audio filter

GB3DC Repeater live - Listen to the live audio stream from the GB3DC repeater

Council Bluffs area Police Scanner - Council Bluffs area Sheriff, Police, Fire, and State Police IOWA

Indiana State Police Live Scanner - Live steaming audio of Allen County Police & Fire dispatch and Indiana State Police dispatch.

Illinois - Chicago Police - Illinois Cook County, police scanner includes Chicago Fire Dispatch channels (North, South, and HazMat)

Detroit Fire Department Scanner feed - Detroit Fire Department Radio Feed

xggcomms.com Interfaces - Xggcomms specialise in producing cost effective, high quality CAT and Audio interfaces for Icom and Yaesu Amateur Radio Equipment

FB-922 Replacement Filter - FB-922 Replacement Filter Capacitor Block for the Kenwood TL-922 & TL-922A

Drake TR-7 Improvements - Installing the Cumbria Designs X-Lock VFO Stabilizer, and Improving The TR7 Audio Quality

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

Fixed Audio Output for the K2 - W3FPR fixed level AF output fot the Elecraft K2

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

Yaesu FT2000 ESSB Audio Setup - Audio setting and improvements for Yaesu FT-2000 by k6jrf

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

Yaesu FT-920 Narrow filters mod - CW and SSB INRAD narrow filters 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

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.