Hot off the press:
Another useful and comprehensive review from you, Tim. Nice work.
One observation: the 240 µV/m field at a 3-meter distance from this setup when it used a 10" stiff wire transmit antenna oriented in the vertical plane probably was measured when the antenna on your FI meter was oriented in the horizontal plane.
Results earlier in your review showed about a 48% increase in the field you measured when the transmit antenna was operating in the horizontal plane (other things equal).
Could the field when using the 10" wire transmit antenna oriented in the horizontal plane be closer to 355 µV/m?
Any idea about this? I do not see anything in the specs or I may have missed it. Thanks, John
Druid Hills Radio AM-1710- Dade City, FL. Unlicensed operation authorized by the Part 15 Department of the FCC and our Resident Hobby Agent.
Great review Tim.
The EDM I used to own had trouble with hum - obviously they've solved that probem. They also appear to have solved the signal bleedover into adjacent channels that I experienced.
I assume that there is no documentation associated with the transmitter telling U.S. purchasers that the power trimmer has to be at the absolute lowest position, and use the rubber duck antenna to be legal. Few of the people who would normally purchase this transmitter would have the necessary test equipment to verify that they are operating legally.
All in all, this appears to be a nudge nudge wink wink transmitter. It can operate legally, but it's highly unlikely that most purchasing it would do so (either knowingly or not). Unless, of course, they read your review.
Seems this, like the Decade, is really HI FI sound.....and from the photos on the website all regular through hole components like the Decade also.
I'm interested, but worried about not being certified for use in Canada.
Wonder if it would be better in the long run to get the rubber duck antenna instead of a 10" wire as the rubber duck is a 50ohm match for the output.
Oh yeah, That new Stones album is great! Liked you used that to test!
I thought I had done a horizontal test with that 10" antenna, but I could not interpret that in my notes when I got back to my office. By the time I got to that test I was about frozen! Certainly the field strength will be greater when both antennas are in the same plane. Although, most people will have it vertical I would think.
I will look through my notes and see. I was pretty sure I had that piece of data.
I was really just trying to see if it would operate as a legal Part 15 transmitter on this last test. Really, to get busted in this case the agent would have to be checking vertical and horizontal and that may not be too likely.
Anyway, I'll have a look, but yes, clearly, the horizontal reading would be higher.
Of the two Part 15 transmitter supplied antennas I've had none of them have been "real" rubber duck antennas. They have been simply a plastic antenna structure with a piece of wire inside. Basically a plastic rod with a hole up the center with a wire inside connected to the center pin of the connector and nothing connected to the shield side at all. Basically, a wire antenna in a plastic tube. The antenna you can order from EDM sure looks like the same one to me.
But of course a better match would almost certainly mean greater output which would make Part 15 operation unlikely.
I can't remember the documentation right now, but I do believe there was some reference either on the website or with the instructions (link at the end of the review) that said something about low power for Part 15 but didn't go into much detail.
I think it's a *wink wink* deal anyway, as is soldeering in ONE part reallly a "kit"? And what's the specific rule about kits anyway? There just seemed to be some "paperwork" details that seemd a little sketchy to me, but a nice operating and sounding transmitter, that's for sure.
Clearly, if you just bought it and started using it, you'd be way over Part 15 limits.
Website info (from the instructions pdf) states they are set for 75 kHz deviation from the factory.
It is worth noting that the documentation on the website is not for the exact same transmitter. It appears the models have changed a bit over the years, and there are several different models. The documentation shows the ability to adjust this, but the transmitter I purchased does not have this adjustment, but other models might, or might not.
Field strength was measured at High Power and with the supplied antenna but I wonder two things:
Is the transmitter 75 uS pre emphasis or 50 uS as with most of the Chinese imported in the USA are?
And finally what was the Range of this transmitter at its High Power mode compared to the Low Power mode which was closer to part 15. This would be nice to know for any attempt to start a separate Hobby Broadcasting service.
All in all sounds like a transmitter that has a great sound quality and could easily meet or surpass Album Rock standard so therefore I’d like to look into this more closely.
Honestly if I had the extra cash I’d like to experiment with this one.
Progressive Rock (Album Rock, Deep Tracks), Classic Rock
More Power for Hobby Broadcasters
I haven't been able to find any data on pre-emphasis for the EDM transmmitters. However, to my ear the audio sounded basically identical played from the mixer directly, as compared to listening through the EDM transmitter. I noticed no tinnyness or odd equalization. I listened for quite some time to both rock and roll and jazz piano. Both sounded exceptionally good.
I didn't do any range testing at all for several reasons. Perhaps the most important is that it's winter here and it was 4 degrees, and I didn't feel like getting out my snow shoes (yes, we actually have them) and trudging around a field checking range. And also, because every transmitter operating at the legal limit is going to have the same range. 250 uV/m is what it is, not matter the device generating it. Operating this or any other transmitter at any higher output would not be legal. Should any other power level become legal in the future, range between transmitters would again be comparable if they were all operating at the maximum limit available. This does allow for a rather extensive range of output so might meet future needs should things change.
This particular transmitter has bascially an infinite range of output within it's limits as there's the hi/lo switch that gives two different ranges, then the adjustable trimmer that lets you vary the power within the switch selected range.
I will say, that if I were going to run a station with this transmitter some processing would be necessary. Don't get me wrong, it sounds great, but modulation levels are not leveled out at all. Quiet passages will drop it to near nothing, loud segments will blast it way above 100%. To find a spot where it didn't surpass 100% left things pretty quiet most of the time. Some processing to smooth things out would be an improvement.
But this is perhaps one of it's advantages in the audiophile market, wide dynamic range.
If you're listening to your own music for your own personal use (and apparently a lot of buyers of the EDM transmitters buy them for this purpose) you can enjoy a pretty full dynamic range from loud to soft. But it you're "broadcasting" you generally want a more consistent level.
I could not find any information anywhere as to where this transmitter was built. One generally assumes China but I could usually find an indication of that on the circuit boards. Nothing on this one. Also no country of Origin as required on products imported into the USA.
I've tested quite a few FM transmitters, so far all were certified except this one. Intersting to note that nearly all the certified units I tested were well over the legal limit.
This little bugger is very well made, although a bit more "industrial" compared to a BV or C. Crane that's more "consumer" looking (e.g. plastic).
I do see the other Part 15 site is planning a review on this in the future. Perhaps he will be able to answer more questions, as his was supplied to him by the company rather than purchased at retail, so he will likely talk with them to learn more.
I'm also amused that the SourceFM website talks about these EDM transmitters and states "Not approved by the FCC and operating them is a violation of Federal law with a penalty in the thousands of dollars and even jail time." Which is not really true. If you have this transmitter set for the legal limit (low switch setting and trimmer all the way down to low, and a short antenna) you'll be at the Part 15 limit. This is where the responsibility of the owner/operator ends. Actually operating it improperly would be a violation. That would be the only possible violation for a user. Otherwise the only people who may get in trouble would be EDM, for selling a transmitter that is not certified, IF in fact it was deemed to NOT be a real kit. But YOU would not be in trouble for OWNING it.
It also comes with a four year warranty!
Kind of makes you wonder why a distributor doesn't get these certified (running at the lowest power level possible) and then resell them legally. After all, that's what Decade did with the CM-10.
From Reply 9: Website info (from the instructions pdf) states they are set for 75 kHz deviation from the factory. ...
An earlier post in this thread inquired about the pre-emphasis this EDM transmitter used.
The pre-emphasis (if any) supplied internally by a transmitter depends on its circuit design and adjustment.
However the carrier deviation of an FM transmitter depends on the audio spectrum of the source, its input level at the transmitter, and the pre-emphasis used (wherever located).
Even if a transmitter has been designed/adjusted to add 75 µs audio pre-emphasis, that would not enable its manufacturer to set it for +/-75 kHz deviation for all input conditions, when shipped from the factory.
The certification process is quite expensive. Also to sell as a certified transmitter all the user adjustable power controls would have to be disabled and they would have to be sold with either a built in antenna or an antenna with a non-standard connector.
As I've poked around trying to learn more about these it seems they actually are made in South Africa, and they've been around for quite a few years, obviously ghoing through model and design changes and updates over the years.
They're quite popular with the Christmas light animation folks, too.
I'm assuming that they're able to sell them because they're kits? I know there has been some discussion of the legality of Part 15 transmitter kits, and soldering on one part is hardly a kit. But it looks like they've been doing it for many many years. This is a transmitter that seems to be quite popular world wide.
Yes. I was clearly bewildered at the moment. Plus, I'm getting information off an older instruction pdf. Their information isn't presented as clearly as one would like, not updated, and I suspect some translation issues as well. What I was trying to refer to is on this page:
But there is no mention anyplace about pre-emphasis. I like to think that if I was listening to 50 us pre-emphasis I would have been able to notice audibly. I listened over the air to recordings I know very very well and they sounded completely perfect to me.
Maybe you can glean more info from that pdf.
Tim, I can understand the antenna connector issue. But even certified transmitters such as the Decade or the C Crane are power adjustable if you know where to do it. I suspect that you could get away with putting a blob of glue on the variable pot that controls power output, and that would satisfy the FCC (that's what Decade did on the MS-100's that I purchased).
I also understand that certification is expensive. But then, so are the potential fines for selling non certified transmitters. It just seems to me that there's a business case there. Although whether they could realistically compete with the C Crane's is up in the air. I'm pretty confident that most who purchase the EDM 'kit' won't run it at the lowest power setting.
People that would buy this like the Decade would buy it for the quality(build and sound) and would pay more for something you don't plan to replace in a year or two.
It could be certified and power set at the factory for part 15 if shipped to the USA and BETS-1 for Canada and set for that if shipped there, like the Decade is. But the antenna would have to be known and equal for all models. Like was mentioned there are certified transmitters where if you know how you can adjust the power.
I like this from looking and Tim's review but worried about not approved for use in Canada even if I am at BETS-1 levels.
I believe they're getting around the non-certified issue by selling these as "kits". Now, I do not claim to know the FCC rules regarding the sales of kit FM Part 15 transmitters, and near as I can tell, neither does anyone else, based on the wide variety of interpretations and statements posted around the internet. It is legal to sell a circuit board and baggie full of parts as a kit? And at what point does it not become a kit? I think they're stretching the rules about as far as possible, selling a "kit" that requires soldering in one part, and that's not even a component, but just a connector. The old instruction sheets they have online indicate you must insert an IC as well, but the one I received did not need that done, just the power connector. And I've read posts about these transmitters from a wide variety of sources and found no one recently who needed to insert the IC. So, I suspect that just barely, they get past the certification, legally, by having "some assembly required".
From the Hamilton Rangemaster site there's this, which is introduced as an actual queery to the FCC, and their response. The introduction to the article is "FCC law does allow for building personal homebrew transmitters. This law is pretty clear that your homebrew is not to be a kit (see below)." That last sentence does not make any sense to me. Nowhere does the response from the FCC saw it can't be a kit. It does say that the builder is responsible for the transmitter to be operating legally. Even if you build a home brew transmitter from old TV parts, it's still up to YOU to be sure it's legal. That's the case for ALL transmitters, even if you buy a nice shiny new certified unit. It's still YOUR butt if it's operating illegally. Having bought a certified transmitter does not remove you from the responsibility to operate it legally. Anyway, here's what they say:
We would like to inquire about the legality of operating a Kit intended for Part 15 use. These kits are prevalent, for both the FM and AM band. Most of them advertise they are Part 15 compliant. Here are applicable rules we have found:
Part 15.3(p)Kit. Any number of electronic parts, usually provided with a schematic diagram or printed circuit board, which, when assembled in accordance with instructions, results in a device subject to the regulations in this Part, even if additional parts of any type are required to complete assembly.
Part 15.23(a)Equipment authorization is not required for devices that are not marketed, are not constructed from a kit, and are built in quantities of five or less for personal use.
We would appreciate direction in this matter, Thank-You.
The kit does not require equipment authorization to be marketed (sold) but they would still need to comply with the limits set forth in corresponding sections of part 15. The responsibility of compliance lies on the user, or the person who assembles the parts together, not on the manufacturer.
So it seems clear that the builder of the kit assumes all responsibility. There is no requirement of compliance on the manufacturer."
So, what gets me is this (which is supposedly from the FCC)
Has it not been determined that in ANY case final responsibility lies with the user, not with the manufacturer? Be it a certified transmitter or not? Can I buy a Fail-Safe transmitter with it's pretty FCC ID and certification on it, run it at it's extremely over the limit output, and if the FCC comes knocking just say "See, it's certified. No need to talk to me about it?" No. It seems to be well established that certified or not, you're still on the hook in the end.
Also I note it states above "any number of parts", so I guess ONE part would be "a number" right? Just gets weirder the more you think about it.
Seems like a great transmitter, I'm all for technical excellence, and that seems better than most at the present time.
I have a rubber duck flexible antenna from one of the earlier transmitter models out there of its kind, years ago now. One day it fell behind my desk and the coveing over the antenna part came off at the base.
It happened to be a long spring, with a small length of wire of the top, one to two inches I guess, which I assume is supposed to be the radiator, with the loading coil below it. I'd wondered what was in there because it wasn't a quarterwave in length.
Good that it was loaded, to make a better match to the transmitter's final. I was able to snap the covering tube back on to the antenna and it seemed to work fine.
What companies should really do to take it easy on their finals is use resistive divider, or pad, to give a proper load to the transmitter, and also provide a tap for the antenna to get some power, especially since there's already enough power to work with.
I like your reviews Tim, solid and thorough, just the info, and not surrounded by all the pageantry I usually expect from people in the radio business when they test equipment or transmitters.
"Kit" seeems to have been defined as some assembly, and I've seen it done that way for decades. One outfit used to sell a kit that was a stereo exciter card, 100 solder connections finished, and you just had to add a few components in the RF section to complete it.
Think too, the majority of the people in this world have never touched a soldering iron, so in a way even one connector might be a chore for a Joe six pack. Now I wish more people would learn to solder and do for themselves, but at least they're not getting burned by sizzling balls of rosin, and the world's probably a safer place because of it.
Here's a photo of the circuit board of the EDM for those who are interested:
And also the correct link for the present exact manual for this transmitter (which is basically the same as the one posted). You get the link for the right paperwork when you return to the ordering pages after making payment. Note it says documentation comes with the transitter (it didn't) and it still says you have to install the processor chip (mine was installed already).
The power output transistor looks like the dreaded GAL5.
That would be a deal breaker for me as that chip was an issue in the Ramsey. With no harmonics or spurs I assume their using the newer BH1415F chip for the actual FM frequency and the built in limiter like those newer Belkin transmitters use.
NO! that is not the dreaded GAL-5. The GAL -5 is not that shape at all. That is just a surface mount output transister. And if you look closely you will see a coil across the output which looks like it functions as a protection for static voltages. With DC you would see continuity from conductor to ground but with RF at the FM frequencies that coil would have a high impedence, same as my Decade MS100.
But it's still a good idea to make sure you have no sparks jumping off your fingers if you touch the arial.
This model shown is the basic one. There's also an audiophile model with all through hole components and no surface mounts except for the display processor. http://edmdesign.com/features-1.html
The GAL5 I installed on a FM-100 looked just like that.
The EDM sounds as if it would be a good candidate for leaky cable (radiating cable) if you were planning on wiring up a church, school campus, auditorium or even an apartment complex. The variable RF control is a nice feature even if the settings are a bit weird and it puts me in mind of my Ramsey FM 25 B. I am able to get pretty low power output by turning the pot almost down to nothing and remain in the expected 200 foot range using just a wire dipole pinned to the wall.Heck, most of the Ramsey Am/Fm transmitters can be adjusted in the same manner with the exception of the AM-1 and the entry level FM transmitter Ramsey used to sell for $40.Edit: ok not so much the Ramsey AM's, but the FM's can be adjusted.Now if i can just convince the gooberment that this is a learning campus and not our house I would string radiating across my yard and fences. lol Tim thanks for doing these tests and reviews.
Barry of Blue Bucket Radio 1620 AM - http://www.geocities.ws/bbrcomms/ - WQYY 664
Today I received two of the antennas that EDM sells to go with their transmitters, and here's what I can tell you.
When put on the MFJ 259B antenna analyzer they tune up at about 103 MHz. I say "about" because the case of the device it's connected to becomes the other side of the antenna and moving near the case with your hand or another metal object dramatically changes the resonating frequency. The antenna is nothing more than a coiled stiff wire inside the rubber sleeve. The shield/chassis side of the connector connects to nothing. There is 0 continuity between the center pin and outside of the connector. Disassembly confirmed that there's nothing connected to the shield side of the connector. This means that the connector and case of your device make up the other side of the antenna. Changes in this device change the resonant frequency of the antenna. E.G. if I add two extra adapters between the antenna connection and the antenna itself, the frequency drops to 100. If I take about 20 inches of wire and clip it to the case (chassis) of the analyzer the frequency drops further. So obviously the amount of metal that is part of the ground side of the connector (the chassis or case of your transmitter if it's metal) will have a profound effect on what frequency is most efficient when transmitting. The antenna has a built in BNC connector and comes with an adapter to facilitate plugging it into the RCA connector on the transmitter. This gives you about 2 inches of total metal on the"shield" side of the antenna.
I'll post a couple pictures and also update the review posted on my testing website with this antenna information.
Looking forward to what you find.
Tim, regarding your comment in post #11 -
"I haven't been able to find any data on pre-emphasis for the EDM transmitters."
I just ordered the basic model EDM-LCD-CS-EP with a mono chip instead of the default stereo chip (for maximum range, given the limited field strength allowance of FM Part 15). After ordering, I began to wonder about the pre-emphasis and, rather wishing I had thought to ask the question beforehand, e-mailed them about it and received the following response,
"All units shipped to the USA get programmed with the correct 75uS pre-emphasis."
- which would explain why your unit sounded so faithful to the original program material. I know this thread is a few months old, but figured this could be useful information to anyone thinking of ordering one of these transmitters.