Note
The MT-1 and MR-1 were Heath’s first mobile rigs. They are a matched set designed primarily for mobile use, though fixed-station operation is possible. QST reviewers were very impressed with the pair. They noted that in spite of their many features, the Cheyenne and Comanche combination required “a mere cubic foot” of space.
The MT-1 transmitter is a 7-tube design (including a 6146 power amplifier) covering the 80-10 meter bands. No PC boards are used—all wiring is point-to-point. The VFO uses a 6AU6 as a series-tuned Colpitts with an output of 1.75 or 7 MHz, depending on the band selected. The VFO is voltage regulated with a 0A2. A spotting switch is provided. Screen modulation is used for AM. The MT-1 will operate AM or CW (no SSB) with an input power of 90 watts and must be used with one of the following power supplies: the MP-1 or HP-10 (for mobile use) or the UT-1 or HP-20 (for 120 VAC use).
Features include a built-in VFO with an illuminated slide-rule dial, a controlled carrier modulator, four RF stages, PTT (no VOX) operation, and a spotting function. There are no provisions for crystal control.
The front panel meter reads PA grid or plate current. Front panel controls include main tuning, band selector, final tune, final load, drive, audio level, mode selector, spotting, and meter function.
Rear panel connections include two 6-pin connectors, which provide connection to the power supply and loop-through power to the receiver. There are also two SO-239s. One is RF out for a 50-75Ω antenna, and the other connects to the receiver. In addition there is a quarter-inch key jack. The microphone connector is on the right side of the chassis.
The main tuning mechanism involves a veritable clockwork of gears and pulleys, including a couple of right-angle gear linkages. As noted elsewhere in this book, repair of these mechanisms presents a challenge.
Some Heath advertising incorrectly states the tuning ratio as 30:1. The MT-1 (and MR-1) tuning mechanism is smooth but rather coarse—about 14:1. That works out to about 35 kHz per turn. Dial markings are printing on a translucent plastic drum that rotates to display band frequencies as the band switch is turned. This drum can crack if the unit is subjected to rough handling. Check it carefully before you buy. It would be very difficult (but not impossible) to make a new one if a salvaged drum could not be found.
In 1962 the MT-1 was completely redesigned to include SSB operation. The new rig was designated the HX-20 (no Indian name used), but is almost identical to the MT-1 in outward appearance. Take care not to confuse them. The MT-1 is dressed in Heath’s standard two-tone green colors. The AK-6 mobile mounting bracket is almost always missing.
The MT-1 was originally shipped with an Electro-Voice 729SR microphone (not sold separately), but by early 1961 (at the latest) was being supplied with a Turner 350C, available separately as Heath’s GH-12 hand mic.
References
Brief description. Radio News, Apr 1959, p. 150.
Review. QST. Apr 1960, p. 43.
Review. CQ. Mar 1960, p. 58.
Crystal control. CQ. Aug 1960, p. 79.
Modification. QST. Oct 1960, p. 50.
Reduce heating. CQ. Apr 1961, p. 112.
Use on 6 meters. CQ. Mar 1966, p. 65
Modulation problems. CQ. Dec 1966, p. 79.
Crystal control. CQ. Nov 1968, p. 115.
Use on 160 meters. CQ. Feb 1976, p. 29.
Power input: 90 watts AM and CW
Output power: 30 watts nominal at 100% modulation
Output impedance: 50 to 72Ω
Frequency coverage (MHz): 3.5 to 4.0, 7.0 to 7.3, 14.0 to 14.35, 21.0 to 21.5 , 28.0 to 29.7
Power requirements:
6 volts at 4.7 amps or 12 volts at 2.35 amps AC or DC
–125 VDC at 20 mA
300 VDC at 100 mA
500-600 VDC at 150 mA
Tubes: (1) 0A2, (1) 6AU6, (1) 6CL6, (1) 6DE7, (1) 12AX7, (1) 5763, (1) 6146
Photos, general information and specifications from "Heathkit: A Guide to the Amateur Radio Products," by Chuck Penson, WA7ZZE. Used with permission.
