Wireless Intercom

[crivoli]

I have built an intercom off of the simple 200 GAIN design specified on the datasheet of the LM386 IC.

http://cache.national.com/ds/LM/LM386.pdf

I have thoughts of trying to get this to be a wireless intercom.
This would be for only one microphone to one speaker.

I am not sure where to proceed from here. I have read that I would need a RF transmitter, but I am not too familiar with all of this.

Does anyone know of any tutorials that would be good to read, or any simple circuits I could look at that could explain how to make this wireless.

Thanks
-newbie

[audioguru]

You could make an illegal radio station with a radio transmitter and a radio receiver. It might not be illegal in your country if you choose an approved frequency and a low transmitting power. The approved frequency might be crowded with other transmitters.The low power would limit its range.

You could make a transmitter and receiver that uses infrared energy, but its range is pretty short, like a TV remote control. Some wireless stereo headphones use this method.

Look in Google for FM transmitter. There are many circuits for low power ones.

[crivoli]

Thanks audioguru.

I will look up something like "low power RF transmitter". I believe I saw a schematic for this here:  http://www.uoguelph.ca/~antoon/circ/rft1.htm

Then I would need a reciever on the speaker end correct?

How do I set the frequency given off by the transmitter and set the receiver to receive that same one?

Thanks again

[audioguru]

That transmitter is too simple. It doesn't have an input for audio to modulate it. It just transmits "silence".
It is used to turn on and off a signal strength circuit that is connected to a radio receiver.
The coil and capacitor's values determines its RF frequency.

That site has many FM transmitters.

[crivoli]

Thanks again audioguru....

One more question.... what exactly is the difference between a FM transmitter and a RF transmitter? Would either work for this project, and would one be a better choice than the other?

Thanks

[SM2GXN]

Hi crivoli!

RF stands for radio requency, FM transmitter is a RF transmitter cause it transmitts RF.
A transmitter use RF (usually called carrier) to carry information to the receiver , the carrier can be modulated in many different ways one of them is FM and also the most common used.
Carrier without any type of modulation does not contain any information I.e speech or music.

[crivoli]

Ok, I have the intercom system working!

I just want to seperate the microphone to one part of the house and leave the speaker on the other side of the house.

What is the most simple way to acheive this?

Please help.  Thanks

[SM2GXN]

Hi crivoli!

Have a look at this link there is some good info on different intercom systems:
http://www.epanorama.net/links/intercom.html

[crivoli]

SM2GXN

Thanks for the link, but I have been there many times and the only info on Wireless intercoms ends with a broken link that doesnt work.

I guess I just need to build a FM transmitter and receiver to get this to work.

I was told there are IC's that already handle this. Is this a better way to go?

Thanks

[SM2GXN]

Yes you can build a small FM receiver out of an IC as you mentioned and a simple FM modulated transmitter with only a few components, both subjects has been discussed on this forum but I don't remember exact name of the thread,you can also visit the project section and RF circuits where you can find both transmitter and receiver circuits that might fit your needs, I hope you find what you are searching for.