need of simple fm (with music) transmitter

[ece_s2dent]

hi guys..
can u please help me on this one...
its a project of mine,
im a newbie in electronics so a simple design but usefull
can be a jumpstart for,,
thanks a lot!!!

 

[chilinski]

I'm old at most stuff but pretty new at electronics stuff. I wanted to be able to hear my XM at the barn and didn't want to have to haul it there every time I went out there. And there was a radio there anyway. So I got the inexpensive kit from Ramsey Electronics. Being new to building this kind of stuff (although when I was a teenager, I had a kit for building tube radios), it was nice to have the printed board, all the parts and step by step instructions. It worked the first time I plugged it in and does a nice job of transmitting the XM radio from the house to the barn a few hundred feet away.

Success building that has increased my interest in learning more and in doing more projects that I really want to do...a headphone amp for my motorcycle, etc. Having success building something you will really use is important to keeping your interest and in promoting the learning process. So I have no problem doing the kit, even though I'm sure people here will tell you there are much better circuits and components, etc.

 

[ece_s2dent]

I'm old at most stuff but pretty new at electronics stuff. I wanted to be able to hear my XM at the barn and didn't want to have to haul it there every time I went out there. And there was a radio there anyway. So I got the inexpensive kit from Ramsey Electronics. Being new to building this kind of stuff (although when I was a teenager, I had a kit for building tube radios), it was nice to have the printed board, all the parts and step by step instructions. It worked the first time I plugged it in and does a nice job of transmitting the XM radio from the house to the barn a few hundred feet away.

Success building that has increased my interest in learning more and in doing more projects that I really want to do...a headphone amp for my motorcycle, etc. Having success building something you will really use is important to keeping your interest and in promoting the learning process. So I have no problem doing the kit, even though I'm sure people here will tell you there are much better circuits and components, etc.

thnks for the advice sir...
but i want to build it not from kits...
and beside, kits are hard to find here in the Philippines...
tnkz!!!

 

[chilinski]

That's great that you have the confidence to do it all from a schematic. I wasn't at that point, and I wanted something that I believed would be fairly foolproof to construct at my relatively ignorant stage of life in electronics.

The Ramsey people (ramseyelectronics.com) ship internationally. I can't find kits locally either, so I use the internet for this stuff. There are FM circuits all over the internet; it's just a matter of using your search engine to locate one.

 

[audioguru]

There are many simple FM transmitter circuits on the web:
1) Their RF frequency drifts when something gets near it or moves away. The frequency drifts as the battery voltage runs down.
2) They don't have pre-emphasis (treble boost) like FM radio stations so they sound muffled without treble on a radio.
3) They are mono, not stereo.

Here we can buy a very good FM stereo transmitter that is made to transmit an MP3 to a car radio. They have an RF attenuator at their antenna to reduce their range but the attenuator can be removed.

Here is the schematic of The Micromitter. It was a project in the Silicon Chip magazine in Australia. It uses a new IC that has a crystal controlled frequency synthesizer with a phase-locked-loop. it is stereo:

 

[valve]

Hi,
Try this transmitter for external audio inputs. It looks like a good design but I didn't try it. As audioguru told, the frequency instability is there for this type of simple transmitters.

 

[audioguru]

Hi Valve,
You posted Rod Elliot's fM transmitter. It has an RF amplifier so that the antenna is isolated from the oscillator so its frequency stability is pretty good, but without a voltage regulator its frequency changes slowly as the battery runs down.
It doesn't have pre-emphasis (treble boost) because a mic preamp is used with pre-emphasis with the transmitter.

 

[valve]

True.
So the required pre-emphasis circuit for both mic and line-in along with a detailed explanation for this cute transmitter is here. Thanks for Rod Elliot!

**broken link removed**

 

[SteveyD]

There are many simple FM transmitter circuits on the web:
1) Their RF frequency drifts when something gets near it or moves away. The frequency drifts as the battery voltage runs down.
2) They don't have pre-emphasis (treble boost) like FM radio stations so they sound muffled without treble on a radio.
3) They are mono, not stereo.

Here we can buy a very good FM stereo transmitter that is made to transmit an MP3 to a car radio. They have an RF attenuator at their antenna to reduce their range but the attenuator can be removed.

Here is the schematic of The Micromitter. It was a project in the Silicon Chip magazine in Australia. It uses a new IC that has a crystal controlled frequency synthesizer with a phase-locked-loop. it is stereo:

Whats the range on this unit?

I'm looking for something that can broadcast about 1km for music while working around the farm.

 

[audioguru]

The FM stereo transmitters have an attenuator to reduce their range to about 3m to be legal. When the attenuator is removed then nobody will have interference on a farm so you will be OK. Its range will depend on the sensitivity of the radio. Not 1km, maybe 200m to a very sensitive home stereo tuner or car radio. Maybe only 30m to a cheap Sony Walkman radio. There are single transistor RF amplifiers on the web.

 

[SteveyD]

Thanks for the info.

I'd still like to find something in the range of 1km.

If I could build it, then I would.

I'm not one for going out to buy one if I can tinker..