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. No AI is used to generate this content.

Monday, August 18, 2014

Completely containing switching power supply RFI

In the old days, radio amateurs were concerned with (or should have been) energy from their transmissions getting into devices unintentiona...

Saturday, July 19, 2014

Replacing the filters in the Drake SP75 Speech Processor

A few months ago I fired up my old Drake TR-7, getting on the air with some friends on 40 meters after not having used the radio for a whil...

Monday, June 30, 2014

A 100 watt "Helical" resonator bandpass/notch filters to increase isolation of 20 meter stations during Field Day

Follow-up: For another article with more measurement and analysis of these filters, see the 31 May, 2019 article - Revisiting the 20 mete...

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