Filters

Tunekit - Filter Tuning Kit for Windows is a electronic filter synthesis program and a practical filter tuning aid for actually designing and building a working filter

A low pass filter circuit - A simple 7 element, Chebyshev low pass filter, rolls of at 30MHz. Attenuation is better than -40dB at 60MHz, -65dB at 90MHz, -80dB at 120MHz.

TVI and BCI Filters - TVI and BCI bandpass and bandstop filters in SMD technique. Schematics and images.

Using ferrite for interference suppression - Excellent guide to using ferrite cores for interference suppression. Understanding and Solving RF Interference and Noise Problems by Jim Brown K9YC Audio Systems Group, Inc. PDF File

Band Filters - Experience of band filters, for a contest multi operator enviroenment

1.8-54 Mhz Low pass filter - An easy to make HF low pass filter form high power by k8cu

Band-Pass Filters for HF Transceivers - Do your multiple-transmitter field day or contest efforts suffer from intrastation interference ?

K2TR Coax Stub Filters - Multi transmitter filters

Clean Up Your Signals with Band-Pass Filters - These inexpensive, easily built filters can be the buffer you need between the signals you want to hear and send and those you don’t!

KI5YN QLF Filter - The QLF filter is a microprocessor based interface designed to go between a standard Morse code key and a radio transmitter

Narrow Band-Pass filter for HF - Band-pass filters can be critical components in competitive stations. This setup may help put your station on the map.

Easy bandpass filters - Quick and easy bandpass filters for receiver input by George Dobbs G3RJV

SSB and CW Filter - A pdf file with schematics of an ssb and cw filter AF amplifier

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.

A diode-switched band-pass filter - High speed silicn diodes work well as RF switches. This article describes how to use diodes for selecting two or more filters ARRL QST article by W1FB

YU1LM Filters  ^new - Bandpass filters designed by YU1LM/QRP. Home brew filters for amateur radio use.

Interactive Digital Filter Design - This is an interactive filter design package, for designing digital filters

1.5KW 6m Low Pass Filter - This filter is designed to follow a FULL legal limit, GS-35B, 6m linear amplifier. Designed and built by Bill Jones, K8CU

1.8-54 Mhz Low pass filter - An easy to make HF low pass filter form high power by k8cu

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

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

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.

5th order High Pass VHF Filter - Sometimes many VHF-UHF modern transceivers have problems with BROADCAST Interference and CROSS-modulation from FM commercial broadcast stations this article shows a simple Batteworth HI-Pass VHF Filter to reduce this problem

A diode-switched band-pass filter - High speed silicn diodes work well as RF switches. This article describes how to use diodes for selecting two or more filters ARRL QST article by W1FB

A low pass filter circuit - A simple 7 element, Chebyshev low pass filter, rolls of at 30MHz. Attenuation is better than -40dB at 60MHz, -65dB at 90MHz, -80dB at 120MHz.

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

Audio CW Filter - A very effective AF Adaptor, with built-in noise blanker and 30 Hz CW filter modules by PA0LQ

Band Filters - Experience of band filters, for a contest multi operator enviroenment

Band filters by PA9M - Band filters for PA6Z made by PA9M, designed by W3NQN.

Band-Pass Filters for HF Transceivers - Do your multiple-transmitter field day or contest efforts suffer from intrastation interference ?

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

Bandpass and I.F. Filters - On this page a popcorn highpass filter, some inductors and their Q , double tuned bandpass filters and simple Cohn Crystal ladder IF filters are presented.

Bandpass filters design - How to design narrowband bandpass filters

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.

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.

Clean Up Your Signals with Band-Pass Filters - These inexpensive, easily built filters can be the buffer you need between the signals you want to hear and send and those you don’t!

Clean Up Your Signals with Band-Pass Filters part 2 - Part 2—You’re now much closer to saying goodbye to your unwanted signal problems!

Coaxial Stub Filters - Coaxial stub filters used at W7GJ

Coaxial Stub Filters - A range of easy-to-build RFI filters by John Regnault, G4SWX

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

Design RF Filter

Easy bandpass filters - Quick and easy bandpass filters for receiver input by George Dobbs G3RJV

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

Filters and Ferrites in EMC - This article is about the characteristics and use of various filters and ferrites for solving amateur radio electromagnetic compatibility problems involving breakthrough of amateur signals into domestic equipment such as television sets, video recorders stereo sytems etc.

Filters for NDB reception - RF Filters to help with NDB reception problems

High Pass Filters - Understand how high pass filters are done

High-Pass Filter Design - Online high pass filter design page with introduction to high-pass filters by K7MEM

Highpass filter calculator - Butterworth Highpass Filter Designer

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.

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

Inrad Roofing Filter in the Yaesu FT-920 - Insalling Inrad roofing filter in the FT-920 with pictures and comments

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

Interferences and filtering - General information on Filter passbands, interferences, TVI and RFI problems

K2TR Coax Stub Filters - Multi transmitter filters

K3NA stub design

KI5YN QLF Filter - The QLF filter is a microprocessor based interface designed to go between a standard Morse code key and a radio transmitter

LC Filter Design - This is an interactive design package for designing analogue (i.e. hardware) filters made of inductors and capacitors (Ls and Cs).

Low Pass Audio Filter - 440 Hertz peaked low pass audio filter experiments

Low Pass Filter Construction - Low Pass Filter Module Construction Manual

Low Pass Filters - Article explaining electronic network of low pass filters

Low-Pass Active Filter Designer - Javascript filter design page with introduction to low pass filters by k7mem

Lowpass filter for 5MHz - The following lowpass filter was built using the tables in the arrl manual, it is a 5 section one and seems to work ok

Mode J Desense Filter - This type of filter can be used in a Mode J satellite station (uplink on 2m, downlink on 70cm) to reduce the problem of the uplink signal desensing the receiver

Narrow Band-Pass filter for HF - Band-pass filters can be critical components in competitive stations. This setup may help put your station on the map.

Noise Bridge Tuner Tuner - Noise bridge circuit to tune your tuner