Shortest Vanity Callsignsupdated
- This is a service for finding the shortest available vanity callsign in your amateur radio class. It filter through all possible callsigns and provide just the unused ones weighted by their length in morse code or their actual number of letters.
Batteries and QRP
- Thanks to the popularity of cell phones, laptops and other personal electronic devices, the battery industry has been market-driven to produce higher capacity batteries in lighter weights than previously possible with yesterday's chemistries.As a result, a wide variety of battery types are available to the outdoor QRP operator.
500 KHz Low Pass Filter
- This article describes a shielded low pass filter with a cut off frequency of about 500 KHz. It is built with components suitable for receiving, and was designed to use in front of a low frequency receiver for LOWFER work.
Homebrew a CW Filter
- An home-brewed morse code CW filter with a central frequency of 800hz and a variable bandwidth from 230hz to 26hz by F5RDH in french.
Interdigital bandpass filter designer
- Fill out the form to design a bandpass filter as described in the January 1985 issue of Ham Radio Magazine. These filters are generally limited to frequencies above 200 MHZ because their size is slightly longer than 1/4 wavelength