Most universal radio receivers have a very wide bandwidth that is not particulary for radio amateurs. The better models with narrower bandwith are almost always priced higher, too high for the reach ...

This audio noise filter circuit is a bandpass filter for audio frequency band. It filters unwanted signals that are lower or higher than the audio frequencies. It has 2 filters: a low pass filter and ...

EIM Technologies' Kickstarter campaign ended on April 16, 2025, reaching ~$108,000 in pledges. The book and associated kits can now be ordered from EIM directly, with details below. EIM used ...