2 Meter Repeater Offset History – by Jim (WB0IYC)

A little History – 2 METER REPEATER OFFSETS – EXPLAINED

It is interesting to see how and why the 600 kHz offset on 2 meters was established.  Originally, it came about because receiver selectivity at 144 MHz was poor, and equipment very expensive.   Affordable radios were crystal controlled, thus two crystals were required for each frequency pair regardless if direct or with repeater offsets.  Standardization of the band came later.

The technology was not far advanced at the time when the 2 meter band became popular, and those limitations drove the band plans. Although there were no legal requirements placed on operators to define channels as in CB, original band plans were established that called for 2 meter FM operation at 30 kHz steps in the segment from 146 to 148 MHz. Repeater offsets were set at 600 kHz negative in the 146 MHz segment, and positive in the 147 MHz segment. It followed that the simplex (direct) frequencies would be located between the repeater offset frequencies and also spaced at 30 kHz intervals.  They began at 146.430 through 146.580 MHz, and 147.420 through 147.570 MHz.

This list shows the original standard. The early popular pairs are shown in bold type.  Radios were supplied with 146.52, and 146.34/146.94 pairs.

146 MHz Simplex frequencies:
146.43, 146.46, 146.49,
146.52, 146.55, 146.58
Repeater frequencies are shown as Input/Output pairs:
146.01/146.61 146.04/146.64 (#3)
146.07/146.67 146.10/146.70
146.13/146.73 146.16/146.76 (#2)
146.19/146.79 146.22/146.82
146.25/146.85 146.28/146.88
146.31/146.91 146.34/146.94 (#1)
146.37/146.97 146.40/147.00
(Note: 147.00 can have both + or – shift)
147.60/147.00 147.63/147.03
147.66/147.06 147.69/147.09
147.72/147.12 147.75/147.15
147.78/147.18 147.81/147.21
147.84/147.24 147.87/147.27
147.90/147.30 147.93/147.33
147.96/147.36 147.99/147.39
147 MHz Simplex frequencies:
147.42, 147.45, 147.48,
147.51, 147.54, 147.57

Popularity increased on the 2 meter band as semiconductor devices became available with improved sensitivity and selectivity.  Consequently, the frequencies were then split into 15 kHz steps.  However, Texas along with a few other contrary states did not follow this rule, and used 20 kHz steps. ¶