Questions Regarding FM Transmitter

Hello Everyone - I'm a newbie interested in using an FM transmitter to broadcast music around my property. I have multiple receivers setup across a couple of acres - each has it's own speaker system. I want to use the transmitter to synchronize them from a single source. I found a device on eBay that looks promising: ST-15B 1.5W/15W stereo PLL FM Transmitter Broadcast Station .. I'm curious whether anyone has any experience with this device and could share their opinion given my situation. I would also be very interested in hearing other recommendations for transmitter. Thank you in advance !

By the way - I did try searching the forum prior to posting the question, but I received an error in both the advanced and regular search. Thanks

The unit you refer to is capable of running FAR more than LEGAL power!! Plus....it's more than likely set up for 50 uS pre-emphasis instead of 75 -- and NOT easily field-adjustable! (DON'T ask me how I know....!!!)
NO LEGAL PART 15 CERTIFIED TRANSMITTER will cover "a couple of acres" reliably! If you "add-on" an antenna you've now made the transmitter ILLEGAL!
The rule-of-thumb for Part 15 FM: Essentially, field strength MUST NOT EXCEED 250uV @ 3 meters (10 feet)....REGARDLESS of other factors (altitude, topography, etc.)
Sorry that this isn't much help to you.....but it's (for NOW, anyway....!) the LAW!

Thank you for the information Oldie919 - that is helpful. I had a feeling that 2 acres would be too much. How about if I were to use the unit without an antenna to cover a 3500SQ FT home ? Do you think that would work ? I have no desire to create issues with the FCC and can figure out another solution for the system on the other side of the property. Thanks again for the response!

That's a transmitter that isn't legal to buy in the US. Even at 1.5 watt, without an antenna and in a basement, your range will likely be in the hundreds of feet. The 250 µV at 3 meters standard is designed to make the transmitter completely unreceivable in 300 feet or less. An old RadioShack transmitter I used in the car for CDs years ago couldn't reliably cover our 1300 square foot house.

Understood. I definitely appreciate the information - I'm not looking to violate laws, I'm just looking for a simplistic way of synchronizing several different stereo systems via FM. Thank you

zooba72 said:

Thank you for the information Oldie919 - that is helpful. I had a feeling that 2 acres would be too much. How about if I were to use the unit without an antenna to cover a 3500SQ FT home ? Do you think that would work ? I have no desire to create issues with the FCC and can figure out another solution for the system on the other side of the property. Thanks again for the response!

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The maximum ERP allowed for a Part 15 FM transmitter is about 0.011 microwatts, which gives a range of roughly 30 feet. If you want to cover 2 acres, you'll have to use the AM band, and even then, that's a stretch.

There is no provision for Part 15 transmitters covering a large property, other than a college campus on AM. That might be a good thing to petition the FCC about, but at least on FM, its chances of passage are zero or less. AM has a better shot, due to the college campus precedent that could be extended to any large private property (farm/ranch, shopping mall, etc.). The pertinent regulation is 47 CFR 15.221(b).

47 CFR 15.221 said:

(b) As an alternative to the provisions in paragraph (a) of this section, intentional radiators used for the operation of an AM broadcast station on a college or university campus or on the campus of any other education institution may comply with the following:

(1) On the campus, the field strength of emissions appearing outside of this frequency band shall not exceed the general radiated emission limits shown in §15.209 as measured from the radiating source. There is no limit on the field strength of emissions appearing within this frequency band, except that the provisions of §15.5 continue to comply.

(2) At the perimeter of the campus, the field strength of any emissions, including those within the frequency band 525-1705 kHz, shall not exceed the general radiated emission in §15.209.

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There are other frequencies you can use to cover that much ground legally under Part 15 -- 13.56, the old RC channels on 27 MHz, 49.82-49.90, 902-928 MHz -- but since they're not audible on standard radios, nobody bothers with them. The first three would be restricted to AM anyway, due to the limited bandwidth allowed.

I think you would be better off building out a wifi network that covered your house and property. I used two, Ubuiqiti AP's on my one acre square lot and have an Ipad and Kidle Fire to watch Food network and Top chef, it also lets me listen to my network music drive. A solid reliable wifi signal property wide is much more valuable than a single small FM signal. Might cost a little more but it gives more.

Steven

I'm actually using hardwired Ethernet & Wifi now - I have computers attached to each of the audio systems and can stream from a central source to synchronize everything. It's kind of a pain though, especially having to connect multiple clients to the stream. I figured it would be much easier just to broadcast FM and pick it up using a receiver or tuner. Others have recommended SONOS - not sure that would work with my existing equipment.

Frank - do you recall whether it was the ST-15B ? Link: http://www.ebay.com/itm/1-5W-15W-st...-radio-station-ST-15B-87-108MHZ-/121343748396

I have not seen a lot of reviews on this unit and am definitely weary of Chinese electronics. Although I did purchase a pretty good portable HAM radio (which I think also violates FCC regulations) that was confusing, but worked after some tweaking.