In article ,
(Bruce Kizerian) writes:

Thanks everyone for the interesting and useful information.

For the record, I am not particularly in love with tubes, but if there
is something they will do better than solid state devices I'm willing
to give it a try. When I can buy PN2222 bipolars for $.02ea and PN4416
JFETS two for a quarter, and dual gate MOSFETS for a nickel, the
expenditure for one of those fragile glass things better be well worth
it. It can' be different or just a little better. It has to be "knock
your socks off" superior...I make radio kits for kids and schools and
I want them to be able to afford the purchase.

Here's something that might be fun to try on a regen or most any
other tuning circuit, a rebirth of the old reactance modulator circuit
to change the parallel capacity across a coil. For 190 KHz band-
width at about 6.1 MHz, this 3N200 dual-gate MOSFET add-on
claims linear-frequency tuning from a potentiometer. That's a bit
like the old "bandspread" tuning of prehistoric times. :-)

From EDN, 5 November 1998, Design Ideas Section, pp 130, 131,
Last idea entitled "Tube" Circuit Provides Linear Tuning. [came
across that one while searching for something else...]

On the Internet at http://www.reed-electronics.com/ednmag/archive/

Select year, then issue date in that year. A table of contents comes
up and scroll down to Design Ideas. Clicking on any Design Idea will
bring up the whole section in HTML. At the top of the HTML first
page is a box for a PDF of the same thing.

EDN has archives back to 1994 if anyone wants to peruse them or get
a copy of an older article.

Len Anderson
retired (from regular hours) electronic engineer person