bh1417f project

Hi,

Currently i'm trying to build a wideband FM transmitter and reciever for my final year project. Anyone got a circuit diagram? Links?

Thanks in advance.
Alex

What's your desired bandwidth? See circuits based on MC13155 wideband FM receiver. Perhaps something like my old project:

http://lea.hamradio.si/~s56jlp/temph...reless_lan.htm

Thanks for the link rfmw,

actually i'm thinking of pluging in a wideband FM transmitter into my audio CD player and transmit the audio signal to the reciever.


( Does this reciever have to be in wideband, or any reciever circuit will do? )

( Is wideband FM a type of FM modulation? cuase i got confuse when i go through my text books)

Alex

Added after 19 minutes:


I found the FM transmiter circuit in the link below. I'm planning to use the 1W transmitter. But there's no reciever circuit here in this link.

http://www.pira.cz/eng/index.htm

But i'm not sure weather it's suitable for my audio ( the signal should be in CD quality ) project.

Alex

If you want to build one yourself, you should use something like a ROHM BH1417F to modulate the FM waveform. It is actually quite complex to get stereo (there are a lot of audio filtering requirements and an extra sideband).

If you want to buy the modulator, then just get one of those things they use for Ipods to transmit to an FM radio.

Realize that your CD signal, sent wirelessly to a standard FM broadcast band receiver will sound like garbage, due to the reduced bandwidth and limited dynamic range.

You can use any amplifier to boost the signal as high as you want, but in each country you need to research how much power you are legally allowed to transmit. For instance, in the USA, FCC regulations Part 15 will limit you to a much lower level than 1 watt.

thanks biff,

in that case, i think i'll build my reciever using philips's TEA 5711, i can find the circuit diagram on the datasheet itself. And i'll build the transmitter using ROHM's BH1417F for FM transmission.

(besides rohm's BH1417F, is there any other ICs?)

Actually, i'm doing this for my final year project, you think this configuration will work?
and, is there anything that i can add in?

Thanks again in advance
Alex

ROHM is the one usually put into commercial products. They have several versions. The serial input one covers the whole band. The parallel input versions cover part of the band.

This explains what you are trying to do:

http://members.tripod.com/~transmitters/stereo.htm

As I recall, the rohm chip suffers from inadequate lowpass filtering and limited dynamic range. If you want to make a cool project, ad an additional 15 KHz lowpass active filter to both audio input channels (will improve stereo crosstalk) and you can ad some sort of clipping/limiter circuit so that you will not have distortion due to overdrive from a CD. Too much drive and the FM modulation spreads out too far, and the receiver does not know what to make of it!

biff,

Ya, i think that's what i wanna do. But from the link i can't find any circuits for MPX coder and decoder circuits.

The limiter and the lowpass filter seem to be cool, and i was thinking to add some pre-amp, signal compressing (Tx) and expanding (Rx). You think it'll work?

Please advise...

Thanks
Alex

You surelly noticed that both chips you selected allready has coder and decoder build in.
I attached a schematics of a MPX coder just for info.

hi again

I found something quite promising, check this link.

http://renaud.cerrato.free.fr/VERONICA.html
http://renaud.cerrato.free.fr/STEREO.html


Just another question, i don't think this 1W FM Tx got any steoreo coder inside, do you think the coder can be cascaded with the Tx?

Assuming this is the case, all i need is a Rx with a decoder. Please correct me if I'm wrong.

Thanks again.
Alex

Added after 2 minutes:

Thanks Borber,

it really helps

Alex

Veronica transmitter has no MPX coder. This is an old kit and not so elegant. You can find simpler circuits with better parameters. Just to get ideas:
http://www.freddospage.nl/
MPX coder is in modulation signal chain and is connected to transmitter at modulation input.