[Milsurplus] Was AN/PRC-66 Guard Channel Module, now Classic UHF sets.

[Rian Robison]

> [Original Message]
> From: Morrow, Michael A. <mamorrow@tva.gov>
> To: WA5CAB@cs.com <WA5CAB@cs.com>; <Milsurplus@mailman.qth.net>
> Date: 9/3/2003 10:22:04 AM
> Subject: RE: [Milsurplus] Was AN/PRC-66 Guard Channel Module, now Classic
UHF sets.
>
> Robert wrote:
>
> > I would have said that the Classic UHF set was AN/ARC-12,
> > a mod of AN/ARC-1.
>
> The RT-58/ARC-12 looks like a neat set.  I've got the manual,
> but not the radio.  It used all the same support components
> as the AN/ARC-1 did, except for antenna.  I suppose the idea
> must have been to be able to pull out the RT-18/ARC-1 and
> replace it and the antenna with AN/ARC-12 units, leaving
> rack, cable, and control box installations intact.
>
> I remember Fair Radio was selling these in the mid-1960s.
> I wanted one, but couldn't afford it or shipping on a junior
> high school student's income.  I've not seen one offered anywhere
> since.
>
> > The ARC-27/55 were made in much larger quantities...
>
> Which is exactly what, IMO, makes them "classic."  The earliest
> contract date I've seen on a RT-178/ARC-27 was 1952, so this RT
> was one impressive piece of electronic and mechanical engineering
> for its era.  I know some were still flying more than 25 years
> later.  The common use of the AN/ARC-27/55 is sort of like the
> AN/ARN-6 ADF, which also was found in almost everything that flew
> during the -27/55 heyday.
>
> I prefer the unpressurized version, the AN/ARC-55.  It is a lot
> easier to pop the top cover and admire the works inside than is
> the AN/ARC-27.
>
> Here's an unrelated question:  What was the difference between the
> AN/ARC-1 and the AN/ARC-1A?  I've got manuals for both and I've
> not been able to detect any difference between the RT-18 and the
> RT-18A, nor in the remainder of the system.
>
> 73, 
> Mike / KK5F


Hi Mike,

The difference that I know about is the ARC-1 has an extra 6AK5 mic
amplifier and a higher value resistor divider network in the mic input
transformer circuit which cuts the input level that is then made up by the
extra tube.  I assume it was discovered that if they increased the mic
input level by reducing the network resistance values that they could get
rid of the mic amplifier tube and save $$ and called the modified unit the
ARC-1A.  There has to be a difference in the filament string also because
of the extra tube but I don't have an ARC-1 diagram to see what.

I have an ARC-1 that I have got working with a bad channel motor (looking
for one).  I have an ARC-1A manual that I have had since the Navy (late
50's, out in 61) when I worked on ARC-1A's along with other aircraft
equipment.  I would like a copy of the ARC-1 diagram and will pay, of
course, if not too much trouble.

Hope this helps.

73,
Rian/W6SVU
>
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