2 Pieces Digital FM Transmitter Module Stereo FM Transmitter DSP PLL 76.0-108.0MHz Stereo Frequency Modulation with LCD Display Line/USB/Mic Input, DC 3.0V - 5.0V

The two units came in anti-static bags. The only documentation is on this listing page.They work right out of the bag with micro USB power connected and no antenna. Adding an antenna is necessary for better range (reception over longer distances).There are volume and frequency up/down buttons as well as a mute ("pause") button. For the frequency buttons: If you long press, they will go up/down in 1 MHz units steadily (i.e., release button when you reach the value). Short presses increment/decrement in 0.1 MHz steps.USB to FM: Plugged into my Macbook Pro, it appears as a USB audio output device, and can broadcast system audio to the displayed FM frequency. This is handy, considering newer Mac's lack headphone outs. The device's microphone is not available as a sound input device via USB.Mic to FM: If I plugged the unit into a power supply, (either USB without a data connection, or the solder points) the microphone became active. The mic signal is actually excellent, with a clear and full response.Line Input to FM: With an external media player plugged into the line input, the mic is disabled. The line input's sound quality is also excellent. It has full frequency range, and the dynamic range is as good as can be expected from FM. A couple of times, I experienced some unexpected background noise, but I suspect it was unrelated to the transmitter.There's an option to connect a single-wire antenna with a thru-hole solder connection. The instructions recommend a 75 cm telescoping antenna. However, as my use is just around the house, and I wanted to keep the unit more portable, I just soldered a 12-inch length of 18 AWG solid copper wire. I can go around my house (away from the transmitter) and the signal strength is quite good.There are also two thru-holes for power, which are clearly labeled. It says 3.0-5.0v. I soldered a 3-AAA battery holder to those points and it works perfectly, even with rechargeables. The seller recommends disconnecting the external power source when connecting to USB (so it is not receiving power from both at the same time).I'm SUPER pleased with this purchase. Getting a two-pack makes this an unbelievably good deal. It's a truly excellent product at a great price. I bought another 2 pack.Though this transmitter does offer "campus" bands (additional frequencies below the standard range), I've never needed these, as I've always found some available frequency.UPDATE SEP 2024: Units are still going strong. Another review mentioned that USB did not work with their more recently purchased units. I also had purchased again more recently and find that the USB works as before, even with a recent Mac.I've been using one of these transmitters with a 12" wire antenna, along with a small MP3/FM player, for my in-ear monitoring system. When I arrive at the venue, I find a quiet, unused FM frequency on the MP3/FM player. Then I set the transmitter to that frequency. I feed my monitor signal into the FM transmitter. After setting correct levels, it just works. I've used it on 20+ gigs and never had an issue. Sounds fantastic.

This transmitter is awesome! I set it up on one end of the house, and it reaches all the way to the opposite end with clear signal. My one and only complaint is that its mounting options are extremely limited, because of how packed the board is. I'm sure this keeps the cost down, though; a worth trade-off, with how well it transmits.It's very nice that it has frequency control buttons, though I haven't found any use for the volume/mute buttons. But, if I ever need them, they're there.Pros:- Transmission distance reaches throughout my whole house- Digital frequency control- Audio comes in clearCons:- Mounting options are extremely limited

Any future updates will be below the Dislikes, under the === line.Dislikes: only complaint on one of the 2 I received, the leading one doesn't display, I use 107.1 and it displays as 07.1. Other than that I can't say how well they transmit yet. I would like both units to work the same, it just looks odd seeing only 07.1, when it should display 107.1 I'll post photo's later when I can get them both powered on at the same time to show this issue.============================================Upfdate 03/29/2024, I haven't gotten photos yet, but I was able to test both units out.I added 3 feet of actual antenna wire to the Ant pad, plugged a stereo audio cable to the transmitter line in jack, other end into my portable CD player. Turned xmtr on, set my receiver to 107.1FM, then plugged power to the xmtr.Reception on the miniature AM/FM/Digital Recorder I used was awesome. The xmtr was tested from inside my storage shed with door completely closed, my shed and its door are all metal, no windows. I walked to the end of my street, 4 houses to the East, and 4 to the West, xmtr worked perfectly, range was far better than I ever really expected.😮I was very impressed with the range of this xmtr. No loss of clarity, music played crisp, clear and clean, no stray sounds heard. Didn't start losing the signal until I just got past the end of the block at each end.I tested BOTH transmitters, and BOTH operated exceptionally well.Again, my only complaint is one of the transmitters display shows 107.1 as 07.1, but still functioned 100% otherwise. Same results with both transmitters.If it weren't for the one not showing the leading # 1, I would have given these very tiny, but powerful xmtrs 5 stars.Now I'm just waiting on some project boxes to mount them in.I have a xmtr I bought years ago[in 2010] which cost me around $249.99 + accessories, and this little tiny transmitter is just as good as my original $250 transmitter!🫨 Which is also a humongous giant compared to this one.Can definitely recommend this to anyone looking for an FM transmitter for a Holiday Display, or any multitude of uses.You just need to know you'll have to figure out a mounting system for it, and an enclosure.And for the price, it sure beats paying $60 and up for one xmtr, when you can buy 14 for that $60 starting price tag, or the money you save buying 2 for the price sold for, less than $10 each, you can buy the extras you need, enclosure, antenna jack connector and build it up yourself for a lot less than that $60 price tag for a fully built-up one.‐---------------- End Update for 03/29/2024 ---------------I just powered them up to make sure they would turn on, which they did. The microphone works, but haven't had a chance to test out the line in from the transmitter to the audio output from my audio player to see how far this unit will actually transmit, and whether I'll be able to utilize it for what I want to use it for.Will update this review after I can do more tests with them after I install an antenna bnc connector on the one with the full frequency display. This is so I can use one of my existing antennas to see how good or bad this transmitter is.

Adding a thin 22 AWG wire as an antenna will improve your range. It's easy to just solder on the board where noted. No problem using the built-on microphone when USB audio, or nothing is plugged into the phono connector. It works fine if pushing audio via USB, or the phono adapter as well. Also, I powered it fine using a USB battery bank, or plugged into a PC or Mac.Additionally, here are the approximate lengths for the wire depending on what you have room for when using 100 MHz as the frequency. Even a short piece of wire 30 cm long would help improve things versus nothing. Still, even without a wire attached it works. I'm currently using 150cm length of wire and no problem with getting 50 meters distance outdoors while the transmitter and antenna are indoors with various walls in the way.λ = 300 cm (This is approximately 10 feet)λ5/8 = 187 cmλ/2 = 150 cmλ/4 = 75 cmλ/10 = 30 cm (This is approximately 12 inches)