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An FM Broadcast Transmitter For Your Home
Bruce Perens writes "I wanted to be able to listen to net audio and my ham station around the house and yard. Those iPod FM transmitters don't have enough range. So, I bought a digital controlled, 100 miliwatt transmitter that covered my whole block the first time I plugged it into what was, until then, a recieving antenna."
Now every kid on the block will have their own radio station!! won't that be fun for like.... a week?
Just look in the DIY kit section of any electronics store, there's always a number of small FM transmitters, some of which get 2km range.
They usually have an electret microphone, but it wouldn't be very hard to modify one to take a line-level source.
should read..
...that covered my whole block the first time I plugged this product on Slashdot."
"
All the images on the linked page are exactly the same as the site selling them.
... has similar stuff - like this. And that's not the only one. they do various versions for, say, in-car use.
interesting way of sharing music - your own mini radio station
Screw you all! I'm off to the pub
if lots of people in the same block start using this?
.at least in europe it is almost completely filled up in the range that all commercial receivers use.
Is there some sort of auto free-carrier slot detection? because if there isn't, it will be nigh-on impossible to listen to the radio without interference.
The fm-band is pretty full already
I'd be pretty miffed if i could not receive my favorite radio stations anymore because some people near me like to listen to deutche schlager zangers or techno.
Didn't we all learn our lesson from "Pump up the Volume"?
you could just turn your speakers all the way up.
If you play music, can the RIAA sue the air for abetting the distribution of copyrighted material?
UTF-8: There and Back Again
So what kinda receiver do you carry around that's more convenient than an ipod?
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Some people are good with words, others,
The VHF broadcast band is a regulated resource. What you have created is, in effect, a pirate radio station with all the regulatory and copyright issues that that entails. If the FCC/Ofcom or whatever regulatory authority covers your area doesn't take an interest in your "personal radio station" in fairly short order, I'll be very surprised. The performing rights organisations may take an interest, too.
In short, you will be very lucky if you get away with this for long.
Resistance is futile. Reactance buggers it up.
Be careful
Here in Israel there are a number of pirate radio stations. This is not itself a problem but they are using poor equipment and blasting harmonics onto aviation frequencies. That is bad. It has gotten to the point where the ATC folks have threatened to strike if something is not done about it because it can threaten aircraft communications.
Erlang Developer and podcaster
It used to be. As a ham you SHOULD know this. The rules regarding unlicensed broadcast transmission in the FM band changed. You can, in fact, use any amount of power you want. That is, as long as you don't excced 250uv/meter measured at a range of three meters.
For most of the unlicensed stuff that translates to roughly 10 to 20 mw. This is governed by part 15 of the FCC code and you can read even more about it at http://www.fcc.gov/mb/audio/lowpwr.html#PART.
That would have been great for around the farm when I was a kid.
While driving the tractor about 60 hours a week throughout the summer, I had my choice of precisely two stations. One was country and western and the other covered things like little league baseball games and the farm reports.
There still would have been a problem -- I didn't have anything at home that would have been worth broadcasting. After all, attaching a microphone and listening to the dogs barking occasionally would have gotten old real quick.
We got a great big convoy...
--
"Insert witty quote here."
Going to the store page reveals that a 0.3W transmitter costs a wild $140. Yes, there's an LCD and menus, but no self-respecting budget-minded geek would lay down that much money to broadcast music over a short distance.
There's plenty of circuit designs at ePanorama that are relatively simple and powerful. DIY; save your money and your honor.
I bought the CCrane transmitter http://www.ccrane.com/fm-transmitter.aspx/ and perfomed the easy mod http://www.xmfan.com/viewtopic.php?t=3257&postdays =0&postorder=asc&start=0/ to increase it's output power.
It works great and covers the entire house. It's cheaper than the original post and includes a case and power supply (problems that the original poster had with the ebay one).
1: You might get surprisingly long range reception. From my experience on the 145 MHz Ham band, I can easily communicate 30 miles with less than 1 watt with a roof-mounted antenna (of course the receiving station also has a good high antenna). There are differences that will reduce your range (particularly the wide bandwidth of the signal), but in general 2 watts can potentially cover a very wide area..
2. Yes, particularly if the antenna is high up and your signal gets into the city, or if your transmission annoys anybody for any reason.
3. $10,000 a day fines and your equipment (and possibly other nasty things I don't know about!)
Ultra cheap FM transmitters use a tuned tank circuit to control frequency (ie - a variable capacitor). These are very difficult to get to the exact center of the frequency you choose, the result will more than likely be poor audio response.
Furthermore, your receiver is probably digitally controlled to an exact FM frequency and the variable cap system will change frequency slightly with temperature and humidity, so that the transmitter will slowly go in and out of channel. The receiver is phase locked to the correct channel, and the result is that the system will gain and lose quality over time. Digitally controlled frequency is a must for this application.
Kit systems are usually poor at doing audio; making a noise-free circuit is somewhat of a black art and it takes a lot of research and tinkering to get it right. For example, Ramsey Electronics makes an FM transmitter kit with digital frequency control and all that. The problem is that the board layout introduces an unacceptablt amount of hiss into the audio signal. No amount of adjustment will fix this, and the average hobbyist is unprepared to even figure out what the problem is.
Finally, Be very careful of high end ($300) transmitters used for gyms. Some of them are mono only (!) but do not specify this on the advert.
Your best bet is to look on the net for reviews of any transmitter you're thinking of buying. When people have good things to say and don't point out the obvious flaws, then the product might be OK.
I purchased several poor FM transmitters before I got one that worked well, and I use it for transmitting FM throughout the house.
That would be the C.Crane FM transmitter. You can get it for about $80, and Froogle lists several vendors.
On FM frequencies, these devices are limited to an effective service range of approximately 200 feet (61 meters).
/ Documents/bulletins/oet63/oet63rev.pdf
source:
http://www.fcc.gov/mb/audio/lowpwr.html
see also:
http://www.fcc.gov/Bureaus/Engineering_Technology
Bottom line:
The transmitter described is not even close to complying with FCC regs. FCC compliance depends not only on transmitter power, but also on antenna gain and several other factors. You cannot simply say "X milliwatts is safe". Not only that, but 100mW into almost any antenna is going to be a violation. Something in the range of 1mW into an omni antenna would be more like it.
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All of whose base are belong to the what-now?
If you just want a radio station in your home it would seem to make more sense to use a Carrier Current transmitter. What this guy is doing is pretty damn illegal and if you do what he did you can be looking at tens of thousands of dollars in fines!
From what I can tell anyone can setup a Carrier Current station(check for yourself), you can find some pretty cheap kits.
This guy doesn't seem to be all there, he says he has a HAM licence, but is stupidly violating FCC laws. He also says the thing has a BNC type connector but the picture looks like a type RG6 connector.
As mentioned here, the unit is not FCC approved. Once this guy comes onto the radar (by a slashdotting, for example) he might well get a call from the FCC.
In Europe it is not permitted to use any transmitter on broadcast frequencies, unless you are a licensed broadcaster. And it doesn't matter how low the output power is, so those Ipod thingies are not allowed either.
Think about it, grab a embedded linux system with onboard sound and network (wifi or ethernet), have a central server broadcast non-RIAA regulated tunes, then find people willing to stick one of these up where they live. Have enough people do this around the area, and boom, you have a radio station which the RIAA can't touch (because they don't regulate the music on it), the FCC can't exactly complain about (broadcast power on each node doesn't warrant a license right?), and annoying the hell out of the local commercial radio stations.
The only problem I could see is keeping each broadcast node in sync, especially if you're all broadcasting on the same frequency.
Thats people power for you.
How exactly does ones ability to learn morse code relate to ones technical skills?
Its one of those BS arguments you hear all the time about morse code.... Its like saying that they are less technically savvy since they don't even have to be able to speak spanish anymore.
I do agree with you on the technical exam however, I think it is e.g. a good thing to require a HAM to be able to explain WHY morse code is a good mode.
Jeroen
Secure messaging: http://quickmsg.vreeken.net/
I was currious too so I did a rough google search, but not interested enough to refine it.
I did however, run across an entertaining article by a pirate radio guy. As a bit of CYA, I whole-heartedly do not recommend breaking the law nor would I suggest taking the article as "truth". It's just fun to read - on to the excerpts:
... Having been visited twice before by the FCC, veteran broadcaster Monk briefed us on what the risks were and how we should handle a visit (see below). We were prepared.
Nonetheless, the FCC visit I experienced was bizarre. I woke up to find two strange men in suits and a uniformed cop in my front yard.
What changed under Obama? Nothing Good
One of my hobby projects is searching the shed and attic for the $5 FM sender (100mW) that I once bought and soldered together to experiment with digital transmission (wanted to hook it up to the serial port) through the radio (cheap...). It would kill any other radio station using the same frequency in my block, and it could be received throughout the street (we did not live in a very long one though). I used half a meter of copper wire as antenna.
I wonder why (1) they are no longer for sale at all in the Netherlands (Velleman kit), and (2) why the alternatives cost over ten times that much, and provide less than a fraction of the output.
Musicians don't die. They just decompose.
To comply with the unlicensed rules, you need to turn that thing down by a couple orders of magnitude. The lower limit isn't actually in watts, it's actually something like 85uv @ 3 meters. I don't recall exactly, but it's not my ass on the line here... go read the rules before yous gets busted. :-)
To comply with the licensed rules (you said you don't wanna lose your ham license), you need to start broadcasting your call sign periodically. Worse, you need to stop broadcasting music - mostly because the FCC will kick your ass for abusing your amateur license (again, go read the rules), but partly because the artists' organizations may kick your ass for not paying royalties. Yeah it's only your neighbors you're entertaining, but they can be every bit as abusive as the FCC.
Wait... did Bruce P write that article, or does the story just link to some random guy who bought one of these things?
Since we are all talking about getting busted and such I thought I might mention Free Radio Santa Cruz which has been around for over 10 years. They were just recently busted and the FCC just shut them down. You are not gonna get busted by the FCC if you do this. If the FCC wants to bust you they must come to the place first and notify you to stop. If you do not stop they can come in and take your equipment . I have never heard of anyone going to court ever. We need more community radio stations with more diverse points of view. So I encourage you to break the law and be a Dj. If you want to learn more about pirate radio go here http://www.frolympia.org/website/index.php?module= pagemaster&PAGE_user_op=view_page&PAGE_id=6&MMN_po sition=6:6
Listen to Free Radio Santa Cruz and Free Radio Olympia.
We've had a similar transmitter in our house for a few years now, and I do recommend it for parties. Basically, the setup is:
1. Switch on machine with mp3 store
2. Create vast randomised playlist
3. Switch on the transmitter
4. Switch on every radio in the house
5. Open case of beer / chosen drink
6. Party party party!
And voila, synchronised music in every room that wants it.
One issue though is that we have to drop the output power of the transmitter to avoid interfering with anyone else's radio - here in the UK they don't take too kindly to that.
or how about anyone come over..
what he is doing is already in violation of the FCC rules. 100 miliwatts is the maximum allowed into the antenna provided in the kit. hooking it up to a gain antenna is illegal as he now went past the 100mw ERP.
all it will take is one phone call by a pseron that does not like him to get the FCC and a 10,000.00US fine on his arse.
Unlicensed operation on the AM and FM radio broadcast bands is permitted for some extremely low powered devices covered under Part 15 of the FCC's rules. On FM frequencies, these devices are limited to an effective service range of approximately 200 feet (61 meters). See 47 CFR (Code of Federal Regulations) Section 15.239, and the July 24, 1991 Public Notice. On the AM broadcast band, these devices are limited to an effective service range of approximately 200 feet (61 meters). See 47 CFR Sections 15.207, 15.209, 15.219, and 15.221. These devices must accept any interference caused by any other operation, which may further limit the effective service range. For more information on Part 15 devices, please see OET Bulletin No. 63 ("Understanding the FCC Regulations for Low-Power, Non-Licensed Transmitters"). Questions not answered by this Bulletin can be directed to the FCC's Office of Engineering and Technology, Customer Service Branch, at the Columbia, Maryland office, phone (301) - 362 - 3000, e-mail LabHelp@fcc.gov.
PENALTIES FOR OPERATION WITHOUT A PERMIT OR LICENSE
The Commission considers unauthorized broadcast operation to be a serious matter. Presently, the maximum penalty for operating an unlicensed or "pirate" broadcast station (one which is not permitted under Part 15 or is not a Carrier Current Station) is set at $10,000 for a single violation or a single day of operation, up to a total maximum amount of $75,000. Adjustments may be made upwards or downwards depending on the circumstances involved. Equipment used for an unauthorized operation may also be confiscated. There are also criminal penalties (fine and/or imprisonment) for "willfully and knowingly" operating a radio station without a license. DON'T DO IT!
He also far exceeds the distance limit set by the FCC.
Nice way to publically admit you are violating FCC rules.
Do not look at laser with remaining good eye.
Bruce
Bruce Perens.
Bruce
Bruce Perens.
"How exactly does ones ability to learn morse code relate to ones technical skills?"
I don't think it does, but removing the morse requirement would tend to make HAM similar to CB radio in some people's eyes.
Incidentally, I had to fight the temptation to try and answer in morse...
"I think it is e.g. a good thing to require a HAM to be able to explain WHY morse code is a good mode."
And not actually know morse?
Oddly Draconis
Too cynical to live, too stubborn to die.
It is absolutely untrue that unlicensed transmitters at 100mW or less are legal in the FM broadcast band in the U.S.
Well, actually, it is true that some unlicensed transmitters at 100mW or less are legal in the FM broadcast band. But only those that operate at far, far less than 100mW.
I'm really surprised that the person who wrote the original article (i.e., the one who posted on technocrat.net) admits to being a ham operator, but then seems to know nothing about part 15 of the FCC regulations. If you want to know all about the limitations on unlicensed operation, you need to know part 15 -- no excuses. And the 100mW limitation applies ONLY to unlicensed transmissions in the AM broadcast band, and NOWHERE ELSE. Instead, each band in which any kind of unlicensed transmission is permitted is subject to its OWN RULES.
See: FCC rule regarding unlicensed operation in the band 88-108 MHz (Note that although this document is served by akamaitech.net, the source of the document is the U.S. Government printing office)
FCC PDF document with all you ever wanted to know about unlicensed operations under Part 15
Ramsey Electronics kit page with FCC information regarding lawful use of low power transmitter kits
American Radio Relay League (ARRL) information on part 15 of the FCC rules (The ARRL is the largest national organization for ham radio operators)
Note that the actual permitted field strength for unlicensed operation translates into the a signal of only a few nanowatts -- around the single digit range -- certainly not anything even remotely resembling 100 milliwatts!
Thus, the immediate parent of this comment should be modded WAY down -- it certainly isn't "informative." If anything, it is perpetuating misinformation that could get someone into serious trouble.
You forget, Bruce, that we in the UK have the 70MHz band which behaves in a similar fashion to Band II VHF. Propagation, even at these frequencies, can occur via Sp-E and tropo-ducting. Your valley, if it is a valley, is an ideal setting for a temperature inversion-type tropo-ducting event (apologies to non-radio types - I'm not going to explain the mechanism, it would take too long).
;-) ) should be treated with respect. That means regulation. You'd be far better off using unlicensed spectrum and building/buying something more suitable for the job. It's OK if it's just you doing this, but can you imagine whole streets of folks running their own transmitters? Not likely, I hear you say. Well, so what? The *theory* is the same. Otherwise, the *possibility* exists for folks driving around listening to Band II picking up a new station on a particular frequency every few hundred yards. If I can see this, you can bet the FCC can too. That they have dropped the limit from 100mW to a field stregth at the boundary (according to posts on here) means they've already taken a look at the problem.
Point taken on the bandwidth, the power being spread between the components of the sidebands. You also make a good point on the capture effect, but for my side. The way this works, using inverse square law, is that anyone in your immediate vicinity is going to receive you rather than a transmitter using significantly more power but significantly further away.
I still think this is a poor idea to project to the masses. Radio, especially in the broadcast bands where it upsets more than a few zany techie types (we amateurs
Over here, one strike against you with regards the Wireless Telegraphy Act (the all-encompassing law that governs radio in the UK, passed in 1949 and amended in 1988) and you lose ALL your licences until the Rehabilitation of Offenders Act kicks in. For me that is three, for five years minimum. One professional, one marine and one amateur, the former two being a huge problem if they were lost. How about you? Is it a chance you're willing to take?
Resistance is futile. Reactance buggers it up.
Than when the topic is P2P everyone either says it's "fair use" or even if it is illegal, you're chances of getting caught are so small it's never going to stop it anyway.
But when the topic is FM transmitter, suddenly everyone comes out of the wood work and posts about the illegality of the situation.
Let's set the record straight. The FCC will shut down your station, if and only if, a broadcaster complains. And because anyone smart enough to set up their own FM transmitter is smart enough to choose a frequency not already occupied by a local station, the FCC will never shut them down. Never.
I know a group of people who run a pirate station which transmits over 20 miles and have run it since the early 90s. At one time the FCC got a complaint from a local station, the FCC investigated, found it didn't really interfere, and so it did nothing.
If someone says he and his monkey have nothing to hide, they almost certainly do.
/. does not let you do a full reply in .- .-- .--
morse.
onepoint
if you see me, smile and say hello.
I am not plugging EITHER of those transmitters, because I'm not USING either of those transmitters.
I AM plugging the utility of having an FM transmitter in the home, because I'm doing it and it is truly useful... I rate it as highly as a fileserver or my wireless link.
Keep in mind, too, that not all transmitters have good quality sound. I'd be leery of the cheap ones.
Murphy was an optimist.
I bought one of those little consumer FM transmitters (this was a Belkin model) that you're supposed to plug into the audio jack of your MP3 player, but it really sucked. The main issue is that reception was so bad it was unacceptble even if I put it on top of my car dashboard.
So, since the thing was so useless I was out thirty five bucks anyway, I took it apart. The antenna turned out to be a length of wire about two inches long stuffed into the same cable used for the audio jack. Obviously, this was nearly worthless. I drilled a small hole in the case and soldered in a piece of wire the right length for a half wavelength antenna -- a little less than 63 inches for the low end of the FM band. As a result, I can now broadcast all over my house.
Now, since I was using it in a car, a five foot piece of wire was a bit unweildy, so I wound it around a pencil to make a loopstick antenna. I don't know anything about designing loopsticks, but it still worked OK for broadcasting around the house. Basically, I'd guess just about any length of wire a few feet long would work way better than the tiny length of wire they were using.
The only remaining issue is that the volume is very low; you have to jack up the volume on your receiver nearly all the way to get acceptable listening levels. If you're planning on driving around town with your windows down so your car's subwoofers won't blow them out, this is not for you. Also, the sound is a bit muddy. I suspect that in order to avoid any FCC issues, they took a number of steps: using a low transmit power, using a worthless antenna, filtering out the high end audio frequencies, and undermodulating the signal. I could probably desolder and replace some resistors and capactitors or something if I were motivated enough to analyze the circuit. Plus, as an old fogie I'd have to learn to deal with surface mounting (I learned to solder on bakelite terminal strips for chrissakes). Altogether this is too much trouble.
I'd recommend that if you bought one of these consumer MP3 transmitters and found it totally worthless, then you should replace the antenna with any old piece of wire and it will gain enough range to be some use to you. If you haven't bought one yet, don't. Getting a device like this guy is using would be a bit more expensive but probably a lot more satisfactory.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
The terrorists have already taken over. ClearChannel killed my favorite 35-year-old rock station in favor of Latino hip-hop. If that's not terrorism, I don't know what is...
Any ideas on a suitable attenuator? I would imagine that you can attenuate the 100mW output down to 20 or 30, and bring it within limits. According to the FCC link in the grandparent, the FCC seems to be concerned more with your transmitter having a range of 200 feet or less, regardless of output power or antenna design.
There is no reasonable defense against an idiot with an agenda
:wq
Roy Neset's Tioga, N.D., farm isn't quite in the middle of nowhere, but it's close. Neset wanted to listen to talk radio while cultivating his fields on his tractor. But the only radio station in the area plays country music and refused to change its programming.
So Neset bought a low-power radio transmitter, got written permission from a Colorado station to carry its signal and began transmitting that station via satellite. Neset's station extends only about five miles in each direction, most of which consists of his farm. His station is also listened to by a handful of people in the area.
When the local radio station manager learned of Neset's broadcasts, he complained to the FCC's field office in Minneapolis. The FCC sent an agent to Tioga on at least two occasions to monitor the station. On learning that Neset was broadcasting on 88.3 FM without a license, the FCC convinced the U.S. Attorney in North Dakota to file a lawsuit.
During a hearing, the FCC admitted that Neset wasn't interfering with any existing station. In fact, no FM stations broadcast in the area. But the agency stuck with its argument that it's illegal to broadcast without a license.
That that is is not that that is not. That that is not is not that that is.
A ham radio license gives you no special rights outside of the ham bands. (And yes, I have one too.) Last I checked, the FM broadcast band (88-108 mHz) is outside the ham bands.
even if he were using the ham bands, it's illegal to broadcast music over them, unless it happens to be incidental music from a rebroadcast from the Space Shuttle (yes, the regulations are that specific :)
The (part 15) rules do permit low power transmitters on the FM broadcast band, but they're based on effective radiated power (i.e. in the direction with the strongest signal), not total radiated power. Specific regulations here. If your signal can be picked up in your entire neighborhood, you're obviously exceeding the power limit.
Sounds like Bruce doesn't understand the regulations very well. He may not be abusing the ham bands, but the FCC can certainly take away his ham license for it. They probably won't for a first offense, but the odds are very good that this article will be all that's needed to get *somebody* to send in a complaint, and the FCC is likely to send him a nasty letter and require him to respond (that's how they do things.)From the article --
He's right -- that's probably a good deal under 100 mW of power, especially with his good antenna. So if he's only turned it down to 100 mW, he's violating the law. But maybe he mispokeBruce
Bruce Perens.
It works with Linux. Doesn't everything, these days?
If you wish to assert that FCC sends the hostage recovery team to prosecute teenagers for out-of-spec transmitters that interfere with private microwave links and sends their moms to jail for 5 years, you will have to show:
Bruce
Bruce Perens.