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BH1417 Stereo PLL FM Transmitter Circuit

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Full Member level 6
May 16, 2008
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Dear friends,
I need to build a stereo fm transmitter using BH1417 chip. Before starting my design, i have some doubts....

1. Is it the crystal 7.6Mhz or 7.68Mhz...? some of the website shows schematic with 7.68Mhz. is it acceptable...?
2. How to select equivalent varactor diode? Can anybody give me the part number available in digikey or mouser?
3. Equivalent part number for inductor from digikey? Can we use fixed aircore inductor for the same?

Thanks in advance...

Using a 7.68MHz will still work but your channel spacing will be wrong. Out put freq = (Xtal(f)/(19*4))*ch(setting); 100.0 MHz would be (1000)

So, if you use a 7.68 MHz Xtal, when set to 100.0 MHz you will actually be transmitting on 101.052 MHz
Thanks for the reply. So i assume the crystal frequency will not affect the 19khz pilot frequency so still i can get stereo encoded output... the carrier frequency offset is acceptable for me while spending time to get 7.6Mhz crystal...

Is there any solution for varactor diode?

Last edited:
Thank you E-design. Yes 7.6Mhz crystal & BH1417 both are available in mouser. Can you please suggest me a suitable varactor diode & inductor from mouser...:)
It will be very helpful to me.
what is the use of adjustable inductor? Is there any tuning required(i hope no need for tuning because of PLL).

Is it possible to replace the inductor with fixed one? If we can, what will be the value. There is no documents regarding this....

Thanks & regards

An alternative more sophisticated, consider it..
**broken link removed**
An alternative more sophisticated, consider it..
**broken link removed**

Cool. Thank you for the wonderful information. The chip looks great. Only the problem is, it should work with a microcontroller. BH1417 is a standalone device & the TX frequency selection is done by switches. But here we have to use a uC for all the operation. But its totally worth for the very minimum component count.

I have some question...
1. There is no information available regarding the transmission power. so i dont know what is the TX range of the device... Even though the datasheet mentioning it as programmable transmit level, but there is no maximum limit.
2. What is use of receive power scan? (Si4712/13) If it is a transmitter then what is the word means "receive power scan"?


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