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Try: http://orenelliottproducts.com/variable.htm -- Never bought any...Good Luck... K2RK
ON5MJ wrote: Hello there, Is this kind of inductors still for sale or still build ? I would like to buy two identical roller inductors of about 20 to 30 µH for an antenna tuner. Does somebody know where I can buy them. In the US or in Europe, no matter. 73 de ON5MJ - Jacques. |
Looking for roller inductors
I stumbled across a few at surplus outlets, I'll see if I can dig up
URL's. $50 to $150 USD, depending on KW rating. You can build your own fairly simple though, for a lot less :-) -- Gregg t3h g33k "Ratings are for transistors....tubes have guidelines" http://geek.scorpiorising.ca |
"Gregg" wrote in message news:t4eld.149312$df2.42254@edtnps89... I stumbled across a few at surplus outlets, I'll see if I can dig up URL's. $50 to $150 USD, depending on KW rating. You can build your own fairly simple though, for a lot less :-) -- Gregg t3h g33k "Ratings are for transistors....tubes have guidelines" http://geek.scorpiorising.ca Wup! Wade-a-minit! You can't go away without telling us how to build our own fairly simply for a lot less. Please. John KD5YI |
John Smith wrote:
"Gregg" wrote in message news:t4eld.149312$df2.42254@edtnps89... I stumbled across a few at surplus outlets, I'll see if I can dig up URL's. $50 to $150 USD, depending on KW rating. You can build your own fairly simple though, for a lot less :-) -- Gregg t3h g33k "Ratings are for transistors....tubes have guidelines" http://geek.scorpiorising.ca Wup! Wade-a-minit! You can't go away without telling us how to build our own fairly simply for a lot less. Please. John KD5YI Indeed -- directions or a URL. Please oh please. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
Leon Heller wrote:
"Gregg" wrote in message news:t4eld.149312$df2.42254@edtnps89... I stumbled across a few at surplus outlets, I'll see if I can dig up URL's. $50 to $150 USD, depending on KW rating. You can build your own fairly simple though, for a lot less :-) An old-timer I used to know made his own from plastic drain pipe. He used a lathe for cutting a spiral grove in the pipe for the wire, and machined most of the other parts himself. 73, Leon I'm not sure I'd qualify anything requiring a machine lathe as being "simple". -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
"Tim Wescott" wrote in message
... Leon Heller wrote: "Gregg" wrote in message news:t4eld.149312$df2.42254@edtnps89... I stumbled across a few at surplus outlets, I'll see if I can dig up URL's. $50 to $150 USD, depending on KW rating. You can build your own fairly simple though, for a lot less :-) An old-timer I used to know made his own from plastic drain pipe. He used a lathe for cutting a spiral grove in the pipe for the wire, and machined most of the other parts himself. 73, Leon I'm not sure I'd qualify anything requiring a machine lathe as being "simple". It is if one has a lathe. 8-) Strictly speaking, he wasn't making roller inductors, anyway, as the contact was moving across the turns giving one turn resolution, like a rheostat. He only used QRP. Making a proper roller inductor for high power like those made by Henry would be quite difficult. 73, Leon |
LOL! OK, ;-)
Delrin rod, Acrylic pipe/rod, PVC plumbing (not to be used for VHF), is key to the project. There are many pubs out there on making variable capacitors, the ARRL Radio Amateur's Handbook, and lots on the net. This is important, because the body is basically the same - rods, two square blocks of plexi or other insulator material, feed through hardware. The difference though, is you can use three threaded rods, but one must be smooth. Use a 1/8" brass hobby rod, threaded at the ends. You'll need a die & handle for that. Wind your rod. 14AWG house wiring is what I used. wind a spiral with one end ending in a near-complete circle. This will be the "common" connection. Your slider. Use a nylon bushing. This will be needed for friction. Electrical will be less important, because there will be no potential difference. Make a brass tab and dremel a notch in one end that'll fit the diameter of the wire used. The end of the tab should be bent back on itself a bit, to reduce binding. The other end of the tab, drill a small hole and attach to the nylon bushing with a 2-56 screw. Solder a flexible wire, litz, or that stuff used on speaker cones, from the tab to the end of the slider rod. Your common. Same tab, only soldered directly to one of the other, probably threaded rods. The tab will touch the end of the roller you made the complete circle of wire. Assembly. Same hardware for making a varicap, only instead of where the plates go, place your roller. I should really make a drawing ;-) -- Gregg t3h g33k "Ratings are for transistors....tubes have guidelines" http://geek.scorpiorising.ca |
"Leon Heller" wrote in message ...
"Tim Wescott" wrote in message ... Leon Heller wrote: "Gregg" wrote in message news:t4eld.149312$df2.42254@edtnps89... I stumbled across a few at surplus outlets, I'll see if I can dig up URL's. $50 to $150 USD, depending on KW rating. You can build your own fairly simple though, for a lot less :-) An old-timer I used to know made his own from plastic drain pipe. He used a lathe for cutting a spiral grove in the pipe for the wire, and machined most of the other parts himself. 73, Leon I'm not sure I'd qualify anything requiring a machine lathe as being "simple". It is if one has a lathe. 8-) Strictly speaking, he wasn't making roller inductors, anyway, as the contact was moving across the turns giving one turn resolution, like a rheostat. He only used QRP. Making a proper roller inductor for high power like those made by Henry would be quite difficult. 73, Leon Difficult indeed! I worked at Barker & Williamson during the early 60s when they were still making these things. First of all, you have to go out and located silver plated bare wire for the coils. Then you're going to have to machine yourself a precision roller that also needs to be silver plated, and a silver plated rod to carry the roller with as little lateral friction as possible. The balance is comparatively simple, if you have a source for G7 or G10 material to fabricate the frame, and are comfortable in machining fiberglass-epoxy laminates to a reasonable degree of precision. (B&W of course used custom molded and glazed ceramics, not laminated fiberblass, but that is simply a nit! I personally wouldn't want to even attempt it. Far cheaper to buy a surplus variable inductor. Harry C. |
The biggest problem with a home brew rotor inductor
is going to be a low resistance contact with no dead spots as the coil is rotated. For an antenna tuner, we can make do with a tapped coil and a small variable inductance in series with the tapped coil to "fill in" the gaps between the taps. To do this I would use a 'blast from the past', a variometer. This consists of two coils, one fixed and one rotating inside the fixed coil. If both are the same inductance (so the outer one is would with wider spacing than the inner) when they are in "series aiding" the total inductance will be the sum, plus the mutal inductance. When they are series opposing, the total inductance will approace zero. (over simplifcation). Variometers have NO moving contacts so they are easier to build than rotary coils. They can't be made as large in inductance without avoiding other problems (large distributed capacitance), but a small variometer in series with a multitapped coil is a good compromise. "Leon Heller" wrote in message ... "Tim Wescott" wrote in message ... Leon Heller wrote: "Gregg" wrote in message news:t4eld.149312$df2.42254@edtnps89... I stumbled across a few at surplus outlets, I'll see if I can dig up URL's. $50 to $150 USD, depending on KW rating. You can build your own fairly simple though, for a lot less :-) An old-timer I used to know made his own from plastic drain pipe. He used a lathe for cutting a spiral grove in the pipe for the wire, and machined most of the other parts himself. 73, Leon I'm not sure I'd qualify anything requiring a machine lathe as being "simple". It is if one has a lathe. 8-) Strictly speaking, he wasn't making roller inductors, anyway, as the contact was moving across the turns giving one turn resolution, like a rheostat. He only used QRP. Making a proper roller inductor for high power like those made by Henry would be quite difficult. 73, Leon Difficult indeed! I worked at Barker & Williamson during the early 60s when they were still making these things. First of all, you have to go out and located silver plated bare wire for the coils. Then you're going to have to machine yourself a precision roller that also needs to be silver plated, and a silver plated rod to carry the roller with as little lateral friction as possible. The balance is comparatively simple, if you have a source for G7 or G10 material to fabricate the frame, and are comfortable in machining fiberglass-epoxy laminates to a reasonable degree of precision. (B&W of course used custom molded and glazed ceramics, not laminated fiberblass, but that is simply a nit! I personally wouldn't want to even attempt it. Far cheaper to buy a surplus variable inductor. Harry C. |
Ken Scharf wrote:
The biggest problem with a home brew rotor inductor is going to be a low resistance contact with no dead spots as the coil is rotated. For an antenna tuner, we can make do with a tapped coil and a small variable inductance in series with the tapped coil to "fill in" the gaps between the taps. To do this I would use a 'blast from the past', a variometer. This consists of two coils, one fixed and one rotating inside the fixed coil. If both are the same inductance (so the outer one is would with wider spacing than the inner) when they are in "series aiding" the total inductance will be the sum, plus the mutal inductance. When they are series opposing, the total inductance will approace zero. (over simplifcation). Variometers have NO moving contacts so they are easier to build than rotary coils. They can't be made as large in inductance without avoiding other problems (large distributed capacitance), but a small variometer in series with a multitapped coil is a good compromise. "Leon Heller" wrote in message ... "Tim Wescott" wrote in message ... Leon Heller wrote: "Gregg" wrote in message news:t4eld.149312$df2.42254@edtnps89... I stumbled across a few at surplus outlets, I'll see if I can dig up URL's. $50 to $150 USD, depending on KW rating. You can build your own fairly simple though, for a lot less :-) An old-timer I used to know made his own from plastic drain pipe. He used a lathe for cutting a spiral grove in the pipe for the wire, and machined most of the other parts himself. 73, Leon I'm not sure I'd qualify anything requiring a machine lathe as being "simple". It is if one has a lathe. 8-) Strictly speaking, he wasn't making roller inductors, anyway, as the contact was moving across the turns giving one turn resolution, like a rheostat. He only used QRP. Making a proper roller inductor for high power like those made by Henry would be quite difficult. 73, Leon Difficult indeed! I worked at Barker & Williamson during the early 60s when they were still making these things. First of all, you have to go out and located silver plated bare wire for the coils. Then you're going to have to machine yourself a precision roller that also needs to be silver plated, and a silver plated rod to carry the roller with as little lateral friction as possible. The balance is comparatively simple, if you have a source for G7 or G10 material to fabricate the frame, and are comfortable in machining fiberglass-epoxy laminates to a reasonable degree of precision. (B&W of course used custom molded and glazed ceramics, not laminated fiberblass, but that is simply a nit! I personally wouldn't want to even attempt it. Far cheaper to buy a surplus variable inductor. Harry C. If your antenna tuner has two caps then you can often just use the tapped inductor, with no rotary at all (says Tim, who's antenna tuner has a rotary inductor...). -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
That's why the contact is spring-loaded in some way.
"Ken Scharf" wrote in message .. . The biggest problem with a home brew rotor inductor is going to be a low resistance contact with no dead spots as the coil is rotated. |
Airy R. Bean wrote:
That's why the contact is spring-loaded in some way. "Ken Scharf" wrote in message .. . The biggest problem with a home brew rotor inductor is going to be a low resistance contact with no dead spots as the coil is rotated. But if you need to install the tuner outdoors remote controled via servo motors, guess how long that sliding tap will give good contact? At least sealed relays can be used for the tap switch. |
"Gregg" wrote in message news:5cAld.151301$df2.57508@edtnps89... LOL! OK, ;-) Delrin rod, Acrylic pipe/rod, PVC plumbing (not to be used for VHF), is key to the project. There are many pubs out there on making variable capacitors, the ARRL Radio Amateur's Handbook, and lots on the net. There are? In the Handbook? Hmmmm. Okay, thanks. John |
"Leon Heller" wrote in message ... "Tim Wescott" wrote in message ... Leon Heller wrote: "Gregg" wrote in message news:t4eld.149312$df2.42254@edtnps89... I stumbled across a few at surplus outlets, I'll see if I can dig up URL's. $50 to $150 USD, depending on KW rating. You can build your own fairly simple though, for a lot less :-) An old-timer I used to know made his own from plastic drain pipe. He used a lathe for cutting a spiral grove in the pipe for the wire, and machined most of the other parts himself. 73, Leon I'm not sure I'd qualify anything requiring a machine lathe as being "simple". It is if one has a lathe. 8-) That's not true. You haven't taken my capabilities into consideration. Even if I had a lathe, I wouldn't know how to use it. John |
If you don't have any technical capabilities, RU a CBer?
"John Smith" wrote in message . net... That's not true. You haven't taken my capabilities into consideration. Even if I had a lathe, I wouldn't know how to use it. |
ON5MJ wrote:
Thank you again all OM for your interesting replies. This one from Ken could be worth the effort of investigation. I also thank Bob who replied me personnally. Did somebody try to replace a roller coil by a serie made of a tapped coil and a variable capacitor ? 73 de Jacques - ON5MJ You could do that, but again, if you have enough other adjustments you can probably make the fine adjustments on the caps. My first antenna tuner, which I used for several months, was just an L-network with a tapped coil (with an alligator clip) and a variable cap. By reversing the direction of the thing and dinking around it always worked for me -- and since it was on an open piece of aluminum I could hear, smell and see when I was putting too much RF into it for the little broadcast tuning cap! -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
......and now I understand your approach to DSP
"Tim Wescott" wrote in message ... My first antenna tuner, which I used for several months, was just an L-network with a tapped coil (with an alligator clip) and a variable cap. By reversing the direction of the thing and dinking around it always worked for me -- and since it was on an open piece of aluminum I could hear, smell and see when I was putting too much RF into it for the little broadcast tuning cap! |
Airy R. Bean wrote:
.....and now I understand your approach to DSP "Tim Wescott" wrote in message ... My first antenna tuner, which I used for several months, was just an L-network with a tapped coil (with an alligator clip) and a variable cap. By reversing the direction of the thing and dinking around it always worked for me -- and since it was on an open piece of aluminum I could hear, smell and see when I was putting too much RF into it for the little broadcast tuning cap! Why thank you. That's very nice. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
I can assure you that it is not. However, if it makes you feel
better then please deceive yourself on that matter as you undoubtedly do upon the religious beliefs of DSP. "Tim Wescott" wrote in message ... Airy R. Bean wrote: .....and now I understand your approach to DSP "Tim Wescott" wrote in message ... My first antenna tuner, which I used for several months, was just an L-network with a tapped coil (with an alligator clip) and a variable cap. By reversing the direction of the thing and dinking around it always worked for me -- and since it was on an open piece of aluminum I could hear, smell and see when I was putting too much RF into it for the little broadcast tuning cap! Why thank you. That's very nice. |
Airy R. Bean wrote:
I can assure you that it is not. However, if it makes you feel better then please deceive yourself on that matter as you undoubtedly do upon the religious beliefs of DSP. I will! Particularly since when _I_ build a system with DSP it generally works exactly as I've predicted it will. If I'm deceived, then so is God -- are you saying that God is deceived by how DSP works? -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
Who is God?
"Generally" works "exactly"? You seem to be somewhat confused. "Tim Wescott" wrote in message ... Airy R. Bean wrote: I can assure you that it is not. However, if it makes you feel better then please deceive yourself on that matter as you undoubtedly do upon the religious beliefs of DSP. I will! Particularly since when _I_ build a system with DSP it generally works exactly as I've predicted it will. If I'm deceived, then so is God -- are you saying that God is deceived by how DSP works? |
Is this kind of inductors still for sale or still build ? I would like to
buy two identical roller inductors of about 20 to 30 µH for an antenna tuner. Does somebody know where I can buy them. In the US or in Europe, no matter. 73 de ON5MJ - Jacques. ====================================== These roller inductors can often be found at ham flea markets . Residing in Belgium you might have an opportunity to visit some of the many flea markets in the Netherlands . There is a really big one in March every year at Rosmalen near 's Hertogenbosch. Another one is the open air ham flea market at the 'Lichtmis' trucker's stop between Zwolle and Meppel (last Saturday of September). I have seen roller inductors for sale at any ham flea market in NL ,also new ones . Good Luck Frank GM0CSZ / KN6WH |
An old-timer I used to know made his own from plastic drain pipe. He used
a lathe for cutting a spiral grove in the pipe for the wire, and machined most of the other parts himself. ========================= Before using drain pipe check it for RF integrity in the microwave oven. The grey stuff seems to have metal containing pigment. The white stuff might be better .....suggest you always check. Another possibility might be a polystyrene cylinder in the shape of a liquid volume measuring gauge as used by photographers in the dark room . I have such a gauge made by JOBO - Germany , volume 500 milli-litre ,diameter 65 mm ( approx 2.6 inch), length 200 mm (8 inch). Frank GM0CSZ / KN6WH |
To do this I would use a 'blast from the past', a variometer.
This consists of two coils, one fixed and one rotating inside the fixed coil. If both are the same inductance (so the outer one is would with wider spacing than the inner) when they are in "series aiding" the total inductance will be the sum, plus the mutal inductance. When they are series opposing, the total inductance will approace zero. (over simplifcation). Variometers have NO moving contacts so they are easier to build than rotary coils. They can't be made as large in inductance without avoiding other problems (large distributed capacitance), but a small variometer in series with a multitapped coil is a good compromise. ======================== Don't know the US situation ,but in Europe the marine 2 MHz band (in particular 2182 kHz emergency channel) is no longer used, with most ships now having satellite comms. All that redundent equipment is now being dumped or made available via the surplus trade . They all have variometers. However these variometers are probably only usable up to 10 MHz. Recently I was given a low power life boat emergency transceiver made by SKANTI (Danemark) for operation on 2182 and 8863 ? khz ,fitted in a water proof enclosure ............beautiful components including a variometer. Skanti also made the wellknown Sailor marine radio ( painted green). Frank GM0CSZ / KN6WH |
In my case I can't have a look into the tuner or handle alligator clips as
the tuner must be remotable and outdoors. The shack will be soon located in the cellar and it will not be possible to pass the ladder line through the house. A coax would be rather acceptable indoors. So I am looking for a good solution for the inductors: roller inductors, tapped inductors, tapped inductors with small variable serie capacitors. Driven by servos or stepper motors. Maybe I don't need a fine tuning of the inductors because of the main variable capacitor could be enough. ========================================== Provided there is not too much metal around you can readily pass a balanced feeder 75 -300 or 450 Ohms ribbon through the house. I use a 'Doublet' 2x 21 metres with a balanced 450 Ohms ribbon feeder running into and over the loft and so into the ground floor shack with a balanced to unbalanced matching unit in the shack next to the transceiver . No RF(I) problems ! Max RF power 100W-PEP Frank GM0CSZ / KN6WH |
To do this I would use a 'blast from the past', a variometer.
This consists of two coils, one fixed and one rotating inside the fixed coil. If both are the same inductance (so the outer one is would with wider spacing than the inner) when they are in "series aiding" the total inductance will be the sum, plus the mutal inductance. When they are series opposing, the total inductance will approace zero. (over simplifcation). Variometers have NO moving contacts so they are easier to build than rotary coils. They can't be made as large in inductance without avoiding other problems (large distributed capacitance), but a small variometer in series with a multitapped coil is a good compromise. ======================== There's a serious shortcoming with variometers for transmitting purposes. As the inductance reduces the wire resistance remains constant. Result - extremely low Q for small inductances. ---- Reg, G4FGQ |
Now I will try to find 4 stepper motors. I also got very good ideas from Bob (anonymous) about the use and control of stepper motors. =================== Good stepper motors for your job would be found in 'ancient' 8 inch floppy drives or the larger Hard Drives . Frank GM0CSZ / KN6WH |
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