Do you mean, the red knob paint means the transmitter was not used in autotune ( preset channel )

mode ?

-Hue Miller

On Behalf Of Doran Platt via ARC5
Sent: Wednesday, February 25, 2026 5:50 PM
To: arc5

Subject: Re: [ARC5] ART-13 knobs question

My experience with over 20 T-47, T-47A, and ATC units has most of the autotune knob locking plates having red triangles painted the to indicate, I think, an unlocked knob.  The locking T bar is black. 

Jeep K3HVG

On 02/25/2026 6:52 PM EST Hubert Miller  wrote:

I  had never noticed the difference in color of the knobs on the ART-13.
Kinda reminds me of this puzzle in the local newspaper – “Find 6 differences in the drawings”

and the tendency is to overlook what’s “not important”.

So why the red knob skirts and some black ?

Photo via Julyah, pres of the PSARA antique radios club.

-Hue Miller