Thanks Peter. Good application of theory. I remember an old radio I had with spherical coils inside each other that changed the L by rotating the inner coil, and as a result tuned the radio to different stations. Fixed capacitors were selected by banna like plugs. Your experiment reminds me of those early tuning systems. Thanks for sharing. Lou, vk3aqz.
Thanks for the videos. I wanted to experiment with loose vs tight coupling with 2 separate coils. There's other ways to do that, but I wound two coils with 40 GA wire. That wire is too small, I know. One coil is 399 uH on a 2" thickwall PVC pipe (275 turns) and the other coil with 25 turns on a smaller pipe that easily slides inside the bigger one. I'll fiddle with making each of the coils with a different number of turns trying to get more stations. Putting a different number turns on both coils will accomplish getting the inductance where I want it. Thanks for the tip. At first tonight I could tune 2 different stations on the broadcast band depending on how far the smaller coil is pushed through the bigger one. I put in a different bigger coil with more turns. That, along with using the sliding cap, allowed me to get 3 stations so far. I made the sliding tube capacitor with paper towel cores and aluminum foil. The capacitor is about 200 pF maximum. The cap changes frequency too slowly, so I'll play with capacitor values in parallel with the sliding cap. OR make an additional sliding cap.
cool, i just finished making a variable inductor with 0.5" (13mm) OD ferrite cylinders on an M8 threaded brass rod, sliding in/out of a coil of 58turns of 18awg magnet wire (wound around a 15mm(ID) 16mm(OD) clear plastic tube). it only gives me 10-60microhenrys, so i'm tempted to try and fit another inner coil (wound around ferrite as long as it still fits in tube) to maybe double((? or not, your vid helps temper my expectations lol, so ok maybe 50% increase, maybe i get 20-90)) the total range of inductance. also very handy, you can gut a jumbo glue stick and epoxy a ferrite bead in place of glue, wind a coil around the outer housing, and u got a threaded slider ready-made. i got inductance range if 10-50 uH with glue-stick var-indictors. im trying to "regulate" a bifilar Tesla coil secondary as shown in Nikola Tesla's Colorado Springs Notes (his so-called 'adjustable inductance'), so I've no clue of range needed, but big range w/low resistance seems ideal (only 0.4ohms for 58t 18awg magnet wire 🤷), peace!
Brilliant! Also could try a variometer or a sliding ferrite or a combo arrangement. Sliding plates for variable caps? Great area for experimentation. 72 N4HAY
Thanks Peter, I'm going to make a crystal set using this inductance method rather than a VC, with the inner tube on a threaded rod so I can wind it in and out. Is the separation of the coils due to the plastic coating of the wire a necessary feature of this device? I would like to try it with varnished .8mm wire I have, but the length of the finished coil will be only about 25mm, much less than yours, unless I string it out with a larger gap between turns. I hope it works, as finding Variable Capacitors is getting hard. Appreciate your videos 👍
Thank you for the vid. I wonder if you tried to actually tune an antenna with this arrangement. Did it work? Was it efficient? Please let us know. Perhaps in a follow up video. Thanks again.
@@vk3ye Thank you for your reply. It would be interesting to see it on transmit. I would like to make a variometer (loading coil) for a 12m Spiderbeam and (1/4 L on 40m) to be able to use it on 40m and 80m. I would put a smaller coil into another much larger one so rather than using taps, I would like to turn a knob. The smaller coil would rotate rather than slide inside. This potentially could work as a remote tuner with a simple gear DC motor (They have them on eBay - 6 rpm. Slow enough to tune). Anyway, just an idea. I do not know if this is even feasible.
Peter, if you flipped the outer inductor, instead of the inner inductor, would that give you another, different values of inductance? Thanks for sharing your video. Bill VE3WAH.
Look up basic electrical concepts like inductance and capacitance and go on from there. Both are needed to form a tuned circuit as widely used in radio circuits.
@@vk3ye I have looked a bit and I’ll keep studying. I was just confused as I upgrade my crystal radio because I sometimes see the two terms used interchangeably on the same tuning device. Perhaps it’s just people who aren’t in the know talking
![Lp. Сердце Вселенной #60 РОЖДЕНИЕ ЛОЛОЛОШКИ [Финал] • Майнкрафт](http://i.ytimg.com/vi/YoR0pAV9FVQ/mqdefault.jpg)
I like it when it is all the way in!
Thanks Peter. Good application of theory. I remember an old radio I had with spherical coils inside each other that changed the L by rotating the inner coil, and as a result tuned the radio to different stations. Fixed capacitors were selected by banna like plugs. Your experiment reminds me of those early tuning systems. Thanks for sharing. Lou, vk3aqz.
Thanks for the videos. I wanted to experiment with loose vs tight coupling with 2 separate coils. There's other ways to do that, but I wound two coils with 40 GA wire. That wire is too small, I know. One coil is 399 uH on a 2" thickwall PVC pipe (275 turns) and the other coil with 25 turns on a smaller pipe that easily slides inside the bigger one. I'll fiddle with making each of the coils with a different number of turns trying to get more stations.
Putting a different number turns on both coils will accomplish getting the inductance where I want it. Thanks for the tip.
At first tonight I could tune 2 different stations on the broadcast band depending on how far the smaller coil is pushed through the bigger one. I put in a different bigger coil with more turns. That, along with using the sliding cap, allowed me to get 3 stations so far.
I made the sliding tube capacitor with paper towel cores and aluminum foil. The capacitor is about 200 pF maximum. The cap changes frequency too slowly, so I'll play with capacitor values in parallel with the sliding cap. OR make an additional sliding cap.
cool, i just finished making a variable inductor with 0.5" (13mm) OD ferrite cylinders on an M8 threaded brass rod, sliding in/out of a coil of 58turns of 18awg magnet wire (wound around a 15mm(ID) 16mm(OD) clear plastic tube). it only gives me 10-60microhenrys, so i'm tempted to try and fit another inner coil (wound around ferrite as long as it still fits in tube) to maybe double((? or not, your vid helps temper my expectations lol, so ok maybe 50% increase, maybe i get 20-90)) the total range of inductance.
also very handy, you can gut a jumbo glue stick and epoxy a ferrite bead in place of glue, wind a coil around the outer housing, and u got a threaded slider ready-made. i got inductance range if 10-50 uH with glue-stick var-indictors.
im trying to "regulate" a bifilar Tesla coil secondary as shown in Nikola Tesla's Colorado Springs Notes (his so-called 'adjustable inductance'), so I've no clue of range needed, but big range w/low resistance seems ideal (only 0.4ohms for 58t 18awg magnet wire 🤷), peace!
is there any relationship between the length of the conductors used to wind the two coils?.
wonder how the self resonance varies as you do that?
Brilliant! Also could try a variometer or a sliding ferrite or a combo arrangement. Sliding plates for variable caps? Great area for experimentation. 72 N4HAY
Peter , you have done it again, great stuff ! G.L. Jerry K9UT
Thanks Peter, I'm going to make a crystal set using this inductance method rather than a VC, with the inner tube on a threaded rod so I can wind it in and out. Is the separation of the coils due to the plastic coating of the wire a necessary feature of this device? I would like to try it with varnished .8mm wire I have, but the length of the finished coil will be only about 25mm, much less than yours, unless I string it out with a larger gap between turns. I hope it works, as finding Variable Capacitors is getting hard. Appreciate your videos 👍
Wonder if you could use the inside on a nylon rod to act as a adjustable inductor for an antenna tuner.
I it use for LW receiver,s LC tank. Works as a magnetic antenna and like a "loose coupler"
Inner coils diameter - 50mm.
Thank you for the vid. I wonder if you tried to actually tune an antenna with this arrangement. Did it work? Was it efficient? Please let us know. Perhaps in a follow up video. Thanks again.
Tom - I did try with a crystal set AM receiver and it seemed to work almost as well as a regular coil (that had thicker wire).
@@vk3ye Thank you for your reply. It would be interesting to see it on transmit. I would like to make a variometer (loading coil) for a 12m Spiderbeam and (1/4 L on 40m) to be able to use it on 40m and 80m. I would put a smaller coil into another much larger one so rather than using taps, I would like to turn a knob. The smaller coil would rotate rather than slide inside. This potentially could work as a remote tuner with a simple gear DC motor (They have them on eBay - 6 rpm. Slow enough to tune). Anyway, just an idea. I do not know if this is even feasible.
yep in MW range 500kc etc maritime transmitters they used this bucket type antena, coil inside coil arrangement for resonance.
Peter, if you flipped the outer inductor, instead of the inner inductor, would that give you another, different values of inductance? Thanks for sharing your video. Bill VE3WAH.
How is a variable conductor different from a variable capacitor
Look up basic electrical concepts like inductance and capacitance and go on from there. Both are needed to form a tuned circuit as widely used in radio circuits.
@@vk3ye I have looked a bit and I’ll keep studying. I was just confused as I upgrade my crystal radio because I sometimes see the two terms used interchangeably on the same tuning device. Perhaps it’s just people who aren’t in the know talking
Great information. 🎩
You're awesome!
Very neat.
Nice........
👍👏👏