“Walkie-Talkies were around then, I’m pretty sure, probably used in the military. The poor mans’ cell phone is still sold today.”
No, in 1939 the transistor had not been invented yet. There were crude military transceivers but they had vacuum tubes in them and huge batteries. Hardly a Walkie-Talkie.
I saw a documentary on WWII development of the proximity fuse at APL and Aberdeen. They were on the leading edge of miniaturization of vacuum tubes, not to mention being able to survive being fired out of a canon.
Wakie-talkies had nothing to do with transistors. A W-T was a multiple tube FM backpack set and was the grandfather of the PRC25 and PRC 77. The Handie-talkie was the handheld set the size of a big brick that you see in war movies. It was a Motorola SCR 536.