[Milsurplus] ARC-2: Smart People Needed

[Ray Fantini]

Just had the opportunity to look at the schematic and now see just what's going on inside the ARC-2 and have to say although I never knew it that radio is way significant, don't know if the Collins collectors know this or not but the design of the radio using a variable IF over a fixed IF may be the first example of this in a Collins design, something almost everything they did for the next twenty years incorporated. Although designs a little later like the 618S/ARC-38 did use double conversion and added an additional stage of fixed frequency IF to resolve the response problem you see this same system, double conversion with variable first IF and fixed IF in all of the 75A, S line, KWM-2, R-388, R-390 and the 618T family of SSB transceivers and signal conversion variable appearing in transmitters like the T-195 and T-368 so with that in mind looks like the ARC-2 transceiver although not all the way to the level of something like an ARC-38 is way ahead of signal conversion prewar design of stuff like the TCS. Think the ARR-15/R-105 may fit in there somewhere but think that's only a signal conversion standard design receiver. It's amazing that just about the time you think you're somewhat familiar with these old radios you discover you don't know anything at all! And I once owned an ARC-2 and never thought much of it or realized its significance.

Ray F

-----Original Message-----
From: David Stinson [mailto:arc5 at ix.netcom.com] 
Sent: Wednesday, April 02, 2014 12:01 PM
To: Ray Fantini; milsurplus at mailman.qth.net
Subject: Re: [Milsurplus] ARC-2: Smart People Needed


----- Original Message -----
From: "Ray Fantini" <RAFANTINI at salisbury.edu>
>... tossing up speculation at this point but isn't there a fixed 
>frequency IF stage after the variable IF? Know all the Collins stuff of 
>the late forties and fifties used a variable IF section and then a 
>second converter to a fixed frequency IF on 455 KHz for civilian stuff 
>and frequencies like 500 and 250 KHz for military radios....

The 3rd IF is just a DC amp driving the 4th IF.
That has only a band-pass filter fixed at 1.0-1.5 MC.
So no help there.