On Tue, 18 Feb 2014, Percy Picacity wrote:

In article ,
Jerry Stuckle wrote:

On 2/18/2014 5:58 AM, gareth wrote:
There was a time, back inthe 1920s and 1930s, that any active device
(valves in them thar days, tubes for the leftpondians) would cost nearly
a week's wages for the average working man, and so it was good economical
sense to try and use it as many ways as possible simultaneously.

Times have changes, and active devices with performance into the tens
of MegaHertz are now ten-a-penny, so what is achieved by competitions
such as the "Two Transistor Challenge" where it is the costs of switching
(manual, relays) which would be the major outlay?

Not carping, just curious.

-----ooooo-----

BUT BUT BUT, this one has no switching, apart from the Morse Key! ...


http://www.vk2zay.net/article/file/1138



I'm not familiar with this particular challenge - but similar ones I've
seen are more about the design than the cost.

Jerry, AI0K

True, but it is still a ridiculous constraint. It is about as sensible
as designing something where the first digit of every component value
had to be '4'.

But the constraint causes some to think.

An analogy is the superregenerative receiver. Forty years ago it as still
used in some places, but the various handbooks would give a very brief
description and basically treat it like a black box. It was like broken
telephone, the basics lost to history, "everyone" knowing the basics but
not really.

I remember later seeing a schematic where the quenching was done with a
separate device. The descriptions I'd previously seen had been mostly
about how the same device does the quenching, as if that was important to
understand why there was quenching. Seeing a separate oscillator made me
realize that the quenching oscillator was in effect modulating the
regenerative receiver. No wonder those things were wideband, put a square
wave on any oscillator and and you'd get multiple sidebands.

If you have a separate quenching oscillator, you can better control the
waveform and the "modulation level".

I didn't pursue it, but I realized that if you fiddle with such things,
you might end up with a narrower bandwidth superregen receiver.

And that's what Charles Kitchin did. He had an article in COmmunications
Quarterly where he went back to the early days of the receiver, understood
what was going on back then, and then tried to update it, with solid state
devices, but also by trying to control the quenching. And he claims he
has narrower superregen receivers.

I never saw the article, I did see some standalone superregen receivers he
talked about. But, the original article got flack "why dredge up the
superregen when nobody uses it and it's obsolete?". Precisely because in
going back to the beginning, he regenerates those beginnnings, so the
knowledge of the early days is out in present view for anyone interested
to pursue further.

He did the same with a similar article later in Communications QUarterly
about the regnerative receiver.

Knowledge gets lost. An idea becomes commonplace so the details are
boiled down, leaving so much that was discovered in the early days, or at
least discussed in the early days, missing from current books and
magazines. Only when you look at something as originally portrayed can
you give it a boost in current technology and maybe leap ahead.

Ladder filters were around for a long time before they made it big.

People spent endless time trying to improve direct conversion receivers
without really looking in the right direction. Yet, I can point to a 1974
article about proper termination of a mixer in a VHF converter that is
exactly what was done a decade or so later to direct conversion receiver
mixers that really seemed to fix some of the problems.

Or, that mid-1980s direct conversion receiver caused a resurgence in
interest in the phasing method, nothing really new initially but times had
changed, some of the problems lessened by newer technology, and then later
suddenly a realization that one could intersect this with digital signal
processing.

But if you don't fully understand the basics (in part because those basics
are assumed rather than stated), you can't make a leap forward, moving
something from the past into the future by applying the new to the old.

These two transistor challenges are like that, cause people to think and
maybe learn something or create something new.

Michael