FM Transmitter...

[kunar]

for a while now i've been thinking about buying a small fm transmitter to use at work. i would like to be able to hook up an mp3 player or similar, and have it broadcast through the shop. im not talking about one of those little chincy things you use so you can listen to your ipod in your car. the ones i have seen for sale for cheep have been chinese made units. it looks like a 1/2w transmitter should give me a 1/2 mile of broadcast range, which is more than enough. a 5w transmitter isnt much more than a 1/2w though, so i may buy a bigger one than i need, especially if you can 'detune' it's broadcast range. the bigger thing i have on my mind is FCC regulations. i dont need any hassle or fines. anybody have any advice or experience?

 

[samsonitesamsonite]

there is no way that you will be able to get fined, they have no way of actually traking down your car and giving you a ticket. With that said, just be careful anything too strong can intefere with aeronautical communication, though I doubt any FM transmitters on the market can are powerful enough to do that.

 

[Roadkill]

Check the FCC site as there IS a limit to how much transmission power you can have on different radio bands before requiring a broadcasting license. The 5W one on the FM band may breach that limit I don't know for sure.

 

[HIPCHIP]

A lot would depend on what freq you transmit on. If you're in the Ham bands the FCC will find you as the local hams police the area. No music is allowed to be transmitted on Ham freq's. Most Ham freq's are shared with other agencies, so they may hunt you down too (we're going through that right now with the military), and if you get on a police freq that's big time no no.

If someone sells a commercial transmitter for local purposes you should be fine. Your best bet would be to just get a nice stereo and wire the shop for speakers or go to an electronics place and purchase some wireless speakers that are already FCC legal rather than trying to find a transmitter and hook everything up. Just too many problems, and trying to find out specifics from the FCC is not all that easy.

 

[kunar]

well i dont want to wire the shop, i want everybody to have the choice of tuning into my player if they so desire. not to mention that if one day i decide to no longer work there... i can just pack my stuff and go. i have seen a couple transmitters that are 'whole house' kits that look promising. they are designed (obviously) to be able to play an mp3 player or something similar throughout your house. that should be okay, but like i said before... if im making the investment, i want something worth while. something i wont be disappointed in. i can get a .5w unit for about $90 and a 5w unit for about $100. the chinese made units i have seen are pretty basic and simple, and im sure the fcc was not a consideration when they were made or sold. ive even seen units as big as 200 watts, but those are just too big, not to mention expensive. i have tried to look on the fcc's web site and everything is just buried in words, nothing is cut and dry. i just want a simple "this many watts is legal for personal use" and as far as the ham m frequencies go... im not even sure what range they broadcast in, but these transmitters are all 87MHz through 107MHz or something in that range. is there anything in particular in the specifications i should be looking for to make sure i wont be disappointed?

 

[kaskirov]

cb frequencies seem to be from 26.9-27.4mhz so you should be fine. got my info from http://www.csgnetwork.com/cbradiofreq.html now i feel smart

 

[HIPCHIP]

well i dont want to wire the shop, i want everybody to have the choice of tuning into my player if they so desire. not to mention that if one day i decide to no longer work there... i can just pack my stuff and go. i have seen a couple transmitters that are 'whole house' kits that look promising. they are designed (obviously) to be able to play an mp3 player or something similar throughout your house. that should be okay, but like i said before... if im making the investment, i want something worth while. something i wont be disappointed in. i can get a .5w unit for about $90 and a 5w unit for about $100. the chinese made units i have seen are pretty basic and simple, and im sure the fcc was not a consideration when they were made or sold. ive even seen units as big as 200 watts, but those are just too big, not to mention expensive. i have tried to look on the fcc's web site and everything is just buried in words, nothing is cut and dry. i just want a simple "this many watts is legal for personal use" and as far as the ham m frequencies go... im not even sure what range they broadcast in, but these transmitters are all 87MHz through 107MHz or something in that range. is there anything in particular in the specifications i should be looking for to make sure i wont be disappointed?

Those freq's are just the standard FM freq's, so shouldn't be a problem unless you're real close to a station. Pretty much anything that comes into the US has to have FCC approval, so being made in China should be OK. They're just low power transmitters, so the range should be real short, but you're transmitting your music to speakers, so everbody get's the same thing. Lots of wireless speaker systems out there so I'd just check at your favorite stereo store and see what they have. Most home theater systems now have wireless speakers and allow you to plug in iPods and such. I'd be weary of super inexpensive stuff, but then again, do you want an expensive system sitting around work? Heck, if ya got a Radio Shack in the neighborhood check with them! I know they make a wireless mic that will transmit to a radio and stuff, so I'm sure they have something that's OK and fairly inexpensive. I'm not sure if you can get something that will transmit on a specific freq and if someone doesn't want to listen to it they can tune to a different channel, so you may have to search around. It sounds like you've found something. Just check to see if it has an FCC sticker on it and if it does you're good to go.
Dan'o :}

 

[MAKG]

To be honest, those FM transmitters SUCK DONKEYS. They add quite a lot of noise, and are likely to be unusable in an electrically noisy place such as a shop. You'll be able to hear every electric motor turn on and off.

And illegal transmitters can be found very easily with a directional receiver and a pair of legs. I doubt the shop owners will take kindly to an FCC fine.

 

[reno]

.5W is fine, tune to a station not being used (static), and enjoy. .5W is capable of going a 1/2 mile depending on atmospheric conditions and the type of antenna you use. If you use the standard antenna that comes with the unit you will be fine. This is the same thing that muscians use for wireless transmission. And FM will never interfere with Aeronautical, different frequency bands. FM Bands go from 81.9 - 107.9. To be traced when running illegally (ham) the FCC comes into the area with a vehicle that has more antennas than you could imagine, and the passenger holds a directional Yagi Antenna out the window trying to locate you. To long to explain all the different antennas/Frequencies and how they actually find you.

Bottom line, as long as you use a frequency that is not used (as not to intefere with others listening to the radio-i.e. cars passing by\employees wanting to listen to the radio, ETC....) you will be fine.

 

[85_Ranger4x4]

To be honest, those FM transmitters SUCK DONKEYS. They add quite a lot of noise, and are likely to be unusable in an electrically noisy place such as a shop. You'll be able to hear every electric motor turn on and off.

I agree, I got one for my MP3 player in my truck and it is a joke. There is one station I can make out the songs halfway decent (I can make out the words) if it was a actual radio station I would change it without a second thought. It might work better in something that isn't moving around, but other radio stations come in and out of range that causes a lot of static, even sitting still it can be hard to find a good station to use. The book for it says that due to FCC regs it is limited to a range of 20' under ideal conditions.

I am going to try an FM modulator next, it mounts between the antenea cable and antenea port of the radio. It is supposed to be able to overpower the other stations much better.

But, I have a set of old computer speakers in my apartment that I plug it into the headphone jack of my player. Chrystal clear music with no interferance, for what you are doing I would look into something like that.

 

[reno]

I agree, I got one for my MP3 player in my truck and it is a joke. There is one station I can make out the songs halfway decent (I can make out the words) if it was a actual radio station I would change it without a second thought. It might work better in something that isn't moving around, but other radio stations come in and out of range that causes a lot of static, even sitting still it can be hard to find a good station to use. The book for it says that due to FCC regs it is limited to a range of 20' under ideal conditions.

I am going to try an FM modulator next, it mounts between the antenea cable and antenea port of the radio. It is supposed to be able to overpower the other stations much better.

But, I have a set of old computer speakers in my apartment that I plug it into the headphone jack of my player. Chrystal clear music with no interferance, for what you are doing I would look into something like that.

Those are the very low watt transmitters, like the CD player (portable) that plays over the radio, between virtually no power,engine noise,electrical (Alternator),your radio antenna on the outside of the vehicle,....WELL..... they suck. The manufacturer makes sure it does not interfere with that vehicle 15 feet away or less right next to you\behind you\front of you.

 

[4x4junkie]

If the channel is clear, ½ watt can go up to about two miles, one mile with reasonable clarity (this is with the TX plugged into a rooftop antenna).
Anything above the power of what those weak little POS "Ipod" type ones put out is technically illegal though (those "chinese" ones you mention are most definitely illegal black-market items, some lack stereo capability as well).

I would think AS LONG AS you don't interfere with any legitimate stations you'd be fine. Interference with other stations should be fairly easy to avoid in rural to semi-rural areas, but may be tough avoiding in urbanized areas. You don't want to use a channel that has even a weak station on it, you'll easily overpower a station in it's fringe reception area. Find a channel that has no stations at all that you can detect whatsoever on your car radio while driving around in the immediate area. Then set up your TX so it's not heard more than a block or two away).
.

Not sure how picky you are about sound quality...
Setting the modulation level can be tricky (and impossible to keep constant without employing some form of active volume normalizing or audio processing).
My Creative mp3 player has some volume limiting options built into it that work fairly decent for this (not sure if Ipods have something similar), although if you use Winamp on an actual computer to play the music, you'll have a far better range of options (plug-ins) available for processing that you can use for keeping the audio level consistent from song to song.
A good soundcard (such as Creative's Soundblaster cards) will be needed if you don't want sampling artifacts mixing in with your audio if you run it on a stereo transmitter (cheap cards (as well as most on-board cards) lack any filtering on their outputs).

 

[Buggyman]

I have a transmitter I bought for my Ipod, it was pretty expensive. Unsure of the wattage, but tunes into almost any station in the truck, and I have managed to over power other peoples radios parked next to me, its quite fun pulling up next to someone blaring rap music and start playing Celtic hymns over their station. I also found a DC converter for it so I can plug it into my lap top and play it over a stereo in the house; and its FCC compliant according to the package.

 

[kunar]

i think im gonna end up getting one of these. its about $100 o the website, and an ebay seller regularly lists them starting at $.99 so ill keep my eye on them and see if i can get one for a decent price. the specs look good, and i wont have to worry about the fcc.

 

[HIPCHIP]

That's pretty much what the wireless speakers use, I believe, just a small transmitter for very local transmission. It should be FCC approved.