Allen Avionics makes precision custom-built LC noise filters including band pass filters (400 Hz to 500 MHz), high pass filters (100Hz to 1000MHz), low pass filters (50Hz to 5000MHz; 20, 200, 500, and 1000 watts), and diplexers, with applications including microwave filtering.

DCI Digital makes custom noise filters including Band Pass filters, high and low pass filters, component sized filters, and ISM filters. Also available are diplexers, with channel isolation from >39dB to >90dB. Models can be built to military specification and are used in fixed and mobile military installations with many frequencies available starting at 30MHz.

Filtronetics makes custom EMI/RFI noise filters such as bandpass, high pass, bandstop, and lowpass filters, with frequencies of >1MHz to 6GHz. They also have LC filters, diplexers, surface mount models, and ISM filters. Some applications include military and microwave filtering.

KR Electronics makes custom and standard filters for commercial and military uses including Low Pass filters, high pass filters, band pass filters, LC filters, Diplexers, and surface mount filters. Their low-pass filters have a cutoff frequency of 5 HZ to 500MHz, while their bandpass filters have a center frequency of 220 Hz to 875 MHz.

Microwave Filter Company makes noise filters and components including LC filters, band-pass filters, miniature filters, ISM filters, and Diplexers. Their high quality passive filters operate on 5 Hz to 50 GHz frequencies and their WiMax diplexers use bands which are mutually isolated by a minimum of 55 dB with a maximum 1dB of insertion loss per band.