I must confess.. I'm trying to make a little FM transmitter. Just transmits beeps on the FM broadcast band 88-108Mhz FM.

There are a gazillion circuits out there.. all with varying degrees of success it seems.

I have a few questions.. things I'd like to understand..;

• is it just not possible to create any decent power output with a supply voltage of 5Vdc..? Seems to me you have to go to 12V, but I'm not sure why.
• Power output needs to be significant.. not huge, but not as tight as the 'iPod' wireless transmiters are. The area around my place is just swamped with radio stations on pretty much EVERY frequency

if anyone has a little simple circuit that they know works.. please post it here, or a link to it

Ian, have you figured this one out? ...I am very interested in designing little FM radio tranceivers for communication between robots. I have seen some inexpensive little modules for sale, but I'd like to understand the theory and design my own! ...I'm also interested in using these transceivers as beacons for triangulation purposes for robot positioning / navigation.

Here in America, we have to design our RF circuits to comply with Part 15 of the FCC rules. Does Australia have any kind of regulatory body like America's FCC?

Also, I know that it must be possible and relatively inexpensive to design RF transmitter circuits on 5-9 VDC because I see cheap toys like Walkie-Talkies and RC cars at stores for $10 all the time! ...And generally, I believe the RF toys here in America have either 27 MHz or 49 MHz crystal oscillators, for what it's worth.

If you figure this one out, please let me know too!

Thanks!
Aaron

I have built several FM bugs and get about 400 meters range out of them.

I have some designs but need you to wind your own coils, so it will require some enamel wire 0.63mm and 0.53mm.

The next problem is the designs are in a magazine and are not easy to follow.
The overall board is about 15mm x 50mm (size of AA battery) and i run it off 2x AA battery.

Im not sure how you would generate the bips you require as most of these have mic's on them.

There is a design called the Cricket for a fox hunt transmitter that chirps like a cricket.

There is another design for a water detector and will transmit up to 1 Km, it produces 3 different tones depending on water level it is monitoring.

I will find the mag and see if i can copy the pages of interest, if you are interested.

Pete.

I done a google search for the magazine and found this site by the same author.

http://talkingelectronics.com/FreeProje ... acker.html

There is several other bug designs listed the same as the magazine i have but not the ones i think are the better stronger designs.

This is the Mag i have but mine costed $3.50 from Dick Smiths a few years back, i did see an Australian dealer for them on the net.

http://www.talkingelectronics.com/shop/ ... rrencyId=1

There is several other designs listed free to download and you will need to search for them.

Talking Electronics is the producer of this.

Pete.