[Fwd: LF: Re: [Lowfer] Question about coil wire]
Andre Kesteloot
akestelo@bellatlantic.net
Wed, 28 Jan 1998 20:06:08 -0500
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More good stuff about high-Q low frequency coils
André N4ICK
******************************
Clifford Buttschardt wrote:
> Many good comments here by Lyle K0LR. I can add some to this from a
> practical standpoint. A simple homemade coil was wound with number 14
> house wire on a twelve inch diameter PVC thickwall water pipe. The
> wire was spaced one wire diameter plus insulation thickness. This of
> course is a practical way to wind the coil using two wires in hand.
> The result was about 4 mHy of inductance and a coil length of about
> three feet. The Q was 300 with the PVC water pipe in place. A hot glue
> gun was then used to fasten the coil to each adjacent turn. The PVC water
> pipe was then removed leaving the coil self supporting due to the hot
> glue. The Q increased to 650!
> Remember this is a simple solenoid, solid #14 wire with insulation,
> ie: house wire---nothing at all fancy. Cliff K7RR
>
> On Wed, 28 Jan 1998, Lyle Koehler wrote:
>
> > Johan Bodin wrote:
> > >
> > > Hello LFers
> > >
> > > PVC has quite bad dielectric properties at higher frequencies,
> > > but does it matter in a coil for 73 or 136 kHz?
> >
> > Actually the dissipation factor may be higher at 100 kHz than it is at
> > 10 MHz. From an old copy of Reference Data for Radio Engineers, the
> > dissipation factor of PVC is given as 0.093 at 1 kHz and 0.055 at 1 MHz.
> > The dielectric constant is shown as 4.8 at 1 kHz and 3.5 at 1 MHz. There
> > can be quite a difference in loss and dielectric constant for various
> > compositions of PVC, but none of the numbers are very encouraging.
> >
> > > Has anyone investigated the loss of a loading coil made of
> > > PVC insulated wire? Is there a considerable difference in
> > > loss compared to a similar coil made with the same wire
> > > area but without the PVC?
> >
> > Brian Beezley, K6STI has a program called COIL.EXE that lets you specify
> > the coil form material. This isn't quite the same as having the wires
> > surrounded by the dielectric material, but it gives an idea of what
> > happens with a lossy dielectric. The loading coil for my 186.75 kHz
> > LowFER beacon is made from #14 (1.63 mm) insulated house wire in a
> > basket-wound, air-supported configuration. The coil has about 75 turns
> > and is 18 inches diameter by 9 inches long. For a straight air-supported
> > solenoid coil with these dimensions, COIL.EXE predicts an effective
> > inductance of 2.93 mH and a Q = 748 at 190 kHz, with a distributed
> > capacitance of 23 pF. The same coil on a PVC form would have L = 3.22
> > mH, Q = 322 and distributed C = 44.6 pF. I measured a Q of over 400 on
> > my basket-wound coil. The basket-wound configuration is probably worth
> > the extra effort when using wire with lossy insulation, because I would
> > expect a coil wound with PVC-insulated wire to have a lower Q than a
> > coil on a PVC form.
> >
> > > PVC insulated wire for mains wiring in houses is very cheap
> > > in Sweden. The most common variety has 1.5 mm2 cupper
> > > area. Outside diameter is about 3 mm while the cupper dia.
> > > is about 1.5 mm.
> >
> > The same thing is true in the US. 500 feet of #14 bare copper wire costs
> > $35 (plus shipping), but I can get insulated #14 at the discount
> > building-supply store for about $15. That's why I use it, even though it
> > isn't ideal for low-frequency loading coils. Besides, if I used bare (or
> > enamelled) wire, I would have to find some kind of large, low-loss form,
> > and wound have to figure out how to wind it with the proper spacing
> > between turns. (Best Q for a given wire size is usually obtained with a
> > spacing between turns of twice the wire diameter.) A basket-wound coil
> > of any size can be constructed by putting an odd number of dowels into
> > holes into a plywood board. The PVC insulation provides the right wire
> > spacing so it isn't too difficult to wind. After "weaving" the coil
> > lacing the crossovers with something like Dacron kite string, and doping
> > the lacings with silicone bathtub sealer, you can pull the whole thing
> > off the dowels and have a reasonably efficient loading coil at low cost.
> > One more note: Farm supply stores often carry 3/8 inch diameter, 4 foot
> > long fiberglass electric fence posts that make nice slippery dowels for
> > the coil-winding operation. Probably they could be left in place to help
> > keep the coil rigid, without too much degradation in Q.
> >
> > 73
> >
> > Lyle, K0LR
> >
> >
> > ---
> > Submissions lowfer@qth.net
> >
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Wed, 28 Jan 1998 10:16:27 -0800 (PST)
Date: Wed, 28 Jan 1998 10:16:27 -0800 (PST)
From: Clifford Buttschardt <cbuttsch@slonet.org>
To: Lyle Koehler <k0lr@emily.net>
cc: Johan Bodin <sm6lkm.jbeab@swipnet.se>, rsgb_lf_group@blacksheep.org,
lowfer@qth.net
Subject: LF: Re: [Lowfer] Question about coil wire
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Many good comments here by Lyle K0LR. I can add some to this from a
practical standpoint. A simple homemade coil was wound with number 14
house wire on a twelve inch diameter PVC thickwall water pipe. The
wire was spaced one wire diameter plus insulation thickness. This of
course is a practical way to wind the coil using two wires in hand.
The result was about 4 mHy of inductance and a coil length of about
three feet. The Q was 300 with the PVC water pipe in place. A hot glue
gun was then used to fasten the coil to each adjacent turn. The PVC water
pipe was then removed leaving the coil self supporting due to the hot
glue. The Q increased to 650!
Remember this is a simple solenoid, solid #14 wire with insulation,
ie: house wire---nothing at all fancy. Cliff K7RR
On Wed, 28 Jan 1998, Lyle Koehler wrote:
> Johan Bodin wrote:
> >
> > Hello LFers
> >
> > PVC has quite bad dielectric properties at higher frequencies,
> > but does it matter in a coil for 73 or 136 kHz?
>
> Actually the dissipation factor may be higher at 100 kHz than it is at
> 10 MHz. From an old copy of Reference Data for Radio Engineers, the
> dissipation factor of PVC is given as 0.093 at 1 kHz and 0.055 at 1 MHz.
> The dielectric constant is shown as 4.8 at 1 kHz and 3.5 at 1 MHz. There
> can be quite a difference in loss and dielectric constant for various
> compositions of PVC, but none of the numbers are very encouraging.
>
> > Has anyone investigated the loss of a loading coil made of
> > PVC insulated wire? Is there a considerable difference in
> > loss compared to a similar coil made with the same wire
> > area but without the PVC?
>
> Brian Beezley, K6STI has a program called COIL.EXE that lets you specify
> the coil form material. This isn't quite the same as having the wires
> surrounded by the dielectric material, but it gives an idea of what
> happens with a lossy dielectric. The loading coil for my 186.75 kHz
> LowFER beacon is made from #14 (1.63 mm) insulated house wire in a
> basket-wound, air-supported configuration. The coil has about 75 turns
> and is 18 inches diameter by 9 inches long. For a straight air-supported
> solenoid coil with these dimensions, COIL.EXE predicts an effective
> inductance of 2.93 mH and a Q = 748 at 190 kHz, with a distributed
> capacitance of 23 pF. The same coil on a PVC form would have L = 3.22
> mH, Q = 322 and distributed C = 44.6 pF. I measured a Q of over 400 on
> my basket-wound coil. The basket-wound configuration is probably worth
> the extra effort when using wire with lossy insulation, because I would
> expect a coil wound with PVC-insulated wire to have a lower Q than a
> coil on a PVC form.
>
> > PVC insulated wire for mains wiring in houses is very cheap
> > in Sweden. The most common variety has 1.5 mm2 cupper
> > area. Outside diameter is about 3 mm while the cupper dia.
> > is about 1.5 mm.
>
> The same thing is true in the US. 500 feet of #14 bare copper wire costs
> $35 (plus shipping), but I can get insulated #14 at the discount
> building-supply store for about $15. That's why I use it, even though it
> isn't ideal for low-frequency loading coils. Besides, if I used bare (or
> enamelled) wire, I would have to find some kind of large, low-loss form,
> and wound have to figure out how to wind it with the proper spacing
> between turns. (Best Q for a given wire size is usually obtained with a
> spacing between turns of twice the wire diameter.) A basket-wound coil
> of any size can be constructed by putting an odd number of dowels into
> holes into a plywood board. The PVC insulation provides the right wire
> spacing so it isn't too difficult to wind. After "weaving" the coil
> lacing the crossovers with something like Dacron kite string, and doping
> the lacings with silicone bathtub sealer, you can pull the whole thing
> off the dowels and have a reasonably efficient loading coil at low cost.
> One more note: Farm supply stores often carry 3/8 inch diameter, 4 foot
> long fiberglass electric fence posts that make nice slippery dowels for
> the coil-winding operation. Probably they could be left in place to help
> keep the coil rigid, without too much degradation in Q.
>
> 73
>
> Lyle, K0LR
>
>
> ---
> Submissions lowfer@qth.net
>
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