If I have a waveguide, coax, or even lumped varactor tuned LC tank,
could I simply select which harmonic I want it to oscillate at, by
tunning a negative resistance?

Perhaps with the use of a "register key", such as is on flutes and
clarinets? I suppose that functions as a high-pass filter on the line,
when the hole is unplugged.

I'm interested in a multi-decade VCO, tuned with one control voltage and
just a few switches.

No, I don't want to heterodyne or synthesize, because I'm interested in
the regenerative/super-regenerative capabilities.

Any applicable app notes or articles? Dream on?

--
Scott

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************

Scott Stephens wrote in message news:tnamc.36397$0H1.3120575@attbi_s54...
If I have a waveguide, coax, or even lumped varactor tuned LC tank,
could I simply select which harmonic I want it to oscillate at, by
tunning a negative resistance?

A coaxial resonator will resonate on (or near) odd harmonics of the
lowest resonance, but you'll probably have trouble getting an LC tank
to have significant response at harmonics. Then the tuning will be
problematic, I think: you need to cover 3:1 for the lowest resonance,
and only 5:3 for the second, 7:5 for the third, etc., but capacitive
tuning would need a capacitance for the lowest resonance which is
awkward for the higher ones. Maybe you could only use the resonator,
say, at and above the 7th harmonic of the lowest resonance, and forget
about the 1st, 3rd and 5th.

Perhaps with the use of a "register key", such as is on flutes and
clarinets? I suppose that functions as a high-pass filter on the line,
when the hole is unplugged.

Just as an overtone crystal oscillator selects the overtone, you
should be able to do similarly with a coaxial resonator oscillator.
There's likely a practical limit. (The coupling will change with
which resonance is selected, no?)

I'm interested in a multi-decade VCO, tuned with one control voltage and
just a few switches.

You can switch both the C and the L of an LC tank and cover a wide
range...but it's often easier to just build separate oscillators and
switch among them.

No, I don't want to heterodyne or synthesize, because I'm interested in
the regenerative/super-regenerative capabilities.

Any applicable app notes or articles? Dream on?

I predict there will be a whole lot to learn on your way to your
goal...but remember the old regen radios that used plug-in coils for
different bands? Some of them could cover quite a range. You may be
able to accomplish something similar with diode switching.

Cheers,
Tom

Scott Stephens wrote in message news:tnamc.36397$0H1.3120575@attbi_s54...
If I have a waveguide, coax, or even lumped varactor tuned LC tank,
could I simply select which harmonic I want it to oscillate at, by
tunning a negative resistance?

A coaxial resonator will resonate on (or near) odd harmonics of the
lowest resonance, but you'll probably have trouble getting an LC tank
to have significant response at harmonics. Then the tuning will be
problematic, I think: you need to cover 3:1 for the lowest resonance,
and only 5:3 for the second, 7:5 for the third, etc., but capacitive
tuning would need a capacitance for the lowest resonance which is
awkward for the higher ones. Maybe you could only use the resonator,
say, at and above the 7th harmonic of the lowest resonance, and forget
about the 1st, 3rd and 5th.

Perhaps with the use of a "register key", such as is on flutes and
clarinets? I suppose that functions as a high-pass filter on the line,
when the hole is unplugged.

Just as an overtone crystal oscillator selects the overtone, you
should be able to do similarly with a coaxial resonator oscillator.
There's likely a practical limit. (The coupling will change with
which resonance is selected, no?)

I'm interested in a multi-decade VCO, tuned with one control voltage and
just a few switches.

You can switch both the C and the L of an LC tank and cover a wide
range...but it's often easier to just build separate oscillators and
switch among them.

No, I don't want to heterodyne or synthesize, because I'm interested in
the regenerative/super-regenerative capabilities.

Any applicable app notes or articles? Dream on?

I predict there will be a whole lot to learn on your way to your
goal...but remember the old regen radios that used plug-in coils for
different bands? Some of them could cover quite a range. You may be
able to accomplish something similar with diode switching.

Cheers,
Tom

I have built numerous VCO's that work as you describe.
A tuned coaxial line is used and the feedback is controlled
by a capacitor. Making the capacitor small will allow harmonic
oscillation, making it small will allow fundamental.

Since you can make say a 9th overtone crystal oscillator,
there is no reason why you can't make a 9th overtone transmission
line resonator oscillator.

Rick N6RK

"Scott Stephens" wrote in message
news:tnamc.36397$0H1.3120575@attbi_s54...
If I have a waveguide, coax, or even lumped varactor tuned LC tank,
could I simply select which harmonic I want it to oscillate at, by
tunning a negative resistance?

Perhaps with the use of a "register key", such as is on flutes and
clarinets? I suppose that functions as a high-pass filter on the line,
when the hole is unplugged.

I'm interested in a multi-decade VCO, tuned with one control voltage and
just a few switches.

No, I don't want to heterodyne or synthesize, because I'm interested in
the regenerative/super-regenerative capabilities.

Any applicable app notes or articles? Dream on?

--
Scott

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************

I have built numerous VCO's that work as you describe.
A tuned coaxial line is used and the feedback is controlled
by a capacitor. Making the capacitor small will allow harmonic
oscillation, making it small will allow fundamental.

Since you can make say a 9th overtone crystal oscillator,
there is no reason why you can't make a 9th overtone transmission
line resonator oscillator.

Rick N6RK

"Scott Stephens" wrote in message
news:tnamc.36397$0H1.3120575@attbi_s54...
If I have a waveguide, coax, or even lumped varactor tuned LC tank,
could I simply select which harmonic I want it to oscillate at, by
tunning a negative resistance?

Perhaps with the use of a "register key", such as is on flutes and
clarinets? I suppose that functions as a high-pass filter on the line,
when the hole is unplugged.

I'm interested in a multi-decade VCO, tuned with one control voltage and
just a few switches.

No, I don't want to heterodyne or synthesize, because I'm interested in
the regenerative/super-regenerative capabilities.

Any applicable app notes or articles? Dream on?

--
Scott

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************

Rick Karlquist N6RK wrote:

Finally a reply =)
thanks,

I have built numerous VCO's that work as you describe.

No technical papers recommendations?

A tuned coaxial line is used and the feedback is controlled
by a capacitor. Making the capacitor small will allow harmonic
oscillation, making it small will allow fundamental.

That was an initial thought, that, given a flat-gain amp, like a MMIC,
the coupling capacitors reactance would determine what frequency maximum
power would be transfered. The reactance the amplifier I/O impedance
matched the line I/O impedance.

Since you can make say a 9th overtone crystal oscillator,
there is no reason why you can't make a 9th overtone transmission
line resonator oscillator.

I'm thinking I should try a binary weighted series-L shunt-C ladder
network, with varactors for the C. Could switch the varactors into
forward conduction to tune out the end of the line, raising the frequency.

Latest Microwave News describes a nonlinear ceramic (BaZrTiO) thin-film
voltage-tuned capacitor. I've read about articles that use common
ceramic caps as VCO's, even the capacitor-equivalent of magnetic
amplifiers. The advantage of thin films is you can fabricate
voltage-tuned filters, as well as individual caps.

Now if I could just fabricate my own, using basement PCB lithographic
techniques, or my microwave oven to plasma sputter the film.

--
Scott

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************

Rick Karlquist N6RK wrote:

Finally a reply =)
thanks,

I have built numerous VCO's that work as you describe.

No technical papers recommendations?

A tuned coaxial line is used and the feedback is controlled
by a capacitor. Making the capacitor small will allow harmonic
oscillation, making it small will allow fundamental.

That was an initial thought, that, given a flat-gain amp, like a MMIC,
the coupling capacitors reactance would determine what frequency maximum
power would be transfered. The reactance the amplifier I/O impedance
matched the line I/O impedance.

Since you can make say a 9th overtone crystal oscillator,
there is no reason why you can't make a 9th overtone transmission
line resonator oscillator.

I'm thinking I should try a binary weighted series-L shunt-C ladder
network, with varactors for the C. Could switch the varactors into
forward conduction to tune out the end of the line, raising the frequency.

Latest Microwave News describes a nonlinear ceramic (BaZrTiO) thin-film
voltage-tuned capacitor. I've read about articles that use common
ceramic caps as VCO's, even the capacitor-equivalent of magnetic
amplifiers. The advantage of thin films is you can fabricate
voltage-tuned filters, as well as individual caps.

Now if I could just fabricate my own, using basement PCB lithographic
techniques, or my microwave oven to plasma sputter the film.

--
Scott

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************

"Scott Stephens" wrote in message
news:hDWqc.26611$gr.2415597@attbi_s52...

I'm thinking I should try a binary weighted series-L shunt-C ladder
network, with varactors for the C. Could switch the varactors into
forward conduction to tune out the end of the line, raising the frequency.

I played with that idea on the simulator. Didn't seem to have
a lot going for it.


Latest Microwave News describes a nonlinear ceramic (BaZrTiO) thin-film
voltage-tuned capacitor. I've read about articles that use common
ceramic caps as VCO's, even the capacitor-equivalent of magnetic
amplifiers. The advantage of thin films is you can fabricate
voltage-tuned filters, as well as individual caps.

I've been following those nonlinear ceramics (ie BST) for years. They
don't seem very promising as a tuning diode replacement. The Q is too
low, the tuning range is too restricted, and there are temperature problems.

Rick N6RK

"Scott Stephens" wrote in message
news:hDWqc.26611$gr.2415597@attbi_s52...

I'm thinking I should try a binary weighted series-L shunt-C ladder
network, with varactors for the C. Could switch the varactors into
forward conduction to tune out the end of the line, raising the frequency.

I played with that idea on the simulator. Didn't seem to have
a lot going for it.


Latest Microwave News describes a nonlinear ceramic (BaZrTiO) thin-film
voltage-tuned capacitor. I've read about articles that use common
ceramic caps as VCO's, even the capacitor-equivalent of magnetic
amplifiers. The advantage of thin films is you can fabricate
voltage-tuned filters, as well as individual caps.

I've been following those nonlinear ceramics (ie BST) for years. They
don't seem very promising as a tuning diode replacement. The Q is too
low, the tuning range is too restricted, and there are temperature problems.

Rick N6RK

Rick Karlquist N6RK wrote:

I'm thinking I should try a binary weighted series-L shunt-C ladder
network, with varactors for the C. Could switch the varactors into
forward conduction to tune out the end of the line, raising the frequency.

I played with that idea on the simulator. Didn't seem to have
a lot going for it.

I just did an FFT on a step-pulse on a diode-switched, binary weighted
LC ladder. Came out as I expected. Problem is the high-frequency
resonances exist on when the low frequency sections are not shorted.
Which will make transistor oscillator design interesting, if I don't use
a 50 ohm MMIC.

I've been following those nonlinear ceramics (ie BST) for years. They
don't seem very promising as a tuning diode replacement. The Q is too
low, the tuning range is too restricted, and there are temperature problems.

The latest Microwave News article showed the Q as being better than
varactor Q's, of under 10, IIRC.

--
Scott KB9ETU

**********************************

DIY Piezo-Gyro, PCB Drill Bot & More Soon!

http://home.comcast.net/~scottxs/

**********************************