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I'm planning on building a FM transmitter and receiver circuit for an electronics project. I was just wondering if these two circuits would work together. Also would they be suitable for transmitting and receiving audio?

The transmitter circuit uses the ba1404 chip, link to circuit info here: http://www.circuitstoday.com/stereo-fm-transmitter-using-ba1404

The receiver circuit can be found here: http://circuits-projects.blogspot.co.uk/2014/07/simple-and-mini-fm-receiver.html

Any other advice would gratefull

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The BA1404 does transmit audio, in stereo.

Whether they are suitable for use together depends on the frequency you use; on whether the receiver circuit will handle the +/-75kHz modulation that the BA1404 will do to the carrier; whether it uses the same time constant for de-emphasis that the transmitter uses for pre-emphasis; whether has a stereo decoder; and of course on whether they are located close enough together for the power of the transmitter to excite the sensitivity of the receiver.

NB The link is incorrect in saying that C13/14 are part of the pre-emphasis circuit. They aren't. It is a simple RC high-pass formed by R6/C15 and R7/C16 respectively. These values will give you 50uS pre-emphasis.

As the receiver is built for 88-108MHz I think it is safe to assume it will handle the modulation, but I don't see any stereo decoder in the receiver circuit. So the answer is 'no' unless you arrange to broadcast in mono, by killing the 19kHz pilot tone in the transmitter, or append a suitable decoder, e.g. the one at http://www.fmmpx.com, which I've built many times for modernising several brands and models of FM tuner.

I would add that the receiver looks pretty basic. I would expect high distortion and poor stereo if any. There are better circuits around. Indeed you don't even need one: just use an old FM tuner. This one talks about component numbers in the text but doesn't show them in the schematic, which isn't too encouraging.

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  • \$\begingroup\$ Could you recommend a receiver circuit to use with the ba1404 circuit? \$\endgroup\$ – Darth Vader Sep 8 '14 at 15:32
  • \$\begingroup\$ Well, what are your requirements? Audio? Stereo? How much bandwidth? How much distortion? How much dynamic range? How sensitive? How selective? \$\endgroup\$ – user207421 Sep 8 '14 at 22:14
  • \$\begingroup\$ Audio, far amount of bandwith, not much distortion, a reciever circuit that is going to pick up audio transmitted by the ba1404 and output audio clearly to headphones. Also how good is the range with the ba1404 circuit? \$\endgroup\$ – Darth Vader Sep 9 '14 at 16:59
  • \$\begingroup\$ That circuit has very low output. It's usual to run it into a FET to amplify the final output to a milliwatt or so. Beware of the FCC regulations on this. Do you have to design it yourself? You can build both items from kits for about $100 from ramseyelectronics.com. \$\endgroup\$ – user207421 Sep 10 '14 at 2:15
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    \$\begingroup\$ Hang on. FM transmits over the air by frequency-modulating a VHF carrier. Bluetooth is a completely different kettle of fish. The BA1401 circuit is OK as is. So is the other one for homework. Just disable the 38kHz oscillator in the transmitter and site them pretty close together with suitable aerials. A normal 4 foot whip will do in both cases. \$\endgroup\$ – user207421 Sep 12 '14 at 1:17

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