All,

I am trying to measure impedance through a balun, or more accurately a 1:1 in
line "transformer". For test purposes the transformer is two windings of 10
turns each on a toroid. The winding are tightly wound on opposite sides. The
material is #43, the toroid is 3/4 inch OD.

If I drive one side of the transformer with one milliwatt at 4 MHz and terminate
the other side into 50 Ohms, and then measure the input voltage and the output
voltage. The output voltage significantly less then the input voltage, about 1/3.

The second measurement that does not support my understanding is: If I connect
the transformer up to an 8450A through appropriate couplers, and then short the
output the 8405A does not show a 180 degree phase shift between 'open' and
'shorted'. If this measurement is made without the transformer then the results
are as expected.

This is obviously something with the transformer. I would like to construct a
simple 1:1 in line transformer good from 3 to 30 MHz and 100 watts. What core
size, material, and windings are a good starting point for this?

Thanks - Dan - kb0qil

dansawyeror wrote:
I am trying to measure impedance through a balun, or more accurately a
1:1 in line "transformer". For test purposes the transformer is two
windings of 10 turns each on a toroid. The winding are tightly wound on
opposite sides. The material is #43, the toroid is 3/4 inch OD.

For 4 MHz, I would use #61 material and
bifilar windings.
--
73, Cecil http://www.qsl.net/w5dxp

On Sun, 05 Mar 2006 12:04:46 -0800, dansawyeror
wrote:

All,

I am trying to measure impedance through a balun, or more accurately a 1:1 in
line "transformer". For test purposes the transformer is two windings of 10
turns each on a toroid. The winding are tightly wound on opposite sides. The
material is #43, the toroid is 3/4 inch OD.

The windings should be bifilar, not wound separately.

Dan, I think #43 is powdered iron, which is fine for high Q inductors, but
not very good for broadband transformers. As has been mentioned by others;
a ferrite core with bifilar windings should do it. Check out:
http://www.oselectronics.com/downloa...ansformers.pdf for more
info.

Frank


"dansawyeror" wrote in message
. ..
All,

I am trying to measure impedance through a balun, or more accurately a 1:1
in line "transformer". For test purposes the transformer is two windings
of 10 turns each on a toroid. The winding are tightly wound on opposite
sides. The material is #43, the toroid is 3/4 inch OD.

If I drive one side of the transformer with one milliwatt at 4 MHz and
terminate the other side into 50 Ohms, and then measure the input voltage
and the output voltage. The output voltage significantly less then the
input voltage, about 1/3.

The second measurement that does not support my understanding is: If I
connect the transformer up to an 8450A through appropriate couplers, and
then short the output the 8405A does not show a 180 degree phase shift
between 'open' and 'shorted'. If this measurement is made without the
transformer then the results are as expected.

This is obviously something with the transformer. I would like to
construct a simple 1:1 in line transformer good from 3 to 30 MHz and 100
watts. What core size, material, and windings are a good starting point
for this?

Thanks - Dan - kb0qil

On Sun, 05 Mar 2006 22:31:05 GMT, "Frank"
wrote:

Dan, I think #43 is powdered iron, which is fine for high Q inductors, but

Type 43 is a nickel zinc ferrite. Spec sheets indicate it is
principally a suppression material, but usable for broadband
transformers up to 10MHz.

Bifilar winding, and possibly better material are probably the key to
improving the transformer, or alternatively making a common mode
choke.

Owen

--

Wow! It is really great when something simple works. Yes, 6 bifilar windings
work really great. Even better the impedance measurements worked as expected.

Now I need to design 2:1 and 4:1 impedance matching transformers for 500 watts.
Those are in anticipation of successfully resolving the ground of the antenna
system.

Thanks - Dan

Frank wrote:
Dan, I think #43 is powdered iron, which is fine for high Q inductors, but
not very good for broadband transformers. As has been mentioned by others;
a ferrite core with bifilar windings should do it. Check out:
http://www.oselectronics.com/downloa...ansformers.pdf for more
info.

Frank


"dansawyeror" wrote in message
. ..

All,

I am trying to measure impedance through a balun, or more accurately a 1:1
in line "transformer". For test purposes the transformer is two windings
of 10 turns each on a toroid. The winding are tightly wound on opposite
sides. The material is #43, the toroid is 3/4 inch OD.

If I drive one side of the transformer with one milliwatt at 4 MHz and
terminate the other side into 50 Ohms, and then measure the input voltage
and the output voltage. The output voltage significantly less then the
input voltage, about 1/3.

The second measurement that does not support my understanding is: If I
connect the transformer up to an 8450A through appropriate couplers, and
then short the output the 8405A does not show a 180 degree phase shift
between 'open' and 'shorted'. If this measurement is made without the
transformer then the results are as expected.

This is obviously something with the transformer. I would like to
construct a simple 1:1 in line transformer good from 3 to 30 MHz and 100
watts. What core size, material, and windings are a good starting point
for this?

Thanks - Dan - kb0qil