noise filter

Filter Concepts - Custom EMI Filters, AC DC Three phase filters by Filter Concepts Inc.

TR-7 Transmit Filter Modification - Drake TR-7 A.M. Transmit Filter Modification

Elecraft K2 Improving CW Filter - Here is a cheap and simple way to significantly improve the K2 CW filter(s). With this mod, even strong signals will fade to black as they tune out of the filter pass band

Kenwood TS-480 Notes  ^updated - N0RQ's brief notes on the Kenwood TS-480

Kenwood TS-850 Noise Blanker Mod - Reduces line noise on TS-850

MPFilters for FT-1000MP - MPfilters is a Windows-based program which enables you to select the Yaesu FT-1000MP and FT-1000MP Mark V main receiver and sub receiver IF filters via the radio’s CAT port

FT-817 NB Improvement - Yaesu FT-817 noise blanker improvement

Yaesu FT-920 Inrad CW Filter Mod - This modification allows the use of two filters. Either one or two filters in cascade may be selected

Yaesu FT-920 filter installation - Inrad Roofing Filter installation instruction

FTdx5000 Filter Setup and MARS mod - Installation of the 300 Hz Roofing Filter in the Yaesu FTdx5000 and MARS modification

Baofeng UV-3R Low pass Filter Mod - This page describes a fix to the Low Pass Filter that provides more filtering of the second harmonic of 144-148 MHz.

NKCCluster - Android ham radio DX Cluster, compatible with DX Spider, AR-Cluster, DxNet, CC Cluster, and CLX nodes. NKCCluster supports connecting to a user-defined DX cluster node, filtering DX spots per bands of interest

TFilter - Free online FIR filter design - Free online FIR filter design application

RF Cool Tools Real Time Design - RFCoolTools RLC Filter Simulation, S-parameter Plotter, Filter Optimization,Broadband Impedance Match

MorseDecoder - HotPaw MorseDecoder for iPhone and iPad. Translates sounds from mic to text. Includes a DSP narrow band filter.

Stub HF filter - Multi transmitter filters for HF Bands

Power netfilter - Homebrew a Power netfilter

Filtering of the Icom IC-775 DSP - Replacing filters on ICOM IC 775

TVI Filter schematic - A simple TVI Filter schematic

PC Board Filters - Offer performance comparable to tin-box filters, and except for being bigger, stack up pretty well with those expensive little helical jobs. You just have to be able to make your own PC boards.

Bandpass Filters for Portable Usage - These are QRP rated 3 Pole Butterworth filters based on a design by K4VX, feature simplicity, almost no insertion loss, and reasonable rejection on the other ham bands.

QLF Filter - Microprocessor based interface designed receives a signal from a Morse key, processes it, and re-transmits it to the radio. A microprocessor in the circuit is pre-programmed with a proprietary algorithm which makes a number of measurements and adjustments to the less percise human generated code.

Guide to Harmonic Filters for QRP Transmitter - A Short Guide to Harmonic Filters for QRP Transmitter Output. - George Dobbs G3RJV

30 m Band Direct Conversion Receiver - The direct conversion receiver described consists of only a bandpass filter, mixer IC, VFO and audio filter. With only 22 parts, this simple circuit should take a few hours at the weekend to construct.

Crystal tester - Crystal tester project, crystals are used to control the operating frequency of transmitters, and it is used in radio frequency converters, oscillators, filters for cw, ssb and many other applications.