Any recommended brands of "inexpensive" Part 15 compliant portable FM transmitters?

Hello all,

I apologize if this has been covered in depth before; I have searched the site.

I am new to the site and have been searching this forum, googling the net, surfing eBay, Amazon, etc and have not yet figured out if anyone makes decent quality, part 15 compliant equipment that would meet my needs. 

My use case is small outdoor events, like car shows.  I'd like to find an FM transmitter that can operate on 12v in a car, where the other cars at a show can tune their radios to the same freq and we can broadcast lower volume music and announcements for nice ambiance at events, as opposed to a pair of loud DJ speakers blaring into the crowd.  Similarly, we could strategically place various inexpensive FM receivers (boomboxes, etc) for an amusment park-like distribution of the audio.  This would be less expensive than wifi transmitters and high-end portable speaker systems.

I would prefer stereo, in case we ever have a desire to actually place speakers to effect stereo sound, but I realize that scattered speakers/car radios defeat the purpose of stereo.  I also know you take a big signal to noise ratio hit with stereo and lose I am considering mono.  (Maybe something out there is switchable?)

However, try as I might, I cannot find a transmitter (say, under $150) that is part 15-compliant AND is more than just a local FM modulator for in-car use.  All the transmitters I have found on Amazon, eBay, etc in that price range, down to about $50 are of the "very shady" variety, with a "low power" mode that is "recommended for FCC compliance" but turn out to be WAY too low in the reviews. Or they are 1 watt or some other ridiculously high output.  Or they bleed across a range a frequencies or cause noise and interference in the closest receivers.  I am talking about stff from Fail-Safe, FMUser, CZH, Signstek, etc. They look ideal, until you look at the details/reviews.

Are there any decent quality manufacturers of 12v powered transmitters that actually provide a "max legal" signal strength, with clean signals, so I can get a range of a couple hundred feet?  Without spending $200 or more ?

A friend who knows such things recommended this mono unit: which is at the max of the budget.  Is there anything else I should consider ?

Any advice is appreciated!

Part 15 Engineer's picture

it would have to be a very small car show, just maybe 100ft radius from tx, you are better off with a procaster on AM, a little more pricy but will do about a 1/4 mile with no issues.

Part 15 Engineer

Hindsight is 2020

I'm not a democrat or a republican, i'm a common sense moderate progressive


please don't forget to register and vote

Mark's picture

Cheap?......well the ACC-100 you mention is your price limit...correct? That's a good one.

Look on Ebay as I think that the Cardio Theater, Waio under a different brand name is for sale as "new other" for $125 now. It is certified.

Look for used but good condition Broadcastvision's which all work on 12 volts, are certified and good quality and a few are on Ebay right now.

The Wholehouse 3 is $100 new with discount and works well but doesn't work on 12 volts, it needs 5 volts with a micro USB jack or 3 AA batteries.

Newer Broadcastvision's, the Wholehouse, and the Cardio theater are mono to stereo switchable.

Welcome to the forum.

ArtisanRadio's picture

I believe that you would be wise to stick to Part 15 certified transmitters.  Testing done on even those certified transmitters has shown that many can be well above the legal field strength limits, but at least you can demonstrate that you attempted to be legal, if questioned.

That being said, things being equal, the range for all certified FM transmitters, if operating at the legal maximum of 250uv/m at 3 meters, will be identical.  The only differences would be sound quality, and the fact that some may be operating at less (intended for in-car use, for example), so you would achieve less range.  200 feet to an ordinary radio is about the most you can expect to get, maybe double that or a bit more to sensitive car radios.  The fact that you will be using your transmitter at a car show gives you a bit more flexibility, particularly if you're using car radios to listen in.

Some of the transmitters mentioned previously are good - I've used the ACC100 (although you need to throw away the supplied adapter and get a good regulated supply), and the Broadcastvision.  Both are good examples of real radio transmitters, as opposed to the car modulators.

If your budget allows, I'd go for a Decade MS-100, which you can pick up for several hundred dollars used on e-bay at times.  It has the highest build and sound quality of all the available certified transmitters.  The Decade CM-10, discontinued but still available sometimes through e-bay, is another great choice.  It basically is a cleaned up Chinese transmitter, but certified.

But some of the car modulators might surprise you.  I recently purchased a new Maxell P-13 which sounds perfectly acceptable, gets about 300 feet range to a car radio, and cost $1.00 (plus shipping, a few dollars).  The Maxell FMT100 was reported to get similar or better range, while sounding great (but you might find it difficult to find one).  If you search around, you can probably find a few others that give you similar range to the 'real' transmitters.

I guess what I'm trying to say is that you could try a bunch of cheaper alternatives and maybe even use multiple transmitters if you need more range than several hundred feet.

Part 15 AM might work outdoors, but you'd probably have noise issues if indoors.  There's no doubt that you'll get much more range using Part 15.219 than Part 15.239 (FM), as previously mentioned.

Carl Blare's picture

Looking for "the right transmitter" is only part of the problem.

What kind of transmitting antenna will be used and where will it be placed?

And let's talk about the radios: "Strategically place various inexpensive FM receivers (boomboxes, etc)."

Most inexpensive FM radios are very insensitive and would perform poorly, and not all expensive radios are much better.

Boombox radios are designed to emit exagerated bass which is counter-productive on voice clarity.

The kind of result being sought in this project will require setting up experiemntal arrangements and tweaking it until it's as good as possible... it can't simply be estimated in advance and expected to work perfectly.

Carl Blare

Mark's picture

Didn't mention Decade because of your price range but the Decade MS-100 is the best of them all and yes there are some on Ebay right now.

Also you said you wanted it to work on 12 volts DC?

The Decade MS-100 needs an A/C power supply not DC and works at anywhere between 15-20 volts. You would need a power inverter to power it from a car to get 120 VAC with the A/C to A/C adaptor.

FiveSpeedV8's picture

Thanks, all.

I am going to continue to shop around.  If I can get one of the decent part 15 compliant transmitters at a resonable cost (used) then I can experiment a bit and hopefully resell if it does not suit my needs.





timinbovey's picture

The trouble is when buying a Decade MS-100 on eBay you have no idea what country it has been set to comply with.  One seller on eBay has them listed, IIRC for $260 (I could be wrong on price).  He's in Canada.  I wrote to inquire if these were Part 15 compliant or if they were set for the Canadian rules.  He had no idea. Was not aware of the difference, and knew nothing about it. My guess would be since he's in Canada, and bought it while in Canada, it's probably set for the Canadian limits which of course would be well over the legal limit in the USA. I do see a couple sellers in the USA too, but it's something to be aware of.