[ARC5] How Edwin Armstrong invented the superhet (according to Wikipedia)

[gaselen at earthlink.net]

Hi,
I don’t know how I end up in your mailing list... However I must say that the super-heterodyne was not the invention of Edwin Armstrong alone. 

While in Paris during WW1, he had the chance to exchange "ideas" with a number of other scientists working at the Eiffel tower radio lab.
What Major Armstrong did was to get a US patent in Dec 30, 1918In fact the very principle of the superhet was described by Meissesner from 
Germany in 1914, tentatively built in France by Laut in 1916 and then improved and patented in Oct 1st, 1918 by Lucien Levy.

The Armstrong patent was reversed in Dec 3, 1928 by the court of appeal of
DC Columbia that assigned the invention to L Levy etc...Of note, Shottky from Germany also got a German patent in June 1918. However he latter recognized the anteriority of Levy’s patent. 

So, for me Edwin H. Armstrong is essentially Mister FM. That is not too bad!
Regards
Gd
-----Original Message-----
From: Mark K3MSB <mark.k3msb at gmail.com>
Sent: Jan 7, 2023 5:38 AM
To: Leslie Smith <lnsmith99 at gmail.com>
Cc: <arc5 at mailman.qth.net>
Subject: Re: [ARC5] How Edwin Armstrong invented the superhet (according to Wikipedia)

" In RDF, the strength of the signal is used to determine the location of the transmitter"
 
No.   In RDF (or radar) it is the time delay between the transmitted pulse and the returned echo that determines the range to the transmitter, not the returned signal strength.
 
Last year I enjoyed reading several books on the development of radar by the British ( the best was "Most Secret War" by R. V. Jones") and I don't recall anything such as " tens or even hundreds of triodes had to be used, connected together anode-to-grid. These amplifiers drew enormous amounts of power and required a team of maintenance engineers to keep them running" during the (pre cavity magnetron) initial testing performed in the mid to late 1930's.
 
" The regenerative system was highly non-linear, amplifying any signal above a certain threshold by a huge amount, sometimes so large it caused it to turn into a transmitter (which was the entire concept behind IFF)."
 
The early British IFF sets used this principle when a radar pulse from the Chain Home radar was received.     
 
I've found that many people do not realize the level of radio-related technology that was already in use when WW II started (radar, IFF etc).  I was surprised to raed the Germans used one of their beam systems (I believe it was Knickebein) when they invaded Poland in 1939.
 
73 Mark K3MSB
 


On Sat, Jan 7, 2023 at 2:22 AM Leslie Smith <lnsmith99 at gmail.com (mailto:lnsmith99 at gmail.com)> wrote:
Hello All:


When the Aircraft Radio Corporation built the superhets we call SCR-274 (or ARC-5) it was all because the British Admiralty felt the high cost of RDF (etc) was justified.  Read all about it below.

>From Wikipedia:  https://en.wikipedia.org/wiki/Superheterodyne_receiver#RDF

"RDF
There was one role where the regenerative system was not suitable, even for Morse code sources, and that was the task of radio direction finding, or RDF."

"The regenerative system was highly non-linear, amplifying any signal above a certain threshold by a huge amount, sometimes so large it caused it to turn into a transmitter (which was the entire concept behind IFF). In RDF, the strength of the signal is used to determine the location of the transmitter, so one requires linear amplification to allow the strength of the original signal, often very weak, to be accurately measured."

"To address this need, RDF systems of the era used triodes operating below unity. To get a usable signal from such a system, tens or even hundreds of triodes had to be used, connected together anode-to-grid. These amplifiers drew enormous amounts of power and required a team of maintenance engineers to keep them running. Nevertheless, the strategic value of direction finding on weak signals was so high that the British Admiralty felt the high cost was justified."


I found the above when hunting for a little history of the development of the superhet.  My first reaction was to send it to "our" resident historian (Hue).  I admire his extensive knowledge of radio history and enjoy reading his postings here.  Then I thought others may find the role of the British Admiralty "interesting" and so I sent it here instead.   


I must seek information about the development of the superhet elsewhere, it seems.


Best 2023 to all


Leslie
 

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