"Michael Black" wrote in message
news:alpine.LNX.2.02.1402181412260.14557@darkstar. example.org...
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.

Both regenerative ans superregenerative RXs are featuring in the approach
known as a "supergainer", as, indeed, are direct conversion RXs, in all
cases, repalcing the IF and product detector stages following the Xtal
filter.


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.

If as above, then the governing BW is determined by the Xtal filter


Knowledge gets lost

An outstanding example of that is over here with the floods on the
Somerset levels, where dredging and pumping knowledge going
back to the 1700s (including involvement by, "The Dutchman")
has been lost in 80 years of changes and mergings in the various
drainage and water catchment authorities and we are now left
with the Environment Agency run by dogooders who though it
to be more appropriate to blow up the pumping stations, omit
the dredging, and devote the money and effort into making
nature reserves!

. 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.

I found this out over 10 years ago, when I wanted to find out how
a railway steam locomotive REALLY worked,
and had to go back
to books from the 1920s and 1930s when it was THE technology of the
day, and every boys' book described it in some detail.