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Digital data and voice on FM or AM signal

Digital data and voice on FM or AM signal

Digital data and voice on FM or AM signal

Hello, this is my first post and i hope it´s in the right place.

My objective is to transmit voice and data trough standard transmitters, like the ones found in ebay, with power of a few watts. This is to be used in urban environments, so wall penetration is one of the more important aspects.
The data signal can be of a low bitrate(1kbps is enough), and voice doesn´t have to be of high quality and can be mono.

Telephone lines since are designed for human voice transmit up to 4Khz, while AM and FM transmitters since are designed for music should transmit up to 20Khz(human hearing limit).

My plan is to use a microcontroler to encode the binary data as FSK in a frequency maybe around 10Khz, and add it to the voice signal. At the receiver, filters would separate the 2 signals, and another microcontroler would decode the digital data(maybe using a pll chip).

For me the data reliability would be the most important thing. Would prefer the loose voice first, in case of bad reception. The 1kbps rate would allow me to use redundancy/error correction codes.

For building penetration should i go for AM or FM? (AM usually lower frequency-better penetration?)

I´ve also looked in to RDS, but was discouraged by the fact that since it´s an harmonic, power is lower. (I usually loose RDS on car radio in areas of low coverage, first, and keep hearing music- the opposite of what i want...)

Don´t want to burden anyone, but would appreciate suggestions/critics, and to be pointed in the right direction. The details i think i can workout on my own.

Thank You

RE: Digital data and voice on FM or AM signal

You didn't specify a range.

It sounds like a lot of work for something you can do with a pair of throwaway computers and a wireless Ethernet link.


Mike Halloran
Pembroke Pines, FL, USA

RE: Digital data and voice on FM or AM signal

were the issue is more on wall penetration

the idea is to communicate between offices in same building, at least 5 to 10 stories apart, so i want to signal to go trough at least 5 to 10 standard floors(concrete, rebar, etc)
i was hoping to avoid ethernet...

RE: Digital data and voice on FM or AM signal

I'm not aware of too many signals (at least ones the average consumer can afford) that will go through 10 stories worth of rebared concrete pads.  Go around, maybe, but not through...

Dan - Owner

RE: Digital data and voice on FM or AM signal

If you want FLOOR penetration,
don't ask for WALL penetration.

In multistory buildings, floors and walls are very different.



Mike Halloran
Pembroke Pines, FL, USA

RE: Digital data and voice on FM or AM signal

If you want wall/floor penetration, AM would serve you better. I doubt the quality transmitted though, but you did say data reliability is the important thing.

Another would be using FM and adding an antenna to act as repeater in case the signals doesn't reach the higher floors.

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