DW Holtman brought a draftsman’s precision to the R-390A community’s most important document. As a credited contributor to “The 21st Century R-390A/URR Technical Reference” — the Y2K Manual — Holtman produced the detailed front panel illustration that appears in Chapter 2 (Operation) and created the digital figures that accompany the AGC modification article in Chapter 11, one of the manual’s most technically significant supplementary sections. His work demonstrates that clear technical illustration is not merely decorative — it is essential to communicating complex information accurately.

The Front Panel Drawing

The R-390A’s front panel is one of the most control-dense interfaces in military communications equipment — a carefully organized array of knobs, switches, meters, and indicators that the operator must understand completely. Holtman’s front panel illustration in Chapter 2 of the Y2K Manual provides the clean, accurately labeled reference drawing that readers need when the text describes control locations and functions. Credited as “Figure 2-1 – Front Panel DW Holtman WB7SSN,” the drawing replaced the often-degraded reproductions in the original military manuals with a crisp digital rendering.

The AGC Modification Figures

Chapter 11 of the Y2K Manual’s Release 3 contains one of the most technically sophisticated modifications documented for the R-390A: David Wise’s AGC improvement, titled “Ending The Moment of Silence: The Way They Should Have Done It.” This modification addresses a long-standing design limitation in the R-390A’s automatic gain control circuit — the several-second muting that occurs when switching between AGC rates, a behavior that Collins’ original engineers could have avoided with a different circuit topology. The modification is elegant but requires careful understanding of the circuit to implement correctly.

Holtman created the digital figures that illustrate Wise’s modification, providing the clear schematic representations that allow a restorer to follow the circuit changes with confidence. Technical illustration for circuit modifications demands absolute accuracy — a misplaced connection in a schematic can lead to component damage or worse. Holtman’s figures meet that standard, supporting one of the most valued technical contributions in the entire Y2K Manual.

The Value of Visual Clarity

In a community where most technical contributions take the form of written procedures, reflector posts, or modification descriptions, the role of the technical illustrator is easy to overlook. But the Y2K Manual’s usability — the quality that makes it a practical bench reference rather than merely an interesting read — depends heavily on the quality of its illustrations. Every time a restorer identifies a front panel control by referring to Holtman’s drawing, or follows the AGC modification by studying his figures, the value of skilled technical illustration is silently confirmed.