I found this unit for sale on the consumer electronics rack of the corner drugstore for about 20$. I noted the notice of FCC part15 compliance on the back of the package, and looking carefully through the side of the clamshell it was in, I noted it had an FCCID #. Oh boy! Another affordable FCC compliant FM transmitter. And this time not quite from the toy department (for those who remember my testing and experiments with the “003” this summer).
The FCCID# for this unit is: SCZPSLFMTX1, and it was easy to find the reports on the unit via the FCC OET generic search using the first 3 letters to locate the manufacturer’s products. It is sold by Maxell, but the actual manufacturer appears to be Phitek Systems Ltd.
I put in fresh batteries (it takes 3 AAA), checked the 4 channels the unit can transmit on and determined 88.5 was the clearest by listening with my stereo, and then set the unit for 88.5. I plugged it into a battery operated cd “walkman” type player, turned the player’s volume all the way down, powered up the cd and turned on the transmitter. The stereo 15 ft away immediately “blanked”, stereo light came on, and I faded up the volume. A very nice sounding little transmitter. I’ve seen a lot of negative comments on various of these little “play your portable music players through your car or home stereo” type devices, so I was pleasantly surprised that the sound was clear and the separation sounded good. I walked to the other end of the house and other than the occasional “dropout” typical with part15 devices as you pass through distances equal to the wave nodes, it was nicely solid. At approx 60 ft indoors, it sounded good.
Ok, time for a better test. I disconnected my kit-built transmitter and hooked the FMT-1 to the “audio out” of my computer. This bypassed my usual eq and brick wall limiter to see how it would do just as it came out of the package. I turned my computer’s volume all the way down, turned on the transmitter and sneaked up the volume. Sounded quite nice on the stereo at the other end of the house. So I hooked a boombox up to a computer on the other end of the house with winscope on it and played a 100% normalized test tone mp3 on the studio machine. Ran back and forth for a few minutes getting it set so there was no distortion showing on the winscope trace of the test tone. Back to some music. It sounded quite good, though a little quieter then the stations near it on the dial. No surprise there, since I don’t use compression. Signal was clean and clear, a bit less than 100% modulation, but that’s fine.
I was about half an hour from doing my usual midnight saturday night show, so I settled down to look over the test info on the FCC OET site. I noted a few points of interest. First, the unit has pre-emphasis built in. The next thing I noticed was that in the test, they plugged the unit into an obviously grounded (it had an AC cord) cd player for taking their measurements. Logically then, any “advantage” due to the presence of a ground via connection to a 110v device was part of the testing and the device was still found compliant.
Then I noticed that the tests mentioned the unit having an internal and external antenna. I did not note any external antenna, as you can also see if you check the pictures on the FCC site. After a bit of puzzling, I noted that there was a wire visible in the battery compartment and measured it with a ruler and yup, it was approximately 9 cm. The OET pages say the antenna is 200 mm total, 110 internal and 90 mm external. I am assuming they counted in the battery compartment as external, and the internal part would be in the circuit board compartment. I am not taking a screwdriver to it to find out, since I currently plan to make use of this unit and prefer to keep it in unmodified condition.
Knowing that some small units like the Belkin use the audio cable as the antenna, and a common (and probably less than legal) mod with the Belkin is to use an audio extension cable to gain more antenna and thus boost more range. Logically it would not work with this unit since it has an internal antenna, but I decided to try it anyway. I tuned it in with my multiband radio (which has an s-meter) which was about 15 ft away and shortened the receiver’s antenna to get an “s6”. I added a 6 ft extension cable between the transmitter and the computer. Moving the cable did not change the meter reading. Getting the transmitter about 4 ft from the computer *did* improve the signal to about an s8, though. So I repeated the experiment with the battery cd player I’d tried first. Keeping the transmitter sitting on a wooden shelf and moving the portable cd player up and down, then towards the receiver and away, no noticeable difference on the receiver’s s-meter. So the unit does not seem to benefit by using an audio cable as an antenna. Time to get the boombox again. The FCC test was done with the unit plugged into a boombox type cd player that had an ac cord and as such would have been electrically grounded. So.. Put the boombox on a shelf about 4 ft over the computer. Plug the transmitter into the boombox. S8. Remove boombox and set the transmitter on the shelf with the 6 ft audio extension cable connecting it to the computer. Still S8. Also a small bit of whine/hum I’d noted during seconds of dead air between songs was gone. Move the unit (still on the cable) near the monitor and the computer. Monitor was the source of the hum, the computer was adding the whine. Tried stopping the cooling fan with a thin screwdriver. Bingo, the whine was fan noise. Both problems solved by putting the FMT-1 unit on the shelf over the computer and using a connecting cable.
To put all that more simply, it does seem to benefit from the presence of a decent ground, and the FCC documentation shows it was tested while connected to a grounded device. However, the length or positioning of the ground wire (via the audio cable shield) does not seem to be a factor that makes a noticeable difference. Plugging it directly into the back of a metal case desktop computer induces noise and cost some signal (very possible due to the receiver being in front of the computer while the transmitter was plugged into the back).
At this point, it was about 5 min from the beginning of my usual midnight show and so I quit experimenting for the time being. I called the neighbor who I knew was home and had him check for the station on the new frequency. Our houses are quite near to each other, and his bedroom clock radio is about 40 ft away. His stereo (which picks up better) is about 60 ft away. Good sounding signal on both. A pleasant surprise considering that is through aluminum siding and house wiring and drywall and who knows what else in the walls of the buildings. He was the only listener I was certain I had at the moment and I had a show to do. So the only other test was how it held up under battery power. 8 hrs later the signal was still good when I went off the air.
In summary, the Maxell FMT-1 did quite well for an inexpensive device. The sound is quite good *except* when the receiver is less than 3 ft from the transmitter. If they are very close the signal sounds distorted, though it is very sharp and clear on a radio any reasonable distance away. I am guessing at saturation. If you’ve ever graphed the equation often used here for the field intensity of an FM transmitter of a given power into a dipole over a range of distances from 0 to 1k meters or so, you’ll note that while it is for all practical purposes linear at any realistic distance, it is a sharply climbing curve as it goes into very short distances like less than 1 meter. Even a tiny transmitter can swamp a reciever at very close range. But since the distance inside a car is so small, it might be why this general type of unit seems to have a reputation for poor sound. The other possibility that comes to mind is they might be overdriving the unit into distortion, since I found that adjusting the unit with a test tone so it didn’t show any “flats” on the waveform resulted in the volume level on the source being lower than I’d usually use for say, headphones. This unit likes a rather low level of audio input.
It’s crystal based PLL, so the frequency is very stable and tunes easily with a digital receiver. It has pre-emphasis, and as such not a lot of eq (if any) is necessary. It’s about the size and shape of those little round plastic containers kids get “bubble tape” bubblegum in, and as such is very portable and takes almost no setup time.
I haven’t checked for range outdoors yet, but indoors it does about as well as the “003” did. I’ll be interested in seeing what it could do in a waterproof housing a ways off the ground, when I figure out a good way of going about it for a long-term installation. My house is about 35 ft X 65 ft and 3 floors counting the attic, and it was easy to pick up the signal over the whole house on anything at least as good as a table radio with a small telescoping antenna.
Last words on the FMT-1 for this post.. If you’re looking for a very inexpensive FCC compliant device for trying part15 FM, you could do a *lot* worse than this unit. This thing cost *less* than it did to kit-build my first transmitter and homebrew a simple antenna. I spent 30$ “saving money” when I could have spent 20$ for this and not had to wonder if I was actually compliant or not. I learned a lot building my first transmitter and getting it to sound decent and put out a fairly clean signal.. But if there had been complaints and the FCC had decided my little home-made-from-a-kit transmitter had been way out of compliance, I could have learned about large fines too. In that sense, this is a far more “newbie friendly” way to get a start in the possible “very near neighborhood” range of legal part15 FM with a compliant transmitter. It doesn’t actually sound bad even if you *do* plug it directly into the back of a computer. The little bit of hum and whine that approach has are only noticeable at moments of full silence and so this little unit is probably as close as anyone can get to “on the air right now” for 20$ (probably less if you shop around a bit). So if someone has been asking for hints of what you might like in your xmas stocking this year, you might consider one of these units as a possible option.
I think this will do what I need quite adequately, and as such the rather “rude and crude” kitbuilt transmitter and homebrew antenna I put together over a year ago are now formally retired from duty. Not sure yet if I’ll strip it down for parts or make a “historic” wall display of it for my station as “our first transmitter”.
I’ll probably post more on it as I figure out the best placement, figure out some of the challenges of mounting, determine if an external power supply is workable or if perhaps a small solar charger would be better and etc.
Daniel
Great Product Review
Thanks, Daniel, for the in depth review of this product. Your “whole house” coverage report is encouraging.
Please keep us informed as you get more experience on how this transmitter compares with your “kit” system.
Neil
Cheap portable radio test
I ran into a little problem in my planned testing. My usual “cheap portable radio”, which is a literal “dollar store special”, couldn’t tune the transmitter at all. Not even 2 ft away. I little bit of experimentation and deduction revealed that the reason is it doesn’t tune any frequencies below about 89.7. So I had to buy a *new* cheap portable for this project’s testing phase.
Sentry AM/FM Pocket Radio Model PR799. Cost 5$ at the local Family Dollar store. It has analog tuning, and a small whip antenna (less than 12 inches fully extended). The whip was nice for being able to compare polarization by rotating the receiver, and I was able to confirm that ability by tuning a local licensed LPFM where I have seen their antenna and know it is currently strictly vertical polarization. Other than that advantage, I would rank this as a *very* poor quality receiver, and I would class it’s selectivity as “crappy”. Also even fresh out of the package, the volume control is a bit unstable and the sound quality is not at all nice. But this isn’t a review of the receiver, and we’ll consider it established that the receiver used was at or below the quality of anything that might typically be used by a potential listener, and it definitely qualifies as a “cheap portable radio” for the purposes of my test.
The transmitter was placed approximately 6 meters above the dirt and 2 meters out from the walls of the building. (ok, to state that more visually, it was taped to the end of a 2X4 board and stuck out an attic window). Fresh batteries in transmitter and receiver, sound source was a small “walkman” type portable CD player running off a small AC adapter.
It was possible to measure in 3 “compass point” directions. My criteria for this measurement was solid reception, allowing only minor “dropouts” that were likely due to passing under or by power lines, cable lines, and who knows what else. I was looking for the definitely usable range where the transmitter signal sounded approximately as good/solid/clear as local commercial stations.
North – 68 meters (approx 223 ft)
East – 65 meters (approx 213 ft)
South – 45 meters (approx 147 ft)
Note the difference between North and South? I live partway up a hill. The range is significantly better broadcasting downhill than uphill, and I’m sure that this comes as no surprise to most of us since the advantages and disadvantages of terrain elevation to FM BCB signals in particular are pretty well known on this forum.
Ok, so that is the definitely *usable* non-fringe range of the 20$ Maxell FMT-1 to a definitely “cheap portable reciever” when the transmitter is gotten at least a couple wavelengths off the surface of the earth and a couple meters away from the building and other physical objects.
I did not go far out into the “fringe” at all, since outside the ranges given above, the signal was not what I would class as being listenable in the sense of being something most people would *want* to listen to. Sure, you could turn just the right way and stand very still at 60 meters or so and be able to make out the audio buried in noise and “bleed” from commercial stations, but the average listener wouldn’t want to try and tune it in. The range I was looking for was what is at least close to “rock solid”.
I would class it as a usable amount of range for a part15 FM transmitter *if* you live in a residential section of a town and are interested in what I would call “Very Near Neighbor” style community radio.
Some other observations.. The FMT-1 did not appear to favor a vertical or horizontal polarization. This might be because the physical size of the unit (and as such it’s antenna) is very small, or because the built in antennas being curved to fit in the case result (intentionally or accidentally) in the design having at least some characteristics of a circularly polarized antenna. Using “headphone extender” audio cable vs plugging the unit directly into the audio source gave no noticeable difference in range. Disconnecting the ac adapter and running the audio source on battery *did* slightly reduce range, but the difference was small, about 2 meters in every direction. Since the documentation on the FCC site shows the transmitter being tested and found compliant while it was plugged into a CD player that had an obvious AC cord attached, I would deduce that the unit is properly designed not to make use of the audio source’s ground or AC line as an antenna in such a way as to make any significant change in it’s range. However it does appear that the unit does perform slightly better with an actual electrical ground present, which comes as no huge surprise. I would *guess* that use of an audio extension cable of a reasonable length to get the unit away from large metal objects with fans and etc generating noise (like computers) does *not* void the conditions typically expected in it’s testing for FCC compliance. It doesn’t look like a “grey area” based on my own tests, but that would be up to your own judgement. In any case, the range is very close to the identical and whether the source is electrically grounded or not doesn’t seem to provide any significant advantage. Personally I would recommend it being attached to properly grounded gear in any case to avoid static electricity and lightning concerns.
And now, on to address Neil’s interest/question:
“Please keep us informed as you get more experience on how this transmitter compares with your “kit” system.”
Well, Neil.. In some ways it’s an “apples and oranges” comparison. My “kit” transmitter was never operated much above the level of the dirt or outside the aluminum siding of the first floor of the house. It also is a mono transmitter, and has added filtering which would somewhat attenuate the signal. Keeping that in mind, the coverage ranges are *very* close to the same, but the Maxell doesn’t take constant retuning, and is a commercial FCC compliant device. It also has a nice stereo signal as opposed to my “kit” transmitter which is mono.
My “kit” took a LOT more work to get a decent sounding signal from, and actually cost more (after shipping) than the commercial Maxell. I did indeed learn a lot from building and running it, but if a person wanted basic “whole house” coverage or maybe “Very Near Neighbor” community coverage via part15 FM, the Maxell FMT-1 would be the clear winner for being able to get a station on the air fast and easy without having to wonder if it is within compliance or not.
I would say it does a better job than the one I built from kit, is easier to use, and is less expensive.
I have a bit more testing to do yet, but this probably concludes the “cheap portable radio” section of the tests.
Daniel
Car Stereo test
The receiver is an Alpine Com9821 with a stock antenna. The manual says it needs 1.3 uV at it’s 75 ohm antenna terminal to achieve full quieting for stereo. .8 uV for usable mono.
This test was for full quieting with a solid stereo signal.
The transmitter was in the same location as for the “cheap portable” test, plugged directly into the CD player which was powered by an AC adapter.
North – 241 meters (approx 790 ft)
South – 155 meters (approx 508 ft)
The Eastern direction wasn’t possible to determine the edge range because of how streets are laid out here.
241 meters is about .15 miles. That was the best range we could get for “rock solid” reception that could be as appealing to an average listener as the commercial stations. But the signal was detectable beyond that and even *barely* recognizable at some spots as far out as 790 meters (2591 ft, or almost half a mile).
Daniel
Summary
The Maxell FMT-1 did quite well. Sound quality is very good, stereo separation is nice and evident, and the range it can get is surprisingly good for a unit that is basically a 2 inch wide disk with no external coax/antenna at all.
For use as the transmitter for a very small scale community radio project, it could do the job. For 20$ it *may* be the lowest priced answer to the question of “where can I start if I want to do part15 FM?”.
It does have some drawbacks.
The choice of frequencies it can transmit on is very limited. 88.1, 88.3, 88.5, or 88.7 Mhz. But that would only be a problem if none of those frequencies are usable in your area.
It is not waterproof/weatherproof for outdoor mounting. But small tupperware and etc containers are cheap.
The “on/off” switch isn’t a type that stays on if power is removed. The most obvious remedy for that would be to modify the circuit, but since that could void the FCC approval, some sort of a mechanical trigger could be added in the waterproof/weatherproof container mentioned above.
The unit is battery powered. It’s 4.5 volts and the current seems to be quite low (I haven’t made any measurements yet, but the signal was still good after 6 hrs of continuous operation off 3 AAA batteries), so adding a small power supply of the right voltage and current wouldn’t be too difficult. One would have to check as with the audio extension cable to make sure it doesn’t significantly add to the ERP of the installation and also do what is necessary to prevent/eliminate hum, but those aren’t at all impossible issues to cope with.
Overall, for the money, it’s an extremely nice little transmitter. It could be workable for many people looking for a simple and inexpensive way to have their own little house or very small community station.
Now “what’s it’s range” would depend on how you figure and think of such things. *I* would tend to say it has a nominal range of 150 ft. Which is the smallest distance it “got out” with a good signal to a really cheap portable radio.. Someone trying to market it as a possible station transmitter might say it has a range of “over 1/4 mile”, taking the diameter measurement of how far away it could be picked up by a reasonably good car receiver. Someone really pushing it and trying to stretch the “specs” as optimistically as possible might say “a mile or more!”, since you can just *barely* recognize the signal on a good car radio in some spots up to a half mile from the transmitter and taking the barely recognizable signal range as the radius of the circle and as such defining “range” as the diameter. But that’s advertising/marketing type claims. I tried to keep my measurements for this review as practical and commonsense as possible.
Being realistic and stating the range the way I *think* Keith states the Rangemaster’s range on the AM (based on the many assorted discussions here about the Rangemaster), I’d say it’d be reasonable to say the Maxell FMT-1 has a range of about 1/10th of a mile. And like the Rangemaster, it comes fully assembled, has good sound, is FCC approved, and requires no license.
Could someone buy an FMT-1 for 20$, have (or get) a microphone and some sort of audio source like a CD player or whatever and a small mixer (or even just a simple switch or 2 potentiometer homemade mixer), could they have their own part15 FM station on the air? Yes. I would say so. Very much “bare bones”, but it’s a nice little transmitter.
Daniel
Addenda
A few brief observations after having used the FMT-1 as my part15 FM station’s transmitter for over a month:
1.) The sound is extremely good provided the audio isn’t overdriven. It definitely is not a “toy” quality sound if you watch levels. Drive it modestly, and if you like more “beef”, use a compressor in your audio chain. I prefer the sound without compression, personally.
2.) The unit does not seem to have any internal clipping for frequencies at 16khz and up, so if you don’t clip those with an equalizer, it will interfere with the stereo pilot tone and that doesn’t sound good. Easy to fix, I just used my equalizer. (It *does* have pre-emphasis built in, however.)
3.) It is very good on batteries. I prefer not to modify the unit at all and as such I’ve been running it on battery power. I’m not on the air 24/7, but I get over 24 hrs (close to 30 total) from a set of generic alkaline batteries. When the batteries start to weaken though, the audio and signal decline rapidly. So when the audio starts to sound slightly distorted, time to change batteries.
Overall I’ve been pleased with it, and even if you don’t have much interest in the rather short range of FM part15, you might still want to consider it with a small reciever as an STL for your AM part15 station.
Daniel
Certified unit designed for outdoor use needed
Although I’m doubtful that millions of dollars could be made from it, this interesting review demonstrates that useful Part 15 FM operation lies within the realm of possibility. It would be great if someone were to offer a certified Part 15 compliant transmitter designed for outdoor mounting.
Other features that I would consider essential:
Unlike AM, non-certified FM operation is just not worth it unless you are using a device that only goes a few feet. And what’s the fun of that? 🙂
WEAK-AM
Classical Music and More!
Here’s an interesting review site for these FM Modulators
http://fmtransmitterreview.com
I see they also have a blog:
http://fmtransmitterreview.blogspot.com
From the fmtransmitterreview.com web site:
We rate each FM Transmitter based on 4 qualities that we feel are critical to a customer having an enjoyable, versatile user experience. (i.e. you feel it was worth the money). We admit that no FM Transmitter has been able to achieve a 5 out of 5 star rating. We keep a strict quantitative analysis of each FM Transmitter.
The highest rank a FM Transmitter was able to achieve was by the Whole House FM Transmitter with 4.25 stars. There were several that fell below 2 stars and most within 2.5 to 3 stars.
Those 4 qualities are:
The Number of Frequencies the FM Transmitter Can Broadcast On –
(The more frequencies you have available the more choices you have in a populated area.)
The Number of Audio Sources the FM Transmitter is Able to Broadcast From –
(The more audio sources you have the more things you can broadcast like computer, satellite radio, TV, etc.)
What Ways a Person Can Power the FM Transmitter –
(This is important if someone wants to use it in multiple settings like their car, home, office, boat, deck, etc.)
How Far the FM Transmitter Will Broadcast in a Typical Setting –
(This is the “name-of-game” with FM Transmitters. The FM Transmitter may cover the entire public FM band but if it can’t broadcast then what’s the point of using it.)
View a quick list of all the FM Transmitters reviewed
Experimental broadcasting for a better tomorrow!
Yeah WEAK, now for
Yeah WEAK, now for home/community station use, all those qualities would just rock! I’d be very surprised to see them in anything as low-cost as the unit I was reviewing here, but that’d definitely be more optimal.
I don’t use this unit outdoors, though I used a temporary rig to have it outdoors for the testing. I’ve thought about the possibilities of a weatherproof container, maybe a mechanical actuator to hit the “on” button, and figuring some sort of power supply.. But.. adding a power supply might or might not void the certification. And since it does what I want it for with the xmitter indoors, I’m not likely to go to much in the way of heroics to mount it outside.
scwis: Neat little review site. I’d agree with them on the # of frequencies being very limited. So far as # of “audio source options”, well, there are adapters. Power source options, yup, it only comes with one. I’d really wonder where they got their distance estimate though, since I didn’t find 10 ft to be true in actual testing. Even a handheld portable receiver that might win my nomination for “worst receiver I’ve ever owned” could pick it up clearly at well over that.
“The distance seems to be similar to other FM Transmitters of around 10 feet. This would also be expected since it only usese 3 “AAA” batteries.”
… is perhaps not the best way to estimate FM transmitter performance. Since the power output of a legal part15 FM system is in the nanowatt range, 3 AAA batteries could easilly manage it and even exceed it by a lot. In fact, I suspect that if a part15 FM transmitter were made “as efficient as possible” by leaving off things like LED indicator lights and leaving out audio circuitry so it could be done outboard? Probably the batteries would last close to their shelf life, since the actual power output for legal part15 FM is so small.
As a sidenote to this review, I gave 3 of the Maxell units as Xmas presents to people who had found my little station highly interesting. One was to a person who was here for the holidays and we compared the range and found it to be similar to mine. So I don’t figure I just “got a good one”, the performance appears to by typical. Or perhaps typical when the unit is *not* used in a car. I did no testing of the unit with it inside a vehicle, since that isn’t my interest.
Daniel
Outdoor use
It wouldn’t be that hard to put one of these commercially available units in a weatherproof enclosure, and I don’t think that alone would violate its certification. But when you start hooking on additional cables, that’s where it starts to get into a gray area, I think.
As an example, it would not be that hard to modify the C Crane transmitter to do just about everything I suggested. It is synthesized, so it covers the whole band. You could mount it in a weatherproof box. You could run audio and power cables to it and put ferrite isolators on them to stop them from radiating. It would not be necessary to remotely control the frequency, though that would be a nice feature. It might be argued that if you don’t open the unit, you haven’t modified it.
The main problem with the C Crane appears to be its lackluster range. If there was a synthesized unit that had good range and audio quality, that would be interesting.
WEAK-AM
Classical Music and More!
Another “Review Document”
I almost forgot about this one
The NAB took the time to create a list of the most powerful FM modulators:
http://www.nab.org/xert/corpcomm/NAB_Part15_Study.pdf
In this test, certified units by Akron, Belkin and iRiver/iRock were found to be the most powerful aftermarket devices, while the kits (Ramsey/Hobbytron) and manufacturers’ dedicated devices (like Sirius units) that were NOT certified (how’d they get away with that?) were way too powerful .
FCC ID numbers were provided, so they should be easy to locate.
Experimental broadcasting for a better tomorrow!