KA7OEI's blog

Random musings - usually on a technical (nerdy) subject - perhaps related to amateur radio and things found at ka7oei.com and modulatedlight.org

Saturday, April 11, 2026

A (simple) WWVB loop amplifier for radio-controlled clocks

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Note: The techniques described below should work - with only minor adaptation - for any "Longwave" time signal used by these radio...
Wednesday, March 18, 2026

Repairing a ("smoked") MFJ-998 1.5kW automatic antenna tuner

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Figure 1: The (repaired) MFJ-998 front, now working, sitting atop my Heathkit SA-2060 manual tuner and underneath my homebrew neon bar-graph...
Wednesday, March 4, 2026

Modifying the MFJ-5008 parabolic ultrasonic receiver for better sensitivity and wider frequency response

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Figure 1: Front view MFJ-5008 parabolic dish with integrated microphone and receiver (located on the back side). Click on the image for a la...
Wednesday, February 25, 2026

Impedance matching (auto) transformer and common-mode choke for the JPC-7 dipole and other electrically-short (loaded) dipoles and verticals

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Figure 1: The JPC-7 loaded dipole out in the wild! Click on the image for a larger version. Loading coils and "electrically-short"...
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