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Amplitude Modulation

AM: Operating, Maintaining, Repairing, Building, Learning, New Technology!

From vintage tube-based gear, to military surplus, to modern, ultra-efficient FET-based Class E transmitters, Amplitude Modulation (AM) offers the experimenter, homebrewer, and radio restoration buff great opportunities to learn, build, and enjoy radio. AM was once the main voice mode in amateur radio. Now it is a well regarded specialty within the hobby. AM offers a warm, rich audio quality that provides for more personal interaction. The simplicity of AM circuit design encourages hands-on restoration, modification and homebrew construction to an extent no longer found among contemporary radios.



THE AM operating event of the year, open to all who wish to make AM contacts. For more information than you want to know, please click here:

Hint: The video is a must see!

2020 AM Rally, W1AW operation at ARRL Laboratory, using the Gates BC1T transmitter and FlexRadio Systems FLEX5000C (receiver only).  Ladies night!  (NEW!)

n1BCG Operating Events

n1BCG 2016:  Story of the special event operation in Greenwich, CT, honoring a milestone in radio technology, crossing the Atlantic using short wave, achieved first by Radio Amateurs in 1921.

n1BCG 2019:  Operation at W1AW for the 98th Anniversay.

Celebrating 98 years of short wave radio. Stand by for the really, really reeeeealy big event in 2021 !!!


The ARRL Laboratory recommends using a modulation monitor to maintain high level, but undistorted transmit modulation in the AM mode. An excellent example of a modern modulation monitor is made my Radio Engineering Associates

Here's a Demonstration Of a Modern AM Modulation Monitor, made by Radio Engineering Associates


Gates BC1T at the ARRL Lab


Tim Smith converted a Gates BC-1T AM Broadcasts Transmitter to 160 and 75 meters. The Transmitter is owned by the Vintage Radio and Communications Museum of CT and was acquired from the Nation Capital Museum of Radio and Television. Restoration to 1340 kHz was done by VRCMCT's Dan Thomas, NC1J. Renowned AM enthusiast, Tim Smith, WA1HLR had the task of converting the Gates for Amateur use. Watch him do this here! If you like large tubes, big components and dangerous lethal voltages, you'll enjoy this video.

Articles, Forums and More

AM FONE; A forum site dedicated to Amplitude Modulation.

AM FORUM on QRZ:  See what the AM Community is talking about.  Also a good place to discuss problems with vintage equipment, finding parts and meeting others with the same technical interests.

AM & FM Tutorial    Understand how Amplitude and Frequency Modulation works.  Most popular video explanation on Youtube. (NEW)

AM & FM Tutorial   1964 Army Training 16 mm Film. The presentation is vintage, but informative. (NEW)

AM Tutorial & AM Low Power Transmitter Circuit   Excellent explantation of a basic low power AM transmitter  (NEW)

QST Product Review of the K7DYY Super Senior 80 and 40 Meter AM Transmitter, Class D Modulation.

Classic Rigs and Amplitude Modulation: Friendly, Nostalgic Ham Radio Partners
QST February 1993, pp. 43
An introduction to current day AM activities within Amateur Radio.

Some Principles of Radiotelephony:
QST 1954

The basics of AM in four easy parts.

·A Course in Radio Fundamentals, Part 6 -- Modulation
QST November, 1942, p. 53
Another good AM primer.

Introducing: The AM Radio Network
QST December 1995, pp. 46
More on current day AM operation.

Hams Redeem Old Transmitter at Fountain of Youth Members Only
QST November 2003, pp. 56
The story of a rescue and Restoration of a Collins 300G Broadcast Transmitter

Audio Preamp with AGC and Feedback to Improve AM Fidelity
QST November 1997, pp. 36
A sweet little mic preamp that also helps control modulation levels.

Constant-Carrier AM for the Drake Twins (Hints and Kinks)
QST November 1994, pp. 85
Make these venerable radios sound much better.

Technical Topics - Some Facts on Modulation 
QST March 1951, pp. 49-51, 116.
An excellent explanation of how AM works. A good read for beginners and old-timers alike.

Technical Topics - Linear Amplifiers for AM  Members Only
QST Feb 1956, pp. 39-41
There's more than one way to generate AM. Get the scoop on using a linear.

Radiotelephone Transmission Members Only
ARRL Handbook, 1929, pp. 98-107
See how AM was done in the early days.

Lop Sided Speech and Modulation Members Only
QST February, 1940, p.14
Get the straight dope on speech asymmetry and its application to AM.

Three Control Six-Band 813 Transmitter

o    QST, Jan 1954, pp. 11-16, 112, 114, 116
o    QST, Jun 1954, pp. 37-39, 118  
o    QST October 1956, pp. 33-38
o    ARRL Handbook 1957, pp.192-197 

This transmitter was all the rage in its day and would be the envy of many AMers today.

The Ultra Modulation System Using Higher Audio Power Without Splatter
QST, October 1956, pp. 27-29
Shows how to increase modulation peaks for more effectiveness.

An AM/CW Exciter for 144 Mc.  Members Only
QST September 1965, pp. 39
Try some local contacts without the repeater.

Synchronous Detection of AM Signals
QEX September 1992, pp. 9

Nov. 1992 p. 21
Dec. 1992 p. 15

A great primer on sync detection and the advantages of using it for AM signals.

A Simple Synchronous-AM Demodulator and Complete Schematics for the DDC-Based Receiver
QEX September 1997, pp. 3

A Synchronous Detector for AM Transmissions
QST July 1993, pp. 28
Build a sync detector for yourself.

Synchronous AM Detectors Members Only
QST September 1992, pp. 65 

Web Links

 ·         The AM Window
This web site, previously featured in the Surfing' column, contains extensive coverage of AM topics, including information on construction and modifications, AM operating events and social gatherings, AM Nets worldwide, audio and visual coverage of AM stations and operators, and much more.

 ·         AM
A vast storehouse of AM information and regional coverage of AM operators and activity. This site also feature a bulletin board for quick and easy access to AMers around the globe and their radio knowledge.

 ·         The Official Class E Transmitter Web Site
The goal of this site is to present a working, practical tutorial on class E transmitters (a complete explanation of class E is included), and to provide sufficient information to allow someone with reasonable radio experience, technical skills and knowledge to construct a working class E transmitter or design a transmitter using similar RF and modulation methods.



AM Activity On the Dial

AM Activity typically takes place around the following frequencies:

160: 1.875 to 1.890 MHz, also 1.945 MHz and also around 1.990 MHz. Call Frequency: 1.885 MHz.

80: 3.690 to 3.725, 3870 to 3890 MHz, also 3.945 MHz. Call Frequency: 3.885 MHz.

60: AM Not Permitted..

40: 7.290 to 7.295 MHz. Call Frequency: 7.290 MHz.

30: CW ONLY Band

20: 14.280 to 14.290 MHz. Call Frequency: 14.285 MHz.

17: No AM Activity Observed

15: 21.400 to 21.445 MHz

12: No Am Activity Observed

10: 29.000 to 29.100 MHz. Call Frequency is 29.000 MHz.

6: 50.400 to 50.550 MHz. Call Frequency is 50.400 MHz.

2: 144.400 MHz. 

The above frequencies are not consdiered to be AM only; they are areas on the dial where AM activity can be heard. Please be considerate when operating AM and listen first before transmitting to see if the frequency is clear, as you would with any other mode.

Fun Notes:

Retired Marine Radios that originally operated from 2 to 3 MHz, AM, can be easily re-crystaled for the top end of 160 meters. Listen for AM at 1.990 MHz, you may run into an OP using one of these former-marine radios.

29 MHz is fun when the band opens. Cheap fun can be had by re-crystalling a 5 watt CB hand-held for 29.0 and another frequency in this part of the band. They work great locally, providing greater coverage than a typical 2 meter hand-held/rubber duck, and at times, DX contacts can be made using one of these radios.

Bob Allison, WB1GCM

Send us Your Photos!

Would you like to see your AM station on our web site? Send your photo as a JPEG file to me and if it's of good quality, I'll post it!

Send to Bob Allison, WB1GCM ARRL Test Engineer at:

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