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Joel Koltner · Guest

"Vladimir Vassilevsky" <antispam_bogus@hotmail.com> wrote in message
news:tZqjk.14957$cW3.4887@nlpi064.nbdc.sbc.com...
[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.
[/quote]
Yes, although varactors sometimes win if you need to pass high power (say,
>>0dBm) through your circuit.

Joerg · Guest

Joel Koltner wrote:
[quote]"Vladimir Vassilevsky" <antispam_bogus@hotmail.com> wrote in message
news:tZqjk.14957$cW3.4887@nlpi064.nbdc.sbc.com...
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.

Yes, although varactors sometimes win if you need to pass high power (say,
0dBm) through your circuit.

[/quote]
Nah, real men use those:

http://www.ph.utexas.edu/~phy-demo/demo-txt/5c10-11.html

--
Regards, Joerg

http://www.analogconsultants.com/

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

legg · Guest

On Mon, 28 Jul 2008 08:43:16 -0700 (PDT), Michael <mk5778@yahoo.com>
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]
Composite cores are available from a few mfrs, inluding some parts
that are basically two toroids glued together. The most common
application is in a swinging choke, used to reduce minimum continuous
load current levels in power supply unregulated auxiliary outputs.

A part stressed over the full flux range (+/-) will show a change of
permeability at fairly low flux levels - a monitored current waveform
produced by a fixed alternating voltage will show 2 different current
di/dt slopes, before saturation.

RL

Vladimir Vassilevsky · Guest

Joerg wrote:

[quote]Vladimir Vassilevsky wrote:

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.

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.
[/quote]
I meant pure electronic solution by affecting the permeability of the
core by the magnetic field of the external solenoid. This variant can
have much better linearity and Q then attainable with varactors, which
can be important for LO and input filters. AFAIK some early FM
transmitters used this idea, too.

[quote]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.
[/quote]
Speaking of the motor tuning:

http://www.armyradio.com/publish/Articles/William_Howard_Russian/Pictures/R-155A-01.jpg

IIRC this R-155 receiver has 8-section variable capacitor bank tuned by
the electric motor. The input section is built using tubes (total of 6),
and the rest of the schematics is made from the discrete BJTs and
crystal filters. In the old times, they knew how to do the real stuff.

[quote]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
[/quote]
I put a notice on that. If there is PITA for whatever reason, the
ballistol should help, is that right?

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

Joerg · Guest

Vladimir Vassilevsky wrote:
[quote]

Joerg wrote:

Vladimir Vassilevsky wrote:

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.

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.

I meant pure electronic solution by affecting the permeability of the
core by the magnetic field of the external solenoid. This variant can
have much better linearity and Q then attainable with varactors, which
can be important for LO and input filters. AFAIK some early FM
transmitters used this idea, too.

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.

Speaking of the motor tuning:

http://www.armyradio.com/publish/Articles/William_Howard_Russian/Pictures/R-155A-01.jpg

IIRC this R-155 receiver has 8-section variable capacitor bank tuned by
the electric motor. The input section is built using tubes (total of 6),
and the rest of the schematics is made from the discrete BJTs and
crystal filters. In the old times, they knew how to do the real stuff.

[/quote]
They sure did but they were blissfully ignorant when it came to power
consumption. Power just came out the wall outlet and was free ;-)

[quote]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

I put a notice on that. If there is PITA for whatever reason, the
ballistol should help, is that right?

[/quote]
According to the movie "My Big Fat Greek Wedding" Windex would be the
answer. Very worthwhile to watch BTW, great fun.

--
Regards, Joerg

http://www.analogconsultants.com/

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

Vladimir Vassilevsky · Guest

Joerg wrote:

[quote]Vladimir Vassilevsky wrote:
Joerg wrote:
Vladimir Vassilevsky wrote:

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.

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.

I meant pure electronic solution by affecting the permeability of the
core by the magnetic field of the external solenoid. This variant can
have much better linearity and Q then attainable with varactors, which
can be important for LO and input filters. AFAIK some early FM
transmitters used this idea, too.

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.

Speaking of the motor tuning:

http://www.armyradio.com/publish/Articles/William_Howard_Russian/Pictures/R-155A-01.jpg

IIRC this R-155 receiver has 8-section variable capacitor bank tuned
by the electric motor. The input section is built using tubes (total
of 6), and the rest of the schematics is made from the discrete BJTs
and crystal filters. In the old times, they knew how to do the real
stuff.

They sure did but they were blissfully ignorant when it came to power
consumption. Power just came out the wall outlet and was free ;-)
[/quote]
At the old times, it was the different engineering paradigm: design for
the best performance whatever it takes. With the use of the well
designed stuff we defeat all enemies so the power in the wall outlet
will be completely free.

[quote]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

I put a notice on that. If there is PITA for whatever reason, the
ballistol should help, is that right?

According to the movie "My Big Fat Greek Wedding" Windex would be the
answer. Very worthwhile to watch BTW, great fun.
[/quote]
I don>t watch TV or movies, and I am not subscribed for the cable.

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

Joerg · Guest

Vladimir Vassilevsky wrote:
[quote]

Joerg wrote:

Vladimir Vassilevsky wrote:
Joerg wrote:
Vladimir Vassilevsky wrote:

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.

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.

I meant pure electronic solution by affecting the permeability of the
core by the magnetic field of the external solenoid. This variant can
have much better linearity and Q then attainable with varactors,
which can be important for LO and input filters. AFAIK some early FM
transmitters used this idea, too.

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.

Speaking of the motor tuning:

http://www.armyradio.com/publish/Articles/William_Howard_Russian/Pictures/R-155A-01.jpg

IIRC this R-155 receiver has 8-section variable capacitor bank tuned
by the electric motor. The input section is built using tubes (total
of 6), and the rest of the schematics is made from the discrete BJTs
and crystal filters. In the old times, they knew how to do the real
stuff.

They sure did but they were blissfully ignorant when it came to power
consumption. Power just came out the wall outlet and was free ;-)

At the old times, it was the different engineering paradigm: design for
the best performance whatever it takes. With the use of the well
designed stuff we defeat all enemies so the power in the wall outlet
will be completely free.

[/quote]
That goes back all the way to Caesar and the Romans. They clear-cut
pretty much all of what>s now Italy to build one armada after the other,
thinking that>ll make them own the world. It didn>t and now the soil on
all those mountains has eroded. Nothing big will grow there anymore.

[quote]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

I put a notice on that. If there is PITA for whatever reason, the
ballistol should help, is that right?

According to the movie "My Big Fat Greek Wedding" Windex would be the
answer. Very worthwhile to watch BTW, great fun.

I don>t watch TV or movies, and I am not subscribed for the cable.

[/quote]
This one>s worth it. You can rent it at video places and watch it with
friends that have a VCR. No idea whether it made it onto DVD. We have
friends who said their (Greek Orthodox) wedding was an almost verbatim
repeat of that story and we all laughed really hard because all of us
had seen that movie. To this day the husband has refused to show us
pictures of his baptism right before the wedding. Too embarrassing, he says.

--
Regards, Joerg

http://www.analogconsultants.com/

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

legg · Guest

On Mon, 28 Jul 2008 12:26:20 -0700 (PDT), Michael <mk5778@yahoo.com>
wrote:

[quote]On Jul 28, 3:05 pm, Joerg <notthisjoerg...@removethispacbell.net
wrote:

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]
A quick estimate would assume that during the first interval, only the
ferrite path stores energy. As it>s ungapped permeability is a number
or orders of magnitude higher than the compounded material, this is
valid.

This duration can be derived from the B= Vt/NA equation.

deltaB = ( V . t ) / ( N . A )

deltaB= flux density change in Teslas ( 1T = 10,000gauss)
V= Voltage applied across the inductor winding (volts)
t= period of applied voltage (seconds)
N= number turns in the coil
A= physical cross-section (ferrite only) of the magnetic medium
(meters^2)

If the applied voltage is unipolar and reset to ~zero, the period to
saturation corresponds to a B value of between 0.3 and 0.4 T (.35
nominal), depending on material grade and temperature.

If the applied voltage is AC, the period of the ferrite operation will
be for double this value, as the flux will swing from + to -
saturation levels.

RL

whit3rd · Guest

On Jul 28, 5:15 pm, Tim Wescott <t...@seemywebsite.com> 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
[/quote]
My favorite old keyboard (it was a Burroughs, which should
give a hint of its age) had keyswitches that moved a small
magnet to saturate a core, which had two one-turn windings
(looked like staples), one to excite and one to sense.
It had great key feel...no mechanical damping or hysteresis
like a buckling switch. Hall switches exist, too, but
this was ... elegant.

John Popelish · Guest

whit3rd wrote:

[quote]My favorite old keyboard (it was a Burroughs, which should
give a hint of its age) had keyswitches that moved a small
magnet to saturate a core, which had two one-turn windings
(looked like staples), one to excite and one to sense.
It had great key feel...no mechanical damping or hysteresis
like a buckling switch. Hall switches exist, too, but
this was ... elegant.
[/quote]
I still have a little bag of the ferrite cores used in that
kind of keyboard.

--
Regards,

John Popelish


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