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

[Brooke Clarke]

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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