[Milsurplus] ARC-38 and 618S1

[Ray Fantini]

I use to have a 618S1 that I used for AM until I obtained my ARC-38, the 618S1 is almost identical to the ARC-38 less the SMO assemblies and the radio chasse itself. Don't know exact details and although the PA, modulator, servo receiver and slug rack are all the same. Have also learned that there is no difference between things like the servo, PA and slug rack between the ARC-38 and its evil SSB descendant the ARC-38A although you will find "Modified for SSB" stamped on all those parts if they were in a ARC-38 first. Have to wonder if there were ever any new ARC-38A sets that were produced or if all ARC-38A sets were converted Collins ARC-38 sets? I know that most of the ARC-38A set I have come across are all Collins manufacture and have the logo painted over on the front cover.
Little known Trivia, the control head for the 618S1 has two selector knobs, one picks the appropriate crystal in the crystal pack and the second knob selects the band the radio is operating on. Band one is 2.0 to 3.75 band two 3.75 to 7.25 band three 7.25 to 14.25 and band four being 14.25 to 25.0 so with a rock for 3.475 you can operate on band 1 at 3.725 or band 2 at 7.200 or band 3 at 14.150 by using just the band selector and the same crystal.

I have a web page with a lot of my ARC-38/618S1 stuff on it:
http://staff.salisbury.edu/~rafantini/618S1.htm

It's an amazing radio along with all that generation of autotune radios with the mechanical and servo system to get them to work. With today's wide band low Q solid state we are not likely to see anything like that again.

The last several years I have been working with a lot of the first generation of synthesized HF radios like the R-1051, T-827 and the GRC-106 and its incredible how the engineers of the day had to use all sorts of systems and sub systems to design radios that were able to work from 2 to 30 MHz Nothing like the direct digital synthesizers that we take for granted today. You can clearly see that the designs by General Dynamics and others were mission driven and not cost driven or else you can never account for the cost and complexity.
If there is any interest I can always go into the theory and applications of multipole injection and band pass filtering synthesizers like the six pack and why things like the thirty band turrets in all that first-generation stuff was so important.

Ray F/KA3EKH


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/milsurplus/attachments/20201029/6ff5c471/attachment.html>