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We need to get all the tech heads and engineers to work together on the forum.
under part 15.247 we are allowed 1 watt into a 6db gain antenna when we employ spread spectrum.
We need to get all the tech heads and engineers to work together on the forum.
under part 15.247 we are allowed 1 watt into a 6db gain antenna when we employ spread spectrum.
using this logic there is no limitation on the gain at receiving end.
what we need. a FHSS Tx that is able to encode a 15 Khz Stereo Audio Signal on a 1 Watt FHSS 900 MHz Carrier similar to what IBOC does on an FM Carrier.
the transmitter would have a external antenna connector and be adjustable in power to allow the user experimentation on antenna setups to find the best antenna gain vs. rf power combo for their situation.
then we need to design a component 900 mhz FHSS Receiver capable of translating the Received Signal back to 15 KHz stereo line level audio and a +4DBU 600 Ohm Balanced Mono output and the receiver should feature an external antenna connector.
in short we would be pioneering a new broadcast medium under part 15 microwave. and it would be legal and all the big broadcast and NAB could do is Sit and Spin!!!!!
this could also be used as an STL for a rangemaster cluster and should include a sync signal built into the TX/RX System.
Total posts : 45366Oh boy, a discussion on spread spectrum! This has always been in the back of my mind since it was first described to me, but when Part 15 came up as a hobby I’d forgotten about it.
To review what little I know, I think spread spectrum means the actual transmission frequency changes every few seconds so that it jumps from frequency to frequency, with the receiver synchronized to every change, so that the program arrives intact as if it had been “beamed up” Star Trek style. People with ordinary listening setups can’t get it because they can’t out-guess the changes.
What’s next to be done?
Total posts : 45366Thanks for the interesting suggestion. I was not aware that this power level is permitted in the 900 MHz band but I will take your word for it.
I have done some experimenting here with a 900 MHz tx/rx in good old analogue mode and operating under the part 15 signal strength limits with expected results. The range is approximately equal to that from my FM BCB transmitter but this is for analogue mode. My units also have a digital mode (not spread spectrum) but I haven’t done anything with this.
Carl is pretty much on target with how spread spectrum works, the difference being that the frequency changes in milli or microseconds rather than seconds. (The actress Hedy Lamarr held the original patent on this by the way http://en.wikipedia.org/wiki/Hedy_Lamarr#Frequency-hopping_spread-spectrum_invention.) Spread spectrum is used for two main reasons, first, secure transmission, and second, multiple users can share the same spectrum. Cell phones use this technology. When a digital signal is transmitted it is sent as “chips” rather than bits. The receiver, programmed to follow the frequency changes, puts together the “chips” to produce bits which are put together to make bytes and words and etc. There is a thing called the auto correlation function which is a math construct that makes this magic happen. I just drop the name in case anyone wants to pursue it further.
Back to the original post, this is a classic chicken and egg situation. We can look to Sarnoff of RCA and Crosley of Crosley Radio for hints here. They built both the transmitters and receivers since they knew one without the other wasn’t going to work. Crosley, especially, also built a cadre of celebrities (anyone remember Durward Kurby?) and local programming so people would want to tune in. Perhaps part 15ers could piggyback on some existing service where folks already have the receiving equipment. This was suggested in another post here concerning WiFi.
Our local “public radio” station, WOSU-FM switched their usual daytime classical programming to HD FM and they lost both me and my wife as listeners since we would have had to purchase a new receiver just for the purpose of listening to them. I wish I knew what this did to their overall listenership but I suspect that few folks bought the radios just to hear them. I think your suggestion, though technically good, will be severely limited by the willingness of people to “tool up” to receive your broadcasts and you will have to have programming which they will go out of their way to receive. Been wrong before, and maybe this time too, but it is something to consider.
Neil
Total posts : 45366give away receivers to local businesses, etc so the public will be exposed to it. and also give those businesses some receivers to sell to the public.
all this could be done at cost. no profit from the hardware.
pull a page out of the cable industries book.
no commercials and when the technology gets embedded then we start slowly adding commercials.
Total posts : 45366Rev,
I like the way you are thinking outside the box! And I hope by my remarks I have stimulated this and in some way made a contribution.
Neil
Total posts : 45366In apartment communities we use wireless audio video links that operate at 5.8ghz in addition to our AM & FM broadcast. Sure they only cover about 300ft, but that is more than enough to cover a decent size apartment complex.
The item I’m talking about is here:
http://www.outlawradio.us/image/Studio_Transmitter_Link-250-labled.jpg
The listener simply plugs the receiver into their audio system or television aux inputs; the video has song info and local weather on it.Thinking way outside the box.
Total posts : 45366I like this thinking. But on 2.4 & 5.8 Ghz you already have readily available transmitters & receivers – 802.11 whatever wireless networking stuff. I still think that it would be better to use these rather than wait for some new development that may never take place. You’ll get more range line of sight on those frequencies as well; 900 Mhz would be better for non line of sight, I admit.
Giving away radios was also exactly what I was thinking. In my plans (to stream over a private hotspot on my island), businesses would get the use of Internet radios as long as they played the station. Internet radios would also be available for resale. Internet streaming would still be available outside of the hotspot.
Now all I have to do is to find a portable Internet radio that runs on batteries and/or something that can be fitted inside a car (both able to function without a computer – there are some that need that computer), and we’ll be able to cover all possible listening situations.
Total posts : 45366what i am looking at is something high quality that offers the highest legal power antenna gain combo for omnidirectional broadcast applications.
instead of using AM and FM where your operation hangs on the interpretation of the inspecting agent or his particular bias under part 15.247 there is really no room for interpretation of the rules and it would be a lot harder for a licensed am/fm to get you off the air let along even know you are there.
what i am talking about is pioneering the 900 mhz ism band as a new broadcast band for unlicensed broadcasting that offers superior range and audio quality in a single site package, while also offering features to make it specifically attractable to am 1000 user for stl and transmitter clustering / carrier syncing use.
something like this is not readily or cheaply available and over the counter wifi stuff and mesh stuff has the problem of the receiving user needing to be able to talk back to the AP and the issues involving limited bandwidth as users on an AP increase which significantly increases infrastructure costs.
right now the harris starlink system which is ptp costs $10k.
a system like i describe can be built, certified and sold cheaply.
Total posts : 45366I like it when people think outside the box, one thing to consider is doing something where licensed broadcasters will ask the FCC to give independant broadcasters a space of some type of public bandwave. That happened in early FM days with offshore broadcasters. I’m not sure how but I knew a guy who had one of the first FM pirate stations here by (piggybacking) his FM signal onto the edge of the local 50kw monster AM station. That AM station is licensed for 770AM but spreads from 750AM to 820AM. He simply cliped his transmitter (a modified walkie talkie and an auto battery) onto their antenna, car radios picked it up easily for 60 miles. People tunning into the AM station couln’t pick him up and listening to him on FM didn’t bleed any of the AM station through.
I don’t know about everywhere but there are plenty of licensed AM stations here that broadcast and drift outside of their licensed frequencies all the time. It might be possible with how much rf that surrounds us to tap into some of this as a carrier for public broadcasts. I noticed that our cable TV carrier is super sloppy with its lines and grounds and such that might be something as well. There is an area in our neighborhood where you can get sports radio FM from 2 states away on AM that bleeds through the cable TV lines I”m guessing or possibly through telephone lines.Some thoughts
Total posts : 45366I guess the question is: Who would listen to it? How would people receive it on, say, their car radios?
Total posts : 45366well considering the properties of 900 mhz and the power allowed under part 15 this would be more of a home based receiver than a mobile one.
which in reality is what part 15 am is as well.
Total posts : 45366Curly Howard
Total posts : 45366I was at a HS basketball game the other night and many people were listening to the game on their cell phones, palms, blackberries etc. I know very little about how it works but supposedly a guy with a mixer, an mp3 player and a cell phone was broacasting it from the gym. They called it a flycast and he was the flycaster. Some people got it from the internet some called a number etc., it seemed to me like there was not a perfect sync between the cell and internet connected devices but still less than a half second apart.
The thing with it is that TV broadcasting has been a flop on cell, but people seem to like cell radio. One of the things about something new is that if it is not self serve, it needs to be free. If people have to buy something they will spend their money on a self serve devise. Those who are bottle fed TV and radio as it is now don’t care to buy anything new.
But those who already have cell phones don’t mind cell radio. XM has not been as accepted as was originally planned even with it already being available in their cars. I listened to the flycast on a freinds phone and the game was a pro job, the pre-recorded breaks and sponsor ads and player/coach interviews that were loaded in the MP3 player gave it a professional sound and the kid had a decent broadcast voice and attitude. It seemed on some devices like it was packet fed simular to internet packet TV like sky angel.
Cell casting has replaced radio in real estate already.
Total posts : 45366I don’t recall where the thread is, but I think I previously posted a message about using cellphones to broadcast to the internet.
I webcast the last half of our high school homecoming game. Here’s how I did it, but there are much better ways:
I have a Radio Shack device which was given to me by a friend who works there, cat. no. 17-855. I believe it has been eliminated from their catalog, however. You can get a similar device here:
http://www.dynametric.com/cell_and_cordless_phone_recording/Cordless_Phone_Recording_Adapter.htm… look for better prices.
1) There was no one available in the booth to work the phone properly, so I just set one on a table hoping it would pick up the P.A. loudspeakers OK. I told the scoreboard operator to just answer it when it rang then set it back down.
2) Back at my studio, I plugged together my other cell phone and the mixer using the device mentioned above … which was in turn connected to my digital interface and so to the computer. I opened Nicecast to ‘system’ and began broadcasting. I called the other phone. When it answered, I adjusted sound levels, EQ, etc.
The sound was poor, but a decent headset/microphone on the game end would’ve cured that problem.
3) A better way is to take a wifi-connected laptop to the game and just use that. You could even use a tethered cellphone or a bluetooth headset to get even more freedom … 20-30 ft from the laptop, if you or someone using your gear is doing the announcing.
Now, I have an older laptop I’m not afraid to break, but it may not have enough guts to stream. I will try, though.
In any case, it’s simple enough. You could use the line out from the P.A. system, or a good mic, wireless device, or whatever, plugged into an interface to a laptop with a wifi connection, and a decent account with Live 365 or Shoutcast (what I use) to get it to a website.
In addition, the new Android phones (using Google’s Android OS), such as Verizon’s Droid, or iPhones, can run a piece of phoneware called iPadio:
http://www.ipadio.com/… which allows you to broadcast live to the internet from the phone, with surprisingly good quality. In my case, the intent is to use the studio or TX computer to pick the sound off my own website and send the audio to the AM TX here in town.
The business with calling a number has to do with your service provider. They can either use their servers or provide a number to allow access to yours. Just depends what you want to do.
… those are just a few ways you can skin that cat … have fun 😉
Total posts : 45366I don’t recall where the thread is, but I think I previously posted a message about using cellphones to broadcast to the internet.
I webcast the last half of our high school homecoming game. Here’s how I did it, but there are much better ways:
I have a Radio Shack device which was given to me by a friend who works there, cat. no. 17-855. I believe it has been eliminated from their catalog, however. You can get a similar device here:
http://www.dynametric.com/cell_and_cordless_phone_recording/Cordless_Phone_Recording_Adapter.htm… look for better prices.
1) There was no one available in the booth to work the phone properly, so I just set one on a table hoping it would pick up the P.A. loudspeakers OK. I told the scoreboard operator to just answer it when it rang then set it back down.
2) Back at my studio, I plugged together my other cell phone and the mixer using the device mentioned above … which was in turn connected to my digital interface and so to the computer. I opened Nicecast to ‘system’ and began broadcasting. I called the other phone. When it answered, I adjusted sound levels, EQ, etc.
The sound was poor, but a decent headset/microphone on the game end would’ve cured that problem.
3) A better way is to take a wifi-connected laptop to the game and just use that. You could even use a tethered cellphone or a bluetooth headset to get even more freedom … 20-30 ft from the laptop, if you or someone using your gear is doing the announcing.
Now, I have an older laptop I’m not afraid to break, but it may not have enough guts to stream. I will try, though.
In any case, it’s simple enough. You could use the line out from the P.A. system, or a good mic, wireless device, or whatever, plugged into an interface to a laptop with a wifi connection, and a decent account with Live 365 or Shoutcast (what I use) to get it to a website.
In addition, the new Android phones (using Google’s Android OS), such as Verizon’s Droid, or iPhones, can run a piece of phoneware called iPadio:
http://www.ipadio.com/… which allows you to broadcast live to the internet from the phone, with surprisingly good quality. In my case, the intent is to use the studio or TX computer to pick the sound off my own website and send the audio to the AM TX here in town.
The business with calling a number has to do with your service provider. They can either use their servers or provide a number to allow access to yours. Just depends what you want to do.
… those are just a few ways you can skin that cat … have fun 😉
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