Best method for household FM xmitter

[peace brainerd]

I've really been getting into web broadcasts for a huge variety of music. I have a little hp mini in my workshop that feeds the stereo system.

I live on two acres of property in a lightly populated rural area. I'd like to be able to xmit the station I'm currently listening to on an open freq so that I can listen via any portable FM radio that's handy for yard projects, working on my motorcycle out in the driveway, etc.

I did a little googling but am not really sure what might be the most appropriate, straightforward, and cheapest solution. Have seen many types of USB fm xmitters that I suspect are for very very short distance (same room). There are also the more involved fm xmitter standalone devices that are more powerful and expensive.

I might be wrong, but I suspect that a small fractional wattage xmitter for personal use like this is not bending any rules or requiring any paperwork.

Any suggestions?

[kevinkr]

There are some legal transmitter kits sold here in the USA, (some by Ramsey) most of the ones sold on eBay have power levels that are too high to be legal.. I think something like 100mW is all that is permitted, however my recollection could be quite faulty, but as long as you are not interfering with others reception and the signal does not extend much beyond your property line you'll probably not have an issue.

[gray5596]

You are correct that a small powered FM transmitter is legal as long as you don't exceed 25mW (approximately) and you don't interfere with any commercial stations.

Some of the units listed on eBay exceed the legal power limit and you could run the risk of getting a hefty fine from the FCC. If you stick to known brands, such as Ramsey and Decade, you shouldn't have a problem.

I have used both the Ramsey FM100B and the FM30B for setting up sound for hard-of-hearing at large events with excellent results. For the money, you can't beat the FM30B at around $200.00. It has an excellent s/n ratio and the oscillator is rock solid. Either unit can easily transmit a block away. Ramsey also makes a FM antenna that legally increases the transmit range.

The only drawback to the Ramseys is you have to assemble them. The Decades are more expensive but come assembled.

To find vacant channels, use this URL http://www.radio-locator.com/cgi-bin/vacant

[gray5596]

I found the FCC limit for flea powered transmitters "Any unlicensed 88 to 108 MHz broadcasting with a signal strength greater than 250 µV/m at a distance of 3 m from the antenna is punishable by law and confiscation of all broadcast equipment."

This requirement is kinda tricky because it deals with the radiated signal instead of just the amplifier power. You could have a 1/2 watt transmitter and a lousy antenna and still be legal. However you could exceed the limit with a 1/4 watt transmitter and an efficient antenna.

[DigitalJunkie]

It is tricky,and kinda screwy. Partly because no 'average Joe-radio' with a small transmitter kit can manage to afford a calibrated field strength meter ($$$) to ensure he is in compliance with the rules. It's sort of an impossible standard.

There was a paper somewhere online showing the signal strength at various power levels,using a basic half wave dipole antenna in an open field.
The Legal limit (in the US; 250uV@3meters) was reached with something like 15_nano_watts of power,IIRC. Basically,the FCC's limit is a gnat-fart's worth of power,You can get a signal a few hundred feet on a good day,if you're lucky.
(IIRC the Part-15 rules even state something along the lines of 250ft,or the edge of your property. -but don't quote me on that.)

The thing is,Most all of the kits sold (even ones type-accepted for Part-15 use in the US) have a couple dozen _milli_watts or so of output. With a half-decent antenna you can cover a couple blocks.
With a good antenna up somewhere high,and some low loss feed cable,people have been known to get out 1/4mile or more.

I'd think one of the various kits (Ramsey comes to mind) and some kind of antenna up in a tree/roof/attic you should be able to cover your target area nicely. Being in a rural area helps also,There's nobody around to complain to the FCC.
Some of the Ramsey kits even have adjustable RF power output,so you can dial it in for the coverage area you want,and no more,just to be extra careful.

[Wavebourn]

Let's wait for Michael Koster, he should have some interesting information, AFAIK.

[peace brainerd]

I was a little premature with this post perhaps. As usual, just coming up with the right search wording opened up the field considerably.

USB FM Transmitter - Enjoy online radio, music, and MP3, anywhere at home or office by using this extended range USB FM Transmitter - USB FM Transmitter

Amazon.com: Mac PC USB Wireless FM Transmitter 4 Home Stereo Audio: Electronics

Best Fm Transmitter: Bundle Deal: Fail-Safe 0.5 W Long Range FM Transmitter + 1/4 Wave GP Antenna Kit ($200 Value) Review

How to Use a FM Transmitter to Listen to Internet Radio | eHow.com


I'm clearly not the only one seeking to do this. So let me rephrase this since I'm here among the more technically competent. What would you choose? Or can you even conceive of a more elegant way of doing this? I don't mind using the workshop HP mini pc as a base. It's on all almost 24/7 anyway. So I don't need the flexibility of a stand alone unit that connects directly to the modem.

I was frankly hoping that I might discover a 39 dollar usb fm xmitter no larger than the typical wifi dongle that takes audio/power from the usb connection (without overriding the speaker-out feed via the headphone jack which is feeding the shop stereo). A little 5vdc powered FM stereo xmitter with an ext antenna plug that I could use to reach out a bit. (or just hardwire an ext antenna to its board)

[peace brainerd]

Keene USB FM Transmitter ? reghardware

...getting closer here.

Another neat part of using the dedicated mini pc for this is being able to greatly simplify the device, just a usb dongle, and handle the interface commands via the desktop where all my favorites and settings etc are located in the first place.. That one doesn't appear to have an external antenna option, but that's an easy workaround.

Please pass along any other ideas or links you have here.

[Bone]

Note if you live in the UK any transmissoins on the 88-108MHz band are not lawful. If you get caught then a fine and confiscation of your equipment including anything connected to the transmitter is the penalty.

[peace brainerd]

Note if you live in the UK any transmissoins on the 88-108MHz band are not lawful. If you get caught then a fine and confiscation of your equipment including anything connected to the transmitter is the penalty.

So there's probably a better place to keep your bong than on top of the transmitter?