[ARC5] Lear Radio

[Robert Nickels]

On 8/3/2023 8:37 PM, Rich Post wrote:
> Learavian RM-402C "Beacon, Broadcast, and Airline Receiver".  Cool 
> piece. It's an AC-DC-Battery 3-way portable, receive-only. Has an 
> intercom feature built in.  It was apparently made for private 
> aircraft that had no radio built-in.

Those are pretty cool portables, Rich.  I've got one torn apart 
somewhere, it whipped me at the time and I can't remember why.   I do 
remember being disappointed when I discovered the "mic" jack was just so 
you could plug a carbon mic in and talk to passengers wearing 
headphones, not a transmitter ;-)

The simplest "carry-on" light aircraft radios were not only used on 
planes without built-in radios, but on planes that didn't even have an 
electrical system or battery - just magneto ignition. But hey, in 1939 a 
Piper Cub 40 (as in 40 HP) could be purchased for $1098, so there wasn't 
room for frills!

The very simplest radio equipment was receive-only, to hear instructions 
from the tower on 278 kc which the Learavian could do, as well as radio 
direction finding.   But before long it became necessary to have 
transmitting capability, where all planes shared ONE frequency, 3105 
kc.   The 2nd harmonic 6210 kc was available for night use.    
Transmitters were very simple MOPA jobs with carbon mic, plate 
modulator, and loading coils to match a wire antenna.   Some ran from A 
and B battery packs, others had vibrator supplies as they only needed a 
few watts of RF.   Lear made those too.

Bill Lear is best remembered for the Learjet, or perhaps the invention 
of the 8-track tape, but he's really a forgotten hero of the early radio 
industry.   A self-taught radio man, he is credited with inventing the 
B-battery eliminator, the use of Litz wire to miniaturize radios, and in 
conjunction with Paul Galvin, came up with the name "Motorola" for their 
fledgling car radio (which Lear designed) and at the time owned 1/3 of 
the company. He veered away from his radio radio and into aviation, but 
he did OK there ;-)

73, Bob W9RAN