Ferrite core : can I use this kind ?
 

Dear all,

I have, from an old bunch of computer wires in the disposal place of my office,
some ferrite cores such as the ones described here :
http://www.tdk.com.tw/ctl_pdf/ctl_1.1.pdf

I have two with the following spec : ZCAT2032-0930

I can possibly use one on the feed line to the radio to reduce some noise, but,
can this kind of material be used for building a balun/unun ? It is a tube of
ferrite instead of a toroid, so the windings might be a bit different...

Any hints out there ???

Thanks for your inputs,

Charly

Ferrite core : can I use this kind ?
 

Old computer power supplies might have toroids.

I guess this is a function of where you live. I can go to at least 3
stores and get ferrite cores off the shelf.


Charly wrote:
Dear all,

I have, from an old bunch of computer wires in the disposal place of my office,
some ferrite cores such as the ones described here :
http://www.tdk.com.tw/ctl_pdf/ctl_1.1.pdf

I have two with the following spec : ZCAT2032-0930

I can possibly use one on the feed line to the radio to reduce some noise, but,
can this kind of material be used for building a balun/unun ? It is a tube of
ferrite instead of a toroid, so the windings might be a bit different...

Any hints out there ???

Thanks for your inputs,

Charly

Ferrite core : can I use this kind ?
 

Ferrite core : can I use this kind ?
 

Even if you get the core off the shelf, you still need ot wind the
coil.

Any home-brew coil should be frequency swept. The parasitic capacitance
can really limit the performance.


Charly wrote:
wrote:
Old computer power supplies might have toroids.

I guess this is a function of where you live. I can go to at least 3
stores and get ferrite cores off the shelf.


Yes sure : I can drive to some shops, but it will take me 2 or 3 hours way and
back...

I feel it is more funny to make my own, and I learn much more as well...

Charly

Ferrite core : can I use this kind ?
 

I spent sixty dollars plus ten dollars S&H for a fifteen foot long long
computer to computer monitor VGA cable from www.si87.com in
Bozeman,Montana a few years ago.My cable has two (count em,two) big
ferrite toroids on it,,, to help prevent ghosting images on my Multisync
22 inch flat screen CRT computer monitor.I never stint on quality (I
dont give a d..n what it cost) thingys for my computer. www.google.com
cantaria.com Ragland Road.
cuhulin

Ferrite core : can I use this kind ?
 

Bill Mutch wrote:
http://www.amidoncorp.com/aai_ferritecores.htm

Thanks for the link Bill...

Charly

Building a Matching Transformer ? Ferrite Core ? - TIP - Start with a "Know Quantity" and Build-from-there !
 

Charly - Check-Out these Items ~ RHF

TOROID FERRITE QRP HAM RADIO BALUN MATCHING TRANSFORMER
http://cgi.ebay.com/_W0QQitemZ5873245727

FERRITE BALUN QRP HAM RADIO CORES
http://cgi.ebay.com/_W0QQitemZ5873851905

Check-Out eBay Seller RF Junkie (rfjunkie)
ERICKSON ENGINEERING
http://search.ebay.com/_W0QQsassZrfjunkieQQhtZ-1

Amidon Associates produces a broad line of ferrite beads,
coil forms, cores and specialty items for the electronic
experimenter. {Via Universal-Radio.Com}
http://www.universal-radio.com/catalog/misc/amidon.html

#1542 FT 50-43 Ferrite Toroidal Core Qty = 3
0.500" x 0.281" x 0.188" AL=523

#1544 FT 82-43 Ferrite Toroidal Core Qty = 3
0.825" x 0.520" x 0.250" AL= 557

#0471 BN-43-202 Two Hole Core = Qty 4
0.525" x 0.150" x 0.550" x 0.295 AL=2890

Building a Matching Transformer ? Ferrite Core ?
TIP - Start with a "Know Quantity" and Build-from-there !


hope this helps - iane ~ RHF
.
.
Tous Sont Bienvenus ! - - - Groupe par Radio
d'auditeur d'onde courte pour des Antennes de SWL
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
Alle Sind Willkommen ! - - - Shortwave Radiozuhörer
Gruppe für SWL Antennen
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
Tutti Sono Benvenuti ! - - - Gruppo Radiofonico
dell'ascoltatore di onda corta per le Antenne di SWL
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
Todos São Bem-vindos ! - - - Grupo de Rádio
do ouvinte do Shortwave para Antenas de SWL
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
Ð’Ñ�е Ð*адушны ! - - - Группа оператора
на приеме коротковолнового диапазона
Radio дл� Aнтенн SWL
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
¡Todos Son Agradables! - - - Grupo de Radio del oyente
de la onda corta para las Antenas de SWL
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
= = = = = Translation = = = = =
All are Welcome - - - To Join the Shortwave Listeners
(SWL) Antenna Group on YAHOO !
http://groups.yahoo.com/group/Shortwave-SWL-Antenna/
.
.
.. .

Ferrite core : can I use this kind ?
 

In article ,
Charly wrote:

Dear all,

I have, from an old bunch of computer wires in the disposal place of my
office,
some ferrite cores such as the ones described here :
http://www.tdk.com.tw/ctl_pdf/ctl_1.1.pdf

I have two with the following spec : ZCAT2032-0930

I can possibly use one on the feed line to the radio to reduce some noise,
but,
can this kind of material be used for building a balun/unun ? It is a tube of
ferrite instead of a toroid, so the windings might be a bit different...

Any hints out there ???

Thanks for your inputs,

Charly

Fig. 4 is your model. You will get 50 ohms impedance per turn at 10 MHz,
75 ohms at 20 MHz and 100 ohms at 30 MHz. Regressing the chart I
estimate 20 ohms at 5 MHz.

Two problems is BALUN/UNUN are a little more picky about the core and
these are two pieces. Better to have one piece core. Depending on the
type of impedance transformer you want to make this could be an OK value
of inductance for the frequencies you want it to operate on for a
voltage type but you would want more for a current type.

--
Telamon
Ventura, California

Ferrite core : can I use this kind ?
 

How about adapting (somehow or the other) computer monitor VGA cables
that already have a big ferrite core on each end of the cables to use
with radio antenna hookups? Only wondering.
cuhulin

Ferrite core : can I use this kind ?
 

Telamon wrote:
Fig. 4 is your model. You will get 50 ohms impedance per turn at 10 MHz,
75 ohms at 20 MHz and 100 ohms at 30 MHz. Regressing the chart I
estimate 20 ohms at 5 MHz.

Two problems is BALUN/UNUN are a little more picky about the core and
these are two pieces. Better to have one piece core. Depending on the
type of impedance transformer you want to make this could be an OK value
of inductance for the frequencies you want it to operate on for a
voltage type but you would want more for a current type.


BIG THANKS !!!

This the kind of info I was looking for....

Charly

Ferrite core : can I use this kind ?
 

Ferrite core : can I use this kind ?
 

Well,my computer to computer monitor fifteen feet long VGA has a big
ferrite core on each end of the cable.I paid sixty dollars plus ten
dollars shipping & handling for my cable,I bought it from
www.si87.com in Bozeman,Montana about three years ago.The two ferrite
cores on the cable help to reduce/prevent ghosting images on my 22 inch
screen CRT Multisync computer monitor.Sure,I could have connected two
cheap cables together,but I wont go any cheapo route as regards my
computer equipment.My computer monitor sits on my coffee table and my
computer is about fourteen feet away on an end table by doggys
couch.Three big eyes (two tv sets and my computer monitor) staring back
at me.I dont know if a VGA computer cable will work for hooking up to a
radio though,I guess it's worth a try if it doesn't blow up the radio.I
wont be the one to try it first.
cuhulin

Ferrite core : yes it works... Now for the antenna...
 

Thanks to all for the replies...

With the hints received here and elsewhere, I finaly made my firt unun with the
piece of ferrite I found...

I used magnet wire retrieved from an old broken AC/DC adaptor :
- 2 turns for the radio side,
- 8 turns of wire antenna side, making a 4:1 unun.
Currently the unun is just beside the radio (no coax or whatever : just a few
centimeter of wire connected in the radio), grounded via the outer radio/antenna
connector.

And yes it works ! At least connected to the ATS909 : it increases the signal
level by two bars and the sound is clearer. The result is not that obvious with
the SW100, perhaps due to a different antenna connection impedance (anyone knows
the Sony SW100 or AN100 antenna connection impedance ?).

Next step : mounting an inverted L antenna between my house the one of the tree
near-by : connection in the attic, going through the attic length (to have a
longer wire), passing through a tiny hole between the wall and the roof,
reaching the tree at something like 5 meters above the ground, then going down
the tree.

At what heigth should I stop the vertical leg above ground ?

The horizontal leg will around 12 meters (say 8 meters in the attic, 4 meters
outside : I can't go longer in this city environment).

Feeding will be a 75 ohms coax grounded via some house's water pipe : it seems
that the 909 has a 100 ohm antenna connection impedance... so it will be a
better match than 50 ohms (unless I put another 2:1 unun just before the radio
of course).

In radio with my (poor) electronic knowledge, the more fun is building the
antenna stuff... :-)

Oh yes : I need to try the snake-in-the-attic antenna as well...

Charly

Ferrite core : yes it works... Now for the antenna...
 

In article ,
Charly wrote:

Thanks to all for the replies...

With the hints received here and elsewhere, I finaly made my firt
unun with the piece of ferrite I found...

I used magnet wire retrieved from an old broken AC/DC adaptor : - 2
turns for the radio side, - 8 turns of wire antenna side, making a
4:1 unun. Currently the unun is just beside the radio (no coax or
whatever : just a few centimeter of wire connected in the radio),
grounded via the outer radio/antenna connector.

And yes it works ! At least connected to the ATS909 : it increases
the signal level by two bars and the sound is clearer. The result is
not that obvious with the SW100, perhaps due to a different antenna
connection impedance (anyone knows the Sony SW100 or AN100 antenna
connection impedance ?).

Next step : mounting an inverted L antenna between my house the one
of the tree near-by : connection in the attic, going through the
attic length (to have a longer wire), passing through a tiny hole
between the wall and the roof, reaching the tree at something like 5
meters above the ground, then going down the tree.

At what heigth should I stop the vertical leg above ground ?

The horizontal leg will around 12 meters (say 8 meters in the attic,
4 meters outside : I can't go longer in this city environment).

Feeding will be a 75 ohms coax grounded via some house's water pipe :
it seems that the 909 has a 100 ohm antenna connection impedance...
so it will be a better match than 50 ohms (unless I put another 2:1
unun just before the radio of course).

In radio with my (poor) electronic knowledge, the more fun is
building the antenna stuff... :-)

Oh yes : I need to try the snake-in-the-attic antenna as well...

The impedance ratio of your transformer is 50 ohms to 800 ohms.

p= primary
s=secondary

Turns p/Turns s = the square root of (impedance p / impedance s)
so
2/8= square root(50/s)
800 = s

The turns ratio is 1:4 and the impedance ratio is 1:16. In other words
the impedance ratio is the square of the turns ratio. This is a little
high and I would go for more like turns ratio 1:3 for impedance ratio
of 1:9, which would be 50 ohms : 450 ohms. For example you could use 3
turns primary and 9 turns secondary.

The sloping wire characteristic impedance will change with the height
above ground so I expect that you would want an impedance number at the
coax/wire junction.

The core will have a frequency range it will work over so test it at
three places. Test it at the lowest, highest and some place in the
middle of the intended frequency range. You may find the response falls
off on the low or the high end. When you do this wind the primary and
secondary apart from each other so you get the core response.

When you are done testing the core range wind them together so the two
windings couple better enhancing whatever coupling the core is
providing for you.

--
Telamon
Ventura, California

Ferrite core : yes it works... Now for the antenna...
 

Good morning Telamon,

Telamon wrote:
The impedance ratio of your transformer is 50 ohms to 800 ohms.

p= primary
s=secondary

Turns p/Turns s = the square root of (impedance p / impedance s)
so
2/8= square root(50/s)
800 = s

The turns ratio is 1:4 and the impedance ratio is 1:16. In other words
the impedance ratio is the square of the turns ratio. This is a little
high and I would go for more like turns ratio 1:3 for impedance ratio
of 1:9, which would be 50 ohms : 450 ohms. For example you could use 3
turns primary and 9 turns secondary.

Thanks for the formula...

The sloping wire characteristic impedance will change with the height
above ground so I expect that you would want an impedance number at the
coax/wire junction.

You mean that the impedance of the core will depend on its altitude ?

The core will have a frequency range it will work over so test it at
three places. Test it at the lowest, highest and some place in the
middle of the intended frequency range. You may find the response falls
off on the low or the high end. When you do this wind the primary and
secondary apart from each other so you get the core response.

When you are done testing the core range wind them together so the two
windings couple better enhancing whatever coupling the core is
providing for you.

Thanks, I will try that...

Charly

Ferrite core : yes it works... Now for the antenna...
 

Telamon wrote:
[...]
The turns ratio is 1:4 and the impedance ratio is 1:16. In other words
the impedance ratio is the square of the turns ratio. This is a little
high and I would go for more like turns ratio 1:3 for impedance ratio
of 1:9, which would be 50 ohms : 450 ohms. For example you could use 3
turns primary and 9 turns secondary.
[...]

Another question please... Will a 2 / 6 turns balun behave the same as a 3 / 9
turns balun ?

I suspect not, but what will be the difference ?

Thanks again for teaching a newbie...

Charly

Ferrite core : yes it works... Now for the antenna...
 

In article ,
Charly wrote:

Good morning Telamon,

Telamon wrote:
The impedance ratio of your transformer is 50 ohms to 800 ohms.

p= primary
s=secondary

Turns p/Turns s = the square root of (impedance p / impedance s)
so
2/8= square root(50/s)
800 = s

The turns ratio is 1:4 and the impedance ratio is 1:16. In other words
the impedance ratio is the square of the turns ratio. This is a little
high and I would go for more like turns ratio 1:3 for impedance ratio
of 1:9, which would be 50 ohms : 450 ohms. For example you could use 3
turns primary and 9 turns secondary.

Thanks for the formula...

The sloping wire characteristic impedance will change with the height
above ground so I expect that you would want an impedance number at the
coax/wire junction.

You mean that the impedance of the core will depend on its altitude ?

Snip

The impedance of the wire will change with its height above ground. You
are trying to transform that impedance to that of the coax.

Basically the higher the wire the higher the impedance. Smaller diameter
wire for the same height will be higher in impedance.

--
Telamon
Ventura, California

Ferrite core : yes it works... Now for the antenna...
 

In article ,
Charly wrote:

Telamon wrote:
[...] The turns ratio is 1:4 and the impedance ratio is 1:16. In
other words the impedance ratio is the square of the turns ratio.
This is a little high and I would go for more like turns ratio 1:3
for impedance ratio of 1:9, which would be 50 ohms : 450 ohms. For
example you could use 3 turns primary and 9 turns secondary.
[...]

Another question please... Will a 2 / 6 turns balun behave the same
as a 3 / 9 turns balun ?

I suspect not, but what will be the difference ?

Snip

In a voltage type transformer the impedance and resulting
voltage/current changes are based on the ratio of the windings. The core
and number of turns in the windings change the inductance of the primary
and secondary windings and the mutual inductance between them.

You are trying to make an RF voltage type so generally shorter windings
are better so go with the minimum turns to get the ratio you want.

2/6 and 3/9 are both 1:3 winding ratio so the impedance transformation
is the same. The impedance conversion is 1:9 so 50 ohms : 450 ohms.

The mutual inductance between the windings will be greater with the 3/9.

--
Telamon
Ventura, California

Ferrite core : yes it works... Now for the antenna...
 

Thanks again Telamon for your time...

I will take your advices in account.

Charly

Ferrite core : yes it works... Now for the antenna...
 

Telamon -

Can you please explain mutual inductance? Is that like coupling
coeficcient sp?

If we short one winding out and measure the other winding's inductance
then we will have a measure of the coupling between the two coils. The
lower the inductance measured then the lower the stray inductance - or
supposedly the better the coupling. With fewer turns then I think
maybe the lower the stray leakage we will measure.

Am I on the right track?

I think the balun design can use the very small cores as long as we
dont want to transmit. Correct? I am thinking that since the voltage
we will see across the coil In receive mode is microvolts then we don't
have to worry too much about wasting power magnitizing the core. So
then use only a very small number of turns.

I have to build a balun too for a T2FD I am putting in the attic. I
have Doug DeMaw's ferrite design book that I will open tonight when I
get home.

Not so many good places to find info on receive baluns on www.

regards,
Bob
N9NEO

Ferrite core : yes it works... Now for the antenna...
 

In article . com,
"N9NEO" wrote:

Telamon -

Can you please explain mutual inductance? Is that like coupling
coeficcient sp?

Yes. Here is an interesting physics experiment with explanation.
http://www.allaboutcircuits.com/vol_1/chpt_14/6.html

If we short one winding out and measure the other winding's inductance
then we will have a measure of the coupling between the two coils.

The problem with this is if you short either coil the other will also be
shorted. The transformer through the mutual inductance coupling between
them effects an impedance transfer dependent on the turns ratio. You
short one coil and guess what? The 0 ohm short is coupled to the other
coil. If you have the equipment you can measure the self inductance of
one coil and watch that value drop when you short the ends of the other
coil together. Better coupling will result in a bigger change in
inductance.

The lower the inductance measured then the lower the stray inductance
- or supposedly the better the coupling. With fewer turns then I
think maybe the lower the stray leakage we will measure.

Am I on the right track?

The idea here is high mutual inductance or coupling between the coils
and have the self inductance of each coil approximate the impedance of
the wire on one coil and the value of coax on the other.

Also you want the path through the windings to be an electrically short
path so the UNUN will work on the high frequency end.

I think the balun design can use the very small cores as long as we
dont want to transmit. Correct? I am thinking that since the voltage
we will see across the coil In receive mode is microvolts then we don't
have to worry too much about wasting power magnitizing the core. So
then use only a very small number of turns.

I have to build a balun too for a T2FD I am putting in the attic. I
have Doug DeMaw's ferrite design book that I will open tonight when I
get home.

Not so many good places to find info on receive baluns on www.

There is stuff around on the net but a good book is better bet.

BALUN and UNUN design can get a little complicated when you want broad
bandwidth. If you have a book with a proven design worked out for an
antenna that is a great way to hack a BALUN or UNUN.

The thread started out with you grabbing what was on hand and just
following a few rules will get an UNUN working pretty close to optimal
with just the stuff on hand on at least part of the SW spectrum.

With the unknown core on hand the hack would be the minimum or nearly
minimum number of turns in both primary and secondary windings to get
the impedance ratio you need to get.

The winding technique changes the performance character of the
transformer.

If you wind primary and secondary apart from each other you will cause
all or nearly all the flux linkage to go through the core. The
consequence of this is the cores have an efficient frequency range and
chances are it will not work so well through the entire SW band range
of 3 to 30 MHz.

If you wind them together then the two coils couple to each other
directly in addition to the common flux linkage generated in the core.
If the core response is good on the low end and drops off on the high
end the close coil to coil coupling will help on the high end as an
example.

--
Telamon
Ventura, California

Ferrite core : yes it works... Now for the antenna...
 

I wonder if magnet wire is a good idea? Generally magnet wire is
designed to get the turns as close as possible. I'm not sure that is
best for high frequency use since you want to minimize stray
capacitance.

Charly wrote:
Thanks to all for the replies...

With the hints received here and elsewhere, I finaly made my firt unun with the
piece of ferrite I found...

I used magnet wire retrieved from an old broken AC/DC adaptor :
- 2 turns for the radio side,
- 8 turns of wire antenna side, making a 4:1 unun.
Currently the unun is just beside the radio (no coax or whatever : just a few
centimeter of wire connected in the radio), grounded via the outer radio/antenna
connector.

And yes it works ! At least connected to the ATS909 : it increases the signal
level by two bars and the sound is clearer. The result is not that obvious with
the SW100, perhaps due to a different antenna connection impedance (anyone knows
the Sony SW100 or AN100 antenna connection impedance ?).

Next step : mounting an inverted L antenna between my house the one of the tree
near-by : connection in the attic, going through the attic length (to have a
longer wire), passing through a tiny hole between the wall and the roof,
reaching the tree at something like 5 meters above the ground, then going down
the tree.

At what heigth should I stop the vertical leg above ground ?

The horizontal leg will around 12 meters (say 8 meters in the attic, 4 meters
outside : I can't go longer in this city environment).

Feeding will be a 75 ohms coax grounded via some house's water pipe : it seems
that the 909 has a 100 ohm antenna connection impedance... so it will be a
better match than 50 ohms (unless I put another 2:1 unun just before the radio
of course).

In radio with my (poor) electronic knowledge, the more fun is building the
antenna stuff... :-)

Oh yes : I need to try the snake-in-the-attic antenna as well...

Charly