On 4 Dec 2003 17:30:27 -0800, Winfield Hill
wrote:

As John has said, that's a very low inductance that should not
present any problems at such a low power level. But perhaps for
a more detailed answer you can tell us the frequencies your coil
will experience. At high frequencies skin and proximity effects
dominate, and these can be evaluated with an Rac/Rdc ratio. If
a ferrite is used its high-frequency core loss can also be modeled
as an inductor resistance.

Thanks, Win! You're a diamond. John's formulae didn't appear on his
post for some reason, but you've given me the info I need to start
winding and be slap in the ball park right away. Great.
BTW, the factory inductors I have already are only about the size of
the newest half-watt resistors, so I was reluctant to chance it. I
know things keep getting smaller and somehow seem to defy the laws of
physics, but just call me old fashioned. :-)
Thanks again.

P.


--

"I expect history will be kind to me, since I intend to write it."
- Winston Churchill

Paul Burridge wrote:

...John's formulae didn't appear on his
post for some reason,

I hate it when I find a page and forget to paste the link:
http://www.qsl.net/wa7zcz/area2/page34.html
from (remember this old book of electronic data?):
http://www.qsl.net/wa7zcz/area2/t_of_c.html
--
John Popelish

Paul Burridge wrote:

...John's formulae didn't appear on his
post for some reason,

I hate it when I find a page and forget to paste the link:
http://www.qsl.net/wa7zcz/area2/page34.html
from (remember this old book of electronic data?):
http://www.qsl.net/wa7zcz/area2/t_of_c.html
--
John Popelish

"Paul Burridge" wrote in message
...
On 4 Dec 2003 17:30:27 -0800, Winfield Hill
wrote:

As John has said, that's a very low inductance that should not
present any problems at such a low power level. But perhaps for
a more detailed answer you can tell us the frequencies your coil
will experience. At high frequencies skin and proximity effects
dominate, and these can be evaluated with an Rac/Rdc ratio. If
a ferrite is used its high-frequency core loss can also be modeled
as an inductor resistance.

Thanks, Win! You're a diamond. John's formulae didn't appear on his
post for some reason, but you've given me the info I need to start
winding and be slap in the ball park right away. Great.
BTW, the factory inductors I have already are only about the size of
the newest half-watt resistors, so I was reluctant to chance it. I
know things keep getting smaller and somehow seem to defy the laws
of
physics, but just call me old fashioned. :-)
Thanks again.

P.


--

"I expect history will be kind to me, since I intend to write it."
-
Winston Churchill

Paul, I really don't think you need to wind your own. For example,
a Coilcraft 1008CS 180nH part is rated at 620mA rms:

http://www.coi1craft.com/1008cs.cfm

The "trick" is that the dissipation is a function of the series
resistance, which is very low (0.77 ohms) as long as the core
doesn't saturate.

If you want to get really silly, their "Spring" inductors are rated
at 3A rms.

Regards
Ian

"Paul Burridge" wrote in message
...
On 4 Dec 2003 17:30:27 -0800, Winfield Hill
wrote:

As John has said, that's a very low inductance that should not
present any problems at such a low power level. But perhaps for
a more detailed answer you can tell us the frequencies your coil
will experience. At high frequencies skin and proximity effects
dominate, and these can be evaluated with an Rac/Rdc ratio. If
a ferrite is used its high-frequency core loss can also be modeled
as an inductor resistance.

Thanks, Win! You're a diamond. John's formulae didn't appear on his
post for some reason, but you've given me the info I need to start
winding and be slap in the ball park right away. Great.
BTW, the factory inductors I have already are only about the size of
the newest half-watt resistors, so I was reluctant to chance it. I
know things keep getting smaller and somehow seem to defy the laws
of
physics, but just call me old fashioned. :-)
Thanks again.

P.


--

"I expect history will be kind to me, since I intend to write it."
-
Winston Churchill

Paul, I really don't think you need to wind your own. For example,
a Coilcraft 1008CS 180nH part is rated at 620mA rms:

http://www.coi1craft.com/1008cs.cfm

The "trick" is that the dissipation is a function of the series
resistance, which is very low (0.77 ohms) as long as the core
doesn't saturate.

If you want to get really silly, their "Spring" inductors are rated
at 3A rms.

Regards
Ian

I need to wind 180nH inductor for a parallel tuned circuit I'm
building,

Paul-

I suggest you find some stiff wire, wind about five turns using a pencil as a
form, and stretch or compress it to tune the circuit.

If you want a more stable inductor, then wind it on a high value, one or two
watt resistor. Once the desired inductance is set, put some kind of varnish
(coil dope) on it to hold the winding in place.

73, Fred, K4DII

I need to wind 180nH inductor for a parallel tuned circuit I'm
building,

Paul-

I suggest you find some stiff wire, wind about five turns using a pencil as a
form, and stretch or compress it to tune the circuit.

If you want a more stable inductor, then wind it on a high value, one or two
watt resistor. Once the desired inductance is set, put some kind of varnish
(coil dope) on it to hold the winding in place.

73, Fred, K4DII

On Fri, 5 Dec 2003 15:37:15 -0000, "Ian Buckner"
wrote:

Paul, I really don't think you need to wind your own. For example,
a Coilcraft 1008CS 180nH part is rated at 620mA rms:

http://www.coi1craft.com/1008cs.cfm

The "trick" is that the dissipation is a function of the series
resistance, which is very low (0.77 ohms) as long as the core
doesn't saturate.

If you want to get really silly, their "Spring" inductors are rated
at 3A rms.

Thanks, Ian, but it only took about 15 seconds to wind the coil
according to Win's spec and more importantly, winding my own enables
me to take a tap off it, which I believe may be necessary in this app.
--

"I expect history will be kind to me, since I intend to write it."
- Winston Churchill

On Fri, 5 Dec 2003 15:37:15 -0000, "Ian Buckner"
wrote:

Paul, I really don't think you need to wind your own. For example,
a Coilcraft 1008CS 180nH part is rated at 620mA rms:

http://www.coi1craft.com/1008cs.cfm

The "trick" is that the dissipation is a function of the series
resistance, which is very low (0.77 ohms) as long as the core
doesn't saturate.

If you want to get really silly, their "Spring" inductors are rated
at 3A rms.

Thanks, Ian, but it only took about 15 seconds to wind the coil
according to Win's spec and more importantly, winding my own enables
me to take a tap off it, which I believe may be necessary in this app.
--

"I expect history will be kind to me, since I intend to write it."
- Winston Churchill

On Fri, 05 Dec 2003 08:38:18 -0800, Bill Turner
wrote:

As you may know, the inductance of a coil is not a fixed value, but
varies dramatically with frequency.

Er, you mean *reactance* of a coil varies dramatically with frequency,
don't you?
--

"I expect history will be kind to me, since I intend to write it."
- Winston Churchill