[Milsurplus] [ARC5] GP with ARB?

Sat Oct 29 15:33:42 EDT 2022

MikeThanks for the explanation.  
I can see where the flex in the splined cable would make precise tuning a bit difficult but perhaps with the constant jiggling during flight, tuning in the airplane was a bit easier then on the workbench?  <grin>  I guess that this is just another reason for the broad IF bandwidth of military receivers of this era, along with LO instability caused by rapid changes in ambient temperature.
I have to say that the ARB is a favorite, mostly because it's contract date is my birth date for the day and month although I came along some seven years later.  Also because of the novel use of two IF frequencies to gain full frequency coverage with no gaps.  My next favorite receiver is the ARR-15.  It to had a unique slant on the IF section of the superhetrodyne.  Although the wide IF bandwidth in the ARR-15 is easily changed since it is controlled by capacitive coupling between IF stages.  
Been thinking on how to narrow the IF bandwidth in the ARB.  Too difficult to move the primary and secondary coils away form each other.  Has anyone experimented with a few turns of wire between the two coils to reduce the coupling?Regards,Jim

Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy

-----Original Message-----
From: Michael Hanz <aaf-radio-1 at aafradio.org>
To: Jim Whartenby <old_radio at aol.com>; milsurplus at mailman.qth.net <milsurplus at mailman.qth.net>
Sent: Sat, Oct 29, 2022 6:48 am
Subject: Re: [Milsurplus] [ARC5] GP with ARB?

 I was referring to the procedure that was required to tune to any given signal, Jim.  Both the RU and ARB were primarily designed as remote control radios (though it was certainly possible to use a spinner wheel on one of the two cable ports).  The remote location required a different procedure for tuning to a signal because of the different cable lengths in different aircraft.  With longer splined cables, there was more torsional flex and less "precise" control than one experienced with a radio like the BC-348 or the RAX-1, for example.  For all the improvements on the ARB, it wasn't perfect by a long shot.  The direct reading dial with all the frequencies printed on it (while certainly an improvement over the RU's 0-100), was never dead-nuts on and required some operator intuition.  At least that has been my experience with it.  But the roots of its moment-by-moment operation were formed by the RU.  Radio operators were required to use either set and do so without blinking an eye.  

 I guess I don't look at the ARB or any other WWII radio with quite the same lens as many others use (the ham radio/SWL perspective).  Engineers are forced to keep looking toward the requirements that the customers stipulate...it's always about the requirements.  From that perspective, the designers of the time seem to have done a fairly decent job.

 Happy Hallow-e'en,
 - Mike  KC4TOS

 On 10/29/2022 1:40 AM, Jim Whartenby via Milsurplus wrote:

    Mike What do you mean by "procedural roots"? Jim     Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy    

 -----Original Message-----
 From: Michael Hanz <aaf-radio-1 at aafradio.org>
 To: Hubert Miller <Kargo_cult at msn.com>; milsurplus at mailman.qth.net <milsurplus at mailman.qth.net>; ARC-5 List <arc5 at mailman.qth.net>
 Sent: Fri, Oct 28, 2022 9:29 pm
 Subject: Re: [Milsurplus] [ARC5] GP with ARB?

     Well, Hue is right in a sense.  But the ARB was intended to replace the RU as the whole Megillah of the moment - liaison and/or  command receiver.  Of course, that was in the time when the specialization movement began in earnest.  By the end of the war, you had specialized liaison, command, automatic compass, landing, and what-all receivers going into aircraft.  The ARB was certainly the equal of the BC-348 performance-wise, but for hams it is a lot clumsier to use from the user-friendly perspective, and as a general search receiver, its RU procedural roots are less than stellar.  I think that is why is rates lower on the scale these days.  

 Contrasting opinions are encouraged.

 - Mike  KC4TOS

  On 10/28/2022 8:44 PM, Hubert Miller wrote:

 You're thinking of the ARB + ATB, which was the pilot's Command radio. 
The radioman for CW position reports and so on, was GO + RU.  
I do not know for sure what Command sets were used when some of the PBYs were given instead BC-348 and ATC for liaison radio. 
-Hue Miller  

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