Interference Primer - Parts 1 and 2 Derived from QST February and March 1992 Lab Notes columns.  Copyright © 1992 by the American Radio Relay League, Inc. All rights reserved.

Prepared as a membership service by the American Radio Relay League, Inc., Technical Information Service.

The ARRL RFI Book, American Radio Relay League, 225 Main St., Newington CT 06111, (860) 594-0200.

AC Power Interference Handbook, By Marv Loftness, KB7KK

The Radio Amateur's Guide to EMC, Radio Society of Great Britain, 3 Abbey Court, Fraser Road, Priory Business Park, Bedford MK44 3WH Great Britain

Ordering information for the above three books and more can be found on in ARRL Web store.

The ARRL Technical Information Service (TIS) has prepared a series of additional EMI web pages. The "EMI/RFI Page" (this page) provides a menu for more comprehensive pages related to RFI, such as "EMI/RFI - Telephone."

Contact the ARRL "RFI Desk" for additional information and help with interference problems involving Amateur Radio stations (email rfi@arrl.org).

For interference involving other radio services contact the FCC Consumer and Governmental Affairs Bureau (FCC CGB), 1270 Fairfield Road, Gettysburg, PA 17325, National Call Center phone: 888-CALL-FCC, email fccinfo@fcc.gov, web: www.fcc.gov/cgb

An extensive list of free pamphlets about electromagnetic interference and lightning protection is available from Industrial Communications Engineers. Request their free publications list.

Barker and Williamson Model FL10/1500

Bencher Model YA-1

Bird Electronics Corporation Model 5040 series

Industrial Communications Eng Model 400 series band-pass, Model 420 series low-pass

MFJ Enterprises Model MFJ-704

Radioware

Unadilla Antenna Model WA2ZOT, WA2ZOT-6 Meter

The high-pass filter is the first line of defense against TVI to antenna-connected televisions that is caused by HF radio transmitters! A high-pass filter is not usually needed or effective with interference problems to CATV-connected TVs. For cable interference problems, use a common-mode choke. Note: High-pass filters are usually available from the local electronics distributor that sells parts to your local electronics service businesses. Consult the Yellow Pages under "Electronic components - wholesale and manufacturer."

Channel Master several models

Industrial Communications Engineers Model 430 series high-pass

Radio Shack 15-579 75-ohm, 15-582 or 15-581 300-ohm

Winegard Model HP-2700

A 50 MHz High Pass TVI Filter you can build from the United Kingdom Six Metre Group (UKSMG).

The Yankee Clipper Contest Club has an article on common mode chokes by Chuck Counselman, W1HIS.
Alternate formats: PDF MS Word.

Industrial Communications Engineers

Starplex, Inc Model Ghost Buster dual-ferrite choke

The following set-top converters have been reported as being relatively immune to cable-TV interference: (Additional reports are sought.)

General Instruments/Jerrold: Bar code - TOA1104176B5

Amateur VHF stations can interfere with antenna-connected televisions. Television tuners do not often have much adjacent-channel rejection, resulting in severe fundamental overload. These tunable notch filters will reject the strong amateur signal, allowing the television to function normally. Note: these filters will not help when an amateur signal is interfering with cable channel 18 (channel E). In that case, the problem results because cable channel 18 and the Amateur 2-meter band occupy the same frequencies. Some of these filters are expensive. Contact the vendor before ordering.

Microwave Filter Company: 5KMT-A-I (reject 108-170 MHz) Filter: 5KV-E (Channel E (146.25 MHz) (Cable ch 18) trap) Filter: 5KV-K (Channel K (223.25 MHz) (Cable ch 24) trap) Filter: F6367-2 (Notch filter 50-108 MHz, 75-ohm) Filter: F6367-3 (Notch filter 108-216 MHz, 75-ohm) Filter: F6367-4 (Notch filter 216-450 MHz, 75-ohm) Filter: F6367-5 (Notch filter 450-900 MHz, 75-ohm) Note: They will sell single units.

Winegard Model: UT-2700 notched 470 to 800 MHz Model: BF-1700 attenuates 110-170 MHz (eliminates 2M signal)

K-Y Filter Company Model RF-1 and Model AM-1 for telephones.

Coilcraft Filter models RJ-11 (single line) and RJ-14 (2 line) - filters 150 kHz to 25 MHz.

Industrial Communications Engineers Model 460 series telephone/audio filters

Sparrevohn Engineering Model F-1 (single-line), Model F-2 (two-line)

OLD AT&T telephones, made by several different companies, notably models 300, 500 (rotary), 2500 (DTMF), 2554 (DTMF wall phone,). These phones are made by AT&T (Western Electric), Comdial (Stromberg Carlson), Northern Telecom, and ITT. These phones have no semiconductors in them and have a carbon microphone, hence the RF immunity. The only devices that can produce problems are the silicon carbide varistors. Most of these phones are no longer being manufactured but are sometimes found used at garage sales or flea markets.

The ARRL Technical Department has received one report (each) that the following telephones are immune to EMI. Additional reports about these telephones are sought. (Note - just because one phone by a particular manufacturer is immune does not indicate that ALL phones by that manufacturer are immune! Several of these manufacturers have phones for which we have received inteference reports.)

Phonemate 8250

AT&T 5300 and 5400 (cordless telephones.)

Conairephone PR1001

NT Meridian Centrex telephone sets

Understanding How Ferrites Prevent and Eliminate RF Interference to Audio Systems. Jim Brown, K9YC shares three years worth of practical engineering research on the use of ferrites to prevent RFI. Also of interest is Understanding and Eliminating RF Interference. Jim prepared this Power Point presentation for his local ham club. This discussion is focused on RFI to and from ham stations.

Common Mode Chokes by Chuck Counselman, W1HIS

Amidon Associates 

Fair-Rite Products Corp Note: Call to locate nearest distributor. Distributor Dexter Magnetic Materials has a number of locations around the US. Call 800-949-8950 to automatically connect to nearest Dexter office.

MFJ Enterprises

Ocean State Electronics

Palomar Engineers

Radio Shack catalog #s 273-105 and 273-104

ICE ac line filter products (such as the ICE Model 475-3 AC Line Filter described in Short Takes) are now available from a former subcontractor, Morgan Manufacturing.  Additional links now or previously associated with these filters include:

• Morgan Manufacturing Filters
• Industrial Communications Engineers, LTD
• Industrial Communications Engineers, LTD (Alternate ICE link)

Array Solutions provides the W3NQN ac line filter

Corcom provides RFI Line Filters as well as numerous other types of filters.  They also carry a Variable-Frequency Drive (VFD) Line Filter, which may work on variable speed washing machines and similar appliances.

Radio Shack Catalog: 15-1111 brute-force AC-line filter, 26-1395 surge- protection filter (it contains common-mode and differential mode AC-line filtering. Note: This model has been discontinued.)

Electronic Specialists, Inc.  Carries a wide range of AC Power Line Protectors, industrial surge suppressors, ac power line voltage conditioners and regulators.

ETS-Lindgren offers a wide variety of power line filters and phone/signal/control filters plus related products.

Spectrum Control Inc. offers power line filters, EMI filters & filtered interconnects, and related products.

LCR Electronics offers power line filters, power entry filters and EMC filters.

HSC Electronics carries a wide variety of ac line filters.

Amazon offers a 15A Homeplug Noise Filter for Powerline Networks by ZyXEL.

Industrial Communications Eng Model 461 stereo , Model 440 mobile, Model 488 video.  Some former ICE filter products are now provided by a former subcontractor, Morgan Manufacturing.

Radio Shack (mobile) 270-051, 270-055, 270-054, 270-012, 272-1085, 270-030

Wacom Products

Winegard Model FT-7600 variable FM trap, Model VF-3000 VCR, Model VF-4000 VCR

The Technician's EMI Handbook, Clues and Solutions by Joseph J. Carr is published by Elsevier. You may obtain a copy from Purchase at Amazon or Purchase at Barnes and Noble. Also available is a Google Preview. 

AC Electronics offers a fluorescent lighting ballast especially suitable in the presence of Power Line Carrier Signals (PLCS).  This device provides additional filtering (and probably a higher impedance looking into the filter from the AC mains) over conventional ballasts.

The COMspkr is an RF interference resistant computer speaker system from West Mountain Radio.

Useful links for tracking lightning include:

• Vaisala Lightning Explorer
• Strike Star from Astrogenic Systems
• Intellicast

RFI - Regulatory Information--This web page contains information about Federal Communications Commission rules that apply to FCC preemption of local laws about RFI.

A summary of the FCC's study on telephone interference

FCC Policy for handling complaints of interference to home electronic equipment

• A Ham's Guide To RFI, Ferrites, Baluns, And Audio Interfacing by Jim Brown, K9YC.
• Audio Systems Group, Inc. Publications 
  Provides a number of articles and application notes related to sound systems.  Some of these articles pertain to interference to audio systems from both power and RF sources.
• eEngineer provides an EMI/EMC Glossary as well as several other RFI pages pertaining to RFI.
• Lutron provides both Applications Notes as well as RFI filtered dimmers in a variety of types, including low voltage.
• V-Soft Communications® LLC
  Provides AM FM Zip Code Based Signal Strengths: Field strength vs. Zip Code
• RFI Enforcement Pages
  • FCC Enforcement Activities and the Electric Utility Industry
    Information on the ARRL and FCC cooperative agreement followed by a link list to FCC enforcement letters sent to electric-utility companies concerning harmful interference reports.
  • FCC Part 15 Enforcement Letters
    Information on Part 15 rules followed by links to a list of FCC enforcement letters sent to Part 15 device operators (other than power-line) about harmful interference reports.
  • FCC Enforcement News and Web Links
    • FCC to Utilities: Don't Look to Hams to Pay for Your Testing (Aug 27, 2009)
    • FCC Issues Citation to Washington Company for Selling, Importing Unauthorized RF Devices (August 4, 2009)
    • FCC Issues Citation to Part 15 Marketer (July 30, 2009)
    • FCC Issues Two Citations in Longstanding Power Line Noise Case (August 30, 2007)
    • FCC Cites Florida Utility for Interference to Radio Amateur (June 8, 2006)
    • FCC Continues Crack Down on Marketing of Unauthorized Equipment appeared in the April 20, 2006 of Conformity eNewsBreaks
    • FCC Proposes $1 Million Forfeiture for Marketing Unauthorized Equipment appeared in the March 9, 2006 edition of Conformity eNewsBreaks.
    • KCBD-TV news story video about the FCC citations to Lubbock Power and Light and Xcel Energy in Lubbock, TX  A complete video of the original news broadcst is also being made available for the ARRL Web site with the permission and courtesy of KCBD-TV Channel 11 in Lubbock, TX.  (Play Video): KCBD-TV Broadcast August 27, 2007
    • KCBD-TV news story video about the safety hazards of poorly maintained power lines in Lubbock, TX.  A complete video of the original news broadcast is being made available for the ARRL Web site with the permission and courtesy of KCBD-TV Channel 11 in Lubbock, TX.  (Play Video): KCBD-TV Broadcast September 24, 2007
    • ARRL Helps to Clear the Air in Line Noise Cases, August 21, 2001

Information for Electric Utilities Center for Devices and Radiological HealthAddressing EMI in medical devices Welcome to the RSGB EMC Web PagesE-book-"The RSGB Guide to EMC" (Electromagnetic Compatibility) NARTE Certified EMC/ESD ConsultantsA listing of NARTE Certified EMC/EMI and ESD Professionals who offer their services as consultants and/or contractors. EMC StandardsContains a list that details some of the major electromagnetic compatibility (EMC) standards in place worldwide. Radioing eEngineer has a page on Radio Frequency Interference (RFI) The United Kingdom's Radiocommunications Agency has a Radiocommunications Agency EMC Awareness page with EMC/RFI information for the non-technical person and the general public. FAQ: The 411 On Radio Frequency Interference See www.aerorfi.org for information on interference in the aircraft band.  Much of this information also applies to the broadcast and Amateur bands.

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 Hints for more successful searching

Suggested keywords for more articles like the ones on this page are: RFI