How to design an Interesting inductor

[amdx]

On 8/20/2019 11:11 AM, Tim Williams wrote:

"amdx" <nojunk@knology.net> wrote in message
news:qjgbfo$1la$1@dont-email.me...
In previous responses I gave the proposed use is for a
"Beverage on Ground" antenna.
 I had a GOG before and used a beds that had a Q of 1 or 2.
 so if I could get 20 it would be better.

What power level?  Frequency range?

Tim

Man, what time did I write the above?
What I meant to say was,
I had a BOG before and used a bedds that had a Q of 1 or 2.
so if I could get 20 it would be better.

It's for a receive only antenna, so microwatts, maybe milliwatts.
500kHz to 4 MHz.

Mikek

Another possible solution,
Is there a combination of L's and Cs the would approximate such an L
reduction over frequency?

 

[amdx]

On 8/20/2019 9:11 AM, Clive Arthur wrote:

On 20/08/2019 14:57, amdx wrote:
On 8/20/2019 3:41 AM, Clive Arthur wrote:
On 20/08/2019 01:53, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to
full saturation with dc through the 100uh coil.
  I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
  Is this possible?

                Thanks for your thoughts, Mikek

Some RM cores and pot cores have a central hole through which you
could wind your 100uH, and the DC winding goes on the bobbin...

https://uk.farnell.com/ferroxcube/rm10-i-3c95/ferrite-core-rm-i-3c95/dp/2103458?st=rm%20core


...this is a 5.5uH core so approx 4 turns for 100uH if it were wound
on the bobbin, I don't know how many if wound through the hole, but
I'd guess it would be similar.  I'd try to grind the hole edges to
take off the sharp edge if possible.

Cheers

  Sorry, responses have made it clear I didn't ask my question well.
  I only want one winding of 100uh, that winding will both the ac and
the dc.

                            Thanks, Mikek

OK, so the DC is from a high impedance current source I guess.

I don't have a good understanding of the (I'm guessing) loading that
power supply connection will cause, but I did have the thought of a high
voltage dc supply and a big series resistor.


As an

indication, a 100uH inductor on an RM4 3C92 core 722nH/T^2 will be 12
turns and saturate at around 500mA.  There's a program, ferroxcube.exe
entitled Ferroxcube SFDT 2010 which is handy.

Cheers

I'll look for that program.
Does a reduction in area requiring more turns for the same inductance
then saturate at a lower current? (because more turns)

Thanks, Mikek

 

[amdx]

On 8/20/2019 11:41 AM, legg wrote:

On Mon, 19 Aug 2019 19:53:28 -0500, amdx <nojunk@knology.net> wrote:

I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
Is this possible?

Thanks for your thoughts, Mikek
A cpnventional current-controlled inductor has two magnetic paths that
are configured to carry antiphase windings, with the third 'inductor
winding sharing both. The control windings' AC flux, from the third
winding, cancels out.

You can do this with an e-core (control windings on outer arms), two
toroids (each with control winding - sandwitched to support single
'inductor' winding around both) or solenoids (two solenoid cores
support control windings, 'inductor' wound around both.).

RL

As state previously, My question was not ask well, I only want one
winding with both ac and the dc to saturate it.

Thanks, Mikek

 

[amdx]

On 8/20/2019 11:28 AM, Phil Hobbs wrote:

On 8/20/19 4:41 AM, Clive Arthur wrote:
On 20/08/2019 01:53, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to
full saturation with dc through the 100uh coil.
  I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
  Is this possible?

                Thanks for your thoughts, Mikek

Some RM cores and pot cores have a central hole through which you
could wind your 100uH, and the DC winding goes on the bobbin...

https://uk.farnell.com/ferroxcube/rm10-i-3c95/ferrite-core-rm-i-3c95/dp/2103458?st=rm%20core


...this is a 5.5uH core so approx 4 turns for 100uH if it were wound
on the bobbin, I don't know how many if wound through the hole, but
I'd guess it would be similar.  I'd try to grind the hole edges to
take off the sharp edge if possible.

Cheers

One minor tweak to that idea is to run an odd number of half-turns on
the bobbin, and use a high-mu pot core with an adjustable centre gap.

The extra half-turn will generate a large field going round the outside
of the core (avoiding the post) and so will saturate it fairly readily.

Cheers

Phil Hobbs

Can you explain physically how that would look? My only experience
with half turns is, we put a 4-1/2 turn inductor in a medium power circuit.
The coil over heated, 4 turns were fine, 5 turns were fine, we never did
a half turn inductor again.
OH wait you only mean a single half turn as we did above, so if I need
12 turns make it 12-1/2 turns. Is that correct?
Any way to do 1/2 turn on a toroid?

Thanks, Mikek

 

[amdx]

On 8/20/2019 10:05 AM, jlarkin@highlandsniptechnology.com wrote:

On Tue, 20 Aug 2019 07:15:10 -0700 (PDT), Lasse Langwadt Christensen
langwadt@fonz.dk> wrote:

tirsdag den 20. august 2019 kl. 15.57.08 UTC+2 skrev amdx:
On 8/20/2019 3:41 AM, Clive Arthur wrote:
On 20/08/2019 01:53, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
  I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
  Is this possible?

                Thanks for your thoughts, Mikek

Some RM cores and pot cores have a central hole through which you could
wind your 100uH, and the DC winding goes on the bobbin...

https://uk.farnell.com/ferroxcube/rm10-i-3c95/ferrite-core-rm-i-3c95/dp/2103458?st=rm%20core


...this is a 5.5uH core so approx 4 turns for 100uH if it were wound on
the bobbin, I don't know how many if wound through the hole, but I'd
guess it would be similar.  I'd try to grind the hole edges to take off
the sharp edge if possible.

Cheers

Sorry, responses have made it clear I didn't ask my question well.
I only want one winding of 100uh, that winding will both the ac and
the dc.

Thanks, Mikek

https://www.frostburg.edu/personal/latta/ee/qsk5/pindiodes/spstswitch.jpg

replace diode with your inductor and adjust values to match your freqency range

One could also use PIN diodes, or relays, or latching relays to switch
taps on an air-core inductor, in interesting combinations. Q would be
high.

Would that require running a second control wire parallel to the BOG,
if so, probably not a good solution. Remember there are at least nine
spread out over the 250ft wire.

Thanks, Mikek

 

[amdx]

On 8/20/2019 9:15 AM, Lasse Langwadt Christensen wrote:

tirsdag den 20. august 2019 kl. 15.57.08 UTC+2 skrev amdx:
On 8/20/2019 3:41 AM, Clive Arthur wrote:
On 20/08/2019 01:53, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
  I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
  Is this possible?

                Thanks for your thoughts, Mikek

Some RM cores and pot cores have a central hole through which you could
wind your 100uH, and the DC winding goes on the bobbin...

https://uk.farnell.com/ferroxcube/rm10-i-3c95/ferrite-core-rm-i-3c95/dp/2103458?st=rm%20core


...this is a 5.5uH core so approx 4 turns for 100uH if it were wound on
the bobbin, I don't know how many if wound through the hole, but I'd
guess it would be similar.  I'd try to grind the hole edges to take off
the sharp edge if possible.

Cheers

Sorry, responses have made it clear I didn't ask my question well.
I only want one winding of 100uh, that winding will both the ac and
the dc.

Thanks, Mikek

https://www.frostburg.edu/personal/latta/ee/qsk5/pindiodes/spstswitch.jpg

replace diode with your inductor and adjust values to match your freqency range

Well that was my next question, will the big inductors isolate the coil
and preserve the Q even though dc loaded?
I think I attached a preliminary drawing but here it is again.
> https://www.dropbox.com/s/f0l1kneuh0izqds/BOG%2C%20with%20variable%20inductor.jpg?dl=0

Thanks, Mikek

 

[amdx]

On 8/20/2019 7:51 PM, amdx wrote:

On 8/20/2019 9:15 AM, Lasse Langwadt Christensen wrote:
tirsdag den 20. august 2019 kl. 15.57.08 UTC+2 skrev amdx:
On 8/20/2019 3:41 AM, Clive Arthur wrote:
On 20/08/2019 01:53, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
   I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
   Is this possible?

                 Thanks for your thoughts, Mikek

Some RM cores and pot cores have a central hole through which you could
wind your 100uH, and the DC winding goes on the bobbin...

https://uk.farnell.com/ferroxcube/rm10-i-3c95/ferrite-core-rm-i-3c95/dp/2103458?st=rm%20core



...this is a 5.5uH core so approx 4 turns for 100uH if it were wound on
the bobbin, I don't know how many if wound through the hole, but I'd
guess it would be similar.  I'd try to grind the hole edges to take off
the sharp edge if possible.

Cheers

   Sorry, responses have made it clear I didn't ask my question well.
   I only want one winding of 100uh, that winding will both the ac and
the dc.

                             Thanks, Mikek

https://www.frostburg.edu/personal/latta/ee/qsk5/pindiodes/spstswitch.jpg

replace diode with your inductor and adjust values to match your
freqency range


 I'm looking t 2.5mH inductors, What spec am I looking for that says it
can have 500ma of dc current and still be 2.5mH, ie it's not saturated.
                                    Mikek
Never mind went to Digikey, more data than Amazon.

 

[amdx]

On 8/20/2019 9:15 AM, Lasse Langwadt Christensen wrote:

tirsdag den 20. august 2019 kl. 15.57.08 UTC+2 skrev amdx:
On 8/20/2019 3:41 AM, Clive Arthur wrote:
On 20/08/2019 01:53, amdx wrote:
I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
  I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
  Is this possible?

                Thanks for your thoughts, Mikek

Some RM cores and pot cores have a central hole through which you could
wind your 100uH, and the DC winding goes on the bobbin...

https://uk.farnell.com/ferroxcube/rm10-i-3c95/ferrite-core-rm-i-3c95/dp/2103458?st=rm%20core


...this is a 5.5uH core so approx 4 turns for 100uH if it were wound on
the bobbin, I don't know how many if wound through the hole, but I'd
guess it would be similar.  I'd try to grind the hole edges to take off
the sharp edge if possible.

Cheers

Sorry, responses have made it clear I didn't ask my question well.
I only want one winding of 100uh, that winding will both the ac and
the dc.

Thanks, Mikek

https://www.frostburg.edu/personal/latta/ee/qsk5/pindiodes/spstswitch.jpg

replace diode with your inductor and adjust values to match your freqency range

I'm looking t 2.5mH inductors, What spec am I looking for that says it
can have 500ma of dc current and still be 2.5mH, ie it's not saturated.
Mikek

 

[Tim Williams]

"amdx" <nojunk@knology.net> wrote in message
news:qjhbo9$uq0$1@dont-email.me...

Man, what time did I write the above?
What I meant to say was,
I had a BOG before and used a bedds that had a Q of 1 or 2.
so if I could get 20 it would be better.

I still don't know what you're writing. It ain't English...

Well, "bog" aside. But that means something different in English English.
;-)

It's for a receive only antenna, so microwatts, maybe milliwatts.
500kHz to 4 MHz.

What about just low noise JFETs? It's not like you need any antenna gain in
those bands.

Another possible solution,
Is there a combination of L's and Cs the would approximate such an L
reduction over frequency?

Sure. But not just L and C, R is required. Necessarily has a very low Q
(from Kramers-Kronig relations). Ferrite beads for example.

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

 

[amdx]

On 8/20/2019 12:47 PM, amdx wrote:

On 8/20/2019 11:11 AM, Tim Williams wrote:
"amdx" <nojunk@knology.net> wrote in message
news:qjgbfo$1la$1@dont-email.me...
In previous responses I gave the proposed use is for a
"Beverage on Ground" antenna.
 I had a GOG before and used a beds that had a Q of 1 or 2.
 so if I could get 20 it would be better.

What power level?  Frequency range?

Tim

 Man, what time did I write the above?
What I meant to say was,
I had a BOG before and used a bedds that had a Q of 1 or 2.
  so if I could get 20 it would be better.

It's for a receive only antenna, so microwatts, maybe milliwatts.
500kHz to 4 MHz.

                                 Mikek

 Another possible solution,
 Is there a combination of L's and Cs the would approximate such an L
reduction over frequency?

One of those times, I could see you posted but nothing in the post, so
I went to google groups.

Man, what time did I write the above?
What I meant to say was,
I had a BOG before and used a bedds that had a Q of 1 or 2.
so if I could get 20 it would be better.

I still don't know what you're writing. It ain't English...

Well, "bog" aside. But that means something different in English
English.
;-)

I'll try to get a good nights sleep tonight!
BOG = Beverage On Ground
bedds was supposed to be beads/sleeves which were actually a #73
binocular core that I only used one hole of. I just passed the antenna
wire through it. About 24 ohms R and 42 ohm XL at 1MHz.

It's for a receive only antenna, so microwatts, maybe milliwatts.
500kHz to 4 MHz.

What about just low noise JFETs? It's not like you need any antenna
gain in
those bands.

Well, maybe, but usually the receive has enough gain, the bog signal is
down, maybe -25dbi to -40dbi.
But that is not the problem, by adjusting characteristics with frequency
you can narrow the beam width and increase the front to back ratio.
btw, I do have a high input impedance FET follower with low output
impedance, no gain but you do unload the antenna so get 3db. I'll be
trying that.

Another possible solution,
Is there a combination of L's and Cs the would approximate such an L
reduction over frequency?

Sure. But not just L and C, R is required. Necessarily has a very low >Q
(from Kramers-Kronig relations). Ferrite beads for example.

Yes, that surprised me very much, but with low inductive reactance
values and losses in the ferrite, you get Q's of 1 or 2. I tried and
tried to get the meter on my Q meter to move, could not find any
resonance, so pulled out an inductance meter and used that.


Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

 

[legg]

On Tue, 20 Aug 2019 14:06:17 -0500, amdx <nojunk@knology.net> wrote:

On 8/20/2019 11:41 AM, legg wrote:
On Mon, 19 Aug 2019 19:53:28 -0500, amdx <nojunk@knology.net> wrote:

I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
Is this possible?

Thanks for your thoughts, Mikek
A cpnventional current-controlled inductor has two magnetic paths that
are configured to carry antiphase windings, with the third 'inductor
winding sharing both. The control windings' AC flux, from the third
winding, cancels out.

You can do this with an e-core (control windings on outer arms), two
toroids (each with control winding - sandwitched to support single
'inductor' winding around both) or solenoids (two solenoid cores
support control windings, 'inductor' wound around both.).

RL


As state previously, My question was not ask well, I only want one
winding with both ac and the dc to saturate it.

Thanks, Mikek

An ideal current source is easy to simulate, but in real life, it's
voltage compliance limits, stray loading and real power loss will set
limits on what you can do.

The conventional multiple winding is the more realistic approach.

Parasitics from the lower-powered control circuit are also easier to
isolate.

RL

 

[Jasen Betts]

On 2019-08-21, legg <legg@nospam.magma.ca> wrote:

On Tue, 20 Aug 2019 14:06:17 -0500, amdx <nojunk@knology.net> wrote:

On 8/20/2019 11:41 AM, legg wrote:
On Mon, 19 Aug 2019 19:53:28 -0500, amdx <nojunk@knology.net> wrote:

I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
Is this possible?

Thanks for your thoughts, Mikek
A cpnventional current-controlled inductor has two magnetic paths that
are configured to carry antiphase windings, with the third 'inductor
winding sharing both. The control windings' AC flux, from the third
winding, cancels out.

You can do this with an e-core (control windings on outer arms), two
toroids (each with control winding - sandwitched to support single
'inductor' winding around both) or solenoids (two solenoid cores
support control windings, 'inductor' wound around both.).

RL


As state previously, My question was not ask well, I only want one
winding with both ac and the dc to saturate it.

Thanks, Mikek

An ideal current source is easy to simulate, but in real life, it's
voltage compliance limits, stray loading and real power loss will set
limits on what you can do.

The conventional multiple winding is the more realistic approach.

Parasitics from the lower-powered control circuit are also easier to
isolate.

RL

AIUI this is for a recieve antenna so the AC signal will be failrly
small, I expect that the current source only needs enough compliance
to overcome earth resistance and a little headroom.

--
When I tried casting out nines I made a hash of it.

 

[Tauno Voipio]

On 21.8.19 05:22, Tim Williams wrote:

"amdx" <nojunk@knology.net> wrote in message
news:qjhbo9$uq0$1@dont-email.me...
 Man, what time did I write the above?
What I meant to say was,
I had a BOG before and used a bedds that had a Q of 1 or 2.
  so if I could get 20 it would be better.

I still don't know what you're writing.  It ain't English...

Well, "bog" aside.  But that means something different in English
English. ;-)



It's for a receive only antenna, so microwatts, maybe milliwatts.
500kHz to 4 MHz.

What about just low noise JFETs?  It's not like you need any antenna
gain in those bands.


 Another possible solution,
 Is there a combination of L's and Cs the would approximate such an L
reduction over frequency?

Sure.  But not just L and C, R is required.  Necessarily has a very low
Q (from Kramers-Kronig relations).  Ferrite beads for example.

Tim

The OP is attempting to make a tuned circuit with transductor tuning.

The linear equations of a tuned circuit (here: an antenna system) fall
apart as soon as the reactive element (transductor coil) is saturated
into non-linear operating range for control of effective inductance.

I just wonder how much unwanted crud such a system will radiate on
un-intended freqiencies when a bunch of strong local stations meet
the saturating inductor.

There ain't such thing as a good MF antenna tuner in small size.

--

-TV

 

[Bill Sloman]

On Wednesday, August 21, 2019 at 11:16:41 PM UTC+10, amdx wrote:

On 8/21/2019 3:26 AM, Tauno Voipio wrote:
On 21.8.19 05:22, Tim Williams wrote:
"amdx" <nojunk@knology.net> wrote in message
news:qjhbo9$uq0$1@dont-email.me...

<snip>

I'm Sorry, I don't have any understanding of the "non-linear operating
range". Is this like a diode causing mixing of two RF signals creating
other products?
If that is the case, will millivolt level signals in a non-linear
inductor create objectionable mixing?
Aren't all ferrite inductors non-linear, even in normal operation?

Sure but they are mostly built with gapped ferrites, and the harmonic products tend to be 80 or 90dB below the fundamental.

They get a lot worse when driven close to saturation.

LTSpice offers the John Chan model to work out how hysteresis actually affects the voltage-current relationship - just for inductors as opposed to coupled inductors and transformers. It gave the right answer, the one time I used it.

--
Bill Sloman, Sydney

 

[amdx]

On 8/21/2019 3:26 AM, Tauno Voipio wrote:

On 21.8.19 05:22, Tim Williams wrote:
"amdx" <nojunk@knology.net> wrote in message
news:qjhbo9$uq0$1@dont-email.me...
 Man, what time did I write the above?
What I meant to say was,
I had a BOG before and used a bedds that had a Q of 1 or 2.
  so if I could get 20 it would be better.

I still don't know what you're writing.  It ain't English...

Well, "bog" aside.  But that means something different in English
English. ;-)



It's for a receive only antenna, so microwatts, maybe milliwatts.
500kHz to 4 MHz.

What about just low noise JFETs?  It's not like you need any antenna
gain in those bands.


 Another possible solution,
 Is there a combination of L's and Cs the would approximate such an L
reduction over frequency?

Sure.  But not just L and C, R is required.  Necessarily has a very
low Q (from Kramers-Kronig relations).  Ferrite beads for example.

Tim

I appreciate your input but not sure I understand.


> The OP is attempting to make a tuned circuit with transductor tuning.

The circuit is a classic tuned circuit, it is not at resonance.

The linear equations of a tuned circuit (here: an antenna system) fall
apart as soon as the reactive element (transductor coil) is saturated
into non-linear operating range for control of effective inductance.

I'm Sorry, I don't have any understanding of the "non-linear operating
range". Is this like a diode causing mixing of two RF signals creating
other products?
If that is the case, will millivolt level signals in a non-linear
inductor create objectionable mixing?
Aren't all ferrite inductors non-linear, even in normal operation?
Thanks, Mikek

I just wonder how much unwanted crud such a system will radiate on
un-intended freqiencies when a bunch of strong local stations meet
the saturating inductor.

There ain't such thing as a good MF antenna tuner in small size.

 

[amdx]

On 8/21/2019 1:55 AM, Jasen Betts wrote:

On 2019-08-21, legg <legg@nospam.magma.ca> wrote:
On Tue, 20 Aug 2019 14:06:17 -0500, amdx <nojunk@knology.net> wrote:

On 8/20/2019 11:41 AM, legg wrote:
On Mon, 19 Aug 2019 19:53:28 -0500, amdx <nojunk@knology.net> wrote:

I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
Is this possible?

Thanks for your thoughts, Mikek
A cpnventional current-controlled inductor has two magnetic paths that
are configured to carry antiphase windings, with the third 'inductor
winding sharing both. The control windings' AC flux, from the third
winding, cancels out.

You can do this with an e-core (control windings on outer arms), two
toroids (each with control winding - sandwitched to support single
'inductor' winding around both) or solenoids (two solenoid cores
support control windings, 'inductor' wound around both.).

RL


As state previously, My question was not ask well, I only want one
winding with both ac and the dc to saturate it.

Thanks, Mikek

An ideal current source is easy to simulate, but in real life, it's
voltage compliance limits, stray loading and real power loss will set
limits on what you can do.

The conventional multiple winding is the more realistic approach.

Parasitics from the lower-powered control circuit are also easier to
isolate.

RL

AIUI this is for a recieve antenna so the AC signal will be failrly
small, I expect that the current source only needs enough compliance
to overcome earth resistance and a little headroom.

It is a receive only antenna.
And if you are suggesting a dc return through the earth, that was not
part of my plan. I think electrolysis would be a problem..
So a two wire dc system.
Mikek

 

[legg]

On Wed, 21 Aug 2019 07:59:39 -0500, amdx <nojunk@knology.net> wrote:

On 8/21/2019 1:55 AM, Jasen Betts wrote:
On 2019-08-21, legg <legg@nospam.magma.ca> wrote:
On Tue, 20 Aug 2019 14:06:17 -0500, amdx <nojunk@knology.net> wrote:

On 8/20/2019 11:41 AM, legg wrote:
On Mon, 19 Aug 2019 19:53:28 -0500, amdx <nojunk@knology.net> wrote:

I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
Is this possible?

Thanks for your thoughts, Mikek
A cpnventional current-controlled inductor has two magnetic paths that
are configured to carry antiphase windings, with the third 'inductor
winding sharing both. The control windings' AC flux, from the third
winding, cancels out.

You can do this with an e-core (control windings on outer arms), two
toroids (each with control winding - sandwitched to support single
'inductor' winding around both) or solenoids (two solenoid cores
support control windings, 'inductor' wound around both.).

RL


As state previously, My question was not ask well, I only want one
winding with both ac and the dc to saturate it.

Thanks, Mikek

An ideal current source is easy to simulate, but in real life, it's
voltage compliance limits, stray loading and real power loss will set
limits on what you can do.

The conventional multiple winding is the more realistic approach.

Parasitics from the lower-powered control circuit are also easier to
isolate.

RL

AIUI this is for a recieve antenna so the AC signal will be failrly
small, I expect that the current source only needs enough compliance
to overcome earth resistance and a little headroom.

It is a receive only antenna.
And if you are suggesting a dc return through the earth, that was not
part of my plan. I think electrolysis would be a problem..
So a two wire dc system.
Mikek

I don't see such a restriction to be a valid design goal in a new
product. What's the selling point? Electrolysis????? Even in a
retrofit, the addition of an external field-generating winding might
be easiest.

A modest current source can be decoupled from a tuned/tuning circuit,
over a known frequency range using a series choke. In small signal
circuitry, it's an issue you'd try to avoid, as resistors do the job
pretty well at low current.

A tuned circuit with an ungrounded terminal might benefit from a
re-examination of the schematic. Ground is, after all, everywhere. You
should use that feature, rather than compound it's potential problems.

If the aim is repeatable, calibratable 'L' values, I forsee a host of
issues with this technique.

Closed circuit, low frequency magnetics have to be re-evaluated for
function, when located within close proximity to large magnets, but a
magnet on a stick doesn't fit in well with typical solid-state circuit
aims.

RL

 

[amdx]

On 8/21/2019 11:10 AM, legg wrote:

On Wed, 21 Aug 2019 07:59:39 -0500, amdx <nojunk@knology.net> wrote:

On 8/21/2019 1:55 AM, Jasen Betts wrote:
On 2019-08-21, legg <legg@nospam.magma.ca> wrote:
On Tue, 20 Aug 2019 14:06:17 -0500, amdx <nojunk@knology.net> wrote:

On 8/20/2019 11:41 AM, legg wrote:
On Mon, 19 Aug 2019 19:53:28 -0500, amdx <nojunk@knology.net> wrote:

I'd like to have a Variable 100uh inductor, that is controlled to full
saturation with dc through the 100uh coil.
I see some two winding coils, but the dc control winding has huge
inductance. Working range 500kHz to 4MHz.
Is this possible?

Thanks for your thoughts, Mikek
A cpnventional current-controlled inductor has two magnetic paths that
are configured to carry antiphase windings, with the third 'inductor
winding sharing both. The control windings' AC flux, from the third
winding, cancels out.

You can do this with an e-core (control windings on outer arms), two
toroids (each with control winding - sandwitched to support single
'inductor' winding around both) or solenoids (two solenoid cores
support control windings, 'inductor' wound around both.).

RL


As state previously, My question was not ask well, I only want one
winding with both ac and the dc to saturate it.

Thanks, Mikek

An ideal current source is easy to simulate, but in real life, it's
voltage compliance limits, stray loading and real power loss will set
limits on what you can do.

The conventional multiple winding is the more realistic approach.

Parasitics from the lower-powered control circuit are also easier to
isolate.

RL

AIUI this is for a recieve antenna so the AC signal will be failrly
small, I expect that the current source only needs enough compliance
to overcome earth resistance and a little headroom.

It is a receive only antenna.
And if you are suggesting a dc return through the earth, that was not
part of my plan. I think electrolysis would be a problem..
So a two wire dc system.
Mikek


I don't see such a restriction to be a valid design goal in a new
product. What's the selling point? Electrolysis????? Even in a
retrofit, the addition of an external field-generating winding might
be easiest.

A modest current source can be decoupled from a tuned/tuning circuit,
over a known frequency range using a series choke. In small signal
circuitry, it's an issue you'd try to avoid, as resistors do the job
pretty well at low current.

A tuned circuit with an ungrounded terminal might benefit from a
re-examination of the schematic. Ground is, after all, everywhere. You
should use that feature, rather than compound it's potential problems.

If the aim is repeatable, calibratable 'L' values, I forsee a host of
issues with this technique.

Closed circuit, low frequency magnetics have to be re-evaluated for
function, when located within close proximity to large magnets, but a
magnet on a stick doesn't fit in well with typical solid-state circuit
aims.

RL

Start here.
> https://www.w8ji.com/beverages.htm

Then see Loaded beverages here,
> https://www.w8ji.com/slinky_and_loaded_beverages.htm

Now, I want to load a beverage on ground.
I don't have enough room for BOG long enough to have good
directionality in the BCB, therefore, I want to load it,
reducing the VF and changing the pattern.
If it is loaded to make it directional at 1MHz then it doesn't look
good at 4 MHz, So I want variable inductors.
It doesn't look good, the mixing products concerns me and finding a
material or combination that I can cause to reduce inductance as
frequency increases is not jumping out.

Thanks, Mikek

 

[Tauno Voipio]

On 21.8.19 16:16, amdx wrote:

On 8/21/2019 3:26 AM, Tauno Voipio wrote:
On 21.8.19 05:22, Tim Williams wrote:
"amdx" <nojunk@knology.net> wrote in message
news:qjhbo9$uq0$1@dont-email.me...
 Man, what time did I write the above?
What I meant to say was,
I had a BOG before and used a bedds that had a Q of 1 or 2.
  so if I could get 20 it would be better.

I still don't know what you're writing.  It ain't English...

Well, "bog" aside.  But that means something different in English
English. ;-)



It's for a receive only antenna, so microwatts, maybe milliwatts.
500kHz to 4 MHz.

What about just low noise JFETs?  It's not like you need any antenna
gain in those bands.


 Another possible solution,
 Is there a combination of L's and Cs the would approximate such an
L reduction over frequency?

Sure.  But not just L and C, R is required.  Necessarily has a very
low Q (from Kramers-Kronig relations).  Ferrite beads for example.

Tim

 I appreciate your input but not sure I understand.


The OP is attempting to make a tuned circuit with transductor tuning.

The circuit is a classic tuned circuit, it is not at resonance.


The linear equations of a tuned circuit (here: an antenna system) fall
apart as soon as the reactive element (transductor coil) is saturated
into non-linear operating range for control of effective inductance.

I'm Sorry, I don't have any understanding of the "non-linear operating
range". Is this like a diode causing mixing of two RF signals creating
other products?
 If that is the case, will millivolt level signals in a non-linear
inductor create objectionable mixing?
 Aren't all ferrite inductors non-linear, even in normal operation?
                                        Thanks, Mikek

Yes, but they are not intentionally driven hard out of the linear range.

The control in a transductor is based to driving the core
into saturation with the control current and thus controlling
the effective inductance.

--

-TV

 

[amdx]

On 8/20/2019 10:00 PM, amdx wrote:

On 8/20/2019 12:47 PM, amdx wrote:
On 8/20/2019 11:11 AM, Tim Williams wrote:
"amdx" <nojunk@knology.net> wrote in message
news:qjgbfo$1la$1@dont-email.me...
In previous responses I gave the proposed use is for a
"Beverage on Ground" antenna.
 I had a GOG before and used a beds that had a Q of 1 or 2.
 so if I could get 20 it would be better.

What power level?  Frequency range?

Tim

  Man, what time did I write the above?
What I meant to say was,
I had a BOG before and used a bedds that had a Q of 1 or 2.
   so if I could get 20 it would be better.

It's for a receive only antenna, so microwatts, maybe milliwatts.
500kHz to 4 MHz.

                                  Mikek

  Another possible solution,
  Is there a combination of L's and Cs the would approximate such an L
reduction over frequency?

 One of those times, I could see you posted but nothing in the post, so
I went to google groups.

  Man, what time did I write the above?
What I meant to say was,
I had a BOG before and used a bedds that had a Q of 1 or 2.
   so if I could get 20 it would be better.

I still don't know what you're writing.  It ain't English...

Well, "bog" aside.  But that means something different in English
English.
;-)

I'll try to get a good nights sleep tonight!
 BOG = Beverage On Ground
 bedds was supposed to be beads/sleeves which were actually a #73
binocular core that I only used one hole of. I just passed the antenna
wire through it. About 24 ohms R and 42 ohm XL at 1MHz.



It's for a receive only antenna, so microwatts, maybe milliwatts.
500kHz to 4 MHz.

What about just low noise JFETs?  It's not like you need any antenna
gain in
those bands.

Well, maybe, but usually the receive has enough gain, the bog signal is
down, maybe -25dbi to -40dbi.
But that is not the problem, by adjusting characteristics with frequency
you can narrow the beam width and increase the front to back ratio.
btw, I do have a high input impedance FET follower with low output
impedance, no gain but you do unload the antenna so get 3db. I'll be
trying that.

I had the Gain from adding a FET follower incorrect, unloading the
antenna gets you 3 db, then not have a 450ohm:50ohm impedance matching
(step down) transformer gives you another ~10db. Probably not quite as
much on a BOG because it has a lower feed impedance.
> https://www.okdxf.eu/lankford/J310%20-%20J271%20FET%20Follower.pdf

Ignore the chest pounding by Lankford he had a spat going with Trask,
may still have.
Mikek