Ferrite loop antenna for LW/MW band
 

Hi,

Is there any kind of program that makes the calculations a bit easier? If I
knew how to do the calculations, I could throw the formula into a
spreadsheet. What I need to do is calculate the inductance with the
parameters of cross sectional area, length, position on the ferrite rod,
number of turns, and permeability of the ferrite material itself.
I would like to throw these parameters into the spreadsheet/program, and let
the software calculate the inductance for me.

Pete

Ferrite loop antenna for LW/MW band
 

On 2008-01-17, Pete KE9OA (71.239.37.56) wrote in
message


Hi,

Is there any kind of program that makes the calculations a bit easier? If I
knew how to do the calculations, I could throw the formula into a
spreadsheet. What I need to do is calculate the inductance with the
parameters of cross sectional area, length, position on the ferrite rod,
number of turns, and permeability of the ferrite material itself.
I would like to throw these parameters into the spreadsheet/program, and let
the software calculate the inductance for me.

Pete

Have a look here, see section 2 "Practical antenna design"

http://www.c-maxgroup.com/tech/antenna.php

--
Dirk.
No trees were killed in the creation of this message;
however, many electrons were terribly inconvenienced.

Ferrite loop antenna for LW/MW band
 

Is there any kind of program that makes the calculations a bit easier? If
I knew how to do the calculations, I could throw the formula into a
spreadsheet. What I need to do is calculate the inductance with the
parameters of cross sectional area, length, position on the ferrite rod,
number of turns, and permeability of the ferrite material itself.
I would like to throw these parameters into the spreadsheet/program, and
let the software calculate the inductance for me.

Pete

GM Pete. Sorry I had to be short on the telephone call, I had a doctors
appointment and was running late already. WRT your "antenna problem or
opportunity". I made an antenna for WWVB, and also use it for NAA at 24 KHz
by adding an additional cap across it for resonance down there. It's better
heads and shoulders than any ferrite antenna I ever made. 24 inch bicycle
wheel, spokes removed and a space made in the wheel continuity by sawing it
apart and adding a small block of wood. This also serves to hold an old ARCO
tuning cap of high value, and an instrumentation amplifier made from three
LM833 op amps.

A layer of shipping plastic foam between the rim and 120 turns of HPT wire
(#26 is a good number), then wrap it all up with a bit of squeezed on
aluminum wrap. (Also not continuous, and grounded at the spacer.)

With the inst, amp set for 60 dB of gain, I receive WWVB at about -40 dBm
into the 50 Ohm input to a HP selective Voltmeter. Best ever ferrite was
around 30 dB worse than this. I use it almost continuously for NAA
monitoring of SIDs, and they never go out of detection even in the basement
workshop.

Regards and happy New Year.
W4ZCB

Ferrite loop antenna for LW/MW band
 

Harold E. Johnson wrote:

I made an antenna for WWVB, and also use it for NAA at 24 KHz
by adding an additional cap across it for resonance down there. It's better
heads and shoulders than any ferrite antenna I ever made. 24 inch bicycle
wheel,...

Please consider photographing this device from a number of angles,
annotating the images with construction data, and making the results
available. I am very interested.

Regards,

Michael

Ferrite loop antenna for LW/MW band
 

Thanks Harold...........I whill give it a whirl. For the past few days, I
have been experimenting with the ferrite loopstick. Either winding works ok
(LW or MW), but if the LW winding is connected, it appears to cause some
self resonance problems with the MW winding in the middle of the band,
unless I ground both ends of the LW winding. Right now, I am trying a
multi-layer winding for the LW section to see if I can eliminate the
interraction. It should work..........my Grundig Satellit 3400 appears to
use this principle, unless there is a seperate pickup winding for each band.
Oh, about the call..............don't worry about it. I had to go to the
doctor myself today. Must keep appointments!

Pete

"Harold E. Johnson" wrote in message
news:UqMjj.39622$Ux2.21213@attbi_s22...
Is there any kind of program that makes the calculations a bit easier?
If I knew how to do the calculations, I could throw the formula into a
spreadsheet. What I need to do is calculate the inductance with the
parameters of cross sectional area, length, position on the ferrite rod,
number of turns, and permeability of the ferrite material itself.
I would like to throw these parameters into the spreadsheet/program, and
let the software calculate the inductance for me.

Pete

GM Pete. Sorry I had to be short on the telephone call, I had a doctors
appointment and was running late already. WRT your "antenna problem or
opportunity". I made an antenna for WWVB, and also use it for NAA at 24
KHz by adding an additional cap across it for resonance down there. It's
better heads and shoulders than any ferrite antenna I ever made. 24 inch
bicycle wheel, spokes removed and a space made in the wheel continuity by
sawing it apart and adding a small block of wood. This also serves to hold
an old ARCO tuning cap of high value, and an instrumentation amplifier
made from three LM833 op amps.

A layer of shipping plastic foam between the rim and 120 turns of HPT wire
(#26 is a good number), then wrap it all up with a bit of squeezed on
aluminum wrap. (Also not continuous, and grounded at the spacer.)

With the inst, amp set for 60 dB of gain, I receive WWVB at about -40 dBm
into the 50 Ohm input to a HP selective Voltmeter. Best ever ferrite was
around 30 dB worse than this. I use it almost continuously for NAA
monitoring of SIDs, and they never go out of detection even in the
basement workshop.

Regards and happy New Year.
W4ZCB

Ferrite loop antenna for LW/MW band
 

Thanks Dick........it looks like a good site. It also shows that I have
quite a bit to learn about these things.

Pete

"Dirk Claessens" wrote in message
...
On 2008-01-17, Pete KE9OA (71.239.37.56) wrote in
message


Hi,

Is there any kind of program that makes the calculations a bit easier? If
I knew how to do the calculations, I could throw the formula into a
spreadsheet. What I need to do is calculate the inductance with the
parameters of cross sectional area, length, position on the ferrite rod,
number of turns, and permeability of the ferrite material itself.
I would like to throw these parameters into the spreadsheet/program, and
let the software calculate the inductance for me.

Pete

Have a look here, see section 2 "Practical antenna design"

http://www.c-maxgroup.com/tech/antenna.php

--
Dirk.
No trees were killed in the creation of this message;
however, many electrons were terribly inconvenienced.

Ferrite loop antenna for LW/MW band
 

On Jan 17, 3:23�am, "Pete KE9OA" wrote:
Hi,

Is there any kind of program that makes the calculations a bit easier? If I
knew how to do the calculations, I could throw the formula into a
spreadsheet. What I need to do is calculate the inductance with the
parameters of cross sectional area, length, position on the ferrite rod,
number of turns, and permeability of the ferrite material itself.
I would like to throw these parameters into the spreadsheet/program, and let
the software calculate the inductance for me.

Pete


Hello Pete

AFAIK there is no set of formulae which will do the job for you. What
follows comes from E.C. Snelling, "Soft Ferrites: Properties and
Applications", 2nd ed, 1988, p 155. Sadly this book's quality is
exceeded by it's rarity.

Snelling starts off by saying that the inductance ratio mu(coil), or
apparent permeability, of a coil when it has a ferrite core is
diffiult to calculate, "since it depends upon on the geometry of the
winding and the core and to some extent the core permeability".

Snelling goes on to present a simpler approach which "applies only to
centrally placed windings". He starts by assuming that a
"magnetically long cylinder" is covered over its whole length. (I do
not know if these means that the coil is tight wound or not, or even
whether this matters). He then goes on to state that the inductance
of the coil is proportional to mu(rod) times the area times the
number of turns squared divided by the length of the rod.

He then presents curves based on experimental data, based on coils
where the centrally placed winding covered 5-100% of the coil, the
initial permeability ranged from 15 to 1000, and the length/diameter
ratios of the rod varied from 3 to 18. The results are shown on p.
155. Snelling comments that using the mean curve will produce an
error of 12% or less.

The curve plots 10exp09 times L / (A.N.N.mu(rod)), against the
fraction of the rod which is covered. The approximate values
(fraction of rod covered first) a
0.1 2.75
0.2 2.25
0.3 2.1
0.4 1.85
0.5 1.7
0.6 1.5
0.7 1.35
0.8 1.15
0.9 1.05
1.0 0.95

Note that you have to calcluate mu(rod), which depends upon the
initial permeabilty of the ferrite, and the demagnetization factor.
The demagnetization factor depends up the length /diameter ratio, and
to some extent the intial permeability of the rod. You can read the
demagnetization factor off a chart (Snelling p. 151), or read mu(rod)
directly from a chart based upon the initial permability and l/d radio
(Snelling p. 152). You will see the same chart at, eg,:
http://www.magneticsgroup.com/pdf/erods.pdf
To calculate mu(rod) you would have to able to calculate the
demagnetization factor. I do not know how to do this. The
calculation of mu(rod) is straightforward once the demagnetization
factor is known.

Apparently the whole process above is only approximate. If you slide
the winding away from the center of the core, then the inductance will
decrease.. By how much I do not know. BTW, was this the way in which
the coil inductance was adjusted in LW/MW radio sets during intial
alignment?

I also vaguely recall reading some work done by W.J. Polydoroff on the
inductance of coils with ferrite cores. A paper in 1945, and a book
in 1960 come to mind. He took a slightly different approach. In
those days the permeability of ferrite was relatively low. I have
never compared his approach to Snelling's to see if they give
approximately the same results. If I can find the stuff here, I will
look a little harder.

73 John KC0G

Ferrite loop antenna for LW/MW band
 

Thanks John,

I appreciate the info. I had a couple of databooks/textbooks about this
years ago, but of course in my infinite wisdom I gave them away a few years
back. I didn't think I would need them!

Pete

wrote in message
...
On Jan 17, 3:23?am, "Pete KE9OA" wrote:
Hi,

Is there any kind of program that makes the calculations a bit easier? If
I
knew how to do the calculations, I could throw the formula into a
spreadsheet. What I need to do is calculate the inductance with the
parameters of cross sectional area, length, position on the ferrite rod,
number of turns, and permeability of the ferrite material itself.
I would like to throw these parameters into the spreadsheet/program, and
let
the software calculate the inductance for me.

Pete


Hello Pete

AFAIK there is no set of formulae which will do the job for you. What
follows comes from E.C. Snelling, "Soft Ferrites: Properties and
Applications", 2nd ed, 1988, p 155. Sadly this book's quality is
exceeded by it's rarity.

Snelling starts off by saying that the inductance ratio mu(coil), or
apparent permeability, of a coil when it has a ferrite core is
diffiult to calculate, "since it depends upon on the geometry of the
winding and the core and to some extent the core permeability".

Snelling goes on to present a simpler approach which "applies only to
centrally placed windings". He starts by assuming that a
"magnetically long cylinder" is covered over its whole length. (I do
not know if these means that the coil is tight wound or not, or even
whether this matters). He then goes on to state that the inductance
of the coil is proportional to mu(rod) times the area times the
number of turns squared divided by the length of the rod.

He then presents curves based on experimental data, based on coils
where the centrally placed winding covered 5-100% of the coil, the
initial permeability ranged from 15 to 1000, and the length/diameter
ratios of the rod varied from 3 to 18. The results are shown on p.
155. Snelling comments that using the mean curve will produce an
error of 12% or less.

The curve plots 10exp09 times L / (A.N.N.mu(rod)), against the
fraction of the rod which is covered. The approximate values
(fraction of rod covered first) a
0.1 2.75
0.2 2.25
0.3 2.1
0.4 1.85
0.5 1.7
0.6 1.5
0.7 1.35
0.8 1.15
0.9 1.05
1.0 0.95

Note that you have to calcluate mu(rod), which depends upon the
initial permeabilty of the ferrite, and the demagnetization factor.
The demagnetization factor depends up the length /diameter ratio, and
to some extent the intial permeability of the rod. You can read the
demagnetization factor off a chart (Snelling p. 151), or read mu(rod)
directly from a chart based upon the initial permability and l/d radio
(Snelling p. 152). You will see the same chart at, eg,:
http://www.magneticsgroup.com/pdf/erods.pdf
To calculate mu(rod) you would have to able to calculate the
demagnetization factor. I do not know how to do this. The
calculation of mu(rod) is straightforward once the demagnetization
factor is known.

Apparently the whole process above is only approximate. If you slide
the winding away from the center of the core, then the inductance will
decrease.. By how much I do not know. BTW, was this the way in which
the coil inductance was adjusted in LW/MW radio sets during intial
alignment?

I also vaguely recall reading some work done by W.J. Polydoroff on the
inductance of coils with ferrite cores. A paper in 1945, and a book
in 1960 come to mind. He took a slightly different approach. In
those days the permeability of ferrite was relatively low. I have
never compared his approach to Snelling's to see if they give
approximately the same results. If I can find the stuff here, I will
look a little harder.

73 John KC0G

Ferrite loop antenna for LW/MW band
 

"Pete KE9OA" wrote in message
. ..
Hi,

Is there any kind of program that makes the calculations a bit easier? If
I knew how to do the calculations, I could throw the formula into a
spreadsheet. What I need to do is calculate the inductance with the
parameters of cross sectional area, length, position on the ferrite rod,
number of turns, and permeability of the ferrite material itself.
I would like to throw these parameters into the spreadsheet/program, and
let the software calculate the inductance for me.

Pete

Here's a great site with detailed info about ferrite rods.
http://www.bentongue.com/xtalset/29MxQFL/29MxQFL.html

Here's a long list of articles by the same author.
http://www.bentongue.com/xtalset/xtalset.html

The home page of all the above.
http://www.bentongue.com/

Mike