[ARC5] AN/ARC-5 support for CW

[Mike Morrow]

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