Low powered FM transmitter

[StormShadow]

Hi there is there a low powered FM transmitter 87-108 MHz that I can get that will be powerful enough to go about 100 meters in radius? My purpose for wanting one of these is so that I can stream music around the house onto an analog radio receiver. I have already tried those in car MP3 FM transmitters and they are rubbish, I know some can be modified to extend the range but that doesn't always work and is really fiddly to do. I suppose if I could add a better antenna to one it might do something, I just need something with a tiny bit more power to work with but to much obviously, I've seen some on the auction site that will do 500mw but thats far to much power to be using for the purpose I want it for, maybe 10mw or something like that would be more ideal and something that can be powered from a USB port as well so I don't have to keep changing batteries all the time.

Has anybody got any ideas

Many thanks.

[Admiral]

This concept has been around since the last King died, all you ever saw in Exchange and Mart (remember that?) was adverts for bugging transmitters either in kit form for 11s 6d or built for £1 3s.

A Google search will bring up a zillion pages with DIY designs and complete units for a few quid, and Youtube has tons of stuff of them in action so you can gauge your mW to range calculation.

Nothing personal, but this stuff is 20th Century methodology, we use wifi and bluetooth these days, 100m is very doable with bluetooth, and it's stereo and no interference or de-emphasis.

EDIT: Typos

[Mattylad]

Bluetooth is also not illegal....

[albrecht]

The Chinese have plenty of them on a well known auction site if you really want one . . .

[GeeFull]

If you are not bothered about stereo, there are a plethera of low powered 88 - 108 Mhz "bug" designs kicking around!
Really easy to build from junk component bits piles, most dabblers have around them!
Most will easily do 100 metres with a short bit of wire for an antenna!
Just omit the usual electret mic input circuitry, pad it down a bit with a resistive network and fit a phono socket or whatever!
Despite most being very crudely tuned, they are remarkably stable for what they are on a good regulated supply!
It is technicaly illegal of course, the MP3/Ipod player types sold legaly are extremely low powered, hence their virtualy next to the "in car radio" or home FM radio receiver range!
Usualy across the room, or if lucky the next room, or bedroom directly above is about their limit, from ones I have tried.

[radtech]

You would be better off getting some wireless headphones if you want to listen to music. I use some fantastic Sennheiser HDR140 units which are analogue 860MHz and have about 150m range.

The batteries last ages and I can also tune my Uniden scanner into the 862 channel and listen in, good when streaming radio audio.

[kr0ne]

If you are streaming from a PC, you can encode a stereo multiplex using a 24bit sound card and can even add RDS should you see fit.

The higher powered chinese transmitters on eBay are mostly pretty horrible but there are some lovely kits available from dutchrfshop.nl for not a lot of money.

Be careful!

[albrecht]

Anyone know what kind of distance can be achieved with Bluetooth? They are 2.4 GHz. I don't think that there are any antenna restrictions on that band, you can buy quite large parabolic antennas if you can connect them up. My Motorola 2.4GHz handsets have connectors for larger antennas.

[Admiral]

In the good old days, bluetooth stuff had either a 10 or a 100 in it's name or on the box, that was your meters, so 100m kit is out there very cheap.

I would suggest that sticking an antenna on a bluetooth device kind of negates its original purpose, and don't forget that bluetooth data can be intercepted.

[MrWeetabix]

How's this?

http://www.ebay.co.uk/itm/FM-Stereo-Tra ... 33a1ad3f0b

[MrWeetabix]

or this

http://www.ebay.co.uk/itm/WHOLE-HOUSE-F ... 4640dd05d3

If you have money to burn, you're scared of a soldering iron and can't be bothered to do some googling that is :-p

[radiogaga]

Or this: http://www.ebay.co.uk/itm/PYE-TVT-10-ki ... 3ab06d5447

[Admiral]

How's this?

http://www.ebay.co.uk/itm/FM-Stereo-Tra ... 33a1ad3f0b

That's only half of it, you need a Raspberry Pi or Arduino to control it.

[MrWeetabix]

How's this?

http://www.ebay.co.uk/itm/FM-Stereo-Tra ... 33a1ad3f0b

That's only half of it, you need a Raspberry Pi or Arduino to control it.

where's the fun if it's straight forward anyways

[Admiral]

Or this: http://www.ebay.co.uk/itm/PYE-TVT-10-ki ... 3ab06d5447

Ye gods, you would certainly get 100m with that monster.

I notice the final 10kw tube is missing, that's probably worth five grand and the rest is scrap metal.