[Milsurplus] ARC-38/618S1

[Mike Morrow]

Ray wrote:

>...it appears that the 618 can be converted to an
>ARC-38 by inserting those three modules.

Ray,

I don't think I have a schematic of the 618S-1, and I don't have my ARC-38/38A manuals with me now, so I'm writing vaguely now.  I think the job will involve more than just swapping out modules.  In addition to the several modules that are different in a RT-311/ARC-38 compared to a 618S-1, you have completely different control box configurations and cabling from rack to controls.  The 618S-1 control box (channel selector, primarily) is not even remotely similar to the main ARC-38 or -38A control box (which can select frequencies in 0.5 or 1.0 kc intervals depending on frequency from 2 to 25 mc, using code wheels or pins IAW the book stored in the bottom of the control box).

The large stabilized master oscillator (SMO) assembly of the RT-311/ARC-38 is of course very different from the crystal bank oscillator of the 618S-1.  It has its own JAN nomenclature of O-215/ARC-38.  And the SMO of the USB RT-594/ARC-38A is a quite heavily modified version of the one that was in the RT-311.

>And the next question is should I order all the above
>modules from Fair at a high cost or just buy a dozen crystals
>and what would be cheaper? 

Several years ago, Fair sold O-215/ARC-38 SMOs for $35, but they're long gone.  Unless they've recently discovered a hoard they didn't know they had, it may be hard to locate this key unit.

And don't forget the cost of the maintenance manuals for the 618S-1 and the ARC-38/38A.  You'll need both to have much chance to successfully engineer a Frankenradio.

As late as late 2002, Fair still had real RT-311/ARC-38 units in the warehouse, though they weren't advertised.  I picked out one in excellent condition for $125.  If you want something that acts like an RT-311, I'd search for a real RT-311.

On the other hand, it would seem to me that putting a few appropriate crystals in a stock 618S-1 would be a relatively easy way of putting a radio of this type and vintage on the air.  The ARC-38 and -38A SMOs have histories of being problematic after decades of dis-use and possible mis-storage.  But just what can go wrong with a bank of crystals, such as found in the 618S-1?  Plus, 618S-1 units are very common.  I've seen a stack at Dayton go unsold even at $50 each.  I think Fair sells them for $75.  Cheap either way, and easy to get parts for cannibalization!  The appropriate rack, control box, power unit, and 400 cps power are much more challenging!

73,
Mike / KK5F