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.pdfIgnore the chest pounding by Lankford he had a spat going with Trask, may still have. Mikek
How to design an Interesting inductor
Started by ●August 19, 2019
Reply by ●August 21, 20192019-08-21
Reply by ●August 21, 20192019-08-21
On 8/21/2019 4:45 PM, Phil Hobbs wrote:> On 8/20/19 3:04 PM, amdx wrote: >> 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? > > 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. > > >> 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? > > Nope. It's just the threading count. > > Cheers > > Phil HobbsThread count? Huh? ^ Room for explanation ^ Just because I left out the details, my 4-1/2 turn inductor was a potcore inductor, easy to add that 1/2 turn.
Reply by ●August 21, 20192019-08-21
On 8/21/19 7:50 PM, amdx wrote:> On 8/21/2019 4:45 PM, Phil Hobbs wrote: >> On 8/20/19 3:04 PM, amdx wrote: >>> 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? >> >> 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. >> >> >>> 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? >> >> Nope. It's just the threading count. > > Thread count? Huh? > > ^ Room for explanation ^Not like bed sheets. ;) The inductance contributed by the toroid goes as N**2, where N is the number of times the wire goes through the aperture of the toroid. No half turns need apply.> > Just because I left out the details, my 4-1/2 turn inductor was a > potcore inductor, easy to add that 1/2 turn.Right. And that half turn completely changes the saturation behaviour, at least if the centre post has a gap. 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
Reply by ●August 21, 20192019-08-21
On 8/21/2019 7:36 PM, Phil Hobbs wrote:> On 8/21/19 7:50 PM, amdx wrote: >> On 8/21/2019 4:45 PM, Phil Hobbs wrote: >>> On 8/20/19 3:04 PM, amdx wrote: >>>> 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? >>> >>> 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. >>> >>> >>>> 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? >>> >>> Nope. It's just the threading count. >> >> Thread count? Huh? >> >> ^ Room for explanation ^ > > Not like bed sheets. ;) > > The inductance contributed by the toroid goes as N**2, where N is the > number of times the wire goes through the aperture of the toroid. No > half turns need apply. > > >> >> Just because I left out the details, my 4-1/2 turn inductor was a >> potcore inductor, easy to add that 1/2 turn. > > Right. And that half turn completely changes the saturation behaviour, > at least if the centre post has a gap. > > Cheers > > Phil Hobbs >I found something I can at least try.> https://www.dropbox.com/s/ogpkx881d33m9mb/saturable%20core%20inductor%20db%20improved.jpg?dl=0I got a strong magnet to change the inductance from 100uH to 4.6uH. Mikek
Reply by ●August 21, 20192019-08-21
On Wed, 21 Aug 2019 20:36:36 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 8/21/19 7:50 PM, amdx wrote: >> On 8/21/2019 4:45 PM, Phil Hobbs wrote: >>> On 8/20/19 3:04 PM, amdx wrote: >>>> 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? >>> >>> 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. >>> >>> >>>> 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? >>> >>> Nope.� It's just the threading count. >> >> Thread count? Huh? >> >> �^� Room for explanation ^ > >Not like bed sheets. ;) > >The inductance contributed by the toroid goes as N**2, where N is the >number of times the wire goes through the aperture of the toroid. No >half turns need apply. >A half turn in a pot core can have impressively bad effects.
Reply by ●August 21, 20192019-08-21
On 8/21/19 8:57 PM, jlarkin@highlandsniptechnology.com wrote:> On Wed, 21 Aug 2019 20:36:36 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 8/21/19 7:50 PM, amdx wrote: >>> On 8/21/2019 4:45 PM, Phil Hobbs wrote: >>>> On 8/20/19 3:04 PM, amdx wrote: >>>>> 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? >>>> >>>> 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. >>>> >>>> >>>>> 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? >>>> >>>> Nope. It's just the threading count. >>> >>> Thread count? Huh? >>> >>> ^ Room for explanation ^ >> >> Not like bed sheets. ;) >> >> The inductance contributed by the toroid goes as N**2, where N is the >> number of times the wire goes through the aperture of the toroid. No >> half turns need apply. >> > > > A half turn in a pot core can have impressively bad effects. > >Yup. Or in this case, potentially useful ones. 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
Reply by ●August 22, 20192019-08-22
"amdx" <nojunk@knology.net> wrote in message news:qjhg76$qde$1@dont-email.me...> 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?I wrote an article in part discussing that, recently: https://www.seventransistorlabs.com/DC-DC_RE/index.html Measurements are included, showing the imbalance in external flux. The correct way to make half turns is to put a figure-eight winding on the legs to enforce flux balance. These can even be intentionally unbalanced (say 1:2), to get even more interesting fractions of turns (1/3, 1/4, etc.). With a corresponding hit in Phi_sat of course, because the one side saturates first. I link to a Unitrode appnote which discusses this. Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Design Website: https://www.seventransistorlabs.com/
Reply by ●August 22, 20192019-08-22
On Tue, 20 Aug 2019 12:47:54 -0500, amdx <nojunk@knology.net> 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 have some understanding of normal Beverages, but are there reliable comparative data for BOG or slinky antennas ? Until there are some reliable comporarative and calibrated comparison betwen real Beverages an BOGs and slinki antennas I really do not want to mess with them.>>> �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.The main selling point of Beverages is that it is wide band, you definitely _do_not_ want any high-Q (i.e. low bandwidth) constructs.>> >> 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?
Reply by ●August 22, 20192019-08-22
On Wed, 21 Aug 2019 16:52:01 -0500, amdx <nojunk@knology.net> wrote:>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. > MikekA simple passive stage (such as a transformer), can have voltage or current gain but the power gain is at best 0 dB. To have real power gain, you need an active device.
Reply by ●August 22, 20192019-08-22
On Wed, 21 Aug 2019 14:37:58 -0500, amdx <nojunk@knology.net> wrote:>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,Beverages are nice, _if_ you have space for 0.5 - 2 wavelengths long wires. If you don't have that space, you should seriously really study other antenna alternatives.>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.So a 150 m long Beverage is 0.5 wavelengths at 1 MHz and 2 wavelengths at 4 MHz. Have you considered installing a grounding resistor at 38 m (for 4 MHz) and at 75 m (for 2 MHz) and final termination resistance at 150 m (for 1 MHz) ? The intermediate grounding resistors are then selected by relays. Feed some audio tones along the wire to activate those intermediate relays (with some audio frequency selective rectifiers).> 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.If you use relays to select grounding point no need to worry about ferrite nonlinearity or mixing products.> > Thanks, Mikek > > >
