[ARC5] AN/ARC-5 support for CW

Thu Mar 24 20:42:59 EDT 2016

I must admit to being very curious to know why a BFO was even included in the receivers if 
the use of CW was never contemplated under any circumstances.

The same question applies as to why a key jack was included in the MD-7.

Then there is that somewhat rare local control which includes a switch to turn the BFO off 
and on. What was the purpose of that?

Seems to me that the ARC-5 setup included both a way to transmit CW and a way to 
receive it, and that therefore the designers did foresee a necessity to be able to use CW.

Ken W7EKB

On 25 Mar 2016 at 13:13, AKLDGUY . wrote:

> Tell us how you want the Wikipedia article to read and we'll
> discuss it. There is one other poster here who is discussing
> this with me in private, so it's better that we arrive at a
> consensus.
> 
> I'm at a total loss to see how the pilot of a single-seater plane
> can be expected to send CW by removing 2 screws while in
> flight, and somehow plugging a key into the MD-7 modulator
> somewhere behind him. As I said, he could do those things
> only if downed in an emergency.
> 
> It's a misnomer to call the sending of Morse code by pressing
> the mike key CW. That results in Morse code, but it isn't CW,
> it's keyed AM. Effectively, not the provision of CW mode.
> 
> In a bomber with radio op, the situation is different. There, the
> radio op could certainly open the switch cover and plug the key
> into the MD-7.
> 
> This needs more complex wording than it first appeared. The
> Wikipedia article was not entirely correct in its original version
> and I attempted to set it right.
> The original version gave prominence to CW operation as
> though that were the primary mode used. That was clearly
> wrong, since the primary mode was AM voice, with CW as
> secondary and probably not intended at all.
> 
> I would suggest that the description of the locking of the C30A
> later in the article be made clearer as to how this affects
> operation in single-seat and bomber aircraft, since those two
> cases are clearly different.
> 
> If you are unable to edit Wikipedia yourself, please tell us how
> you want it to read. Copy and paste to this group and we'll
> discuss it and hopefully reach consensus.
> 
> 73 de Neil ZL1ANM
> 
> 
> On 3/25/16, Mike Morrow <kk5f at earthlink.net> wrote:
> > Neil wrote:
> >
> >>> KK5F wrote:
> >>> FWIW, he could key the mic even with the inaccessible control box
> >>> emission switch still in VOICE position.  A situation requiring that is
> >>> rather incredible.
> >>
> >> If you think keyed AM is CW, well, a pilot COULD send CW that way,
> >> but the circuit is definitely not optimized for CW in that state. This is
> >> not what I would call "providing CW capability".
> >
> > I guess I think that because any unmodulated "AM" signal is
> > indistinguishable from...er...a carrier, except what small amount of audio
> > the insensitive RS-38 carbon mic would pick up from ambient noise.  The real
> > problem trying to key a transmitter in VOICE mode is that the dynamotor
> > starts and stops as the PTT switch is operated, so that's good only for
> > prolonged carrier transmission.
> >
> > You persist in a straw man argument over which there has NEVER been
> > disagreement:  CW was not a mode often used in the AN/ARC-5 command set.
> > The real argument which you  avoid addressing is whether or not the AN/ARC-5
> > **system** supports CW operation.  Very demostrably it does, yet you altered
> > the wiki article to state that it does NOT!  You have futher stated here
> > that AN/ARC-5 was explicitly designed for AM (VOICE) only.  That also is
> > quickly dismissed by even a superficial examination of the associated
> > technical documents.  Please download the AN 16-30ARC5-2 handbook from the
> > link at the wiki article.
> >
> > To select CW emission from the C-30A, the emission switch cover held in
> > place by two small screws needs removal and the emission switch under it
> > centered to the CW position.  After that the dynamotor starts.  Anything
> > used to ground the keying bus, even a mic PTT button, keys the selected
> > transmitter in CW mode.  It's ALL EXACTLY like the earlier ATA and SCR-274-N
> > sets...exactly!
> >
> >>> KK5F wrote:
> >>> Beyond that, the R-25 through R-27 communications receivers were
> >>> frequency-stabilized so that they could be pre-set and locked before
> >>> flight, needing no remote in-flight tuning capability.  That allowed
> >>> elinination of tuning dials, cranks, and cables from installations using
> >>> the C-38 control mentioned above, or the C-27 individual receiver
> >>> simplified  control box which consists of audio output controls only.
> >>
> >> So, the receiver tuning controls have been eliminated to stop pilots
> >> fiddling and the BFO cannot even be turned on. How then does a pilot
> >> tune the receiver to get a beat note that is satisfactory to him? What
> >> happens if the receiver happens to be tuned so that it is zero-beat
> >> with the transmitting station. Frequency stabilization in that era was
> >> not
> >> good enough for precise CW setting and forgetting.
> >
> > It is impossible for an AN/ARC-5 installation that uses the only C-38.  But
> > that isn't the only receiver control box.   Any receiver controlled by a
> > C-26 has BFO and remote tuning controls.  Many AN/ARC-5 command set
> > installations that used
> > the C-38 and lock-tuned receivers included one C-26 and cables in standby
> > for use with an R-23* for A-N beacon and control tower reception in place of
> > either the HF command receiver or the R-4* homing receiver, for ferry and
> > other stateside flights (see Figure 8-55 sheet five in the manual cited
> > above for an example).  The C-26 may be used with any one LF/MF/HF
> > receiver.
> >
> >> It's obvious that the intention was to eliminate CW as a normal function.
> >> Only if the pilot could remove the cover, gain access to the modulator
> >> to plug in the key, somehow turn on the BFO (how?), and somehow
> >> tune the receiver for acceptable note (how?) could he send true CW.
> >> This implies that the plane is downed and the situation is an emergency.
> >
> > Once again you attack the straw man, not the real issue.  You do NOT address
> > the issue you raised with your claim that "the AN/ARC-5 doesn't do CW".  You
> > did not say (correctly) that "some installations make it hard for the pilot
> > to do CW".  Instead you flatly state without qualification that the AN/ARC-5
> > *system* does not do CW.  Incontestably, it does.  Just because it was not
> > often configured for ready CW use does not alter the fact that the system
> > allowed many configurations that support CW...no gimmicks or tricks
> > required.
> >
> > All it takes is the use of the appropriate standard control boxes...any of
> > the three transmitter control boxes (C-30A with cover removed), plus the
> > C-26 receiver control box.   That's hardly a "heroic" configuration.
> >
> >> I can't see that CW under those conditions is anything but a heroic
> >> attempt to modify the installation under emergency conditions.
> >> Nevertheless, I'll think about rewriting the Wikipedia article to make
> >> clear
> >> that CW is possible only under exceptional emergency conditions.
> >
> > Also inaccurate...very.
> >
> > As I have tried to make clear, a 100-percent "kosher" AN/ARC-5 system may be
> > very simply configured for CW operation,  It takes no "exceptional emergency
> > conditions".  It seems you believe erroneously that there was ONLY ONE
> > SYSTEM CONFIGURATION possible.  The manual I have cited may help disabuse
> > you of that impression.  But I'm not optomistic.  :-)
> >
> > Mike / KK5F
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