it oscillates!

[TTman]

Phil H helped me think about this. Thanks.


The laser designator that I worked on just used the FPGA to do all the
timing.. Laser diode firing and Q switch opening and range detection...

Did the FPGA initiate each shot? What sort of timing resolution are
you getting?

Our trigger is asynchronous to our main clock, and we have to time
everything off that.

Some lasers just fire when they feel like, or are triggered by someone
not-us.

10 M over 10Km out and 10Km back?.I seem to recall 100M clock. 10 pulses
per second.~150A @90V for laser diode array and 3Kv for Q switch. I
designed a 'test pulse generator using 20Mhz atmel which gave ball park
50 M resolution check- to check FPGA timing was functional.Test software
fired the laser UUT, test box picked up the fire pulse and generated a
'return pulse'. Test software then got the 'distance' from the FPGA.
Don't slate me on the numbers, it was a few years ago and I'm retired now.


--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

[Phil Hobbs]

On 2020-04-16 20:54, Clifford Heath wrote:

On 17/4/20 2:42 am, jlarkin@highlandsniptechnology.com wrote:
On Thu, 16 Apr 2020 07:57:06 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:
What do you mean the first circuit oscillated at more frequencies
than you intended? Isn't that circuit tuned?

I think the NPN was also oscillating at some microwave
frequencies, all on its own. Fast emitter followers do that. It was
probably still oscillating when the 120 MHz tank was quenched and
the oscillator theoretically stopped. Touching various
counter-intuitive nodes with a tiny screwdriver changed things a
lot. I even stopped the extra oscillations by touching something
that made no sense.

A series base resistor is the usual fix for an oscillating emitter
follower, but that would need a hack and might reduce Q. Going to
a slower transistor seems like the best fix. It's only 120 MHz.

I've seen (LTSpice and bench) Colpitts oscillators that produce
pulses of much-higher-frequency oscillation near the fundamental's
zero crossing.

That's called a 'snivet'.

So you might have 125MHz with synchronously amplitude-modulated
900Mhz overlaid.

Also beware of paralleling larger and smaller capacitors, as is often
recommended for decoupling. The ESL of the larger capacitor can form
a surprisingly high-Q resonant tank with the smaller capacitor,
causing all kinds of interesting birdies.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 2020-04-16 15:01, John Larkin wrote:

On Thu, 16 Apr 2020 19:02:49 +0200, Gerhard Hoffmann <dk4xp@arcor.de
wrote:

Am 16.04.20 um 18:48 schrieb bitrex:

Modern DSOs also double as a portable gaming device; Doom runs even
better on this Rigol than some of the Nintendo home video game systems
it was ported to from the PC in the late 90s:

I have booted my Infiniium 54846B scope with a Linux variant to make
backups of its windows disk. It even ran open office, but sloooow.
That looked weird.


Cheers, Gerhard


The LeCroy is a Win7 machine.

You really need a mouse to use it.

There are a bunch of the 13 GHz version on eBay for about $22k, probably
not unrelated to Win7 being out of support.

40 GS/s simultaneous on four channels isn't bad going for $20k,
especially since it has a built-in 2.5 GHz FET probe on each channel for
lower-bandwidth measurements.

I might get one if my clients don't start paying late.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[John Larkin]

On Fri, 17 Apr 2020 16:08:14 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-16 15:01, John Larkin wrote:
On Thu, 16 Apr 2020 19:02:49 +0200, Gerhard Hoffmann <dk4xp@arcor.de
wrote:

Am 16.04.20 um 18:48 schrieb bitrex:

Modern DSOs also double as a portable gaming device; Doom runs even
better on this Rigol than some of the Nintendo home video game systems
it was ported to from the PC in the late 90s:

I have booted my Infiniium 54846B scope with a Linux variant to make
backups of its windows disk. It even ran open office, but sloooow.
That looked weird.


Cheers, Gerhard


The LeCroy is a Win7 machine.

You really need a mouse to use it.


There are a bunch of the 13 GHz version on eBay for about $22k, probably
not unrelated to Win7 being out of support.

40 GS/s simultaneous on four channels isn't bad going for $20k,
especially since it has a built-in 2.5 GHz FET probe on each channel for
lower-bandwidth measurements.

I might get one if my clients don't start paying late.

Cheers

Phil Hobbs

They followed the grand Windows traditions: it's really hard to find
things. After you find something, it's hard to find it again. And HELP
isn't much.

I beginning to like it, but they sure don't make it easy to love.

I did discover that my two Lascar bench power supplies were increasing
the jitter about 10:1. And I just discovered that the frequency is
radically sensitive to the -5 volt supply.

Such a simple circuit!

https://www.dropbox.com/s/iqcbnhrbknsp01w/Z482_scope_J1.jpg?raw=1

That's 4.5 ps RMS jitter after almost 200 cycles of oscillation. Gotta
track down the -5 thing.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Phil Hobbs]

On 2020-04-17 18:06, John Larkin wrote:

On Fri, 17 Apr 2020 16:08:14 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-16 15:01, John Larkin wrote:
On Thu, 16 Apr 2020 19:02:49 +0200, Gerhard Hoffmann
dk4xp@arcor.de> wrote:

Am 16.04.20 um 18:48 schrieb bitrex:

Modern DSOs also double as a portable gaming device; Doom
runs even better on this Rigol than some of the Nintendo home
video game systems it was ported to from the PC in the late
90s:

I have booted my Infiniium 54846B scope with a Linux variant to
make backups of its windows disk. It even ran open office, but
sloooow. That looked weird.


Cheers, Gerhard


The LeCroy is a Win7 machine.

You really need a mouse to use it.


There are a bunch of the 13 GHz version on eBay for about $22k,
probably not unrelated to Win7 being out of support.

40 GS/s simultaneous on four channels isn't bad going for $20k,
especially since it has a built-in 2.5 GHz FET probe on each
channel for lower-bandwidth measurements.

I might get one if my clients don't start paying late.


They followed the grand Windows traditions: it's really hard to find
things. After you find something, it's hard to find it again. And
HELP isn't much.

I beginning to like it, but they sure don't make it easy to love.

I did discover that my two Lascar bench power supplies were
increasing the jitter about 10:1. And I just discovered that the
frequency is radically sensitive to the -5 volt supply.

That I believe. Cap multipliers are your friend when building sensitive
discrete circuitry. Negative PSR can easily be negative in dB as well,
and is never very high.

Such a simple circuit!

https://www.dropbox.com/s/iqcbnhrbknsp01w/Z482_scope_J1.jpg?raw=1

That's 4.5 ps RMS jitter after almost 200 cycles of oscillation.
Gotta track down the -5 thing.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[John Larkin]

On Fri, 17 Apr 2020 18:15:54 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-17 18:06, John Larkin wrote:
On Fri, 17 Apr 2020 16:08:14 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-16 15:01, John Larkin wrote:
On Thu, 16 Apr 2020 19:02:49 +0200, Gerhard Hoffmann
dk4xp@arcor.de> wrote:

Am 16.04.20 um 18:48 schrieb bitrex:

Modern DSOs also double as a portable gaming device; Doom
runs even better on this Rigol than some of the Nintendo home
video game systems it was ported to from the PC in the late
90s:

I have booted my Infiniium 54846B scope with a Linux variant to
make backups of its windows disk. It even ran open office, but
sloooow. That looked weird.


Cheers, Gerhard


The LeCroy is a Win7 machine.

You really need a mouse to use it.


There are a bunch of the 13 GHz version on eBay for about $22k,
probably not unrelated to Win7 being out of support.

40 GS/s simultaneous on four channels isn't bad going for $20k,
especially since it has a built-in 2.5 GHz FET probe on each
channel for lower-bandwidth measurements.

I might get one if my clients don't start paying late.


They followed the grand Windows traditions: it's really hard to find
things. After you find something, it's hard to find it again. And
HELP isn't much.

I beginning to like it, but they sure don't make it easy to love.

I did discover that my two Lascar bench power supplies were
increasing the jitter about 10:1. And I just discovered that the
frequency is radically sensitive to the -5 volt supply.

That I believe. Cap multipliers are your friend when building sensitive
discrete circuitry. Negative PSR can easily be negative in dB as well,
and is never very high.

I'm going to see of the emitter current of the Colpitts transistor is
super sensitive, or maybe it's something else.

This is fun: if the guard pour is grounded, the frequency tempco is
negative. If it's connected to the emitter, it's positive. So some
capacitor value between the emitter and the guard should make it have
a zero TC.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Phil Hobbs]

On 2020-04-17 19:25, John Larkin wrote:

On Fri, 17 Apr 2020 18:15:54 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-17 18:06, John Larkin wrote:
On Fri, 17 Apr 2020 16:08:14 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-16 15:01, John Larkin wrote:
On Thu, 16 Apr 2020 19:02:49 +0200, Gerhard Hoffmann
dk4xp@arcor.de> wrote:

Am 16.04.20 um 18:48 schrieb bitrex:

Modern DSOs also double as a portable gaming device; Doom
runs even better on this Rigol than some of the Nintendo home
video game systems it was ported to from the PC in the late
90s:

I have booted my Infiniium 54846B scope with a Linux variant to
make backups of its windows disk. It even ran open office, but
sloooow. That looked weird.


Cheers, Gerhard


The LeCroy is a Win7 machine.

You really need a mouse to use it.


There are a bunch of the 13 GHz version on eBay for about $22k,
probably not unrelated to Win7 being out of support.

40 GS/s simultaneous on four channels isn't bad going for $20k,
especially since it has a built-in 2.5 GHz FET probe on each
channel for lower-bandwidth measurements.

I might get one if my clients don't start paying late.


They followed the grand Windows traditions: it's really hard to find
things. After you find something, it's hard to find it again. And
HELP isn't much.

I beginning to like it, but they sure don't make it easy to love.

I did discover that my two Lascar bench power supplies were
increasing the jitter about 10:1. And I just discovered that the
frequency is radically sensitive to the -5 volt supply.

That I believe. Cap multipliers are your friend when building sensitive
discrete circuitry. Negative PSR can easily be negative in dB as well,
and is never very high.


I'm going to see of the emitter current of the Colpitts transistor is
super sensitive, or maybe it's something else.

This is fun: if the guard pour is grounded, the frequency tempco is
negative. If it's connected to the emitter, it's positive. So some
capacitor value between the emitter and the guard should make it have
a zero TC.

You might be able to get rid of the varactor!

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Clifford Heath]

On 18/4/20 8:15 am, Phil Hobbs wrote:

On 2020-04-17 18:06, John Larkin wrote:
I did discover that my two Lascar bench power supplies were
increasing the jitter about 10:1. And I just discovered that the
frequency is radically sensitive to the -5 volt supply.

That I believe.  Cap multipliers are your friend when building sensitive
discrete circuitry.

Phil, why not take the capacitor -ve to the output and make a gyrator,
instead of just a capacitance multiplier?

Question asked for a mate, who's used gyrators like to make clean power
in every RF gadget he's designed in the last 30 years

Clifford Heath.

Negative PSR can easily be negative in dB as well,
and is never very high.

Such a simple circuit!

https://www.dropbox.com/s/iqcbnhrbknsp01w/Z482_scope_J1.jpg?raw=1

That's 4.5 ps RMS jitter after almost 200 cycles of oscillation.
Gotta track down the -5 thing.

Cheers

Phil Hobbs

 

[Clifford Heath]

On 18/4/20 6:04 am, Phil Hobbs wrote:

On 2020-04-16 20:54, Clifford Heath wrote:
On 17/4/20 2:42 am, jlarkin@highlandsniptechnology.com wrote:
On Thu, 16 Apr 2020 07:57:06 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:
What do you mean the first circuit oscillated at more frequencies
 than you intended? Isn't that circuit tuned?

I think the NPN was also oscillating at some microwave
frequencies, all on its own. Fast emitter followers do that. It was
probably still oscillating when the 120 MHz tank was quenched and
the oscillator theoretically stopped. Touching various
counter-intuitive nodes with a tiny screwdriver changed things a
lot. I even stopped the extra oscillations by touching something
that made no sense.

A series base resistor is the usual fix for an oscillating emitter
follower, but that would need a hack and might reduce Q. Going to
a slower transistor seems like the best fix. It's only 120 MHz.

I've seen (LTSpice and bench) Colpitts oscillators that produce
pulses of much-higher-frequency oscillation near the fundamental's
zero crossing.

That's called a 'snivet'.

Thanks!

CH

 

[Phil Hobbs]

On 2020-04-18 01:58, Clifford Heath wrote:

On 18/4/20 8:15 am, Phil Hobbs wrote:
On 2020-04-17 18:06, John Larkin wrote:
I did discover that my two Lascar bench power supplies were
increasing the jitter about 10:1. And I just discovered that the
frequency is radically sensitive to the -5 volt supply.

That I believe.  Cap multipliers are your friend when building
sensitive discrete circuitry.

Phil, why not take the capacitor -ve to the output and make a gyrator,
instead of just a capacitance multiplier?

Question asked for a mate, who's used gyrators like to make clean power
in every RF gadget he's designed in the last 30 years

You only get one pole per section, and there's a sneak path via the
series RC that trashes the high frequency rejection. Plus you need an
additional (and much bigger) cap to ground for the same corner frequency
because you lose the effect of beta.

My most commonly-used circuit is a two-pole cap multiplier with an RC
lowpass in series with the collector, which pretty well eliminates
feedthrough due to interelectrode capacitance and Early effect.

That'll get you 140 dB or more rejection if the layout is good, and
since you don't need the big bypass on the output, it'll probably wind
up being cheaper and smaller than the gyrator approach.

The gyrator approach is good for making quiet currents, provided you
come out of the collector. I use a modified version for driving diode
lasers. You can use 2 poles there, too, usually with a slow op amp loop
keeping the DC constant.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[Phil Hobbs]

On 2020-04-18 11:12, jlarkin@highlandsniptechnology.com wrote:

On Sat, 18 Apr 2020 07:57:52 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-18 01:58, Clifford Heath wrote:
On 18/4/20 8:15 am, Phil Hobbs wrote:
On 2020-04-17 18:06, John Larkin wrote:
I did discover that my two Lascar bench power supplies were
increasing the jitter about 10:1. And I just discovered that the
frequency is radically sensitive to the -5 volt supply.

That I believe.  Cap multipliers are your friend when building
sensitive discrete circuitry.

Phil, why not take the capacitor -ve to the output and make a gyrator,
instead of just a capacitance multiplier?

Question asked for a mate, who's used gyrators like to make clean power
in every RF gadget he's designed in the last 30 years

You only get one pole per section, and there's a sneak path via the
series RC that trashes the high frequency rejection. Plus you need an
additional (and much bigger) cap to ground for the same corner frequency
because you lose the effect of beta.

My most commonly-used circuit is a two-pole cap multiplier with an RC
lowpass in series with the collector, which pretty well eliminates
feedthrough due to interelectrode capacitance and Early effect.

That'll get you 140 dB or more rejection if the layout is good, and
since you don't need the big bypass on the output, it'll probably wind
up being cheaper and smaller than the gyrator approach.

The gyrator approach is good for making quiet currents, provided you
come out of the collector. I use a modified version for driving diode
lasers. You can use 2 poles there, too, usually with a slow op amp loop
keeping the DC constant.

Cheers

Phil Hobbs

I need frequency stability as well as low phase noise. Our DPLL will
discipline the Colpitts at a maybe a 250 KHz bandwidth, so low
frequency modulation, including thermals, are the big issue. If the
system sits around for a while untriggered, and the upcoming
oscillator frequency has drifted, the next trigger+lock event will be
ugly.

If you're only letting it free-run for a couple of microseconds, there's
lots of room to wrap an op amp round the cap multiplier to keep the
voltage stable (or apply temperature compensation, even).

We are being compulsive about jitter here, past what is needed to sell
this product, but then we do have time on our hands, so we can learn
stuff for future use. [1]

Well, better than meeting the spec is nailing it to the floor.

I added a biggish resistor to the emitter, to a hv power supply, so I
can trim the transistor current up/down without affecting impedances
much. More current seems to have a diminishing effect on frequency.

Probably due to the f_T getting high enough not to matter.

> Why are a few parts so complex?

Well, your oscillator probably has 10**22 atoms in it.

[1] We assign a part/experiment number to things like this. This one
is Z482. The oscillator, and its evolution, will be documented and
archived on a server. Lots of dated/titled whiteboard pics, scope
shots, bosrd photos, sometimes a summary Word doc.

I should be more disciplined about that.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

On Sat, 18 Apr 2020 07:57:52 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-18 01:58, Clifford Heath wrote:
On 18/4/20 8:15 am, Phil Hobbs wrote:
On 2020-04-17 18:06, John Larkin wrote:
I did discover that my two Lascar bench power supplies were
increasing the jitter about 10:1. And I just discovered that the
frequency is radically sensitive to the -5 volt supply.

That I believe.  Cap multipliers are your friend when building
sensitive discrete circuitry.

Phil, why not take the capacitor -ve to the output and make a gyrator,
instead of just a capacitance multiplier?

Question asked for a mate, who's used gyrators like to make clean power
in every RF gadget he's designed in the last 30 years

You only get one pole per section, and there's a sneak path via the
series RC that trashes the high frequency rejection. Plus you need an
additional (and much bigger) cap to ground for the same corner frequency
because you lose the effect of beta.

My most commonly-used circuit is a two-pole cap multiplier with an RC
lowpass in series with the collector, which pretty well eliminates
feedthrough due to interelectrode capacitance and Early effect.

That'll get you 140 dB or more rejection if the layout is good, and
since you don't need the big bypass on the output, it'll probably wind
up being cheaper and smaller than the gyrator approach.

The gyrator approach is good for making quiet currents, provided you
come out of the collector. I use a modified version for driving diode
lasers. You can use 2 poles there, too, usually with a slow op amp loop
keeping the DC constant.

Cheers

Phil Hobbs

I need frequency stability as well as low phase noise. Our DPLL will
discipline the Colpitts at a maybe a 250 KHz bandwidth, so low
frequency modulation, including thermals, are the big issue. If the
system sits around for a while untriggered, and the upcoming
oscillator frequency has drifted, the next trigger+lock event will be
ugly.

We are being compulsive about jitter here, past what is needed to sell
this product, but then we do have time on our hands, so we can learn
stuff for future use. [1]

I added a biggish resistor to the emitter, to a hv power supply, so I
can trim the transistor current up/down without affecting impedances
much. More current seems to have a diminishing effect on frequency.
Why are a few parts so complex?

[1] We assign a part/experiment number to things like this. This one
is Z482. The oscillator, and its evolution, will be documented and
archived on a server. Lots of dated/titled whiteboard pics, scope
shots, bosrd photos, sometimes a summary Word doc.



--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

On Fri, 17 Apr 2020 16:04:32 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-16 20:54, Clifford Heath wrote:
On 17/4/20 2:42 am, jlarkin@highlandsniptechnology.com wrote:
On Thu, 16 Apr 2020 07:57:06 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:
What do you mean the first circuit oscillated at more frequencies
than you intended? Isn't that circuit tuned?

I think the NPN was also oscillating at some microwave
frequencies, all on its own. Fast emitter followers do that. It was
probably still oscillating when the 120 MHz tank was quenched and
the oscillator theoretically stopped. Touching various
counter-intuitive nodes with a tiny screwdriver changed things a
lot. I even stopped the extra oscillations by touching something
that made no sense.

A series base resistor is the usual fix for an oscillating emitter
follower, but that would need a hack and might reduce Q. Going to
a slower transistor seems like the best fix. It's only 120 MHz.

I've seen (LTSpice and bench) Colpitts oscillators that produce
pulses of much-higher-frequency oscillation near the fundamental's
zero crossing.

That's called a 'snivet'.

So you might have 125MHz with synchronously amplitude-modulated
900Mhz overlaid.

Also beware of paralleling larger and smaller capacitors, as is often
recommended for decoupling. The ESL of the larger capacitor can form
a surprisingly high-Q resonant tank with the smaller capacitor,
causing all kinds of interesting birdies.


Cheers

Phil Hobbs

My uncle Sheldon, who had a TV repair shop and taught me to solder
when I was three, called it "squegging." The horizontal sweep tube
would burst oscillate (possibly Barkhausen-Kurz oscillation), and make
RF that the tuner would pick up. The result was vertical bars on the
screen. The fix was usually to change the HO tube.




--

John Larkin Highland Technology, Inc

Science teaches us to doubt.

Claude Bernard

 

[Phil Hobbs]

On 2020-04-18 11:22, jlarkin@highlandsniptechnology.com wrote:

On Fri, 17 Apr 2020 16:04:32 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-16 20:54, Clifford Heath wrote:
On 17/4/20 2:42 am, jlarkin@highlandsniptechnology.com wrote:
On Thu, 16 Apr 2020 07:57:06 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:
What do you mean the first circuit oscillated at more frequencies
than you intended? Isn't that circuit tuned?

I think the NPN was also oscillating at some microwave
frequencies, all on its own. Fast emitter followers do that. It was
probably still oscillating when the 120 MHz tank was quenched and
the oscillator theoretically stopped. Touching various
counter-intuitive nodes with a tiny screwdriver changed things a
lot. I even stopped the extra oscillations by touching something
that made no sense.

A series base resistor is the usual fix for an oscillating emitter
follower, but that would need a hack and might reduce Q. Going to
a slower transistor seems like the best fix. It's only 120 MHz.

I've seen (LTSpice and bench) Colpitts oscillators that produce
pulses of much-higher-frequency oscillation near the fundamental's
zero crossing.

That's called a 'snivet'.

So you might have 125MHz with synchronously amplitude-modulated
900Mhz overlaid.

Also beware of paralleling larger and smaller capacitors, as is often
recommended for decoupling. The ESL of the larger capacitor can form
a surprisingly high-Q resonant tank with the smaller capacitor,
causing all kinds of interesting birdies.


Cheers

Phil Hobbs

My uncle Sheldon, who had a TV repair shop and taught me to solder
when I was three, called it "squegging." The horizontal sweep tube
would burst oscillate (possibly Barkhausen-Kurz oscillation), and make
RF that the tuner would pick up. The result was vertical bars on the
screen. The fix was usually to change the HO tube.

AFAIK 'squegging' usually refers to spontaneous rectangular AM caused by
an oscillator whose bias time constant is too slow. It starts up, and
when it goes into Class C the bias starts to shift until the average
gain drops below unity, it stops. Then the bias has to recover till
it's unstable in the small-signal regime, at which point it starts up again.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[John Larkin]

On Sat, 18 Apr 2020 11:27:56 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-18 11:22, jlarkin@highlandsniptechnology.com wrote:
On Fri, 17 Apr 2020 16:04:32 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-16 20:54, Clifford Heath wrote:
On 17/4/20 2:42 am, jlarkin@highlandsniptechnology.com wrote:
On Thu, 16 Apr 2020 07:57:06 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:
What do you mean the first circuit oscillated at more frequencies
than you intended? Isn't that circuit tuned?

I think the NPN was also oscillating at some microwave
frequencies, all on its own. Fast emitter followers do that. It was
probably still oscillating when the 120 MHz tank was quenched and
the oscillator theoretically stopped. Touching various
counter-intuitive nodes with a tiny screwdriver changed things a
lot. I even stopped the extra oscillations by touching something
that made no sense.

A series base resistor is the usual fix for an oscillating emitter
follower, but that would need a hack and might reduce Q. Going to
a slower transistor seems like the best fix. It's only 120 MHz.

I've seen (LTSpice and bench) Colpitts oscillators that produce
pulses of much-higher-frequency oscillation near the fundamental's
zero crossing.

That's called a 'snivet'.

So you might have 125MHz with synchronously amplitude-modulated
900Mhz overlaid.

Also beware of paralleling larger and smaller capacitors, as is often
recommended for decoupling. The ESL of the larger capacitor can form
a surprisingly high-Q resonant tank with the smaller capacitor,
causing all kinds of interesting birdies.


Cheers

Phil Hobbs

My uncle Sheldon, who had a TV repair shop and taught me to solder
when I was three, called it "squegging." The horizontal sweep tube
would burst oscillate (possibly Barkhausen-Kurz oscillation), and make
RF that the tuner would pick up. The result was vertical bars on the
screen. The fix was usually to change the HO tube.

AFAIK 'squegging' usually refers to spontaneous rectangular AM caused by
an oscillator whose bias time constant is too slow. It starts up, and
when it goes into Class C the bias starts to shift until the average
gain drops below unity, it stops. Then the bias has to recover till
it's unstable in the small-signal regime, at which point it starts up again.

Cheers

Phil Hobbs

That's the super-regen mechanism, but Sheldon didn't know that.

Superregens are really interesting. Chaotic too.

I had to solder for Uncle Sheldon because he always had a cigarette in
one hand and a Dixie beer in the other.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Fri, 17 Apr 2020 20:18:55 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-17 19:25, John Larkin wrote:
On Fri, 17 Apr 2020 18:15:54 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-17 18:06, John Larkin wrote:
On Fri, 17 Apr 2020 16:08:14 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-16 15:01, John Larkin wrote:
On Thu, 16 Apr 2020 19:02:49 +0200, Gerhard Hoffmann
dk4xp@arcor.de> wrote:

Am 16.04.20 um 18:48 schrieb bitrex:

Modern DSOs also double as a portable gaming device; Doom
runs even better on this Rigol than some of the Nintendo home
video game systems it was ported to from the PC in the late
90s:

I have booted my Infiniium 54846B scope with a Linux variant to
make backups of its windows disk. It even ran open office, but
sloooow. That looked weird.


Cheers, Gerhard


The LeCroy is a Win7 machine.

You really need a mouse to use it.


There are a bunch of the 13 GHz version on eBay for about $22k,
probably not unrelated to Win7 being out of support.

40 GS/s simultaneous on four channels isn't bad going for $20k,
especially since it has a built-in 2.5 GHz FET probe on each
channel for lower-bandwidth measurements.

I might get one if my clients don't start paying late.


They followed the grand Windows traditions: it's really hard to find
things. After you find something, it's hard to find it again. And
HELP isn't much.

I beginning to like it, but they sure don't make it easy to love.

I did discover that my two Lascar bench power supplies were
increasing the jitter about 10:1. And I just discovered that the
frequency is radically sensitive to the -5 volt supply.

That I believe. Cap multipliers are your friend when building sensitive
discrete circuitry. Negative PSR can easily be negative in dB as well,
and is never very high.


I'm going to see of the emitter current of the Colpitts transistor is
super sensitive, or maybe it's something else.

This is fun: if the guard pour is grounded, the frequency tempco is
negative. If it's connected to the emitter, it's positive. So some
capacitor value between the emitter and the guard should make it have
a zero TC.


You might be able to get rid of the varactor!

Cheers

Phil Hobbs

I need the varactor for the DPLL. What I can get rid of is the N7400
cap and its series padder. Especially if the tempco is already
positive.



--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Phil Hobbs]

On 2020-04-18 13:45, John Larkin wrote:

On Fri, 17 Apr 2020 20:18:55 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-17 19:25, John Larkin wrote:
On Fri, 17 Apr 2020 18:15:54 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-17 18:06, John Larkin wrote:
On Fri, 17 Apr 2020 16:08:14 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-16 15:01, John Larkin wrote:
On Thu, 16 Apr 2020 19:02:49 +0200, Gerhard Hoffmann
dk4xp@arcor.de> wrote:

Am 16.04.20 um 18:48 schrieb bitrex:

Modern DSOs also double as a portable gaming device; Doom
runs even better on this Rigol than some of the Nintendo home
video game systems it was ported to from the PC in the late
90s:

I have booted my Infiniium 54846B scope with a Linux variant to
make backups of its windows disk. It even ran open office, but
sloooow. That looked weird.


Cheers, Gerhard


The LeCroy is a Win7 machine.

You really need a mouse to use it.


There are a bunch of the 13 GHz version on eBay for about $22k,
probably not unrelated to Win7 being out of support.

40 GS/s simultaneous on four channels isn't bad going for $20k,
especially since it has a built-in 2.5 GHz FET probe on each
channel for lower-bandwidth measurements.

I might get one if my clients don't start paying late.


They followed the grand Windows traditions: it's really hard to find
things. After you find something, it's hard to find it again. And
HELP isn't much.

I beginning to like it, but they sure don't make it easy to love.

I did discover that my two Lascar bench power supplies were
increasing the jitter about 10:1. And I just discovered that the
frequency is radically sensitive to the -5 volt supply.

That I believe. Cap multipliers are your friend when building sensitive
discrete circuitry. Negative PSR can easily be negative in dB as well,
and is never very high.


I'm going to see of the emitter current of the Colpitts transistor is
super sensitive, or maybe it's something else.

This is fun: if the guard pour is grounded, the frequency tempco is
negative. If it's connected to the emitter, it's positive. So some
capacitor value between the emitter and the guard should make it have
a zero TC.


You might be able to get rid of the varactor!

I need the varactor for the DPLL. What I can get rid of is the N7400
cap and its series padder. Especially if the tempco is already
positive.

Well, it depends on how large a range you get from the power supply. (*)

Cheers

Phil Hobbs

(*) Not seriously suggesting this for a product, but I've done lots
hackier things in protos.



--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[John Larkin]

On Sat, 18 Apr 2020 11:44:13 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-18 11:12, jlarkin@highlandsniptechnology.com wrote:
On Sat, 18 Apr 2020 07:57:52 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-18 01:58, Clifford Heath wrote:
On 18/4/20 8:15 am, Phil Hobbs wrote:
On 2020-04-17 18:06, John Larkin wrote:
I did discover that my two Lascar bench power supplies were
increasing the jitter about 10:1. And I just discovered that the
frequency is radically sensitive to the -5 volt supply.

That I believe.  Cap multipliers are your friend when building
sensitive discrete circuitry.

Phil, why not take the capacitor -ve to the output and make a gyrator,
instead of just a capacitance multiplier?

Question asked for a mate, who's used gyrators like to make clean power
in every RF gadget he's designed in the last 30 years

You only get one pole per section, and there's a sneak path via the
series RC that trashes the high frequency rejection. Plus you need an
additional (and much bigger) cap to ground for the same corner frequency
because you lose the effect of beta.

My most commonly-used circuit is a two-pole cap multiplier with an RC
lowpass in series with the collector, which pretty well eliminates
feedthrough due to interelectrode capacitance and Early effect.

That'll get you 140 dB or more rejection if the layout is good, and
since you don't need the big bypass on the output, it'll probably wind
up being cheaper and smaller than the gyrator approach.

The gyrator approach is good for making quiet currents, provided you
come out of the collector. I use a modified version for driving diode
lasers. You can use 2 poles there, too, usually with a slow op amp loop
keeping the DC constant.

Cheers

Phil Hobbs

I need frequency stability as well as low phase noise. Our DPLL will
discipline the Colpitts at a maybe a 250 KHz bandwidth, so low
frequency modulation, including thermals, are the big issue. If the
system sits around for a while untriggered, and the upcoming
oscillator frequency has drifted, the next trigger+lock event will be
ugly.

If you're only letting it free-run for a couple of microseconds, there's
lots of room to wrap an op amp round the cap multiplier to keep the
voltage stable (or apply temperature compensation, even).

We are being compulsive about jitter here, past what is needed to sell
this product, but then we do have time on our hands, so we can learn
stuff for future use. [1]

Well, better than meeting the spec is nailing it to the floor.

I added a biggish resistor to the emitter, to a hv power supply, so I
can trim the transistor current up/down without affecting impedances
much. More current seems to have a diminishing effect on frequency.

Probably due to the f_T getting high enough not to matter.

Why are a few parts so complex?

Well, your oscillator probably has 10**22 atoms in it.


[1] We assign a part/experiment number to things like this. This one
is Z482. The oscillator, and its evolution, will be documented and
archived on a server. Lots of dated/titled whiteboard pics, scope
shots, bosrd photos, sometimes a summary Word doc.

I should be more disciplined about that.

Cheers

Phil Hobbs

We now have 132 Z-folders in the J:\Protos\ collection. There is a
procedure and a text index file that people use to log an experiment.
I figure that whenever someone learns something, they should share and
preserve it. Some are actual PCB layouts, some are breadboards, some
just a graph or whiteboard photo or something. Anything interesting.

Our parts database also saves data sheets and notes about parts, and
references a Zxxx folder when appropriate.

--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[TTman]

The laser designator that I worked on just used the FPGA to do all the
timing.. Laser diode firing and Q switch opening and range detection...

Did the FPGA initiate each shot? What sort of timing resolution are
you getting?

Our trigger is asynchronous to our main clock, and we have to time
everything off that.

Some lasers just fire when they feel like, or are triggered by someone
not-us.

The FPGA triggerd the laser via user pressing the trigger button.Target
designator for laser guided bombs...Complex stuff... energy and pulse
width is variable for Diode array.Qswitch window is variable.Better not
say much more than that..

--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

[Phil Hobbs]

On 2020-04-18 14:16, John Larkin wrote:

On Sat, 18 Apr 2020 11:27:56 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-18 11:22, jlarkin@highlandsniptechnology.com wrote:
On Fri, 17 Apr 2020 16:04:32 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 2020-04-16 20:54, Clifford Heath wrote:
On 17/4/20 2:42 am, jlarkin@highlandsniptechnology.com wrote:
On Thu, 16 Apr 2020 07:57:06 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:
What do you mean the first circuit oscillated at more frequencies
than you intended? Isn't that circuit tuned?

I think the NPN was also oscillating at some microwave
frequencies, all on its own. Fast emitter followers do that. It was
probably still oscillating when the 120 MHz tank was quenched and
the oscillator theoretically stopped. Touching various
counter-intuitive nodes with a tiny screwdriver changed things a
lot. I even stopped the extra oscillations by touching something
that made no sense.

A series base resistor is the usual fix for an oscillating emitter
follower, but that would need a hack and might reduce Q. Going to
a slower transistor seems like the best fix. It's only 120 MHz.

I've seen (LTSpice and bench) Colpitts oscillators that produce
pulses of much-higher-frequency oscillation near the fundamental's
zero crossing.

That's called a 'snivet'.

So you might have 125MHz with synchronously amplitude-modulated
900Mhz overlaid.

Also beware of paralleling larger and smaller capacitors, as is often
recommended for decoupling. The ESL of the larger capacitor can form
a surprisingly high-Q resonant tank with the smaller capacitor,
causing all kinds of interesting birdies.


Cheers

Phil Hobbs

My uncle Sheldon, who had a TV repair shop and taught me to solder
when I was three, called it "squegging." The horizontal sweep tube
would burst oscillate (possibly Barkhausen-Kurz oscillation), and make
RF that the tuner would pick up. The result was vertical bars on the
screen. The fix was usually to change the HO tube.

AFAIK 'squegging' usually refers to spontaneous rectangular AM caused by
an oscillator whose bias time constant is too slow. It starts up, and
when it goes into Class C the bias starts to shift until the average
gain drops below unity, it stops. Then the bias has to recover till
it's unstable in the small-signal regime, at which point it starts up again.

Cheers

Phil Hobbs

That's the super-regen mechanism, but Sheldon didn't know that.

Yeah, it's neat being able to make a single tube superregen. External
quench has its advantages, but when you start piling on parts, the
superregen starts to lose its charm. Still, being able to amplify
thermal noise up to headphone volume with a single triode is pretty
amazing. Edwin Armstrong was a very smart guy.

Superregens are really interesting.

Agreed. I've mentioned a truly wonderful book on superregens here
before: "The Superregenerative Receiver" by J. R. Whitehead. I have a
hard copy, but you can also get an OCRed scan:

<https://archive.org/download/in.ernet.dli.2015.16956/2015.16956.Super---Regenerative-Receiver_text.pdf>

Really a good read for radio buffs. I've often wanted to do an optical
version, but so far it's never been the right solution to the problem at
hand.

> Chaotic too.

Dunno about that. Since a superregen's oscillations build up from noise
on every cycle, it seems like it should be fully deterministic apart
from the noise statistics.

I had to solder for Uncle Sheldon because he always had a cigarette in
one hand and a Dixie beer in the other.

Well, he didn't have grad students available.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com