filter

QRZCQ.com - The DataBase for radio hams, callsign database, DX Cluster filtering, forum calendar and resources

L-com - WiFi Antenna, WiFi Amplifier, RF Splitters, RF FIlters, Adapter, Video Cable and Custom Connectivity Products

K-Y Filter Company - Modem Telephone Super Filters For HF and AM Radio Interference.

Olympix - Performance RFI Filters that work right at the noise sources, ferrite cores.

AC0C Roofing Filter - Yaesu FT-950 and FT-2000 Roofing Filter Optimization and Improvement

NexTek - Lightning Arrestors, High current filters manufacturer

HF Projects Kits - Provide service, quality home construction projects, travel antennas, masts and bases, hf and vhf amplifiers, low pass filters and z-match tuners

Audio filters and speakers - Review of common audio speakers for mobile setups

Baofeng LPF mod by G0FTD - A modification of the UV3R Baofeng handheld transceiver to improve the built in low pass filter

Radius Power - DC Filters - DC filters from radius power are specifically optimized for applications with DC supply like e.g. photovoltaic inverters. Radius Power provides total power solutions, EMI filters solutions from design to manufacturing, Three Phase, Single Phase, Power Line, IEC inlet, Power entry modules Filters.

Wadsworth Repeaters - The GE Master Exec II receiver employs a five cavity helical input filter to insure out of band rejection.

EvoSpice - A numerical optimizer (solver) for LTSpice IV. Uses a fast evolutionary algorithm. You can use EvoSpice to design high efficiency power supplies, audio filters, low noise RF amplifiers and an endless list of other applications

Band-stop filter - Wikipedia page on Notch filter, a narrow stopband - high Q factor filter

TVI Filters - Schematic and diagrams for TVI Filters by G4WPW

440Mhz Interdigital Bandpass Filter - Homebrew Amateur Radio 440Mhz Interdigital Bandpass Filter

23 cm filters - 2 filter designs a 3-pole and a 5-pole

Notch Filter Designer - Online calculator, Butterworth Bandstop (Notch) Filter Designer

Constant k Lowpass Filter Design - Online Constant - k Lowpass Filter calculator

Homebrew Crystal Filter Design - Desgining crystal filters and find out crystal data by measuring it.

Highpass filter calculator - Butterworth Highpass Filter Designer

About Cavity Filters - Cavity filters are tipically circuitry behind a duplexer that allow only certain frequencies to pass

Cheap Crystal Filter - An economical way of building an SSB filter. The circuit is for a filter with a 6 DB band width of roughly 2.2 KHz.

Bandpass filters design - How to design narrowband bandpass filters

Switched Capacitive Audio Filter - NEScaf: A Switched Capacitive Audio Filter

RF Probe Project - If you needed the ability to quickly measure RF voltage for tuning filters and cavities this RF Probe probe is for you