FM stereo to mono (Si4712)

[Amper]

Hi!

For my 10GHz transmitter Project i need a 81.5MHz reference signal and since this frequency is in the range of the Si4712 fm transmitter chip i decided to give it a go. It generates a nice signal wich then is upconverted to 10G (x128).

Sadly since it is a stereo transmitter the L&R channels then seperate out to 2*19kHz*128= 5MHz wich is far to much for the pll to run after and also far to much for the sdr to demodulate after coming from the lnb.

Is there any way of getting rid of those signals? At 19kHz i cant just use a band pass and i doubt i can turn the chip to mono somehow.

Is there some other simple way of generating the frequency i need without building an entirely new pll FM transmitter?

cheers

[radiolistener]

I think you cannot do it with stereo fm modulator.

If you're need oscillator for 81.5 MHz, you can use Si5351. It allows to program any frequency from 4 kHz to 200 MHz.

https://www.aliexpress.com/item/1Pcs-DC-3V-5V-5351-Si5351A-Si5351-I2C-Clock-Generator-Breakout-Board-Module-Signal-Generator-Clock/32972854971.html

[OwO]

You can disable stereo by setting the TX_COMPONENT_ENABLE register.

http://web.engr.oregonstate.edu/~traylor/ece473/data_sheets/AN332.pdf

[Amper]

Thank you very much! I have missed this one in the datasheet...

I will update when i have tried (probably in the next few hours or so)

[Amper]

Yep, it worked, though its necessary to also disable carrier:

Sadly the 10ghz is still roughly 3MHz wide and i dont know why. Ill now try building a low pass behind my output amp, we will see...