"Steven Swift" wrote in message
...
rar+p and rats:

Okay, here's the answer directly from the Radiotron Designer's
Handbook, fourth edition, pages 1226 and 1227:

"Section 3: The Synchrodyne"
[...]
"and hence the synchrodyne is likely to be most popular for
high-quality local-station reception."


I think the fact that the synchrodyne never became at all popular as an AM
radio detector in the tube era means something. If I recall correctly, I
read that synchrodyne detectors would howl until they sync'd. Also, the
phasing would have to be perfect to get good demodulation from normal double
sideband AM.



There you have it. Are we done. This is a 3-tube design for
local stations. One RF amp, 2 12au7s. Use an IC or two in the
oscillator loop and its perfect, almost a Costas Loop.

Build it; they will come.

Steve.


I suppose it's something worth experimenting with, but diode detectors
aren't bad. Even in the solid state era, sync detectors aren't particularly
popular. The add on sync detectors are expensive. It still doesn't seem to
be easy.

Frank Dresser

"Frank Dresser" writes:

I think the fact that the synchrodyne never became at all popular as an AM
radio detector in the tube era means something. If I recall correctly, I
read that synchrodyne detectors would howl until they sync'd. Also, the
phasing would have to be perfect to get good demodulation from normal double
sideband AM.

Frank Dresser

Yes, they howl. But his channel concept eliminates that problem. In a private
email, I asked Jon if his design can use ICs. If you use a couple of ICs to
generate the "synchronized" signal, I think you can get around the complexity.

Jon has a lot of work. Block diagrams are pretty simple. Details are hard.

Steve.
--
Steven D. Swift, , http://www.novatech-instr.com
NOVATECH INSTRUMENTS, INC. P.O. Box 55997
206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA

"Frank Dresser" ) writes:
"Steven Swift" wrote in message
...
rar+p and rats:

Okay, here's the answer directly from the Radiotron Designer's
Handbook, fourth edition, pages 1226 and 1227:

"Section 3: The Synchrodyne"
[...]
"and hence the synchrodyne is likely to be most popular for
high-quality local-station reception."


I think the fact that the synchrodyne never became at all popular as an AM
radio detector in the tube era means something. If I recall correctly, I
read that synchrodyne detectors would howl until they sync'd. Also, the
phasing would have to be perfect to get good demodulation from normal double
sideband AM.


The quote is about the synchrodyne detector, not synchronous.

While Radiotron mentions "sync'ing" I'd not treat that as a basic of
the synchrodyne. At its basic, it's what we'd now call a direct conversion
receiver, ie beat the incoming signal down to audio. The "high fidelity"
derives from the fact that selectivity comes at audio, and one can build
good audio filters. Because one is translated the RF signal to audio,
any front end selectivity is there to prevent mixer overload. And the
translated signal goes from DC to daylight (a slight exageration), so
putting the filter there is not just a "tone control" but acts the same way
as a good filter further up.

The immediate problem is that such a receiver can do nothing of the audio
image (which is the same thing as the image in a superheterodyne receiver).
This is not a problem with AM, since the audio image (ie the signal on the
other side of the carrier) is the other sideband.

And of course, the lack of anything to sync the local oscillator
to the incomining carrier means that off-tuned receivers will provide
a beat note, and worse, a caucophony of sound as the two sidebands translate
to different audio frequencies and beat against each other.

While obviously there were schemes along these lines, to get better
AM reception, I don't think the synchronous detector was described until
1958 or so. At least, that's when it first hit CQ magazine, and if it wasn't
by Costas himself, it was by a guy named Webb who worked for GE (who were
the commercial proponent of DSBsc).

Michael


There you have it. Are we done. This is a 3-tube design for
local stations. One RF amp, 2 12au7s. Use an IC or two in the
oscillator loop and its perfect, almost a Costas Loop.

Build it; they will come.

Steve.


I suppose it's something worth experimenting with, but diode detectors
aren't bad. Even in the solid state era, sync detectors aren't particularly
popular. The add on sync detectors are expensive. It still doesn't seem to
be easy.

Frank Dresser

Frank Dresser wrote:

"Steven Swift" wrote in message
...
rar+p and rats:

Okay, here's the answer directly from the Radiotron Designer's
Handbook, fourth edition, pages 1226 and 1227:

"Section 3: The Synchrodyne"
[...]
"and hence the synchrodyne is likely to be most popular for
high-quality local-station reception."

I think the fact that the synchrodyne never became at all popular as an AM
radio detector in the tube era means something. If I recall correctly, I
read that synchrodyne detectors would howl until they sync'd. Also, the
phasing would have to be perfect to get good demodulation from normal double
sideband AM.

Most synchrodynes do howl and whistle while a station is tuned
because the oscillator beats with the wanted station carrier until
the the station carrier is the same F as the oscillator.
PLL wasn't used in many early synchronous applications.
Locked osillators were. These used a sample of the station's carrier to
trigger the oscillator's F to be the same when the two frequencies became close
enough.
To get over the howling, muting circuits were devised to block reception
until the station was tuned, so it was there, or it wasn't, it was either tuned,
or not tuned.
By the time you built all the necessary things to make the old style
synchrodyne livable withable, you have used twice the tube count, and that's a
lot more that
could go wrong as tyhe set aged.

Chip technology changed all that, and I have a couple of simple synchronous,
or otherwise known as direct conversion circuits.

Mr D.G.Tucker's synchrodyne circuit of 1947 is a tantalising circuit, but it
needs extremely
careful layout and preparation to get the darn thing to work as suggested.
I couldn't get the balanced demodulator with a 3 winding tranny to work properly

with its 4 diodes, and the oscilations wouldn't lock properly, or became
unlocked when the modulation % became so high there
wasn't enough carrier left to trigger the locking.
If it wasn't one thing, it was another, so I built a superhet.


There you have it. Are we done. This is a 3-tube design for
local stations. One RF amp, 2 12au7s. Use an IC or two in the
oscillator loop and its perfect, almost a Costas Loop.

Build it; they will come.

Steve.


I suppose it's something worth experimenting with, but diode detectors
aren't bad. Even in the solid state era, sync detectors aren't particularly
popular. The add on sync detectors are expensive. It still doesn't seem to
be easy.

It isn't easy with discrete components.
Probably far easier with a chip like the NE602,
or LM2111. The application notes might give info about their radio use;
I have two circuits with each of the above within, but its OT
for a tube group.

It should be possible to apply an locked oscillator signal at 455 kHz to
the IF signal, and recover the audio from a mixer circuit where the product is
the audio.

The synchrodyne is similar to a superhet in that the difference between the
a stations F and the ocsillator F is not 455 kHz, its simply the audio
signal, so its audio that comes out of the frequency converter instead of a
455 kHz IF signal. One tube design uses a the same tube type as one would use
for a normal
F converter, the 6BE6.

A PLL isn't all that easy to do with tubes, since changing an oscillator's F
with a varying DC level isn't easy, since rigging a reactance tube up results in
little F change.
This function is much easier with chips, and varicaps, which were not around in
1947.
I even made a 6AU6 RF amp to synchronize the oscillator on a very low threshold
of station carrier,
by means of using a limiter amp like in an FM set where the last IF amp
is run in seriously over loaded conditions to stop any AM of the IF signal
getting into the discriminator, but it never really worked properly
at 100% modulation; one needed a phase locked set up with a slow time constant
driving the voltage control of oscillator F, so that momentary absenses of
station carrier signal didn't let the oscillator F drift off the station F.

Does anyone have a good phase locked loop schematic using tubes
for between 500kHz and 1,700kHz?
I vaguely remember one in Electronics Australia in the 1960s,
but I became uninterested in electronics about then.



Patrick Turner.




Frank Dresser

Frank Dresser wrote:
I think the fact that the synchrodyne never became at all popular as an AM
radio detector in the tube era means something. If I recall correctly, I
read that synchrodyne detectors would howl until they sync'd. Also, the
phasing would have to be perfect to get good demodulation from normal double
sideband AM.

Now appearing on alt.binaries.pictures.radio

Syncrhodyne three tube receiver from the April 1951 edition of
Radio News.

Jeff

--
"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety." Benjamin Franklin
"A life lived in fear is a life half lived."
Tara Morice as Fran, from the movie "Strictly Ballroom"

Jeffrey D Angus writes:

Now appearing on alt.binaries.pictures.radio

Syncrhodyne three tube receiver from the April 1951 edition of
Radio News.

Jeff

Did anyone actually see this schematic? I can't find it.

Steve.
--
Steven D. Swift, , http://www.novatech-instr.com
NOVATECH INSTRUMENTS, INC. P.O. Box 55997
206.301.8986, fax 206.363.4367 Seattle, Washington 98155 USA

"Steven Swift" a écrit dans le message

Did anyone actually see this schematic? I can't find it.


Right he
http://techpreservation.dyndns.org/b...files/?C=N&O=A

Synchro-1 and -2.jpg

Syl