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Hybrid FM Stereo Encoder for FM Transmitters
Hybrid FM Stereo Encoder for FM Transmitters
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Old 27th August 2012, 06:08 AM   #11
syamkumar is offline syamkumar  India
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Join Date: Aug 2012
Location: Trivandrum, Kerala State
Default Hybrid FM Stereo Encoder for FM Transmitters

I designed an FM Quadraphonic Coder. The circuit diagram of its timing section is attached.
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File Type: pdf FM Quadraphonic Encoder.pdf (42.7 KB, 88 views)
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Old 21st January 2013, 09:38 PM   #12
pipolanar is offline pipolanar
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Join Date: Jan 2013
Originally Posted by syamkumar View Post
Hi Friends,
I am going to make a Hybrid 256x oversampled FM Stereo Encoder. I know only basic idea of FM stereo multiplexing (like 2x, 8x oversampled circuit) also I read in an article circuits like DAC, Sine LUT ROM etc can be used for higher sampled MPX system. But I don't know how to implement the circuit and where to begin.Please help me. I expect good design ideas and circuits. Sorry for my poor English. Have a nice day
Hi Syamkumar, this is a 1KHz tone in a 16x oversampling coder i am working:

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Old 25th January 2013, 08:00 PM   #13
Mad Yank is offline Mad Yank  United States
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Join Date: Jan 2013
Does anyone have a circuit of a MONO FM Transmitter that can be plugged into the USB port of a computer?
In this way it would receive 5 VDC for power and be able to receive audio from the computer.

All the best for 2013 ! Mad Yank
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Old 25th January 2013, 08:09 PM   #14
DF96 is offline DF96  England
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Join Date: May 2007
This thread is about stereo encoding.
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Old 14th January 2017, 05:17 PM   #15
rsavas is offline rsavas  Canada
diyAudio Member
Join Date: Aug 2012
Location: Ontario
Hello folks,

Adding to an old thread instead of making a new one.

I want to build a FM stereo encoder for my RF sig generators, HP 8656B and HP 11715A.
Of course one option is to spend more money and buy yet another RF SG like a ST1000A or Panasonic unit but I want to take the cheaper route and build my own just for the fun of it.
I have copied this design.
How to build an fm-stereo generator.
I have verified that the hex file is good with my MPLab s/w and ICD3 programmer. At this time I did not buy the source code.
Of course I could have paid for the layout files, but I am not sure if they are proper gerber/cnc data or just pdf of the layers. I do not want to pay and find out it is a pdf and I have to etch my own pcb, which is a PITA. Also the size would result in a much more expensive pcb, so did it myself will reduce my costs a fair bit.
So far I have taken this design and done up a small layout(100x100mm) and plan to get it made at pcbway for $10 for 10 deal, which is hard to beat. Since I did the design in smt, I have a fair bit of pcb area left for other circuitry.
I will add an additional composite driver,based on user OS pitchfork headphone amp that I have simulated using ltspice. It offers the performance that I need, so it can drive the 50 ohm input Z of the low THD 11715A AM/FM test source.

I was wondering if anyone has suggestions to add more features?
1) I still need to add the regulators on board, but they do not take up much room.
One thing I should probably add is a couple of low THD oscillators for the left/right channels, instead of having to use external oscillators. I could copy the ST1000A oscillators but their maybe better ckts to use, any suggestions?
I have attached the schematics and pcb placement so far.

Attached Files
File Type: pdf FM STEREO GEN_DDS-6.pdf (52.8 KB, 14 views)
File Type: pdf SCHEMATIC1 _ FM Stereo Gen(DDS).pdf (37.5 KB, 11 views)
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Old 14th April 2017, 08:01 PM   #16
Jlhbd is offline Jlhbd
diyAudio Member
Join Date: Apr 2017
Smile Fm stereo encoder

For those looking at a 256khz oversampled stereo encoder, see the project at radiospurs.uk web site. The design presented is dated around the year 2000 so some of the components used are end of life. Feel free to use the same design principles with newer vesions. I would suggest the Analog Sharc series 5 or the slightly older series 4 as a replacement for the series 2 given
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