cm rigs to use a single antenna feed-line. However both … Continue reading

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KA1QYP Half Pint QRP Transceiver Passes FCC

In our continuing quest to evaluate the output purity of various QRP kits, Willy W1LY constructed a Bill KA1QYP Half Pint Kit. The assembled kit produced a solid 600 mW output and was one of the cleanest radios we’ve seen.  The … Continue reading

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Pixie with 5-pole Axial Filter Passes

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

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?

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

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

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

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

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?

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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