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.

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