[Milsurplus] ARR-41 Info

[Mike Morrow]

Scott wrote:

>The 618S-1 is an ARC-38, the 618S-4 has 144 crystal controlled 
>channels. 

It's the 618S-1 that has 144 crystal controlled channels.  I have a USAF 618S-1.  The RT-311/ARC-38 is an advancement over the 618S-1, because in place of the oscillator and crystal bank assembly, a complex stabilized master oscillator assembly is present.  The SMO is what gives the RT-311 the ability to tune in 0.5 kc increments between 2 to 14.25 mc, and in 1 kc increments from 14.25 to 25 mc, using the C-1398 control box.

Wasn't there a commercial member of 618S-series that was equivalent to the RT-311?

> The 618T-1 was the retrofit for the ARC-38

The 618T-1 was a retrofit for the 618S-series, not the AN/ARC-38.  But I don't know if the 618T-1 backfit could be applied to any 618S installation.  I have a Collins 618T to 618S-rack adapter.  I don't believe it would work in an AN/ARC-38 rack assembly because the connections required to control the SMO in the RT-311 requires the rack and system wiring to be quite different than that of the 618S-series.

I've never come across any example of the AN/ARC-38/38A being replaced by anything other than a full-fledged complete AN/ARC-94 (618T-2) installation.  But the USAF made a lot of use of the 618S-1 without JAN nomenclature.  It not would seem too unlikely that they might backfit a non-JAN 618T into some of those installations.

>The 180L-3 tuner was used with many early and 
>retrofit 618T installations

The AN/ARC-38/38A used a JAN version of the 180L called the CU-351/AR.  The 618S-series used the 180L.  And the AN/ARC-94 (618T-2) and AN/ARC-102 (618T-3) used a version of the 180L called the CU-991/AR, even though the maximum frequency of the 180L-series tuners was 25 mc (at best), 5 mc below the high end of 618T frequency coverage.  Evidence seems to be that the 490T tuner (JAN CU-1669/AR) with full range coverage was less commonly used with the AN/ARC-94 or 102 than was the CU-991/AR, at least through end of the Vietnam War era.

>(excepting the 618S-1MC and the ARC-38A SSB conversions)

What was the 618S-1/MC?  I seem to recall a 618S-4/MC, but in either case, I don't know what distinguished them from the rest of the 618S-series.

The conversion of the AM RT-311/ARC-38 to the USB R-594/ARC-38A was done by RCA.  I wonder what Collins thought about that.  I don't think there was an equivalent Collins USB 618S.

Mike / KK5F