Greetings.

I have a pixie 2 xcvr currently set for 80m. I have been wanting to put it
on the 20m band, so I found that I require a .551uH.

I assume that this would be a terribly easy coil to wind, but I've never
wound a coil w/ intention of achieving a specific inductance. If anyone is
familiar w/ the number of turns/gauge etc... for a .551uH inductor, I would
really appreciate that info.

Thanks much.

James Shrum - KC9FFX

"jim&julz"
wrote in message
...
Greetings.

I have a pixie 2 xcvr currently set for 80m. I
have been wanting to put it
on the 20m band, so I found that I require a
..551uH.

I assume that this would be a terribly easy coil
to wind, but I've never
wound a coil w/ intention of achieving a
specific inductance. If anyone is
familiar w/ the number of turns/gauge etc... for
a .551uH inductor, I would
really appreciate that info.


Use the following formula:

(N^2)*(R^2)
L(uh) = -----------------
(9*R)+(10*L)

L(uh) - Inductance in microhenries
N - Number of turns
R - Radius of single layer coil in inches
L - Length of single layer coil in inches


If the coil is just for RX then you can get away
with using 22 to 24 gage magnet wire. Be sure to
use a coil form to wind the wire on. Then cover
the coil with coil dope, or other material, to
hold the turns in place. That will keep the coil
inductance stable.

Pick a convenient coil form size and just plug in
some numbers, using a spread sheet, until you find
a set of coil dimentions that you like.


--
Leland C. Scott
KC8LDO

ARRL Member
NCI Member

Charter member of the
Lawrence Technological University
Wireless Society W8LTU

"jim&julz"
wrote in message
...
Greetings.

I have a pixie 2 xcvr currently set for 80m. I
have been wanting to put it
on the 20m band, so I found that I require a
..551uH.

I assume that this would be a terribly easy coil
to wind, but I've never
wound a coil w/ intention of achieving a
specific inductance. If anyone is
familiar w/ the number of turns/gauge etc... for
a .551uH inductor, I would
really appreciate that info.


Use the following formula:

(N^2)*(R^2)
L(uh) = -----------------
(9*R)+(10*L)

L(uh) - Inductance in microhenries
N - Number of turns
R - Radius of single layer coil in inches
L - Length of single layer coil in inches


If the coil is just for RX then you can get away
with using 22 to 24 gage magnet wire. Be sure to
use a coil form to wind the wire on. Then cover
the coil with coil dope, or other material, to
hold the turns in place. That will keep the coil
inductance stable.

Pick a convenient coil form size and just plug in
some numbers, using a spread sheet, until you find
a set of coil dimentions that you like.


--
Leland C. Scott
KC8LDO

ARRL Member
NCI Member

Charter member of the
Lawrence Technological University
Wireless Society W8LTU

I require a .551uH.

If anyone is
familiar w/ the number of turns/gauge etc... for a .551uH inductor, I would
really appreciate that info.

Look in the ARRL Handbook, under calculating practical inductors. For a .5uH
inductor I would try as a start, a 1/4" drill bit wound with #20 or #22 solid,
with the length and turns / inch per the Handbook formula.
If you don't have the Handbook, I can post the formula, until you can get a
Handbook :-).












































73 Gary N4AST

I require a .551uH.

If anyone is
familiar w/ the number of turns/gauge etc... for a .551uH inductor, I would
really appreciate that info.

Look in the ARRL Handbook, under calculating practical inductors. For a .5uH
inductor I would try as a start, a 1/4" drill bit wound with #20 or #22 solid,
with the length and turns / inch per the Handbook formula.
If you don't have the Handbook, I can post the formula, until you can get a
Handbook :-).












































73 Gary N4AST

James,

Try this easy way to make .55 microhenry coil:

Take a 1/2 watt resistor of about 1 meg ohm or more in resistance
(value irrevelant, just make sure it is above about a megohm),
put a tiny notch near one end parallel to the leads of the
resistor just large enough for 28 gauge wire to sit in (I use
a small pocket knife or a :Swiss file" whichever is closest at
hand when I wind a coil), solder a length of 28 gauge wire to
one of the resistor leads very close to the body of the resistor.

Now wind 15 1/2 turns of the #28 wire around the body of the resistor
and make a similar notch on the other end of the resistor and solder
the free end of the wire to that lead like you did the first. Keep the
turns touching each other ("closewound".)

Cut off the extra #28 wire and use this homemade .55 microhenry coil
in good health. It may or may not be EXACTLY .551 microhenries,
but it will be pretty close. The calculations come from a BASIC
program published in 73 Magazine years (decades?) ago and seems to
work pretty well.

Good look and post a report of how well this project goes.

Sorry if I made the explanation too simple if you already wind a lot of
coils, but I sometimes get carried away (gets worse the older I get...)

73,

Phil - N4GWV

I have a pixie 2 xcvr currently set for 80m. I have been wanting to
put it on the 20m band, so I found that I require a .551uH.

I assume that this would be a terribly easy coil to wind, but I've
never wound a coil w/ intention of achieving a specific inductance. If
anyone is familiar w/ the number of turns/gauge etc... for a .551uH
inductor, I would really appreciate that info.

James,

Try this easy way to make .55 microhenry coil:

Take a 1/2 watt resistor of about 1 meg ohm or more in resistance
(value irrevelant, just make sure it is above about a megohm),
put a tiny notch near one end parallel to the leads of the
resistor just large enough for 28 gauge wire to sit in (I use
a small pocket knife or a :Swiss file" whichever is closest at
hand when I wind a coil), solder a length of 28 gauge wire to
one of the resistor leads very close to the body of the resistor.

Now wind 15 1/2 turns of the #28 wire around the body of the resistor
and make a similar notch on the other end of the resistor and solder
the free end of the wire to that lead like you did the first. Keep the
turns touching each other ("closewound".)

Cut off the extra #28 wire and use this homemade .55 microhenry coil
in good health. It may or may not be EXACTLY .551 microhenries,
but it will be pretty close. The calculations come from a BASIC
program published in 73 Magazine years (decades?) ago and seems to
work pretty well.

Good look and post a report of how well this project goes.

Sorry if I made the explanation too simple if you already wind a lot of
coils, but I sometimes get carried away (gets worse the older I get...)

73,

Phil - N4GWV

I have a pixie 2 xcvr currently set for 80m. I have been wanting to
put it on the 20m band, so I found that I require a .551uH.

I assume that this would be a terribly easy coil to wind, but I've
never wound a coil w/ intention of achieving a specific inductance. If
anyone is familiar w/ the number of turns/gauge etc... for a .551uH
inductor, I would really appreciate that info.

Dunno how accurate you need it to be "as wound", and dunno what sort
of form factor you want, but if an air-core coil will work for you,
here's one way: get about 18 inches of 18AWG wire, nice and straight,
and a 1/2"x13TPI bolt. Wind 11 turns of that wire into the threads of
the bolt, leaving 1" of wire on either end (or start with a longer
piece if you want longer leads), and unscrew the bolt. The result
should be a coil about 0.85 inches long and 0.424" ID, and 0.600uH.
When you get it mounted near other things, the inductance will go down
a bit, and you can adjust it down further by stretching it a bit. The
Q at 14MHz should be just over 200. Or you can use 10 turns of 16AWG,
done the same way, which will have a slightly larger ID, 0.434 inches,
and about 0.561uH nominal and very slightly higher Q.

In general, the L = (n*r)^2/(9*r+10*l) formula works well, where r and
l are radius and length in inches, n is number of turns, and the
inductance, L, is in uH. My numbers above come from a program that's
easy to use and that I've learned to trust from verified results.
It's convenient to use a bolt to get consistent spacing and diameter,
though for high stability, you'd want some sort of support. For
highest Q in a given volume, go for a coil with roughly equal length
and diameter, though that's not terribly critical.

Cheers,
Tom


"jim&julz" wrote in message ...
Greetings.

I have a pixie 2 xcvr currently set for 80m. I have been wanting to put it
on the 20m band, so I found that I require a .551uH.

I assume that this would be a terribly easy coil to wind, but I've never
wound a coil w/ intention of achieving a specific inductance. If anyone is
familiar w/ the number of turns/gauge etc... for a .551uH inductor, I would
really appreciate that info.

Thanks much.

James Shrum - KC9FFX

Dunno how accurate you need it to be "as wound", and dunno what sort
of form factor you want, but if an air-core coil will work for you,
here's one way: get about 18 inches of 18AWG wire, nice and straight,
and a 1/2"x13TPI bolt. Wind 11 turns of that wire into the threads of
the bolt, leaving 1" of wire on either end (or start with a longer
piece if you want longer leads), and unscrew the bolt. The result
should be a coil about 0.85 inches long and 0.424" ID, and 0.600uH.
When you get it mounted near other things, the inductance will go down
a bit, and you can adjust it down further by stretching it a bit. The
Q at 14MHz should be just over 200. Or you can use 10 turns of 16AWG,
done the same way, which will have a slightly larger ID, 0.434 inches,
and about 0.561uH nominal and very slightly higher Q.

In general, the L = (n*r)^2/(9*r+10*l) formula works well, where r and
l are radius and length in inches, n is number of turns, and the
inductance, L, is in uH. My numbers above come from a program that's
easy to use and that I've learned to trust from verified results.
It's convenient to use a bolt to get consistent spacing and diameter,
though for high stability, you'd want some sort of support. For
highest Q in a given volume, go for a coil with roughly equal length
and diameter, though that's not terribly critical.

Cheers,
Tom


"jim&julz" wrote in message ...
Greetings.

I have a pixie 2 xcvr currently set for 80m. I have been wanting to put it
on the 20m band, so I found that I require a .551uH.

I assume that this would be a terribly easy coil to wind, but I've never
wound a coil w/ intention of achieving a specific inductance. If anyone is
familiar w/ the number of turns/gauge etc... for a .551uH inductor, I would
really appreciate that info.

Thanks much.

James Shrum - KC9FFX

Thanks so much everyone. I was really surprised by the quick and
informational responses.
Everything was in great detail... even detailed enough for me to figure it
out. I'll give it a try and let you know how it worked.

I just got licensed Monday and I've been dying to get on the air. Thanks for
your help.

Regards,
KC9FFX


"jim&julz" wrote in message
...
Greetings.

I have a pixie 2 xcvr currently set for 80m. I have been wanting to put it
on the 20m band, so I found that I require a .551uH.

I assume that this would be a terribly easy coil to wind, but I've never
wound a coil w/ intention of achieving a specific inductance. If anyone is
familiar w/ the number of turns/gauge etc... for a .551uH inductor, I
would
really appreciate that info.

Thanks much.

James Shrum - KC9FFX