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

Monday, July 28, 2025

Reducing RF susceptibility for the HamGadgets "Ultra Pico Keyer" - and mimizing RF issues on portable HF stations in general

Note: While this article describes a modification of the Pico Keyer to reduce RF susceptibility, it also talks about methods to minimize/red...

Friday, June 13, 2025

A 15 (and 10) meter high-pass filter for Field Day

QRM from a transmitter to receivers on lower bands [Go to the end of this article for an "After-Field-Day follow-up" about this f...

Wednesday, June 4, 2025

The construction of a hybrid ring combiner: Using the same duplexer, feedline and antenna for two repeaters/links/transmitters

Two transmitters, one antenna There are occasions when it is desirable to combine two transmitters - and receivers - onto a single antenn...

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