[ARC5] RU, GF, and transmitter stability...

[Kenneth G. Gordon]

On 11 Nov 2015 at 11:57, David Stinson wrote:

> 
> ----- 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.

David: I was not talking about the various U.S. and even some other (U.K.), 
military transmitters of the period, all of which that I am even remotely 
familiar with were "unusually" stable. "Unusually" in the sense that many 
modern hams think they were unstable.

If you will look closely, I said "...SOME of the aircraft transmitters....", and 
some were.

Also, even our stuff was not what I would call "...accurately calibrated..." and 
in addition, there could have been mistakes made in setting the transmitters 
to frequency anyway.

Purposely keeping the receivers relatively broad would, in my opinion, go 
very far towards making communications possible where otherwise it would 
have been difficult if not impossible.

>  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.

There was also a recent article in Electric Radio magazine on, I believe, a 
GF. The author stated that the stability was, in his words, amazing.
 
> 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."

Yes. I have heard that story too, and believe it.

> 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.

As I said above...

> 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.

Again, yes, as I said...

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

Agreed, and I never meant to indicate otherwise.

Ken W7EKB