Multi Broadcast FM Transmitter

Hi! I've an idea of project and looking for some help. I am a SFS firefighter and thought about device, which could broadcast kind of message while fire truck is heading to accident. Example: firefighters heading to the busy streets, so they turn on device and device transmits via RADIO FM "State Fire Service go to the edge of the road" or something like that. What do You think of that? Any hardware and software ideas? Loop jumping around most used radio channels in area? Give me some ideas, because I want to make it and test it! Greetings! :D

broskyr: Hi! I've an idea of project and looking for some help. I am a SFS firefighter and thought about device, which could broadcast kind of message while fire truck is heading to accident. Example: firefighters heading to the busy streets, so they turn on device and device transmits via RADIO FM "State Fire Service go to the edge of the road" or something like that. What do You think of that? Any hardware and software ideas? Loop jumping around most used radio channels in area? Give me some ideas, because I want to make it and test it! Greetings! :D

I have no idea why you ask this on an Arduino forum. How many FM channels are you intending to transmit on? The power of you transmitters will have to be able to override completely any FM station a vehicle is tuned to. What about the people listening to AM radio? What about most of the vehicles are listening to satellite broadcasts? Paul

broskyr: I am a SFS firefighter and thought about device, which could broadcast kind of message while fire truck is heading to accident. Example: firefighters heading to the busy streets, so they turn on device and device transmits via RADIO FM "State Fire Service go to the edge of the road" or something like that.

I would be amazed if any regulator would allow you to do that.

Is it legal to break into the FM frequencies and transmit? It would not be tolerated in my country. Anyway, making a prototype and later make the fire department take on the task, could be a good idea.

Railroader: Is it legal to break into the FM frequencies and transmit? It would not be tolerated in my country. Anyway, making a prototype and later make the fire department take on the task, could be a good idea.

The whole idea is in the same path as a bunch of people wanting to make something to blot out all cell phone reception in given area, like an auditorium. Never ever will be legal. Paul

@Paul_KD7HB You're perfectly right. I missed the need for overpowering the existing FM as well.

Here, in Sweden, we have a service, administrated by the authorities, that uses FM and break into any ongoing program, in order to broadcast important messages. It has happened that warnings have been issued, a long distance ambulance on the way, and so on. It's likely a little bit slow, from the original decision to drive the ambulance until the message has passed the "obstacles", people, on its way.

Railroader:
@Paul_KD7HB
You’re perfectly right. I missed the need for overpowering the existing FM as well.

Here, in Sweden, we have a service, administrated by the authorities, that uses FM and break into any ongoing program, in order to broadcast important messages. It has happened that warnings have been issued, a long distance ambulance on the way, and so on. It’s likely a little bit slow, from the original decision to drive the ambulance until the message has passed the “obstacles”, people, on its way.

Yes, pretty common. But they ALL go through an interface to the actual radio transmitter, not eminating from a moving vehicle.
Paul

Paul_KD7HB:
Yes, pretty common. But they ALL go through an interface to the actual radio transmitter, not eminating from a moving vehicle.
Paul

Yes, correct. Interfaced the proper way.
We also use a service that can be used ordered by the authorities, broadcasting SMS to nearby mobiles.

How about mounting a whole bunch of high frequency emitters on the fire vehicle, in the range, say, 429 or 666 THz?

Sirens? Some blue flashlights as well?

Railroader:
Sirens?

Dammit - forgot AF.

Sorry, missed the Tera Herz... Reading the numbers only.....

Hi, Old Broadcast Engineer here…

Only one way I can think of that could work, but differently than you suggest:

Sirens are effective, but do not transmit messages. So an “RF SIREN” would be a wideband (Optimized for .5 to 1.5 Mhz and 85-110 Mhz) transmitter with something like 200 Hz amplitude modulation. Think of it like the loudest interference source you’ve ever driven under. A bad insulator on a high voltage power line can drown out every AM and FM broadcast signal for several hundred feet. with a loud annoying buzz. If it was keyed on and off in bursts of three and that became known as a ‘siren’ signal, the message could be received.

But you need the loud audio frequency sirens for those who occasionally actually ride with the radio OFF.

Hmmmm…

Paul_KD7HB: The power of you transmitters will have to be able to override completely any FM station a vehicle is tuned to.

That in itself is a very major obstacle, because FM has the characteristic of locking onto the strongest signal and masking anything of lower power. The persistence of AM for emergency frequencies is in part because a weak signal can produce noticeable interference to stronger signals.

I would think a system using cell phones would be much easier to implement, the phone companies could easily direct an alert to specific cell towers, and the phones themselves could further filter the message based on location. As to whether you want someone reaching for a phone instead of paying attention to an approaching siren is another matter.

Someone on your staff has all the knowledge and licenses you seek. We can only tell you what not to do.

And it will still not reach the people listening to personal music/CDs/plugged into phone for MP3s, etc.

CrossRoads:
And it will still not reach the people listening to personal music/CDs/plugged into phone for MP3s, etc.

In the past, I’ve had break-through from airport ground movement radar on my car entertainment system…