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

[Tom Lee]

Hi Brooke,

I'll send you the DA paper shortly.

--Tom

-- 
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
420 Via Palou Mall
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 1/7/2023 16:02, Brooke Clarke via ARC5 wrote:
> Hi Leslie:
>
> I don't understand the comment on the Wiki page about triodes with a 
> gain less than 1.  AFAICR a triode tube can have a stable gain into 
> the hundreds.
> If you want to build an amplifier with the maximum gain bandwidth 
> product the gain of each stage should be e (Wiki: math constant 
> <https://en.wikipedia.org/wiki/E_(mathematical_constant)>) in what's 
> called a distributed amplifier (Wiki 
> <https://en.wikipedia.org/wiki/Distributed_amplifier>).
>
> I have some early RDF information at:
> https://prc68.com/I/RDF.shtml
>
> Also it turns out that Watson-Watt invented a very sophisticated 
> lightening strike locating system when he was working for the UK 
> weather bureau.  In the discussion after he gave the paper it was 
> clear that the same system would also work in aircraft to determine 
> the location of beacons.
> https://prc68.com/I/InstantaneousDirect-readingRadiogoniometer.shtml
> It was later that he invented RADAR.
>
> PS CRT based RDF systems like this that work for lightening strikes 
> that are of very short duration also work for burst transmissions.  
> They were at the heart of the Elephant Cage (Wiki: Wullenweber 
> <https://en.wikipedia.org/wiki/Wullenweber>) systems.
> PPS If there's someone who is a IEEE member could you send me a pdf of 
> the paper Distributed Amplification by Ginzton, Hewlett, Jasberg, Noe 
> et al?
> https://ieeexplore.ieee.org/document/1697772
> -- 
> Have Fun,
>
> Brooke Clarke
> https://www.PRC68.com
> axioms:
> 1. The extent to which you can fix or improve something will be limited by how well you understand how it works.
> 2. Everybody, with no exceptions, holds false beliefs.
> -------- Original Message --------
>> 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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>
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