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wallleyes

Legal FM Transmitter Frequency

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What are the legal frequencies that we are allowed to use with our fm transmitters for our christmas display? Can we use the non-commercial educational (NCE)?Here's what i read at Wikipedia.

The term non-commercial educational (NCE) applies to a radio station or TV station that does not accept on air advertisements (TV adds or Radio adds).


On the FM broadcast band, the FCC has reserved the lowest 20 channels, 201~220 (88.1~91.9 MHz) for NCE stations only. This is known as the reserved band. It also includes channel 200 (87.9MHz), but only for class D NCE stations.

I have planned to use 87.9 but want to make sure iam allowed to use this channel.Or do i have to use a channel between 92.1 - 107.9?

Thanks for any help.

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I think (and I am no expert) you can use any open channel in your area.

Is 87.9 an unused frequency in your area?

You can check using this website:

http://www.radio-locator.com/

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Yes 87.9 is crystal clear.It is the clearest station i could find.

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This has been discussed many times over on PC.

Bottom line, Dont soup up the transmitter trying to get a mile or two out of it. Don't try to xmit over another radio station. Don't try to make money with it.(paid ads)

And you should not have any issues.

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Jeff Millard wrote:

Their coming to take us away ha ha he he ho ho! (They absolutely hate Christmas music!)


LOL...I remember when the ASPCA had that song banned from radio play in Seattle...

ASPCA -

Activists
Stopping the
Playing of
Christmas
Anthems

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From the FCC rules:

§ 15.239 Operation in the band 88–108 MHz.

(;) The field strength of any emissions within the permitted 200 kHz band shall not exceed 250 microvolts/ meter at 3 meters. The emission limit in this paragraph is based on measurement instrumentation employing an average detector. The provisions in § 15.35 for limiting peak emissions apply.

So how many of us have equipment that can determine if we meet this rule? Probably 0. So we rely on rules of thumb, which tell us that if we can hear our signal a mile away, then our signal is most likely too strong.

That's the theory. In practice, the FCC does not drive around in a van searching for illegal FM signals. They will only investigate if they get complaints. So the next rules of thumb are:

  • Keep the neighbors happy.
  • Don't transmit objectionable material.
  • Don't transmit on top of another signal that someone may be listening to.

If there are no complaints, you don't have to worry.

Here's another idea that's working for at least 4 displays in our area: Band together and use the same frequency as another display. If someone has already gone to the trouble to find a frequency that works, just use the same frequency (assuming you're far enough away - this won't work for a display on the same block).

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Under part 15 rules, the broadcast signal should not exceed 200 feet. If you Broadcast under part 15 you must accept any and all interference, and you may not interfere with any other broadcast facility. You are allowed to use any open frequency on the FM/AM band. Generally for licensed stations anything below 91.9 is the education "band" and 92.1 and above is the commercial "band"

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Guest wbottomley

We are fortunate enough to have the Demented Elf to give a presentation on this at the Christmas Carolina Convention on August 28th.

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As long as you are not transmitting on top of another channel and not more than a block away it is unlikely you will have any problems.

Others have already cited the fcc regs on this. Any frequency on AM or FM is allowed with the limitation of a low power transmitter.

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Hi Everyone;

Thought I would share this with you ......

I just received my FM transmitter ... I went with the Magic Black Box Eclipse 4000 Stereo ... It is rated at 500kw ... total cost including shipping was $130.

Of course I had to test it out ...

My office is below ground with a window facing to where the cars would watch my show from. My window was not tall enough so I was not able to extend the antenna completely.

From the road the sound was crystal clear in stereo. I decided to go for a drive and I was surprised to find that I did not start to loose any quality of the music until I was over 1 km ( 0.7 miles ) away.

Happy with the purchase ... all I have to do now is figure where I can put the antenna to get full extension of it.

Can I ask ... would going to a longer wire to the antenna effect the broadcast at all ?!

Dave

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RaceMedic wrote:


Can I ask ... would going to a longer wire to the antenna effect the broadcast at all ?!

Dave


Dave:

I don't know what effect a longer (or shorter) antenna lead would have. But, seems to me if you can hear it at 7/10ths of a mile, that should be all you would need. After all, I would imagine no one could make out different lighting effects at that range! :)

I also bought the 4000. It seems to be a nice unit with a good range. I haven't fully tested it for distance, but it appears to work very well for anyone within sight of my display. Hope yours works out well for you, too!

Cray

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I use a 100 foot coaxial cable attached to a dipole antenna and it was over a mile at 100mW. From what a fellow LOR said he heard it 2 miles away. I turned it down to 10mW and it is clear for .5 mile and could transmit data. If your at .7 mile in your basement I would leave it there. You put up an antenna to high you might transmit several miles. Might get you into trouble if someone 5 or 10 miles away gets a far station and you jump all over them. It would help you go farther but its up to you. I wouldn't if I were you.

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I agree ....

It is futher than I expected so why change it. :D

Dave

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Coax, just for discussion.

Depending on the quality of coax will determine the loss of the signal in the coax. Meaning that no matter what coax you use. The signal coming out of it will be less than the signal going in. And the loss increases with a) the length of the coax. b)the quality of the coax. c)the higher the frequency of the signal.

This loss is usually ofset by using a antenna that has more gain than the coax has loss. And antenna height usually will receive or transmit further.

So, using a low quality coax and an antenna with a gain of 1.0, and mounted low on the house can actually reduce the distance you can receive or transmit to.

Example use RG-58 instead of RG-8 or the better stuff known as hardline. I am just pulling numbers for illustration. At 100 Mhz and 100' RG58 will have a 6db loss (only 1 quarter of the power will exit far end of coax) and RG-8 will have a 3db loss (50% loss of power). Where as hardline might have about 1db loss or about 15% loss of power.

So, your coax is just important as the antenna/height.

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toddmoon wrote:

http://www.tmcnet.com/usubmit/2010/01/08/4565735.htm


The guy in this article should maybe consider moving to one of the moons around Jupiter. Maybe there he could could some peace. However I doubt it there is EM energy everywhere.

I could build himself a EM shielded room and go inside the room when he feels an attack coming on.


That's what I was thinking. Why would you move into a house that is anywhere near another building if you truly have a condition like that?


I wasn't going to say anything because I didn't want Jeff to accuse me of spreading paranoia ;)
But since I'm here, I was visited by the FCC twice in the 70's. Both times it cost me a reasonable amount of money. I doubt they have the resources to go out triangulating people's transmitters any more though.

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Cray Augsburg wrote:

RaceMedic wrote:

Can I ask ... would going to a longer wire to the antenna effect the broadcast at all ?!

Dave


Dave:

I don't know what effect a longer (or shorter) antenna lead would have. But, seems to me if you can hear it at 7/10ths of a mile, that should be all you would need. After all, I would imagine no one could make out different lighting effects at that range! ;)

I also bought the 4000. It seems to be a nice unit with a good range. I haven't fully tested it for distance, but it appears to work very well for anyone within sight of my display. Hope yours works out well for you, too!

Cray





Cray, depends on your location. I also have the Mobile Black Box Eclipse 4000 FM transmitter and my first test (antenna fully extended on a metal plate sitting INSIDE my house behind 2 walls) and my test run netted these results:

I was able to pick up my signal all the way into the back neighborhood which is across a LARGE LAKE, I barely had a signal loss but in one or two places. I could also pick my signal up OVER MY ENTIRE SUBDIVISION and half way into the subdivision that is just to the right of ours. When exiting the subdivision I could pick up my signal (I was using 95.9, an open channel in my area, no bleed over to any active channel) for almost 1 block away after exiting and going left out of our subdivision. Range was WAY over the FCC limits, I was getting basically close to a 5 mile radius with clear transmission of my signal! Now I figure there are possible several factors involved with this, the open lake across the street from my house (there are houses across the street on the lake bank) and weather conditions, this was done during a cold winter night, during a spring day, the distance was diminished somewhat, but still able to receive it in the back neighborhood across the lake, still with little to no signal loss. On a rainy day and night, then the signal dimished quite a bit and was sporadic from the back neighborhood in some areas, but still crystal clear in others. This back neighborhood is aprox 1-1-1/2 miles behind us. But could still pick up my signal over my entire subdivsion, which is a little larger than most being built back in the mid to late 1970's.



So that does tend to make me a little nervous and just a wee bit concerned that the MBB E4000 can transmit in such a range and that, again, being INSIDE my workroom inside the house, antenna on floor on a metal plate to hold it in place behind 2 concrete walls! My workroom is at the front of the house, but is behind the garage, so there is a 2 car garage distance to travel before the signal exits the house.



Needless to say, yes, I am and was impressed with the range, but also concerned since the range is further than FCC limitations do allow.

Thinking of trying to put some kind of dampening system on the antenna output to lower the distance/range and get this more in-line with the FCC requirements. Would have been great if the MBB E-4000 would have had a power adjustment feature to lower the power rating to lower than 500Mw for a lesser range.



But I have seen these in use at other displays and so far as far as I know no one has had any issues, so I'm going to use mine and hope no problems arise. If they would happen, I'd just shut the FM transmitter off and go back to external speakers, which I will also be using for those walking by on the sidewalk in front of the house.



Really hopng no problems crop up. Knock on wood!

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DavidPeterson wrote:

Or maybe fear this guy:

http://www.tmcnet.com/usubmit/2010/01/08/4565735.htm

I've read stories of a few of us being visited by the FCC. Generally they've actually been pretty friendly from the reports and mostly do things to help you come into compliance than to just shut it down. In one case they told the owner that they'd be back, but with the kids.



That guy in the link is PAYING OFF DOCTORS and maybe even lawyers! This is FRIVOULOUS!! He is, to put it bluntly(and somewhat nicely) full of manure!



Electromagnetic radiation is all around us EVERY DAY in EVERY DAY ITEMS!

Does this guy have a refrigerator, electric stove, dishwasher, incandescent lights, a hot water heater, how about a microwave over, TV Set(s)? EVERY SINGLE ONE OF THESE EMIT EMF (Electormagnetic Fields) and thusly if this buffoon is so sensitive to EMF, then he COULD NOT EVEN DRIVE A VEHICLE, vehicles electrical systems, even when using shielded wiring, they still emit HIGH EMF's and microwaves emit really high EMF's when operating, this is why PACEMAKER wearers CAN NOT be exposed or around them. Nor could this person live IN ANY HOUSE ANYWHERE because ALL HOMES have some form of EMF at all times!

I think this guy is just some bozo trying to have his way over something that is totally bogus, because there is NO WAY NOT TO BE EXPOSED TO EMF ANYWHERE or at ANYTIME!



Just buy an EMF detector and go around your home, one of the biggest culprits of EMF, EVEN WHEN OFF, is your TV SET!!!



Far as I am concerned this idiots case should be thrown out and NOT be wasting taxpayer money on such frivolity because EMF is all around us, all the time, there IS NO AVOIDING IT!


BTW: Hope this guys house isn't haunted! Ghosts and spirits also emit EMF and is why EMF Detectors are utilized in the field of paranormal research (of which I am also a part!)

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The dampening system I was referring to, I just couldn't think of the name of the device when I typed the message is an ATTENUATOR. But the drawback here is these things cost just as much, if not more than the FM transmitter they need to be installed on. Usually installed at the antenna output and then the antenna is connected to the other end of the attenuator. And another problem is trying to figure out EXACTLY which attenuator you need as these come in various sizes, configurations and ratings. So the wrong one wouldn't work correctly or would end up blocking the transmissions all together.



After trying to find the correct attenuator myself and because of the cost involved, I said to heck with it and plan on using my MBB E-4000 FM Transmitter as it came from the factory period. (most of the attenuators I found wouldn't even match where I could just install it by itself between the antenna and the tranmitter unit itself. Plus the attenutor that I would need, don't recall the website, but checked several and the one at the time (don't recall now) I'd need was in the price range of $250+ UP! And then I'd need adapters and extra coax to interconnect it as well. This was driving the costs up to well over $300+ and I just don't have that kind of money presently to invest, nor would I even want to on a unit that cost me with shipping and additional 33" telescoping antenna around $130!



There SHOULD be a LESS EXPENSIVE way to lower the range/signal transmission of these things without breaking the bank (if you can afford to do it, great, but I can not being unemployed and trying to find work! So that puts a damper on any extras I may need presently!)

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Gee Orville,

I dont know what gold plated rube goldberg you are looking for, but I found this.

http://www.fairviewmicrowave.com/bnc_attenuators.htm

Maybe if you have a 100 mW and you think that 10mW would work for you. I suggest that you get the top model in 10db. 10db will lower your power to the antenna by 10. And for those of you who still do not understand how the db system works. Every 3db will half the power or if amplifying it will double the power. And 6db will quarter the power to the antenna.


SA01B-10 $19.99 Cheap solution.

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Now THIS might be a stupid question on the same topic.

Would not simply not extending your antena the full length reduce your range of the broadcast ?!

Dave

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Wasn't looking for anything gold plated Max-Paul, just a CHEAP fix, and the ones I found were very expensive, I even contacted at the time, the folks that operated the site asking if there were a cheaper attenutor I needed for my purpose. The MBB E-4000 is 500Mw, so will a 10Db unit drop the range or do I need something more?

Radio is one thing I don't really know that much about, so anyone could probably try and convince me that the most expensive item is what I'd need to do the job, basically, again, not knowing much about how radio works in this type of respect, I am, to put it bluntly quite lost as I am sure a lot of others may be as well!



Thanks for the website link, I did look at many and never found this one, $19.00 isn't bad, but I do wish they showed or had a way to calculate the shipping charges before submitting to actually purchase one of their attenuators.



At least now I know where to find a CHEAP one that will work. All the others I looked at were not BNC male-BNC female, but other types of connectors requiring additional converters or additional coax with either the converter on end end or coax with the BNC-male BNC-female set-up.



The link you gave is the first time I've ever seen any of the attenutors with a BNC-male/BNC-female pass through type.



Once I am positive what Db attenuator I need, then I'll look into purchasing one from the website you posted the link too, just want to be sure I absolutely get the correct one before spending anything!

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RaceMedic wrote:

Now THIS might be a stupid question on the same topic.

Would not simply not extending your antena the full length reduce your range of the broadcast ?!

Dave


Dave from my understanding of reading about this on other forums and posts, just lowering the antenna won't decrease the range output, but it could very well damage the circuitry that outputs the signal to the antenna. I'm sure Max-Paul here could and will explain this in better detail. But I've read and heard loweing the telescoping antenna could possibly do some damage the FM transmitter.

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Max-Paul wrote:

Gee Orville,

I dont know what gold plated rube goldberg you are looking for, but I found this.

http://www.fairviewmicrowave.com/bnc_attenuators.htm

Maybe if you have a 100 mW and you think that 10mW would work for you. I suggest that you get the top model in 10db. 10db will lower your power to the antenna by 10. And for those of you who still do not understand how the db system works. Every 3db will half the power or if amplifying it will double the power. And 6db will quarter the power to the antenna.


SA01B-10 $19.99 Cheap solution.


Now that I know what I'm looking for, I found one closer to home from a company over in Miami Florida, cost $9.95 and $8.13 for S&H to my zip, total cost: $18.08

I found this 10Db Attenuator here for anyone else interested in getting one for their MBB E-4000 FM Transmitter: http://www.mpja.com/prodinfo.asp?number=16547+TE

Best deal I've found on an attenutor so far.

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