Monthly Archives: March 2017

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

Posted on March 28, 2017 by robert

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

Posted on March 24, 2017 by robert

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

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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What’s wrong with the serial port on the Raspberry Pi 3?

Posted on March 3, 2017 by robert

The Raspberry Pi 3 added all sorts of features to the Pi, including a much faster speed adjustable CPU, built-in WiFi, and Bluetooth interfaces. Some of the hardware interfaces on the Pi continue to have limited functionality.  Such is the … Continue reading →

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