[Milsurplus] 618S preliminary manual publication date

Sat Jul 18 00:32:15 EDT 2015

Hi MikeThanks for your reply.Just after I posted my question to the two groups, I Google searched under "Brochure 618S" and found some links which led to this:
http://rockwellcollinsmuseum.org/collins_signal/viewer.php?i=Win53&m=20&r=0&z=1&p=16
On page 17, under the paragraph titled "Design with a Future" the article mentions the development of a SMO for the 618S early on in the design.  So I have an approximate date and my question is answered.  The last quarter of 1953 is the date of this Collins Signal issue which, for my purpose, is close enough after 60+ years have gone by.
In my exchange with Ray, he mentions that there does not seem to be much difference between most of the modules of the 618S and the ARC-38.  Now I have had, at different times, both an ARC-38 and ARC-38A but never did anything with either of them so I passed them on.  I haven't seen a complete 618S but I might have scrapped an 618S mainframe about 30 years ago so if you say that there is a significant difference between the 618S and ARC-38 then that is good enough for me.  
But Collins seems to change the part numbers of modules along with the model number of the end item.  I think that all of the KWT-6, URC-32 and ARC-58 modules, except for those that are mechanically tuned or are 400 cycle servo amps are all interchangeable.  If it fits, it works.  Although to be fair, some improvements were made in similar modules.  For example, the Reference Oscillator initially was an all vacuum tube design but was changed early on to an all transistor design.  Then it went through an iteration from stabilized oven to temperature stabilized crystal with other minor circuit changes.  But even then, any Reference Oscillator module would replace any other.  130 volt B+ is still available at the Reference Oscillator main frame connector which is regulated by zener diode to provide 20 volts for the transistorized Reference Oscillator.
One another thing to note is that the ARC-38 was designed for the Navy which can't help itself, it has to put it's finger prints on the equipment form and fit and possibly the function too!  The Navy always seems to need customized equipment, nothing stock for them, no sir.  My assumption that the ARC-38 is a follow on of the 618S is, in part, that there is no direct frequency input to the control head.  One must use a code book since the design originally supported a 144 crystal module as is in the 618S.
Another example of Navy customizing a stock radio would be the KWT-6 versus the URC-32.  A few boxes were added to the KWT-6 and a better but remotely controlled manual antenna tuner to match the transceiver to ship born whip antennas.  And I think the whole equipment rack is on vibration isolators and there is additional bracing to isolate the rack from the ship's bulkhead and the rack is shorter to boot.  
Now I accept that these mods were needed since a ship is a harsh environment for electronics just as an airplane is for avionics.  But the differences between a KWT-6 Type 5 and the URC-32 aka KWT-6 Type 8 are minimal.  I just assumed that the same conditions exist between the 618S and ARC-38.

Regards,
Jim

      From: Mike Morrow <kk5f at earthlink.net>
 To: Ray Fantini <RAFANTINI at salisbury.edu>; "milsurplus at mailman.qth.net" <milsurplus at mailman.qth.net> 
 Sent: Friday, July 17, 2015 7:55 PM
 Subject: Re: [Milsurplus] 618S preliminary manual publication date

Ray is correct.  The USN RT-311/ARC-38 is definitely NOT a 618S-1 "with SMO".  That's an old old ham-ster claim...made without checking ANY technical details apparently.

However, there was a USB/channelized VFO version of the 618S-1 known as the 618S-1/MC that uses a control box with alpha characters to select the frequency.  It has NO memory drum.  The USAF bought some.  This modification was engineered and performed by RCA.

And FWIW, the USB modification that created the USN RT-594/ARC-38A was engineered and performed by RCA.

And FWIW again, the USB modification of the USAF RT-128A/ARC-21 that created the RT-400/ARC-65 was by RCA...but the original AN/ARC-21 set was an RCA set.  It looks like RCA made a business of USB mods for Collins gear as well as their own.

Mike / KK5F

-----Original Message-----
>From: Ray Fantini <RAFANTINI at salisbury.edu>
>
>If you look at the stenciling on the chassis of the 618S you will find that it list the sections for the 144 channel crystal pack or the SMO version. At first I thought that this was because the 618 was an ARC-38 without the SMO but have learned later that the ARC-38 chassis is way different then the 618S. Over time I have owned and operated the 618S-1 with the crystal pack and later I built a SMO assembly from an ARC-38A chassis that allowed you to QSY, an ARC-38 non "A" that’s a great radio for AM and CW and the ARC-38A that’s a SSB nightmare compared to the simple versions produced before. 
>Have seen these radios a time or two and do not believe that there were any 618S with SMO produced, but that’s just my opinion and I had also thought the non A version of the ARC-38 was extinct, but then saw pictures of one in Australia and have come to own one myself so there at least two out there.
>Trivia the PA, Slug rack, and servo amplifiers are all the same although the last series had "Modified for SSB" stamped all over them and the audio output amplifier system for the receiver is the same in all three radios and the ARR-41 too.
>
>Ray F
>
>
>-----Original Message-----
>From: antqradio at sbcglobal.net
>Pardon the double post.
>Does anyone have a copy of the preliminary instruction manual for the 618S?  The manual on the web, which is for the 618S-1/-4, has a pub date of 15 October 1957 while the preliminary manual I have for the AN/ARC-38 has a pub date of 1 June 1956. So if the ARC-38 is indeed a 618S with a SMO, (why else would you need a code book to set frequency?) then the 618S must be a bit older then June 1956.  Does anyone know for sure when the 618S first entered commercial service?
>Any help appreciated, Jim

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