Introduction

An RF filter is an electrical circuit configuration (network) designed to have specific characteristics with respect to the transmission or attenuation of various frequencies that may be applied to it. There are three general types of RF filters:

A high-pass filter similarly has a cut-off frequency, above which there is little or no loss in transmission, but below which there is considerable attenuation. Its behavior is the opposite of that of the low-pass filter.

A low-pass filter is one that will permit all frequencies below a specified one called the cut-off frequency to be transmitted with little or no loss, but that will attenuate all frequencies above the cut-off frequency. High-pass and low-pass filters can be difficult to construct properly. Whenever possible, many amateurs simply buy them.

A band-pass filter is one that will transmit a selected band of frequencies with substantially no loss, but that will attenuate all frequencies either higher or lower than the desired band.

Additional resources

The ARRL Handbook for Radio Amateurs
The ARRL RFI Book
HF Radio Systems & Circuits

The ARRL has an extensive catalog of books and materials related to Amateur Radio.

Articles

Note: Some of the following articles are in Adobe Portable Document Format (PDF) files. To view and print these files, you'll need a copy of Adobe's Acrobat Reader program. (Version 3.0 or later required). More information here.

• Second-Harmonic-Optimized Low-Pass Filters (160,436 bytes, PDF file)
  February 1999, pp 44-46
  Sometimes we need a little more output filtering than traditional designs offer. This filter can give you that extra boost.
• Bandstop Filters for Attenuating High-Level Broadcast-Band Signals (368,958 bytes, PDF file)
  QEX November 1995, pp. 3-12
• A No-Tune 2-Meter Bandpass Filter (269,473 bytes, PDF file)
  QST May 2000, pp. 54-55
  A homebrew solution to annoying intermod
• Narrow Band-Pass Filters for HF (313,893 bytes, PDF file)
  QEX Sept/Oct 2000, pp. 13-17
  The ability to attenuate frequencies above and below a particular band can be very useful to both the contester and the casual operator.
• Receiver Band-Pass Filters Having Maximum Attenuation in Adjacent Bands (349,219 bytes, PDF file)
  QEX July/Aug 1999, pp. 27-33
• Clean Up Your Signals with Band-Pass Filters - Part 1 (84,538 bytes, PDF file)
  QST May 1998, pp. 44-48
• Clean Up Your Signals with Band-Pass Filters - Part 2 (78,309 bytes, PDF file)
  QST June 1998, pp. 39-42
• Dunestar Model 600 Multiband Bandpass Filter (168,829 bytes, PDF file)
  QST March 1995, pp. 85-86
  This is an in-line filter that operates on both transmit and receive. Its primary application is reducing interference between stations operating in close proximity.
• A Diode-Switched Band-Pass Filter (843,518 bytes, PDF file)
  QST January 1991, pp. 24-26
  How to use high-speed silicon diodes as RF switches for selecting two or more filters.
• Band-Pass Filters for HF Transceivers (1,051,773 bytes, PDF file)
  QST September 1988, pp. 17-19, 23

Note:

Contact information for suppliers mentioned in the above articles should first be confirmed using TIS Address Database Search.

Bibliography (Members Only)

ARRL Periodicals Index Search - This database contains the QST index from 1915 to the present and the QEX index from 1981 to the present. For QST issues from 1970 to the present, and some selected articles back to 1922 (when construction articles featuring tubes began in earnest), identifying keywords have been added to the technical articles. By entering keywords (ANTENNA) or combinations of keywords (CONSTRUCTION ANTENNA VERTICAL HF) into the Title words: field, you may create dynamic bibliographies.
Technical article KEYWORD list. Hints for more successful searching

Suggested keywords for more articles like the ones on this page are: BAND PASS FILTER HIGH PASS FILTER LOW PASS FILTER

Web Links

• Par Electronics - Amateur Radio Filters
• Dunestar Transceiver Bandpass Filters

• How to Specify RF and Microwave Filters by Anatech Electronics, Inc. 

Article Reprints:

You can get a photocopy of any ARRL published article for $3 ($5 for nonmembers) for each article requested. Contact the ARRL Technical Department (reprints@arrl.org ), or 1-860-594-0390, Noon to 5PM, Tuesday though Friday, Eastern Time, if you wish to get photocopies.

This information was prepared as a membership service by the American Radio Relay League, Inc., Technical Information Service, 225 Main St., Newington, CT 06111 (860) 594-0214. Email: tis@arrl.org (Internet). ARRL HQ is glad to provide this information on the Web free of charge as a service to League members and affiliated clubs.

If you have any questions concerning the reproduction or distribution of this material, please contact:

TIS Coordinator
American Radio Relay League
225 Main St., Newington, CT 06111
Tel: 860-594-0214 Fax: 860-594-0259
(email: tis@arrl.org)