The PRC-68 is the first of the synthesized hand held portables designed and

built by what was then Magnavox/Ft. Wayne, Indiana (since swallowed by

Hughes Electronics, which has since been swallowed by Raytheon). As such,

it has some advantages and disadvantages over the units that followed. The

good news...10 channels, small size, simple modular construction (8

modules). The bad news, 50 kHz spacing instead of the now standard 25 kHz,

needs a field strength meter to tune the antenna matching network when

changing channel sets, and the 10 channels are in successive steps of 200

kHz spacing. It is the most available today, selling for $200 up, and is

the easiest to fix. It also covers 51 MHz, which seems to be the place to

be when at a ham and/or a Mil Vehicle event.

The PRC-68A was the first attempt to solve some of the shortcomings of the

PRC-68. They lengthened the case by about an inch, changed to two modules

(One front, one rear), and went to microprocessor control (all of which

became the standard for all models to come). The set has 25 kHz channel

spacing, does not need an FSM for tune up, and allows 10 channels to be

randomly programmed as long as all ten are within one of the 4 slightly

overlapping bands. Not too many are around as I suspect not too many were

bought.

The PRC-68B was ordered by both the Marines and Air Force on what I suspect

was combined funding. As a result, this radio has the most functionality of

any of them, including all that followed. A display was added where the

speaker/mic was, so the spkr/mic was moved to a projection of the top piece

(they call it the "panel"), making the unit 0.6 inches taller than the

PRC-68A (1.6 inches taller than the PRC-68). This size and the display

became the standard for all units to come, the only changes being in the

frequency setting controls. The antenna tuning switch was moved to the

front (the unit beeps at you when you don't have it set right). This allows

all 10 channels to be randomly programmed anywhere in the band of coverage.

This unit also handles Tx to Rx offsets (for repeaters). Two features

unique to the "B" model only are that it allows the channels to be set in

2.5 kHz increments, making it compatible with almost any band plan

anywhere, and each channel can be programmed as a narrow band channel (i.e.

like the hams, police and fire, etc.) or as a wide band channel (military).

The unit could be switched to High Band by swapping out the RF module. Fair

Radio has these for $495 with antenna, low band only. From time to time,

Murphy has these also.

The PRC-126 came along as a simplified PRC-68B. It kept the display, but

lost that complicated wide/narrow and 2.5 kHz stuff. So, it's back to 25

kHz channels, and no possibility some grunt can set it wrong. This is the

present Army/Marine combat hand held. Units sell for $500-750.

The PRC-128 (Scope Shield I)is a PRC-126 but with 12.5 kHz channel spacing

for A.F. guard duty. It also can take a high band module. Market price

seems to be similar to that of the 126.

The PRC-136 is, I suspect, a High Band only PRC-126 or 128, and is in

service with the Marine Corps Crash Fire Rescue Service (CFRS).

Some of these units had a vehicular RF/AF/Power Supply module to allow

powering from the vehicle, amplification of RF and AF signals, and unit

mounting while in the vehicle. These are as follows....

PRC-68A, OG-174 for Army fire control

PRC-68B, AM-7302

PRC-128, OF-185

PRC-138 (Scope Shield II, Racal, not Magnavox), OF-228 (Note: this radio

covers three bands by module replacement, not just the two bands of the

PRC-68B and PRC-128.)

Thanks to Joe Pinner for help on some of the above.

Alan