[ARC5] RU, GF, and What Else?

[David Stinson]

----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>

> I would think that the RU would purposely show wide 
> selectivity, since some
> of the aircraft transmitters were no particularly stable or 
> accurately tuned.

Respectfully:
That the transmitters were "unstable" is myth,
born of inadequate power supplies and
misunderstandings.  I have the sets here, complete
and operational on-the-air.
When employed as-designed, they are far more
stable then, say, expensive Ham equipment of the 50s.
I can use my original-design operating SCR-183
(after a 30 minute warm up, of course) on local AM
nets and never touch the tuning from start to finish.
Not even my Drake TR-7 can say that.

But there is an earlier origin to this myth:
the pilots themselves.  These young, impatient men
would repeat "darn radio" stories they heard from
the "old hands" (back when the radios really were
unstable and "more art than science").  They would
give a call or two and, if not immediately answered,
start cranking-away on the "coffee grinder" receiver
tuning.  Then the second pilot in the flight would do
likewise,  etc.  Before it was done they're all off
freq and unable to find each other, then land and
tell more stories about their "darn radios."
This is one reason the radios were made "broad"
in the first place.  The engineers certainly knew
how to make a "single signal" receiver.
They were also smart enough to know the
hot-heads in the cockpit would "fiddle finger"
the receiver tuning, even when just changing
from one air-to-ground freq to another.

Gordon White can tell you how A.R.C.
was tasked to study this problem mid-war for
application in the new JAN ARC-5 sets.
Their solution was to improve the already good
stability of the receivers and take the manual
tuning crank away from the pilots.
They didn't touch the transmitters, because the
transmitter stability was just fine and not
the root of the problem.

The SCR-183, ATA/ARA.SCR-274N and
AN/ARC-5 are all exceptionally stable for
their time when run as-intended.

Regards,
David S.