Testing and Production are two different animals as Tim said "All the certified transmitters I've tested were rather substantially over the limits in the field, with the exception of the C. Crane." Which leads me and i am sure most of you reading this thread, to believe that C.Crane Co. is the only company so far that does not fudge on their testing for compliance and the transmitters they sell remain legal a the production line and into the hands of consumers.
So what are the other companies doing? Sounds to me like they are jacking with the power after the fact in order to try and stay on top of the game. I mean lets face it, there are thousands of fm modulators out there on the market and they all vary in power output and craftsmanship.
I may just have to retire the Ramsey FM 25B and buy a C.Crane after all.
On the same note, i have one of those modulators that plugs into the cigarette lighter plug made by Memorex (i think) that was damaged in the car one day.
The pigtail or plug that goes into the lighter socket was broken off and the + & - wires were just dangling there, i figured for $15 it was a loss but instead of throwing it out, i put it in a box to tinker with later.
This thing accepts line input, an SD card and a USB flash drive, includes a remote control and has sound settings that are kind of like the standard settings on a Windows OS sound card. Settings include Rock,Soft Rock, Pop, R&B, Flat , Country and Classical. A tiny screen tells you what setting you're using, the name of the mp3 you're listening to,frequency and input volume.
You simply cannot over drive this thing but on the other hand it won't go past 60 feet when plugged into a cigarette plug. Since the plug is broken off, i decided to wire in a new negative and positve wire then plug it into a 12 volt regulated power supply, with three feet of wire and a usb thumb drive the transmitter would not go much further than two rooms away before static started in the walkman. Past that , it was in and out on 89.9 fm.
It did the same thing on 107.9 as well. So you might say without an FIM this modulator might be under the 250 uV/m and could well be counted as a legal certified FM modulator, but wait, there's more! It will transmit below 88.1 mhz so maybe it's not so certified after all.
Thanks for the test once again, Tim.
Barry of BBR Yardwide
What about the transmitters you buy at Wal-Mart or any discount store? I'd also like (even though its not certified) to see what the field strength is for the CZE-T200 which at the 1mW setting goes 200 Ft. I'm betting its close though not certified to legal.
On the point of the better manufacturers are not all sending a unit to be tested and then putting into production something else. To draw a parallel if something is labeled certified organic are we being lied to? If something is certified kosher can you assume it is, passed all the requirements?
I don't believe companies want to operate fraudulantly intentionally.
I would be interested in seeing if you could find out what test facility did the broadcastvision and get some explanation for this.
Maybe there's something to what Rich said about readings in a test facility and a test out in the field.
Mark
I've only tested ONE BV unit. However, previous transmitters that were over were tested. Whole House 3.0 grossly over the limit when I tested it last year. I just purchased and tested five more of these. Everyone, equally over the limit. Yet, I tested ten C. Crane units and all were legal and very close in output.
Anyone can buy a BV transmitter. They're marketed by many sellers and are widely available. It just so happens that the BV site pitches them to fitness centers, byt what about the hundreds of other sellers on the web, Amazon, eBay, etc. Shall they add some qualifications for sale e.g. "Available only to licensed fitness centers. Installation requires the transmitter being located in the bowels of your business, away from any adjacent walls shared with other businesses, ouside walls or windows"?
It's illegal. It can't be certified at these levels.
So far every transmitter tested is substantially over the legal limit except the C. Crane, which tests have shown are actually consistently under the maximum allowed by law.
There areally aren't inconsistencies in test results. There are issues with what the certification lab says, and what the devices are putting out in the real world.
TIB
To me, it looks like there's a precedent for exceptions to be made with a product for a specific use. I'm thinking of the Talking House with external ATU. Many P-15 fans have pondered how that passed certification, being that there's a long feed line between the transmitter and antenna, where 3 meters is supposed to be the total maximum for the antenna system.
Now that I've had more experience with transmitters like the Talking House and other ones now, I can see why the ATU could have been approved, it's that the antenna inside of a house is just not all that good at getting out, I've experienced it now.
Not saying that anything like that has happened with FM transmitters, but a specific business was able to prove a need, and it was accepted, in seeming contradiction of the rules, and anyone could purchase the system.
No, I don't think the FCC allows exceptions.
For one thing, the FCC has no control over how a transmitter will be used. Someone might use, say, a Talking House inside their home, and run the wire up the wall. Someone else might mount it in a weatherproof box up high. Similarly with an FM transmitter, where being out in the open and up high gives you much greater range, particularly at elevated field strength levels.
The lack of control over how a transmitter will be used is why FM field strength legal limits are so low - they practically guarantee that you're not going to interfere with anything. You can't say the same thing about a many milliwatt transmitter, which can get significant range (Tim got over 1700 feet at 25 milliwatts, and that was with it and the receiver at ground level).
That's also why I believe that the ONLY way that FM unlicensed broadcast limits are going to be raised is if they are lumped in with whitespace devices. The spec for whitespace devices states that each device will have a method to determine its geo location, and it will then check the frequency they are going to be transmitting on in a national database for potential interference. That will then determine the power level (if any) that the transmitter can use.
Thelegacy has espoused similar ideas in the past.
If that happens, then the interference issues with unlicensed broadcasting goes away.
Problem solved. Because if there's interesting and meaningful stuff being broadcast in the whitespace frequencies, people WILL get the necessary radios to listen in.
It goes back to my first question when I founded the NRR and that is why the Transmitter Antenna for field strength? It should be from the outside of your building. And these transmitters need variable outputs. Better yet they need to check with the FCC database (the technology is here now) and your allotment should be based on your location. If you live 50-75 miles from the nearest FM station what does it hurt if you put out 7 Watts? On the other hand if your in Dallas, TX in the middle of the city 25 mW on FM could pose a problem with enter modulation or mixing with other frequencies that create a harmonic of its own similar to the pagers and Ham Radio on 2 meters.
Our spokesperson for the NRR and I have gone over this as to why I’m thinking for the Hobby Radio Service for FM it should be required that you live in a rural area. Though he says its unfair for me to add this as a requirement. So I’m thinking Power VS Location should be required but coming up with a formula will take lots of research and paperwork to present to the FCC for proof under real world conditions.
The FCC could be thinking of the old rule of outside the premises and again that is the way it should be. This way you could truly get the maximum range and yet expect no issues no matter where your location may be. Lots to iron out here.
Could all of these research findings make the FCC again take another look at all the FM transmitters just like what happened after the NAB study? Are we shooting ourselves in the foot by uncovering all of this? One thing is for sure I believe somewhere an FCC official is reading these tests.
At the risk of hijacking my own thread.
Only in rural areas is a bad idea. I guess you'd have to define "rural area" as darn near any spot in the USA has an FM station within say 60 miles.
Now, I'm not really rural. There are FM stations all around, but all in towns of less than, say, 20,000 people. You have to go nearly 60 miles to get to a city of over that size.
The commercial stations I work for have assigned EAS stations that we must monitor. The two stations are about 60 miles away and reception is tricky and require a tuned dipole antenna, oriented just right for acceptable reception. We would be very susceptible to interference that would basically wipe out our link to legally required emergency monitoring were there a low power station causing interference near our two assigned receive frequencies.
There are hundreds of stations across the country doing the same thing.
Consider my example in the test above. I tested interference possibilities with an example of a consumer listening to these stations (The stations I reference in my interference test above are the stations we must also monitor for EAS). It was quite easy for the Broadcastvision transmitter to completely wipe out reception of these stations. I know many people who listen to the distant classical music station. A transmitter as you describe, in a "rural area" say, 60 miles away from a station could easily wipe out that station in that rural area that someone is trying to listen to. Remember, in a rural area there are people trying to HEAR those distant stations. Interference from a local hobby FM with any useable power would be a threat to what they can listen to.
Yes, careful choice of a frequency might minimize the problem, but pick a spot on a map, make a circle 60 miles in radius (that would be 120 miles in diameter) and see how many stations including full power, LPFM and translators that are in that circle, and see what's left. You'd wind up with all hobby broadcasters moving to states like Utah, Wyoming, Montana, North and South Dakota, etc trying to find a spot far enough from an established broadcaster.
Just some thoughts on the "rural" concept.
TIB
"The commercial stations I work for have assigned EAS stations that we must monitor. The two stations are about 60 miles away and reception is tricky and require a tuned dipole antenna, oriented just right for acceptable reception. We would be very susceptible to interference that would basically wipe out our link to legally required emergency monitoring were there a low power station causing interference near our two assigned receive frequencies.
There are hundreds of stations across the country doing the same thing."
That is exactly the situation the cluster I work for is in. I was able to get a waiver from the state to monitor closer signals, you might try checking with your state association of broadcasters to see if they offer a waiver for stations in your situation.
Oh Tim you’re right about this as we need to look at that as well. I was thinking that you have to be at least 20 miles away from a City Radio station to be in the Entry point area for Hobby Broadcasting. Your in a Rural area as far as I can tell.
Deltaville is 19.9 miles from Gloucester, VA where everyone tries to listen to 99.1 for the weather reports. On TV they watch Channel 6 in Richmond and the nearest town to Deltaville which is mentioned is Kilmarnock or Mathews, VA. The only way for us to get real time weather reports is through the Internet by using the Viper Weather app.
Since I’m 19.9 miles away from Gloucester and even a 7 Watt signal probably would not hit Gloucester unless you had a 3-6 db gain antenna with good height I could not imagine too much interference happening to Gloucester’s 99.1’s EAS receiver. Again this would be if a Hobby service was legal and we’re looking at around 1 Watt at least.
The big thing would be temperature inversions. In real world experience a 310 mW transmitter can transmit miles further during a good ducting effect. Fog is a great natural artifact that will greatly improve low power signals even across town. In areas and situations where others were able to do experiments and relay them to us we’ve found that a 310 mW transmitter on a 5 Ft wire Indoors will sometimes cover 4 square miles in Full quieting Stereo. So the check every hour after 6PM would have to be strongly imposed. The Transmitter would be required to have a built in clock to which it receives time information and or a thermometer where as the transmitter would have to remain outside. When a 20 degree drop is detected the transmitter turns off and monitors your transmit frequency and the one above and below yours. The sensitivity of that receiver would be required to be at least 0.9 microvolts (same as a car Radio). Then no possible jamming or interference can happen. In other words the service would be stupid proof (if that is a correct way to describe it).
Putting this all back into topic your field tests and range reports do indeed help in trying to form a reasonable solution to this issue so that everyone wins including the listeners who want to still hear their distant stations.
To bring this thread somewhat back on topic, it appears that even certified transmitters are capable of generating interference, particularly the Broadcastvision.
This is reality and it's always good to know the facts. Part of the problem is obviously having a somewhat flawed certification measurement system, and combine that with the fact that the average user of even a certified transmitter doesn't have a clue as to whether they're operating legally.
Whitespace devices are one solution.
Changing the legal limit to something that CAN be easily measured, such as microwatts (or milliwatts) is another.
But it's clear that something needs to be done, particularly since the existing FM band, already crowded, is becoming more so as time progresses, and things are only going to get worse.
RE: ... Changing the legal limit to something that CAN be easily measured, such as microwatts (or milliwatts) is another. ...
Accurate measurement of the r-f output power of an FM transmitter is not easy, or inexpensive.
Even if it was, that isn't the only operating condition controlling the potential of unlicensed FM setups to produce interference to licensed FM broadcast stations.
Such also depends on the gain, and elevation above the earth of both the transmit and receive antennas used for those propagation paths -- as well as _MANY_ other factors.
Recall that while FCC §15.219 included a limit on the input power at the final r-f amplifier of a legal, unlicensed AM system, it also defined the transmit antenna system permissible for it to use.
So far, none of this seems to have been recognized here by the proponents of "higher power for Part 15 FM."
Logically the FCC would be more concerned about preventing interference to licensed AM/FM stations than to relaxing Part 15 rules that could increase it.
A very compelling set of facts would need to be presented to, and accepted by the FCC for them to do so.
Suggested in a few posts back the rule should be like some other countries...say 1.5mW for example and this is..yes...so much easier to measure.
Ramsey had a watt meter that measured to as low as .1 mW if I remember, assembled for $150
The Decade MS-100 is the only transmitter I will use now and is the only one assembled on site by technicians, adjusted for compliance on site by an engineer, certified BETS-1, legal to broadcast outside, built to last indefinitely and in talking to Micheal at Decade, the president, the Ms-100 is max about 1.1 mW with RF set to max. and for BETS-1 the usual setting is 4-4 1/2 turns back from max. Easy for user to adjust for compliance if ever needed.
A Ccrane is not legal here at all because no IC certification and quite underpowered as far as BETS-1 goes and Tim's tests made it clear to be perfectly legal and worry free the Decade is the way to go. The Ccrane would be fine if they got it Canadian BETS certified also. Anyway, who knows how long they will make that one anyways?
But the broadcastvision is SO much over and has the output of a Ramsey FM-25B & 30B so how could this get certified?
That is the million dollar question!
Mark
Thanks you guys for the discussion. I haven't
read to all yet - I just wanted to get this comment
in.
Oh yeah - a person on the thread mentioned that
Walmart has some FM transmitters, and wondered
if they were compliant. Well I just bought a Scosche (sp?)
FMT4R FM transmitter at the local Walmart for about $14.00
(a high price for these) a couple of weeks ago. It has no
transmit antenna, and is certified. I know that mine doesn't
go much farther than my Bluetooth transmitter. And Bluetooth
1.0 (Right? Is that what it's called?) is rated for 32.5 feet, I think.
I'm only interested in covering the yard here on FM. Many
experiments have been done (by me more than 40 years ago...)
I'm just interested in Part 15 AM "DX" now, I guess.
Brooce, PART 15 Hartford