[GreenKeys] Early aviation radio history

[Robert Nickels]

On 12/31/2019 3:52 PM, Al Klase wrote:
>
>
> The two receivers behind the mic, and atop the power supply and coil 
> rack are very likely National Company RHM's.  These were designed for 
> the Lighthouse Service, and were the predecessor to the more familiar 
> National AGS.  I don't recognize anything else.

Thanks Al.   I'm not familiar with them but that makes sense - the 
Velvet Vernier dial sure says "National".

I've found information about early aviation communications to be pretty 
sparse, but if they followed the procedure that was used up til WWII and 
for a bit afterward before the move to VHF, the a/c would have 
transmitted on MF/HF (e.g 3105 or 6210 kHz) and listened for the ground 
station on it's beacon, or in this case on the radio range transmitter, 
somewhere in the 200-400 kHz range.    So having two receivers and what 
might be a speech amplifier at the operators station would make sense.

73, Bob W9RAN