One excellent reason for a crystal regen is to use it after
an upconversion stage as a simplified IF-amp/detector
with (I believe) outstanding sensitivity.

I'm interested in a crystal controlled regen also. Seeing
as I have no back issues, can you point me to a web
page?

The Eternal Squire


Michael Black wrote in message
...
Bill Higdon ) writes:
I need some references on crystal controlled super regens, I know they
have been replaced in most new designs. But I have a idea that would be
easier to do with a super regen as opposed to the new studd.
Thanks,
bILL hIGDON

In the September 1972 issue of CQ, Irwin Math in his Math Notes column had
a circuit for a crystal controlled superregen receiver. The same column
had that then novel transmitter in an IC, the LP-2000.

It was simply a cross-coupled multivibrator made up of two transistors,
running at 20KHz, with a tank circuit with a crystal added in. He said
the one he built at 10MHz worked fine. He pulled the circuit out of
an issue of EDN, but no date is given.

Charles Kitchin had an article in the May 1997 issue of QST about a
crystal-controlled regen receiver (for receiving 80meter W1AW code
practice
runs).

In the Q&A column in CQ for May 1960, there is a circuit for a crystal
controlled Q-Multiplier, which is basically a pierce oscillator.
Apparently,
the circuit was originally in the RSGB Bulletin for February 1960.

In October 1961, there is a simple portable transceiver described in CQ,
and it too uses a crystal controlled regen detector.

Likely there are others, but those are the ones I know about.

Admittedly three of those four are regen and not superregen, but that's
hardly important since a superregen is just a regen detector which
is oscilalting and modulated with an above audible frequency. (And take
note that a Q-Multiplier is just a specific application of regeneration.)

Indeed, a regen is just an oscillator with controlled feedback, or
to look at it another way, a regen is just an amplifier with positive
feedback.

So you can take just about any oscillator circuit, and by adding some
sort of control so you can reduce things so it's on the verge of
oscillation,
you've got a regen detector. Coupling into it may be easier with some
circuits than others. And once you've got a regen circuit, adding
some scheme to modulate it at an ultrasonic frequency will make it
a superregen.

Since a crystal controlled superregen is relatively rare (who knows
why), you might want to start things by going through this sequence
and figuring out the best setup yourself.

Someone once pointed out here that for a lot of uses you don't need ultra
selectivity, and so a crystal in a regen is out of place. I'm not sure
how this translates to a superregen.

Be advised that while there has been some work done on using better
tuned circuits in a superregen, it seems more likely that the reason
for it's passband is because it is in effect an oscillator that is
being modulated. Working on the quench circuit, both amplitude and
waveform, would seem to be a better path. Charles Kitchin has done
some work on this, and he claims he has gotten better results by
fiddling with this. I've never seen the article, but he wrote
about superregens in the Fall 1994 issue of Communications Quarterly.
His article about regens the following year was an interesting mix
of history and new circuits, and I suspect the superregen article is
similar. He's also had a few superregen circuits in QST (and in
the Handbook for an issue or two), but I don't have a bibliography handy.
There was a superregen receiver article of his on the ARRL site,
http://www.arrl.org at one point, and doing a search there would hopefully
find it.

Take note that most superregens use the same active element as both
the RF oscillator and as the quench oscillator. Separating them,
has certain advantages in trying to get the best quench, and these
days it pretty much costs nothing to add the extra circuitry, unlike
in the 30s when the superregen was pretty hot.

I'd be curious about why you think you need a crystal controlled
superregen. Most superregens have been at VHF (indeed, if you go
by some rules of thumb of making the quench frequency a certain percentage
of the operating frequency the quench will be at audio once you get below
a certain frequency), and getting a crystal to oscillate up
there may start being a problem especially the higher you go. Though,
I think some work has been done with SAW controlled superregens.
And whether it adds to selectivity is under question. Stability might
be a factor, but then the traditional wide bandwidth has always offset
any issue of frequency stability. Who cares about drift when a
superregen's
bandwidth would basically cover most of the 2meter band?

Michael VE2BVW