How to design an Interesting inductor

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

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

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.

Thanks, Mikek

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

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

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

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. :-)

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

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

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

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/

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

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.

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.

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/

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.

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

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

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 appreciate your input but not sure I understand.

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

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

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

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

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

Start here.

Then see Loaded beverages here,

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

With pot cores you usually twist the two leads together and bring them out through a slot in the side of the core. If there are two or more slots, the wire goes in through one slot and comes out through a second one, 180 degrees away.

Nope. It's just the threading count.

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