Note
The AM-2 was Heath’s first SWR meter (the AM-1 was an antenna impedance bridge). The AM-2 was designed to match all the DX series gear, using the silver and gray paint scheme. The unit will handle “well over 1 kilowatt” of power, can operate with 50Ω or 75Ω lines, and covers 160-6 meters.
The earliest catalog photos show the AM-2 with a bakelite meter like the DX-100, though as of this writing none with this meter style have been found. By at least 1958 the AM-2 was fitted with a plastic meter like the DX-40. This meter is calibrated to 6:1 and is incorrectly marked so that a 3:1 SWR corresponds to 50 percent reflected power. This is one of the more obvious mistakes Heath let sneak out the door.
The corrected version was calibrated to 3:1 (shown correctly as 25% reflected power) with a red area above. Refer to Figure 1.
Based on assembly manual illustrations, the meter was changed sometime between 1958 and 1960. Both meter versions are common. In 1962, Heath updated the AM-2 by restyling the cabinet with the classic green finish and called it the HM-11. The insides didn’t change.
WIRING OPTIONS
The AM-2 must be wired for a specific impedance, either 50Ω or 75Ω.
References:
Use as a modulation monitor. QST. Mar 1959, p. 54.
Customizing. QST. Feb 1961, p. 39.
Add a built-in tuner. QST. Jan 1966, p. 20.
RF power handling capacity: 2000 watts PEP
Input-output impedance: 50 or 75Ω
Power requirements: none
Band coverage: 160-6 meters
Meter: 100 µA full scale
Weight: 1.5 lbs
Photos, general information and specifications from "Heathkit: A Guide to the Amateur Radio Products," by Chuck Penson, WA7ZZE. Used with permission.
