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FM Transmitter?

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Cessna

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Hey guys. First post here.. I was referred here by someone from diystompboxes.com. I like the looks of this site though. I'm currently a junior in college going for electronics business.. predominantly electrical engineering.. so I think I'll stick around.

Anyway, I'm looking to build an FM transmitter for mostly just a one time use. I found this, and like the simplicity, but I need to boost that power output Free Kit Plans - Build your own FM Transmitter. This is going to be used to broadcast music and announcements throughout a parking lot (car show). It will also need to have enough power to go over one 2 story building. If the building was not there and conditions were perfect, I'd say I only need a 1/4 mile radius to work with. But as we know that won't happen, so I'd like to crank this thing up a bit so it's actually useful.

What do you guys think? Is there an easy way I could get this simple circuit to output a further transmission?
 
It is a garbage circuit that I fixed in 4 stages and made my own that worked very well.
1) Its antenna is connected directly to its tuned LC circuit so its radio frequency changes when something moves toward or moves away from its antenna.
2) It does not have a voltage regulator so its radio frequency changes as the battery voltage runs down, and its preamp transistor is saturated with a new battery and is cutoff with a used battery.
3) It does not have pre-emphasis (treble frequencies boost) like all FM radio stations have but instead it has treble frequencies cut so it will sound awfully muffled.
4) It has low power so it might transmit as far as across the street.

The government will not give you a radio station licence for that piece of garbage.
 
FM transmitter

here is the fm TX by AG


and i drew sch and pcb layout using eagle...for the circuit which u posted....
 

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Wow, that does sound like a pretty bad circuit. I hadn't really analyzed it. So AG, the one that you built is the one that was linked to in the post above mine? What kind of range do you think you could get from it? I realize the FCC wouldn't approve, and my apologies if I should not be discussing this. But it is only for a single day use, I don't think it should be a big problem.
 
The range of my FM transmitter is over 2km to my very sensitive home stereo tuner or to my very sensitive car radio with the antennas 80cm long and parallel and over a large river valley so that there is nothing in between. Its range is about 300m to my cheap Sony Walkman portable radio. Its range is across the street to a cheap clock radio or a $1.00 "radio" from the dollar Store.
It has a voltage regulator so its preamp works fine when the battery is new or old, and so that the radio frequency doesn't change as the battery voltage runs down.
It has an RF amplifier for extended range and to isolate the antenna from the tuned LC circuit.
It has pre-emphasis (treble frequencies boost) so that it sounds perfect like a real FM radio station.
A 9V alkaline battery will power it for about 4 hours but the range will keep dropping as the battery runs down.
 
The range of my FM transmitter is over 2km to my very sensitive home stereo tuner or to my very sensitive car radio with the antennas 80cm long and parallel and over a large river valley so that there is nothing in between. Its range is about 300m to my cheap Sony Walkman portable radio. Its range is across the street to a cheap clock radio or a $1.00 "radio" from the dollar Store.
It has a voltage regulator so its preamp works fine when the battery is new or old, and so that the radio frequency doesn't change as the battery voltage runs down.
It has an RF amplifier for extended range and to isolate the antenna from the tuned LC circuit.
It has pre-emphasis (treble frequencies boost) so that it sounds perfect like a real FM radio station.
A 9V alkaline battery will power it for about 4 hours but the range will keep dropping as the battery runs down.

Sounds good! Would you mind if I used your circuit? And it appears the parts are all simple.. probably about $5 right? Might as well at least try it. Would be fun either way. Are the pcb layouts that were linked to only openable with Eagle? I can't open them. Would it be possible to just send a jpeg of the pcb layout?
 
Other people made pcb layouts for my FM transmitter. I didn't try one (mine was made on stripboard) and I don't know if anybody did.
Here is a pcb design that you can see:
 

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Other people made pcb layouts for my FM transmitter. I didn't try one (mine was made on stripboard) and I don't know if anybody did.
Here is a pcb design that you can see:

whoops, very sorry... bad terminology on my end. i don't know how to make pcb's, so vero is actually what i'd prefer, if you do have that as well.
 
to make the circuit on veroboard/strip-board you need to refer circuit by AG its easy to build....and why don't you try to make the pcb


many people have tried FM mod4 ...it works like charm...
 

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Many people have just moded the Belkin tunecast II with good results.
Andy
 
Many people have just moded the Belkin tunecast II with good results.
Andy

It is only one of many FM stereo transmitters made for MP3 to car radios that use an IC made by Rohm. The "Micromitter" project from Silicon Chip magazine is a good example and is a kit in Australia and New Zealand.
They use an RF attenuator at their output to limit their range to avoid interference but the mod removes it.
 
It is only one of many FM stereo transmitters made for MP3 to car radios that use an IC made by Rohm. The "Micromitter" project from Silicon Chip magazine is a good example and is a kit in Australia and New Zealand.
They use an RF attenuator at their output to limit their range to avoid interference but the mod removes it.
Yes lots of info on the net for modding it. With a good antenna it can go miles. Andy
 
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