[ARC5] How Edwin Armstrong invented the superhet

[William Cromwell]

Thanks Al,

This is one more piece for me to fit into the picture.

73,

Bill KU8H

bark less - wag more

On 1/7/23 11:40, Al Klase wrote:
> OK, let me take a whack at this.
> We have to go back to the WWI era.  Most radio operations were taking 
> place well below 1 MHz. Communication receivers we generally crystal 
> sets connected to large wire antennas.  There was a need for 
> direction-finding on enemy transmitters.  That required a loop 
> antenna, but the output was too low to work with a crystal set or even 
> a one-tube regen.
>
>
> The solution was multi-tube amplifiers.  The French had a leg up here 
> having produced the first mass produced tube, the "TM" valve. See also 
> R. J. Round and the Brit DF "B-Stations."
>
>
>
>
> French amp among the Armstrong artifacts at the former Ft. Monmouth 
> museum.
>
> Armstrong was working at the Division of Research and Inspection in 
> Paris.  This was in effect an AT&T laboratory.
>
> To get amplification at HF frequencies, where the existing tubes 
> didn't have much gain, he leveraged his knowledge of heterodyne 
> frequency conversion gained from his work with the regenerative 
> receivers.  He built a tunable frequency converter to feed a French 
> amplifier operating at about 100 KHz.   The circuit was originally 
> called the supersonic (now we say ultrasonic) heterodyne circuit, 
> where the incoming signal in not converted to audio, but to an 
> intermediate RF frequency.
>
> Hope the pix come through.
>
> Al
>
> ARK Sig Block Al Klase - N3FRQ
> Jersey City, NJ
> http://www.skywaves.ar88.net/
> On 1/7/2023 7:37 AM, releazer at earthlink.net wrote:
>
>
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