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design of muliplex FM transmitter

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fvm

Member
hi
well im new to communication. i need to design this ciruit but didnt know where to begin.
i was able to find multiple circuit on the net but unable to configure major block required for the FM transmitter. In short a block diagram of each portion of the circuit.
your help will be greatly appreciated
regardz
 

canadaelk

Active Member
Your description is rather vague. Do you need to multiplex the input or the output of the transmitter?

I suggest you do overall a block-diagram to show us what you needs to do. E
 

KeepItSimpleStupid

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FM MPX is a way of describing the way a stereo FM signal is created and decoded. The L+R signal is transmitted using FM modulation and the L-R signal is transmitted on a sub-carrier. Each station can contain other sub carriers as well. That was where commercial free Musak was generated from. It was a paid FM service.
 

KeepItSimpleStupid

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fvm

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is it possible to give the signal of 38Khz from function generator to chk the working of circuit for the time been the crystal is not arranged??
 

KeepItSimpleStupid

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You can see a description of the FM signal here: http://en.wikipedia.org/wiki/FM_stereo#Stereo_FM

L is short for LEFT channel and R is short for RIGHT channel. The FM Signal is broadcast in mono and the subcarrier (38 Khz) carries the L-R information. The 19 Khz pilot tone allows the detection of the stereo broadcast and regneration of the 38 Khz Carrier which is 2x19 KHz.

Adding and subtracting the two equations L+R and L-R yields 2L and 2R meaning 2x the amplitude.
 

fvm

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L and R are identical signls of signal audio signal or they transfer different information??
and what sort of information???
 

audioguru

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The BA1404 IC made by Rohm has been obsolete for about 10 years but some cheap kits still use it. It had horrible performance.
It was replaced by the BH151x range of FM stereo transmitter ICs also made by Rohm that had wonderful performance and were used in many MP3 to car radio products. I think they are also obsolete today.

You need to learn what stereo sounds like. It is much better than mono.
 

KeepItSimpleStupid

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LEFT and RIGHT is part of "STEREO" sound. When the audio is mastered, the sound engineer masters the instruments so that they can appear to be coming from either speaker. Bass or low frequencies are usually equally recorded on the LEFT and RIGHT.

Some advanced methods used for recording are described here: http://en.wikipedia.org/wiki/Dolby_Digital

I only set up a surround sound system once: e.g. 5-channel surround (left, center, right, left surround, right surround)

This type of system consists of 2 front left and right speakers, a center channel speaker and two rear left and right speakers. You get a surround-like effect, say if their was a train whistle, the sound could be made to sound coming or going away from you or even circle you. Placement of the speakers is somewhat critical for good sound.
 

audioguru

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Stereo produces sounds that are left, right and anywhere in between.
Good stereo sounds the same as live music. Then mono sounds dead.
 

Menticol

Active Member
and one more question what exactly are L R audio signalz??
You can see a description of the FM signal here: http://en.wikipedia.org/wiki/FM_stereo#Stereo_FM

L is short for LEFT channel and R is short for RIGHT channel. The FM Signal is broadcast in mono and the subcarrier (38 Khz) carries the L-R information. The 19 Khz pilot tone allows the detection of the stereo broadcast and regneration of the 38 Khz Carrier which is 2x19 KHz.

Adding and subtracting the two equations L+R and L-R yields 2L and 2R meaning 2x the amplitude.
KISS patience is made of steel! kudos for that :)
 
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