1:1 Current Balun Testing

[k9fv]

Hello all; first let me say I am having a blast with this new toy ¡V the AIM4170. I would like to ask if I am doing this balun testing correct or should there be some changes. I'm playing with current baluns testing for common mode rejection - this is the Zmag value?

For a 1:1 current mode balun there are 4 main types I'm working (playing?) with and I think all are tested with same method?

1. A simple coil of coax of varying diameters and number of turns depending on freq desired.
2. Coax wrapped around a torrid ferrite (donut shape) with several wraps.
3. Two parallel wires, either insulated or enameled coated wrapped around a torrid ferrite.
4. Coax slipped thru ferrite beads as in the W2DU choke.

I have built a 1:1 balun by wrapping coax around a FT114-43 ferrite, then one end of coax goes to a SO239 connector, other end of coax to two banana plugs with all this mounted in a 2X3" plastic box. The AIM4170 is calibrated with this connected to AIM4170, with OPEN, then CLOSED, then a resistor across banana plug ends. I understand resistor value (50? 200 ohms?) is not important, just enter the value when asked by calibration procedure.

Take the balun under test and peel back a short section of coax shield, then connecting opposite ends (input and output) of coax shield to the banana plugs will allow the common mode resistance (value of Zmag?) to be tested? The parallel wrapped wires would have the two parallel wire ends twisted together and (input and output) ends connected to banana plugs to test.

Is the Zmag the value to watch for determining common mode resistance?

Once I get this figured out, then on to 4:1 balun testing

Thank you to all for good suggestions and advice,

73 de Ken H> K9FV

[dl4raj]

Hi Ken,

the method you describe is a good starting point to see
basically what's going on.
Zmag is the "figure of merit".
BUT,as you have to deal
with (partly) extreme impedances accuracy
may suffer.
A better way is described in
www.audiosystemsgroup.com/RFI-Ham.pdf
page 30 and following.
But for that kind of measurement you would need
the VNA2180 or similar.

73
Clemens

[k9fv]

Thank you for the input Clemens - I have read the RFI-Ham.pdf manual several times and have learned a LOT from it. That is the main source of knowledge for the method I wrote above, but I wanted to be sure I was understanding the process correctly. With all the reading I've done, NO PLACE does it ever say to simply connect to opposite end of shield for this reading. I guess anyone with a grain of knowledge knows that, but someone like me who is still looking for that "first grain" needs all the help he can get

I understand then my process is as "correct" as I can do with the AIM4170? Understanding stray capacitance and other errors abound.

Thank you again.

73 de Ken H> K9FV