[ARC5] Transmitter Control C-30 vs C-30A/ARC-5 Capabilities, Design, and Usage Differences

[Mike Morrow]

Adding to Mike Hanz's great information:
 
The C-30/ARC-5 transmitter control box is mechanically, electrically, and functionally VERY different from the C-30A/ARC-5 control that quickly replaced the poorly-designed C-30.
 
I.  C-30/ARC-5 Pushbutton Selector Control Box
 
a.  At the rear of each AN/ARC-5 transmitter rack bay is a transmitter select plate wired to designate the transmitter number installed in that bay as transmitter no. 1 (2, 3, 4).  [Same as C-30A.]
 
b.  The C-30/ARC-5 may control up to THREE transmitters (1, 2,  3).  The bay in which the VHF T-23 or T-126/ARC-5 is installed MUST ALWAYS be wired as transmitter no. 1.  The normal two-transmitter rack MT-71/ARC-5 transmitter selection plate for the remaining bay is wired as transmitter no. 2.
 
c.  The top row of VHF channel select buttons on C-30 are ALWAYS assigned to transmitter no. 1.  The VHF transmitter MUST be in the rack bay that is wired as no. 1.  Depressing the C-30 pushbutton marked A (B, C, D) always selects transmitter no. 1 and also selects VHF channel A (B, C, D) for BOTH the VHF transmitter T-23 {or T-126) and the R-28/ARC-5 VHF receiver.
 
d.  The C-30 pushbutton marked 2 selects an MF/HF transmitter in the MT-71 if its rack bay is wired as no. 2.
 
e.  If the very rare three-transmitter rack MT-75 is in use, its third transmitter select plate must be wired as transmitter no. 3 for a second MF/HF transmitter.  The C-30 pushbutton marked 3 selects this transmitter.
 
f.  The OFF pushbutton shuts down the transmitters and deselects the crystal controlling the VHF receiver.
 
g.  The C-30 does NOT prevent pilot access to the TONE-CW-VOICE switch on its front.
 
h.  Compared to the C-30A (below) the C-30 was much larger, heavier, and mechanically very complex and of questionable reliability.  It must have been more expensive and resource-intensive while providing far less flexability.
 
 
II.  C-30A/ARC-5 Rotary Selector Switch Control Box
 
a.  At the rear of each AN/ARC-5 transmitter rack bay is a transmitter select plate wired to designate the transmitter number installed in that bay as transmitter no. 1 (2, 3, 4). [Same as for C-30,]
 
b.  The C-30A/ARC-5 may control up to FOUR transmitters.  The VHF transmitter T-23 or T-126/ARC-5 may be installed in ANY bay number, but there may be only one VHF transmitter.  The normal two-transmitter rack MT-71/ARC-5 transmitter selection plate for the remaining bay is wired as transmitter no. 2.
 
c.  The C-30A has a four-position rotary transmitter selector switch on its front with positions 1 (2, 3, 4) to select the rack transmitter bay that is wired for the same numerical designation.  Normally the two-transmitter rack MT-71 has its two bays wired as no. 1 and no. 2.  The C-30A transmitter selector switch allows setting a mechanical stop to prevent switch rotation to unused transmitters no. 3 and 4.
 
d.  The C-30A has a four-position rotary VHF channel selector switch on its front with positions A (B, C, D)  to select the VHF channel for BOTH the VHF transmitter T-23 (or T-126) and the R-28/ARC-5 VHF receiver.  This switch will select the receiver channel even it the transmitters are de-energized.
 
e.  If the very rare three(four)-transmitter rack MT-73(75) is in use, its third(fourth) transmitter select plate may be wired as transmitter no. 3(4) for additional transmitters.
 
f.  The ON-OFF switch on the front shuts down the transmitter system.
 
g.  The C-30A prevents pilot access to the TONE-CW-VOICE switch on its top using a screw-secured cover over the switch, which is normally in the VOICE position.
 
h,  The C-30A is the same size and about the same weight as the rare C-29/ARC-5 control that was designed for AN/ARC-5 transmitter installations which do not use the T-23 or T-126/ARC-5 nor R-28/ARC-5 VHF units.  The C-30A may serve as a direct substitute for the C-29 by leaving the C-30A VHF channel select connector unused.  (That likely explains the great rarity of the C-29 along with the fact that most AN/ARC-5 installations used its VHF capability.  The C-29 was not needed ANYWHERE once the C-30A was available,)
 
 
Today, the C-30A is not rare, but it still may be a challenge to find.  There is a glut of unused C-30 controls "out there" for good and obvious reasons, but they are anachronistic to a faithful historical recreation of a typical in-service AN/ARC-5 installation.
 
 
Mike / KK5F
 
-----Original Message-----
From: MARK DORNEY 
Sent: Oct 26, 2021 9:23 AM
To: Michael Hanz 
Cc: 
Subject: Re: [ARC5] c-30/arc-5 info
 
One thing I have noticed with the C-30 control. Only 1 button will remain pushed at any one time. If you press “2” , and then press “A”, the “2” button pops back up. I am thinking that the C-30 control is deaisigned to operate up to 6 transmitters, especially since the transmitters are not tunable by remote.  Transmitter frequencies were set and locked before flight unless the aircraft had a dedicated radio operator ( in which case both the transmitters and receivers would not use remotes ). 

“In matters of style, float with the current. In matters of Principle, stand like a rock. “.   -   Thomas Jefferson  
Sent from my iPhone


On Oct 25, 2021, at 10:35 PM, Michael Hanz  wrote:


It can, and does control three transmitters when desired.  Page 50 in Volume 2 of AN 08-10-195, "Handbook of Maintenance Instructions for AN/ARC-5 Radio Equipment (VHF Components)" covers the operation and capabilities of this control box.  Its greatest drawback was simply the unreliability of the push button switches, which deficiency it shared with the SCR-522 VHF set control box.  Its replacement,  the C-30-A/ARC-5, reverted to the simple rotary switches used for other functions in the other control boxes and the problems went away.  Too bad they didn't have DeoxIT back then.  😁

- Mike  KC4TOS

On 10/25/2021 8:36 PM, MARK DORNEY via ARC5 wrote:
I also have a C-30/ARC-5 Control Box and am interested. Can this control box be used to control 3 Transmitters?  
Mark D. 
WW2RDO

On Oct 25, 2021, at 1:53 PM, dennis via ARC5  wrote:
i have the C-30/ARC-5 control unit push button type i know abcd are channel select, lower button one is for off/on, the lower nos # 2&3 what are they used for  also can i use the control unit on a T-19 T22 TX if so is this control box wired the same as the C-29/arc-5 or different wiring  any type of help tnx dennis ka9dzr