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Hi,
I would like to know the correct value, in microhenry, of a single
turn air core loop 1 meter diameter (conductor 1 mm ).I tried many
software but they give me different results.
Regards
Franco.-

loopcalc.exe gives 4.8uh

73

jim ab3cv

exnci2000 wrote:

Hi,
I would like to know how may microhenry corresponds to a single turn
air core loop, 1 meter diameter(conductor diameter= 1 mm).I tried many
differents software but they gives different results.
regard

Is this one of the sites you found?

I agree that it doesn't agree very closely with the approximate formula at the bottom of page 2 of:

I tend to trust sources where the formula is given, even if they calculate for me, so I can spot check their program.
Based on the second source I think the inductance of your loop is about 1.2 uH.

1.2 uH sounds low to me, I think it will be higher than 3 uH. But if you
have a signal source and a receiver it is easy to measure. Construct a two
wire line that connects the signal source to the receiver. At some
frequency around 1 -10 MHz, measure the output with the receiver. Then
connect the loop terminals across the line. The loop will load the line to
some degree. The degree of loading can be used to determine the impedance
placed across the line. The impedance can be used to back out the
inductance.




on 3/5/07 3:53 PM, John Popelish at jpopelish@... wrote:

exnci2000 wrote:

Hi,
I would like to know how may microhenry corresponds to a single turn
air core loop, 1 meter diameter(conductor diameter= 1 mm).I tried many
differents software but they gives different results.
regard

Is this one of the sites you found?

I agree that it doesn't agree very closely with the
approximate formula at the bottom of page 2 of:

I tend to trust sources where the formula is given, even if
they calculate for me, so I can spot check their program.
Based on the second source I think the inductance of your
loop is about 1.2 uH.

Ken Javor wrote:

on 3/5/07 3:53 PM, John Popelish at jpopelish@... wrote:
exnci2000 wrote:

Hi,
I would like to know how may microhenry corresponds to a single turn
air core loop, 1 meter diameter(conductor diameter= 1 mm).I tried many
differents software but they gives different results.
regard

Is this one of the sites you found?

I agree that it doesn't agree very closely with the
approximate formula at the bottom of page 2 of:

I tend to trust sources where the formula is given, even if
they calculate for me, so I can spot check their program.
Based on the second source I think the inductance of your
loop is about 1.2 uH.

1.2 uH sounds low to me, I think it will be higher than 3

uH. But if you

have a signal source and a receiver it is easy to

measure. Construct a two

wire line that connects the signal source to the

receiver. At some

frequency around 1 -10 MHz, measure the output with the

receiver. Then

connect the loop terminals across the line. The loop will

load the line to

some degree. The degree of loading can be used to

determine the impedance

placed across the line. The impedance can be used to

back out the

inductance.

I agree that 1.2 uH seems low (gut feel) but that is what the reference says. I checked my old Reference Data for Radio Engineers, 5th Edition. On page 6-9 it gives this formula:
L=(a/100)*(7.353*LOG10(16*a/d)-6.386) microhenries, where a is the radius of the loop (to the center line of the wire), in inches and d is the diameter of the wire, inm inches, and that a/d>2.5

So, replacing the loop diameter of 1 meter with a loop radius (a) of 19.69 inches, and the 1 mm wire diameter to (d) of .039 inxches, I get an inductance of about
4.39 uH.

So we have another random data point. I haven't gone through the formula in the above reference to check their example (that was close ot the O.P.s case).

I built a tuned loop from a 10 ft piece of copper tubing (3.2 ft/ .98
Meter diameter) about three years ago and it measured as 3.1 uH in
free space using the excellent AADE Digital LC Meter (Highly recommended)

JR

...it measured as 3.1 uH in > free space using the excellent AADE

Digital LC Meter ... <<<

Hi JR,
I'm impressed! You're the only person I've ever met who's been to free
space and returned, let alone taken an LC meter there.
(Sorry, I coudn't resist!)
Dave


--- In loopantennas@..., "jr_dakota" <SG2112@...> wrote:

I built a tuned loop from a 10 ft piece of copper tubing (3.2 ft/ .98
Meter diameter) about three years ago and it measured as 3.1 uH in
free space using the excellent AADE Digital LC Meter (Highly

recommended)

JR

--- In loopantennas@..., "exnci2000" <awfhgm@> wrote:

Hi,
I would like to know the correct value, in microhenry, of a single
turn air core loop 1 meter diameter (conductor 1 mm ).I tried many
software but they give me different results.
Regards
Franco.-

and that is indeed one fine meter
P

Hi,thanks to you All for your answers to my question.If 4.38 microhenry
is the correct value,at 2 Mhz the reactance XL will be 55 ohnm..at 4
Mhz 110 ohm.For an untuned one-turn loop," without link", a think I can
match(for 4 Mhz) the impedance at 50 ohm of my receiver with 2
parallel turns.I am not a technician and I ask you an opinion.
regards
Franco
Ps: Please excuse my bad English !

I tend to trust sources where the formula is given, even if
they calculate for me, so I can spot check their program.

The thing you need to keep in mind is that all those formulas are
approximations, mostly fitting to empirical data, and they all come with
limitations. If you use the formula outside of those ranges, the results
will be wrong.

You can also find formulas for the inductance of a straight wire, which is
folly because there is no such thing. There is something called a "partial
inductance," but until you turn the wire into a closed loop, you can't
really talk about the inductance of the wire (loop).

Andy

--- In loopantennas@..., "n2chi" <davidgriffin@...> wrote:

...it measured as 3.1 uH in > free space using the excellent AADE

Digital LC Meter ... <<<

Hi JR,
I'm impressed! You're the only person I've ever met who's been to free
space and returned, let alone taken an LC meter there.
(Sorry, I coudn't resist!)
Dave

I'm too cheap to used paid space so free space it is ....

Open source space. Free GPL. It's a great place!



jr_dakota wrote: