[Milsurplus] Navigation System

[Mike Morrow]

I wrote:

>That would be scary...trying to automate the landing
>of a WWII-era equipment aircraft.

Michael Tauson wrote:

>Good point.  On the other hand, a tired pilot landing
>a damaged airplane wouldn't be any sort of picnic
>either.  I have no idea how they did it once, let
>alone time after time 

Hi Mike,

I think that was likely with the more precise Microwave Landing System, which never really "took off" (hee hee) in North America, but evidently had to some extent in Europe.

>I think I’ve seen an ARN-7 or two floating around
>so that shouldn't be a real headache.  Were the
>control boxes the same as the ones for the SCR-269 or
>were they changed too?

An SCR-269 could be changed to an AN/ARN-7 by replacing the BC-433 receiver with the R-5/ARN-7, and by replacing the BC-434 control box with the C-4/ARN-7 (and depending on SCR-269 model, adding wiring for the CW mode switch).  The main difference between the two systems is that the AN/ARN-7 had four bands vs. three, and covered down to 100 kc vs. 200 kc.

>The Collins 18S-4 (for which I need at least a
>schematic for now) was also the RT-698/ARC-59

This is like the Bendix RTA-1B HF receiver-transmitter of WWII.  It's military version was officially the AN/ARC-9, but no RT number was assigned, and to my knowledge none ever had a name plate with AN/ARC-9 on it.  The military manual was labeled AN/ARC-9. 

Likewise, the Collins 18S-4 had a military version called the AN/ARC-59 (and the manual is labeled thusly), yet there was NO JAN RT number assigned, nor have I ever seen one that even had a military name plate with AN/ARC-59 on it.  Send me your address and I'll get you a schematic WHEN I can find the manual.

The RT-698 goes with the AN/ARC-102, and is the military name for the 618T-3 HF transceiver, a truely beautiful design, likely the most-used and longest-lived airborne HF set of all time!

>while the 618S-1 (non-SSB version) which was a later design
>was the RT-311/ARC-38.

This is a common, but erroneous, opinion.  It arises because most of the modules are the same and the units look similar from outside.  The 618S-1 was used by the military, but it is very very different from the RT-311/ARC-38 in the frequency generation section.  The 618S-1 uses a simple crystal-controlled master oscillator (one crystal required per channel, about 100 channels) whose control box selectes the appropriate channel, while the US Navy's RT-311/ARC-38 used a complex "stabilized master oscillator" that was capable of selecting any of about 38,000 channels spaced at either 0.5 ot 1.0 kc intervals (depending on frequency) from 2.0 to 25.0 mc.  The control box C-1398/ARC-38 did not read out directly in frequency due to the limitations of technology in the mid-1950s (yeah, I know, the USAF's early 1950s RT-128/ARC-21 HF set used direct frequency selection, but that was RCA and not Collins).  It required a code book stored in the box to tell what combo of switch or channel set pin positions resulted in a particular frequency of operation.

> (The SSB version, for which I would like to find a control box,
> was the RT-594/ARC-38A.)

You need the C-3428/ARC-38A, which is a C-1398/ARC-38 modified to eliminate AM and CW SHARP positions on the mode switch and allow selection of AMe(quivalent) and USB modes.  This control box is much easier to find than original C-1398 boxes, of which most were re-worked to be C-3428 units.  I wouldn't be surprised if Fair Radio didn't have those today.  I've got a complete AN/ARC-38A, and I've looking for a C-1398 to complete my original AN/ARC-38.

Any true AN/ARC-38 or -38A installation should also have the associated HF auxiliary receiver, the AN/ARR-41.  The frequency coverage (plus beacon band) and modes are identical to the AN/ARC-38, but features direct frequency readout.  This receiver is also often (very) erroneously described as a replacement for the BC-348, something which it definitely was not.

The AN/ARC-38 with AN/ARR-41 was a US Navy set that was the replacement for the USN AN/ARC-25 (combo of AN/ARR-15 and AN/ART-13) set.  It was replaced by the AN/ARC-38A, then by the AN/ARC-94 (Collins 618T-2).  Sometimes the AN/ARR-41 was left in place with the AN/ARC-94, and some times the AN/ARC-38, 38A and/or ARR-41 would be found in USAF aircraft that had earlier seen US Navy service.

>All three (BC-341, -357 and -1333) are easy to find,
>and I think I can get a BC-1333 still in the box.  NO
>mount, though. Does it fit the same as the others?

Yes, all these receivers mount on the FT-161 shock base.  The hardest MB component to find is the 75 mc dipole antenna and proper hardware.  The BC-1333, unlike the BC-341 or -357, requires no B+ supply, just 28 vdc.

I wrote:

>> The MB indicator used by WWII-era MB receivers was a
>>simple 28 vdc indicator lamp assembly.  

Michael Tauson wrote:

>I presume there was a tag that said something like
>"Marker" or some other thing to uniquely identify it. 

Yes.

>I can get an R-54 or an R-89 so I'm set either way.  I
>would hate to think about having to fabricate mounts
>though.  That would not be pleasant at all.

The R-57/ARN-5 was single channel.  The Radio Operator Information Files (ROIF) of the era mentions that the crystal may have to be swapped in flight.  During late WWII, the R-89/ARN-5A was preferred because it had three crystal-controlled channels selected by the BC-732 control box.

>What would be cool would be the entire set - what we
>discussed above plus the more mundane bits - airspeed,
>altimeter, vertical speed, compasses (gyro and
>magnetic), artificial horizon etc ... all working and
>in an instrument panel - say the driver's side of a
>B-25's or something.  Or capable of working.  Not
>necessarily airworthy but good enough that when power
>is applied, the gyros spin up and stabilize as they
>should.  I'll worry about how to make the rest look
>good some other time. 

Sounds like a challenging project, but worthwhile.  I have my hands more than full just dealing just with the radio stuff, and finding storage for it.  For example, I have either all of, or most of, the HF sets mentioned above except the AN/ARC-21.  It all takes up sooooo much room!

eBay is the best resource ever for finding oddball, limited general interest stuff like this. 

73,
Mike / KK5F