[Milsurplus] ARC model D

[arc5 at ix.netcom.com]

----- Original Message ----- 
From: "Michael" <wh7hg.hi at gmail.com>
Subject: Re: [Milsurplus] ARC model D (actually Stromberg Carlson Model D)



>...  It wasn't until 1934 when the
> GF-2 (which roughly maps to the BC-A*-229/-429 but with a vastly different
> tube lineup) came out that the power settled down at a more reasonable 15
> watts out for the Navy version and slightly less for the AAC version.
------------

Actually, the AAC SCR-183 / -283 never got beyond
the QRP power level, running essentually 1.5-3.5 watts.

> At the same time, I hope to gather enough SCR-A*-183...
>with which I can experiment along the same lines as
>our Mr. Stinson to see if some non-audiophool friendly
> tubes will work just as well with the Tx..........

I've experimented with the MO and PA, but not so far
with the modulator.  1626 triodes work, as do triode-
connected 6AQ5s and 5863s.  All neutralize and tune-up fine.
I'm thinking of running an extra wire through the sockets and
making a real screen circuit for the pentodes, just for fun.
Will get to the modulators one of these days.
Remember, when you build it- as Mike Hanz kindly reminded me-
the entire set, be it SCR-183 or GF/RU or ARC-5 or whatever,
needs to be built on a decent ground plane.  If you don't,
FMing and stray RF will bedevil you, even at 2 watts.
I don't like working with big sheets of metal, so I used
aluminium duct tape, folded along one edge and the ends
to make contact from strip to strip, and layed-out
a grounding grid to which everything connects.
Works great.

>playing with the innards of an otherwise pretty-close-to-parts type Rx to
>see if making something regenerative will help it become a CW Rx.

I tried this with a -183 receiver.   The feedback level was crazy
touchy; a quarter of an inch movement in the feedback lead
meant either readable- if weak- CW signals or completely blocking
the receiver.   I didn't find it to help much with selectivity, either.
There's probably a better way than just running a wire two
stages back from the antenna post, but I haven't gone further yet.

The biggest problem with the 183-type receivers isn't that they
are (intentionally) broad- it's the bandspread, with all of 80-meters
covering a very small portion of the dial rotation.
That was also intentional, since getting every aircraft on
freq and keeping it there was more art than science in
the 1930s, and these guys were supposed to stay physically
close to each other. They weren't out to work DX;
they just wanted to talk to their wingman 100 feet away.
Broad receivers and high signal levels worked well
for the intended missions of training,
short flights around CONUS, etc.
That being said, *my* "mission" for this set is to use it
(and other low-power aircraft sets) into an amp I built to
boast them up to the 100 watt level, and talk to the local
guys on 3890 KC.  They're loud enough to "boom-out"
the side-winders ;-).

73 Dave S.