twisted pair transmission line
Hi,
One of the best infos on your problem is a book from Jerry Sevick:
Transmission Line Transformers, published by ARRL (
www.arrl.org).
ISBN: 0-87259-296-0 but there are newer editions already then this 2nd Edition. See also Noble Publishing.
If you cannot get it from local ham/amateur radio experimenters or friends in your country, then try to turn to any public library and use their inter-library service. This way you may have it in 2-3 weeks's time in your hand.
See also Motorola AN749 app note (**broken link removed**) where on its last page there is a good Reference nr 8 to an IEEE article from 1971. Here I also recommend the library service.
In the meantime I recommend to borrow/obtain a good inductance meter in the some ten/hundred nanoHenry range and a good capacitance meter in the some ten/hundred picoFarad range.
This way you could check your own hand made bifilar wire twists from enameled Cu wires as follows:
1)make at least half a meter long twist from two enameled Cu wires, try to keep uniform twists for a unit-length. Rule of thumb here is that the higher the number of twists, the lower the trl impedance becomes for a given wire diameter. Also, the bigger wire diameter you use (practicality), the lower the trl impedance becomes.
2)measure the capacitance at one end of the wire-pair (leave the other end open!)
3)measure the inductance at one end of the wire-pair (short-circuit the other end!)
4)calculate the impedance by dividing the measured L value with the measured C value and extract the square root of the division. Be careful with turning the nanohenries and picofarads into Henries and Farads to get Ohm for the impedance.
I hope these are of help
rgds,
unkarc