Note
GR-88 1969-1977 $54.95 (152-174 MHz)
GR-98 1969-1976 $54.85 (108-136 MHz)
These 16 transistor portable VHF receivers work surprisingly well. They have reasonable sensitivity and are quite stable and drift free. The units feature a 6-to-1 vernier tuning drive ratio, squelch control, a VFO-XTAL switch with provisions for 1 crystal channel, and an internal telescoping antenna. The receivers have a built-in speaker and a jack for an external 50-75Ω antenna. The IF on both versions is 10.7 MHz. The sensitivity was advertised at 2.0 µV for the GR-88 and 1.5 µV for the GR-98.
Frequency coverage for GR-88 is 152-174 MHz (FM) and 108-136 MHz (the AM aircraft band) for the GR-98. Both versions use PC board construction and feature a factory assembled and aligned tuner.
The units can be powered by six “C” cells or from 120/240 VAC with the optional AC power supply. The AC supply is built into a small metal box and fits inside the case of the receiver. The presence of the power supply can be determined by looking for a slide switch and a two prong connector on the bottom right side of the cabinet.
The units are housed in a leatherette case and have handles that double as a tilt-stand.
To check for battery leak damage, remove the case by removing the handle and handle mounting screws. To remove the handle, put the handle in the vertical position and push down on each side. Refer to Figure 2.
Note: The plastic tuning dials have a tendency to become yellowed with age and exposure to sunlight. This discoloration can sometimes be significant.
CRYSTAL FREQUENCY CALCULATION
Crystal frequency = (operating frequency in MHz – 10.7) / 3
References:
Use on 2-meters and MARS. 73 Amateur Radio. Nov 1978, p. 222.
Tuning range an mode:
GR-88: 152 to 174 MHz (FM)
GR-98: 108 to 136 MHz (AM)
Antenna input: 50 to 75Ω
Sensitivity:
GR-88: 2.0 µV or less for 20 db quieting
GR-98: 1.5 µV or less for 20 db quieting
IF: 10.7 MHz
IF selectivity: ±40 kHz @ 6 db down
Image rejection: 40 db or greater
IF rejection: 80 db or greater
Audio output: 250 mW at less than 10% distortion
Speaker: 3 inch round, 24Ω
Crystal frequency (MHz) = (desired frequency - 10.7 MHz) / 3
Crystal holder: HC-18U
Crystal load capacitance: 32 pF
Power requirements: six “C” batteries, or AC converter
Solid-State: (5) 2N2369, (4) 2N3393, (1) X29A829, (1) 2N2430, (1) 2N2431, (1) 40245, (2) 1N191, (2) 1N4646, (2) 2SC784 (in tuner), (1) SE-5006 (in tuner)
Photos, general information and specifications from "Heathkit: A Guide to the Amateur Radio Products," by Chuck Penson, WA7ZZE. Used with permission.
