The AN/WRC-1 (R-1051 and T-827) was introduced to the fleet in 1963 (500cps increments originally).

http://www.navy-radio.com/journal/wrc1-journal-1963.pdf

The AN/URC-35 (RT-618) wasn't introduced to the fleet until 1967 (and it had 100cps tuning increments then).

http://www.navy-radio.com/journal/urc35-journal-6705.pdf

So I think the RT-618 intro was delayed and incorporated feedback about the early R-1051 lamps, tuning, etc .

This 1962 development report shows the RT-618 prototype with 1kc step tuning and rear access lamps

http://www.navy-radio.com/xmtrs/wrc1/wrc1-urc35-development-6208.pdf

The rear lamps were a holdover from the original SC-series design but I have no idea why they thought that was a good idea!

http://www.navy-radio.com/xmtrs/sc-radio.htm

Nick England K4NYW
www.navy-radio.com

On Sun, Feb 2, 2025 at 12:40 PM Daniel Jones <djones@k6yic.com> wrote:

You’re telling me, especially the one that’s behind the encoder board, what’s interesting is the URC-35 (RT618 Transceiver) which was designed around the same time has bulb access from the front and uses regular 327 bulbs.

On Feb 2, 2025, at 09:34, Edward Larsen <ki6rcm98@gmail.com> wrote:

At the Navcommsta Diego Garcia receiver site in 1981 we had about 30 R-1051 receivers. We'd stock the small bulbs by the case. Not a good illumination design.
73
KI6R, Tucson