Make
Heathkit
Model
HM-11
Year
~1962-1964~
Description
Relected Power Meter and SWR Bridge
Overview
The Heathkit HM-11 is a reflected power meter and SWR bridge introduced in the early 1960s for amateur radio operators. Designed to measure forward and reflected RF power, the HM-11 allowed operators to properly tune antennas and transmission lines while monitoring standing wave ratio (SWR). The unit was sold in kit form, requiring customer assembly, which was typical of Heathkit products during the era.
The HM-11 became a popular accessory in amateur radio stations because it required no external power source, introduced very little insertion loss, and could remain permanently connected in the coaxial feed line for continuous monitoring.
Technical Specifications
| Specification | Details |
|---|---|
| Manufacturer | Heath Company (Heathkit) |
| Model | HM-11 |
| Type | Reflected Power Meter / SWR Bridge |
| Years Produced | Approximately 1962-1965 |
| Frequency Coverage | 160 through 6 meters |
| RF Power Handling | 1 kW |
| Impedance | 50 or 75 ohms |
| Meter Movement | 0-100 µA analog meter |
| Connectors | SO-239 coax connectors |
| Dimensions | Approx. 7.25″ W × 4.75″ H × 4.25″ D |
| Weight | Approximately 3 lbs |
| Power Requirement | None |
Physical Description
The HM-11 uses a compact gray-painted metal cabinet with a large illuminated analog meter centered on the front panel. Front panel controls include a Function switch for selecting Forward or Reflected measurements and a Sensitivity control used for calibration and meter adjustment.
Rear panel connections use standard SO-239 coaxial connectors labeled for transmitter and antenna connections. Internally, the unit uses directional RF bridge circuitry with germanium diodes and coupled transmission-line inductors to detect forward and reflected RF energy.
History
The HM-11 was introduced by Heathkit around 1962 during the peak years of Heath Company’s amateur radio kit business. The design was based on reflectometer circuitry originally developed by the U.S. Naval Research Laboratory and adapted into a low-cost consumer instrument suitable for amateur radio use.
Heathkit marketed the HM-11 as an inexpensive but reliable station accessory that could continuously monitor transmitter tuning, antenna matching, and reflected power. Because the unit handled up to one kilowatt and required no external power, it became widely used with Heathkit transmitters, transceivers, and linear amplifiers of the period including the Apache, Mohawk, DX-series, and SB-series equipment.
The HM-11 remained in production through the mid-1960s and continues to be commonly found in vintage amateur radio stations and collections.