[Milsurplus] A Little on the ARC-2

[WF2U]

I have one of each model. I used the -2 on the air, with the help of an
outboard audio filter. I used the Radio Shack DSP box, which made life much
easier. I worked on 80 M CW with no problems. The radio puts out exactly 40
W. I used my regular station antenna tuner to work it into a coax-fed
dipole. It also works decently on AM. I'll put it back in operation soon, as
I rotate equipment I use on the air.
I haven't used the -2A yet. I got it out of a desert aircraft graveyard and
the sand abraded most of the paint from the front panel - it looks almost
like brushed aluminum... Inside it looks brand new.
I wish I could find an original mounting rack for it, but I'm afraid it's
unobtanium...

73, Meir WF2U
Landrum, SC

> -----Original Message-----
> From: milsurplus-bounces at mailman.qth.net
> [mailto:milsurplus-bounces at mailman.qth.net]On Behalf Of David Stinson
> Sent: Thursday, August 25, 2005 10:19 AM
> To: Milsurplus
> Subject: [Milsurplus] A Little on the ARC-2
>
>
> The AN/ARC-2 doesn't get the attention it deserves;
> it was a big techno-leap forward for a WWII rig.
> The WWII vet is the RT-91/ARC-2; the RT-298/ARC-2A
> is a post-war version with several circuit improvements.
> I have both sets here and will probably be selling
> the -2A model in the near future.
> Other than the obvious addition of a fuse block on the front
> and removing the meter switch, the main changes are
> in the receiver front end and the variable IF.
>
> While both receivers are "broad,"
> the -2 is much broader than the -2A.
> Both ARC-2 sets use small caps to couple between
> tuned circuits in the IF strip.  In the earlier ARC-2,
> these were 12 pFd, which loaded the circuits and
> reduced Q, making them broad.  The ARC-2A design
> changed these to 5 pFd, giving a marked improvement.
> Changing them to 2-3 pFd with improve it more.
> The -2 IF strip is tuned using the coil slugs.
> The -2A has trimmer caps, making the tuning less "touchy."
> In the -2, the forth IF uses degeneration to
> try and "flatten" the gain response of the IF strip.
> The -2A removes degeneration and does this with
> extra tuned circuits.
> There are also changes in the mixer designed to
> "flatten" its freq response and provide better shielding,
> but I don't think that's as important as the IF changes.
>
> There are some differences in the transmitter output networks-
> neither model will tune a 50-ohm antenna without external help-
> but the transmitters are otherwise electrically identical.
>
> A couple of tips, learned the hard way:
> To get the cover off the rig, you first must remove the
> round "air filter" vent covers.  If you have the "C" shaped
> spanner wrench on the back, that's its purpose.
> Yes- I did waste an hour trying to figure it out.
> My only excuse: I didn't have the manual at the time.
>
> The dynamotor mounting is a Rube Goldburg thing-
> it will give you grey hairs.  The dyno comes out
> easy enough, but it has this off-set connector,
> flush with the dyno body, which goes out at a
> 45-degree angle to plug into this bunch of tilted
> connector posts.  That wouldn't be so bad, except that
> the center of gravity of the long axis forces the connector
> down away from the plug when you try and reinstall it
> and there's no room for your fingers.  In other words-
> when you try to engage the connector, the dyno rotates
> away from the plug and you can end up "boogering"
> the connector if not careful.  I don't know how
> to do this better- it took me awhile
> to get the blasted thing back in place.
>
> It's a very cool set.  If you have one,
> you should try it out sometime.
>
> 73 Dave S.
>
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