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Michael · Guest

I thought I posted it already, it did not go through. Grrrrrrrrrrrrr
Suppose I have two toroids sandwiched together. One is powder with
single turn inductance (A1)=96nH. Another is high mu ferrite with
A1=15uH.
I apply 10V to 1 turn. The ferrite will saturate (~200mA) pretty soon
(1/4 us). By that time the inductor will have ~0.26uJ stored in it....
How will current look?
I haven>t got samples yet, I cannot try it...

Michael · Guest

On Jul 28, 12:09 pm, Joerg <notthisjoerg...@removethispacbell.net>
wrote:
[quote]Michael wrote:
I thought I posted it already, it did not go through. Grrrrrrrrrrrrr
Suppose I have two toroids sandwiched together. One is powder with
single turn inductance (A1)=96nH. Another is high mu ferrite with
A1=15uH.
I apply 10V to 1 turn. The ferrite will saturate (~200mA) pretty soon
(1/4 us). By that time the inductor will have ~0.26uJ stored in it....
How will current look?

There will be that classical shark fin, followed by a loud bang, molten
solder splattering about, stuff flying around, smoke alarms blaring ...

I haven>t got samples yet, I cannot try it...

Be careful and make sure there si something that will limit the current.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
[/quote]
Spark, smoke, sirens... I failed to ask why it doesn>t happen

Michael · Guest

On Jul 28, 1:51 pm, Joerg <notthisjoerg...@removethispacbell.net>
wrote:
[quote]Tim Wescott wrote:
Joerg wrote:
Michael wrote:
I thought I posted it already, it did not go through. Grrrrrrrrrrrrr
Suppose I have two toroids sandwiched together. One is powder with
single turn inductance (A1)=96nH. Another is high mu ferrite with
A1=15uH.
I apply 10V to 1 turn. The ferrite will saturate (~200mA) pretty soon
(1/4 us). By that time the inductor will have ~0.26uJ stored in it....
How will current look?

There will be that classical shark fin, followed by a loud bang,
molten solder splattering about, stuff flying around, smoke alarms
blaring ...

I haven>t got samples yet, I cannot try it...

Be careful and make sure there is something that will limit the current.

Aww, Joerg, you take the excitement out of life.

I had the ongoing amusement one project of kibitzing a theoretically
experienced analog guy (from MIT, no less!) on a switching amplifier.
One of the things that I diagnosed was that mysterious (to him) shark
fin, although it was only one of the reasons that things went BANG on
that particular circuit.

Some of the guys also overlook the fact that there is a rather large
tolerance on ferrite core specs. Later, some folks in purchasing think
that a ferrite is a ferrite is a ferrite. Phssst ... *BANG*.

The part that added the most humor (for me) was that my job title (and
function) at the time was very firmly planted in "software engineer",
although I was being allowed to design a (simple) board.

Don>t ya love it when that happens? I once snuck into a mechanical
design review. I wasn>t supposed to be there but urgently needed to pass
a message on to one of the guys. Looked at the PowerPoint screen and
just had to ask: "Looks like there is way too little airflow. And what
happens if that fan up there fails?" ... "Uhm ..., well, ... s..t!"
Major redesign.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
[/quote]
OK, I kind of guessed (qualitatively) that at first dI/dt is "slow"
then there is a step (?? how long does it take for mu to drop??). The
current steps up by sqrt(mu) and then keeps ramping up mu times as
fast.
Does it make sense?

Michael · Guest

On Jul 28, 3:05 pm, Joerg <notthisjoerg...@removethispacbell.net>
wrote:
[quote]Michael wrote:
On Jul 28, 1:51 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
Tim Wescott wrote:
Joerg wrote:
Michael wrote:
I thought I posted it already, it did not go through. Grrrrrrrrrrrrr
Suppose I have two toroids sandwiched together. One is powder with
single turn inductance (A1)=96nH. Another is high mu ferrite with
A1=15uH.
I apply 10V to 1 turn. The ferrite will saturate (~200mA) pretty soon
(1/4 us). By that time the inductor will have ~0.26uJ stored in it....
How will current look?
There will be that classical shark fin, followed by a loud bang,
molten solder splattering about, stuff flying around, smoke alarms
blaring ...
I haven>t got samples yet, I cannot try it...
Be careful and make sure there is something that will limit the current.
Aww, Joerg, you take the excitement out of life.
I had the ongoing amusement one project of kibitzing a theoretically
experienced analog guy (from MIT, no less!) on a switching amplifier.
One of the things that I diagnosed was that mysterious (to him) shark
fin, although it was only one of the reasons that things went BANG on
that particular circuit.
Some of the guys also overlook the fact that there is a rather large
tolerance on ferrite core specs. Later, some folks in purchasing think
that a ferrite is a ferrite is a ferrite. Phssst ... *BANG*.

The part that added the most humor (for me) was that my job title (and
function) at the time was very firmly planted in "software engineer",
although I was being allowed to design a (simple) board.
Don>t ya love it when that happens? I once snuck into a mechanical
design review. I wasn>t supposed to be there but urgently needed to pass
a message on to one of the guys. Looked at the PowerPoint screen and
just had to ask: "Looks like there is way too little airflow. And what
happens if that fan up there fails?" ... "Uhm ..., well, ... s..t!"
Major redesign.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

OK, I kind of guessed (qualitatively) that at first dI/dt is "slow"
then there is a step (?? how long does it take for mu to drop??). The
current steps up by sqrt(mu) and then keeps ramping up mu times as
fast.
Does it make sense?

Depends on the core, it>s in the ferrite datasheet. Usually the "grace
period" ends at some point where the inductor basically acts like an air
coil, as if the core wouldn>t be there anymore. For most practical
circuits such as switch mode supplies that comes pretty close to a dead
short with all its consequences.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
[/quote]
I am not worried about "dire consequences" - I am sandwiching two
cores actually (ferrite and iron powder), what I need to know is HOW
FAST ferrite "disappears". They should use something like this in
series trigger transformers.

Joerg · Guest

Michael wrote:
[quote]I thought I posted it already, it did not go through. Grrrrrrrrrrrrr
Suppose I have two toroids sandwiched together. One is powder with
single turn inductance (A1)=96nH. Another is high mu ferrite with
A1=15uH.
I apply 10V to 1 turn. The ferrite will saturate (~200mA) pretty soon
(1/4 us). By that time the inductor will have ~0.26uJ stored in it....
How will current look?
[/quote]

There will be that classical shark fin, followed by a loud bang, molten
solder splattering about, stuff flying around, smoke alarms blaring ...

[quote]I haven>t got samples yet, I cannot try it...
[/quote]

Be careful and make sure there si something that will limit the current.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Tim Wescott · Guest

Joerg wrote:
[quote]Michael wrote:
I thought I posted it already, it did not go through. Grrrrrrrrrrrrr
Suppose I have two toroids sandwiched together. One is powder with
single turn inductance (A1)=96nH. Another is high mu ferrite with
A1=15uH.
I apply 10V to 1 turn. The ferrite will saturate (~200mA) pretty soon
(1/4 us). By that time the inductor will have ~0.26uJ stored in it....
How will current look?

There will be that classical shark fin, followed by a loud bang, molten
solder splattering about, stuff flying around, smoke alarms blaring ...

I haven>t got samples yet, I cannot try it...

Be careful and make sure there is something that will limit the current.

Aww, Joerg, you take the excitement out of life.[/quote]

I had the ongoing amusement one project of kibitzing a theoretically
experienced analog guy (from MIT, no less!) on a switching amplifier.
One of the things that I diagnosed was that mysterious (to him) shark
fin, although it was only one of the reasons that things went BANG on
that particular circuit.

The part that added the most humor (for me) was that my job title (and
function) at the time was very firmly planted in "software engineer",
although I was being allowed to design a (simple) board.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Joerg · Guest

Michael wrote:
[quote]On Jul 28, 12:09 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
Michael wrote:
I thought I posted it already, it did not go through. Grrrrrrrrrrrrr
Suppose I have two toroids sandwiched together. One is powder with
single turn inductance (A1)=96nH. Another is high mu ferrite with
A1=15uH.
I apply 10V to 1 turn. The ferrite will saturate (~200mA) pretty soon
(1/4 us). By that time the inductor will have ~0.26uJ stored in it....
How will current look?
There will be that classical shark fin, followed by a loud bang, molten
solder splattering about, stuff flying around, smoke alarms blaring ...

I haven>t got samples yet, I cannot try it...
Be careful and make sure there si something that will limit the current.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Spark, smoke, sirens... I failed to ask why it doesn>t happen
[/quote]

Well, if you have a current limit it won>t ;-)

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Joerg · Guest

Tim Wescott wrote:
[quote]Joerg wrote:
Michael wrote:
I thought I posted it already, it did not go through. Grrrrrrrrrrrrr
Suppose I have two toroids sandwiched together. One is powder with
single turn inductance (A1)=96nH. Another is high mu ferrite with
A1=15uH.
I apply 10V to 1 turn. The ferrite will saturate (~200mA) pretty soon
(1/4 us). By that time the inductor will have ~0.26uJ stored in it....
How will current look?

There will be that classical shark fin, followed by a loud bang,
molten solder splattering about, stuff flying around, smoke alarms
blaring ...

I haven>t got samples yet, I cannot try it...

Be careful and make sure there is something that will limit the current.

Aww, Joerg, you take the excitement out of life.

I had the ongoing amusement one project of kibitzing a theoretically
experienced analog guy (from MIT, no less!) on a switching amplifier.
One of the things that I diagnosed was that mysterious (to him) shark
fin, although it was only one of the reasons that things went BANG on
that particular circuit.

[/quote]
Some of the guys also overlook the fact that there is a rather large
tolerance on ferrite core specs. Later, some folks in purchasing think
that a ferrite is a ferrite is a ferrite. Phssst ... *BANG*.

[quote]The part that added the most humor (for me) was that my job title (and
function) at the time was very firmly planted in "software engineer",
although I was being allowed to design a (simple) board.

[/quote]
Don>t ya love it when that happens? I once snuck into a mechanical
design review. I wasn>t supposed to be there but urgently needed to pass
a message on to one of the guys. Looked at the PowerPoint screen and
just had to ask: "Looks like there is way too little airflow. And what
happens if that fan up there fails?" ... "Uhm ..., well, ... s..t!"
Major redesign.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Joerg · Guest

Michael wrote:
[quote]On Jul 28, 1:51 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
Tim Wescott wrote:
Joerg wrote:
Michael wrote:
I thought I posted it already, it did not go through. Grrrrrrrrrrrrr
Suppose I have two toroids sandwiched together. One is powder with
single turn inductance (A1)=96nH. Another is high mu ferrite with
A1=15uH.
I apply 10V to 1 turn. The ferrite will saturate (~200mA) pretty soon
(1/4 us). By that time the inductor will have ~0.26uJ stored in it....
How will current look?
There will be that classical shark fin, followed by a loud bang,
molten solder splattering about, stuff flying around, smoke alarms
blaring ...
I haven>t got samples yet, I cannot try it...
Be careful and make sure there is something that will limit the current.
Aww, Joerg, you take the excitement out of life.
I had the ongoing amusement one project of kibitzing a theoretically
experienced analog guy (from MIT, no less!) on a switching amplifier.
One of the things that I diagnosed was that mysterious (to him) shark
fin, although it was only one of the reasons that things went BANG on
that particular circuit.
Some of the guys also overlook the fact that there is a rather large
tolerance on ferrite core specs. Later, some folks in purchasing think
that a ferrite is a ferrite is a ferrite. Phssst ... *BANG*.

The part that added the most humor (for me) was that my job title (and
function) at the time was very firmly planted in "software engineer",
although I was being allowed to design a (simple) board.
Don>t ya love it when that happens? I once snuck into a mechanical
design review. I wasn>t supposed to be there but urgently needed to pass
a message on to one of the guys. Looked at the PowerPoint screen and
just had to ask: "Looks like there is way too little airflow. And what
happens if that fan up there fails?" ... "Uhm ..., well, ... s..t!"
Major redesign.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

OK, I kind of guessed (qualitatively) that at first dI/dt is "slow"
then there is a step (?? how long does it take for mu to drop??). The
current steps up by sqrt(mu) and then keeps ramping up mu times as
fast.
Does it make sense?

[/quote]
Depends on the core, it>s in the ferrite datasheet. Usually the "grace
period" ends at some point where the inductor basically acts like an air
coil, as if the core wouldn>t be there anymore. For most practical
circuits such as switch mode supplies that comes pretty close to a dead
short with all its consequences.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Joerg · Guest

Michael wrote:
[quote]On Jul 28, 3:05 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
Michael wrote:
On Jul 28, 1:51 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:
Tim Wescott wrote:
Joerg wrote:
Michael wrote:
I thought I posted it already, it did not go through. Grrrrrrrrrrrrr
Suppose I have two toroids sandwiched together. One is powder with
single turn inductance (A1)=96nH. Another is high mu ferrite with
A1=15uH.
I apply 10V to 1 turn. The ferrite will saturate (~200mA) pretty soon
(1/4 us). By that time the inductor will have ~0.26uJ stored in it....
How will current look?
There will be that classical shark fin, followed by a loud bang,
molten solder splattering about, stuff flying around, smoke alarms
blaring ...
I haven>t got samples yet, I cannot try it...
Be careful and make sure there is something that will limit the current.
Aww, Joerg, you take the excitement out of life.
I had the ongoing amusement one project of kibitzing a theoretically
experienced analog guy (from MIT, no less!) on a switching amplifier.
One of the things that I diagnosed was that mysterious (to him) shark
fin, although it was only one of the reasons that things went BANG on
that particular circuit.
Some of the guys also overlook the fact that there is a rather large
tolerance on ferrite core specs. Later, some folks in purchasing think
that a ferrite is a ferrite is a ferrite. Phssst ... *BANG*.
The part that added the most humor (for me) was that my job title (and
function) at the time was very firmly planted in "software engineer",
although I was being allowed to design a (simple) board.
Don>t ya love it when that happens? I once snuck into a mechanical
design review. I wasn>t supposed to be there but urgently needed to pass
a message on to one of the guys. Looked at the PowerPoint screen and
just had to ask: "Looks like there is way too little airflow. And what
happens if that fan up there fails?" ... "Uhm ..., well, ... s..t!"
Major redesign.
--
Regards, Joerg
http://www.analogconsultants.com/
"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
OK, I kind of guessed (qualitatively) that at first dI/dt is "slow"
then there is a step (?? how long does it take for mu to drop??). The
current steps up by sqrt(mu) and then keeps ramping up mu times as
fast.
Does it make sense?
Depends on the core, it>s in the ferrite datasheet. Usually the "grace
period" ends at some point where the inductor basically acts like an air
coil, as if the core wouldn>t be there anymore. For most practical
circuits such as switch mode supplies that comes pretty close to a dead
short with all its consequences.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

I am not worried about "dire consequences" - I am sandwiching two
cores actually (ferrite and iron powder), what I need to know is HOW
FAST ferrite "disappears". They should use something like this in
series trigger transformers.
[/quote]

All I can tell you is "really fast". For example, it can take just a few
nanoseconds to drive Fair-rite #43 material into complete saturation.
BTDT, got broom and shovel and cleaned up the mess ;-)

The voltage applied to a transformer usually determines that. The higher
it is the faster the primary current will rise and will core saturation
be reached.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Tim Wescott · Guest

Michael wrote:
[quote]I thought I posted it already, it did not go through. Grrrrrrrrrrrrr
Suppose I have two toroids sandwiched together. One is powder with
single turn inductance (A1)=96nH. Another is high mu ferrite with
A1=15uH.
I apply 10V to 1 turn. The ferrite will saturate (~200mA) pretty soon
(1/4 us). By that time the inductor will have ~0.26uJ stored in it....
How will current look?
I haven>t got samples yet, I cannot try it...
[/quote]
I>m kinda side-stepping Joerg>s whole thread with this reply -- what he
has to say makes oodles of sense in a switching-supply frame of
reference, but I doubt that that>s what you>re thinking of (or you are
trying to make a switched supply with your oddball stacked cores, which
means you may be cracked -- go look in the mirror and ask yourself if
you>re sane as a check).

The total voltage on the coil is equal to the IR drop of the wire plus
the back-emf on the coil. The back-emf of the coil is proportional to
the the rate of change of the product of the current and the
permeability of the core material -- and while the current (and
magneto-motive force) is going up, the permeability of the core material
is going down.

So initially your inductor will have high inductance and the current
will ramp up at a more or less constant rate commensurate with the
zero-current inductance. At some point the ferrite in the core will get
saturated with flux and won>t accept any more than air does and your
current will start ramping up at a more or less constant rate
commensurate with whatever else you have in your coil -- if it>s just
air, then it>ll ramp up pretty darn fast, if that iron powder coil
hasn>t saturated yet it>ll ramp up at a rate commensurate with the iron
powder coil (until it saturates).

I _don>t_ know how fast the transition will be between the two straight
ramps, or how straight they>ll really be (the coil resistance will
affect that to some extent anyway).

You ought to be able to make an estimate of the transition if you can
get your hands on a B-H curve of the material -- the sharper the
transition between the sloped part around 0 H and the nearly level part
around high H, the sharper the transition between the two 'modes' of the
core.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Joerg · Guest

Tim Wescott wrote:
[quote]Michael wrote:
I thought I posted it already, it did not go through. Grrrrrrrrrrrrr
Suppose I have two toroids sandwiched together. One is powder with
single turn inductance (A1)=96nH. Another is high mu ferrite with
A1=15uH.
I apply 10V to 1 turn. The ferrite will saturate (~200mA) pretty soon
(1/4 us). By that time the inductor will have ~0.26uJ stored in it....
How will current look?
I haven>t got samples yet, I cannot try it...

I>m kinda side-stepping Joerg>s whole thread with this reply -- what he
has to say makes oodles of sense in a switching-supply frame of
reference, but I doubt that that>s what you>re thinking of (or you are
trying to make a switched supply with your oddball stacked cores, which
means you may be cracked -- go look in the mirror and ask yourself if
you>re sane as a check).

The total voltage on the coil is equal to the IR drop of the wire plus
the back-emf on the coil. The back-emf of the coil is proportional to
the the rate of change of the product of the current and the
permeability of the core material -- and while the current (and
magneto-motive force) is going up, the permeability of the core material
is going down.

So initially your inductor will have high inductance and the current
will ramp up at a more or less constant rate commensurate with the
zero-current inductance. At some point the ferrite in the core will get
saturated with flux and won>t accept any more than air does and your
current will start ramping up at a more or less constant rate
commensurate with whatever else you have in your coil -- if it>s just
air, then it>ll ramp up pretty darn fast, if that iron powder coil
hasn>t saturated yet it>ll ramp up at a rate commensurate with the iron
powder coil (until it saturates).

I _don>t_ know how fast the transition will be between the two straight
ramps, or how straight they>ll really be (the coil resistance will
affect that to some extent anyway).

You ought to be able to make an estimate of the transition if you can
get your hands on a B-H curve of the material -- the sharper the
transition between the sloped part around 0 H and the nearly level part
around high H, the sharper the transition between the two 'modes' of the
core.

[/quote]
Good explanation. "Pretty darn fast" means just that, it gets down to
nanohenries and the current (hopefully) pegs against some limiter.
Michael should keep in mind that B-H curves and such are just typical
data. There can be huge tolerances in core behavior, I have seen in
excess of 30%. Us analog/RF dudes usually stay a good 40% below the
"pretty darn fast" range.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Tim Wescott · Guest

Joerg wrote:
[quote]Tim Wescott wrote:
Michael wrote:
I thought I posted it already, it did not go through. Grrrrrrrrrrrrr
Suppose I have two toroids sandwiched together. One is powder with
single turn inductance (A1)=96nH. Another is high mu ferrite with
A1=15uH.
I apply 10V to 1 turn. The ferrite will saturate (~200mA) pretty soon
(1/4 us). By that time the inductor will have ~0.26uJ stored in it....
How will current look?
I haven>t got samples yet, I cannot try it...

I>m kinda side-stepping Joerg>s whole thread with this reply -- what
he has to say makes oodles of sense in a switching-supply frame of
reference, but I doubt that that>s what you>re thinking of (or you are
trying to make a switched supply with your oddball stacked cores,
which means you may be cracked -- go look in the mirror and ask
yourself if you>re sane as a check).

The total voltage on the coil is equal to the IR drop of the wire plus
the back-emf on the coil. The back-emf of the coil is proportional to
the the rate of change of the product of the current and the
permeability of the core material -- and while the current (and
magneto-motive force) is going up, the permeability of the core
material is going down.

So initially your inductor will have high inductance and the current
will ramp up at a more or less constant rate commensurate with the
zero-current inductance. At some point the ferrite in the core will
get saturated with flux and won>t accept any more than air does and
your current will start ramping up at a more or less constant rate
commensurate with whatever else you have in your coil -- if it>s just
air, then it>ll ramp up pretty darn fast, if that iron powder coil
hasn>t saturated yet it>ll ramp up at a rate commensurate with the
iron powder coil (until it saturates).

I _don>t_ know how fast the transition will be between the two
straight ramps, or how straight they>ll really be (the coil resistance
will affect that to some extent anyway).

You ought to be able to make an estimate of the transition if you can
get your hands on a B-H curve of the material -- the sharper the
transition between the sloped part around 0 H and the nearly level
part around high H, the sharper the transition between the two 'modes'
of the core.

Good explanation. "Pretty darn fast" means just that, it gets down to
nanohenries and the current (hopefully) pegs against some limiter.
Michael should keep in mind that B-H curves and such are just typical
data. There can be huge tolerances in core behavior, I have seen in
excess of 30%. Us analog/RF dudes usually stay a good 40% below the
"pretty darn fast" range.

My second professional consultation job was for a company that LF[/quote]
transmitters that used magnetic amplification -- basically they used
toroidal inductors that were varied by modulating the field in which
they sat, to actively change their inductance.

I thought that was a fascinating turnaround -- take a problem (coil
saturation), and turn it into an advantage.

Dunno how they controlled the huge tolerances in core behavior, though
-- I would assume they calibrated individually, though.

About that same time (grad school) I had a direct-conversion 40 meter
radio whose receive frequency would shift a few hundred Hz in the
presence of a strong magnet outside the case.

I>ve always wanted to build a radio that tunes the LO that way on
purpose -- just an iron powder coil, a rare earth magnet, and a
mechanism to bring them together in a controlled way. Of course I have
No Clue how well it would work, but you could sure have fun with writing
some marketing hype to go with the technique!

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

Vladimir Vassilevsky · Guest

Tim Wescott wrote:

[quote]About that same time (grad school) I had a direct-conversion 40 meter
radio whose receive frequency would shift a few hundred Hz in the
presence of a strong magnet outside the case.

I>ve always wanted to build a radio that tunes the LO that way on
purpose -- just an iron powder coil, a rare earth magnet, and a
mechanism to bring them together in a controlled way. Of course I have
No Clue how well it would work, but you could sure have fun with writing
some marketing hype to go with the technique!
[/quote]
BTW, the magnetically controlled inductance is the old trick for
electronic tuning of the LC tanks while keeping good Q and linearity.
The parameters attainable are better then what can be done with varactors.

Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

Joerg · Guest

Vladimir Vassilevsky wrote:
[quote]

Tim Wescott wrote:

About that same time (grad school) I had a direct-conversion 40 meter
radio whose receive frequency would shift a few hundred Hz in the
presence of a strong magnet outside the case.

I>ve always wanted to build a radio that tunes the LO that way on
purpose -- just an iron powder coil, a rare earth magnet, and a
mechanism to bring them together in a controlled way. Of course I
have No Clue how well it would work, but you could sure have fun with
writing some marketing hype to go with the technique!

BTW, the magnetically controlled inductance is the old trick for
electronic tuning of the LC tanks while keeping good Q and linearity.
The parameters attainable are better then what can be done with varactors.

[/quote]
It was also a nice method to achieve a mostly frequency-linear tuning
range for oscillators. IIRC Drake and Collins used that. The downside
was that the worm gear needed constant attention. So the usual setup was
the receiver or tranceiver itself with a screwdriver (no, not the drink
....) and a bottle of rifle oil sitting next to it. In Germany we used
the Ballistol brand which supposedly was also good to cure other
ailments such as saddle sores after too much horseback riding. I don>t
know about that and would not do it but the stuff sure is quite
universal in use:
http://www.ballistol.com/uses.htm

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.


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