quadrature coil fm

Anyone know where to get it? I found some from TOKO but i could not understand its specification. There are two types: 10.7 MHz coil with and without internal capacitor. and many models how can i choose it? Also, the internal capacitor version has a turn ration, I dont know why? I will use the quad coil for a philip FM receiver IC. In it appication note, there use 455KHz for IF but i want to use 10.7 MHz. Thank you.


http://www.toko.com/passives/inducto...ls/7phigh.html

http://hem.passagen.se/communication/quadcoil.html

You can use one of the Toko inductors that have 47pF internal, in the configuration shown in the link above.

The turns ratio doesn?t matter in this case because you are using only the coil of the resonant LC circuit.

Thank vfone, I also see in the philip data sheet and application note that there is a resistor in pararell. What is the use of that resistor?

The reason of that resistor is to lower the Q of the LC circuit, to improve the linearity of the demodulator output. Usually this is used in WFM (Wide FM) system and is not necessarily in a NFM (Narrow FM) FM.