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Topic: FM transmitter using Arduino (Read 28852 times) previous topic - next topic

keeper63


So your attitude to legality is just governed by your chance of detection? Not the potential life threatening consequences of interfering with emergency services, life support systems and the rest. What a nice chap you are.


Which is what I was trying to get at in my original post; furthermore, "big brother" really meant the ton of HAM radio enthusiasts out there, who, if they detect such interference, etc - might decide to do a "fox hunt", find the source - and then they would alert the FCC (or whatever agency is in your area/country). The government doesn't need to drive around a van looking for violaters - they have a built up HAM operator network composed of many that don't like to see such interference from unlicensed operators.
I will not respond to Arduino help PM's from random forum users; if you have such a question, start a new topic thread.

jremington

Don't be silly, folks. In the U.S. such low power transmissions are expressly authorized, and I imagine that a similar situation holds true in many other countries. Specifically, the ATtiny45 transmitter would be a PART 15 FM device under the FCC rules: https://www.fcc.gov/guides/low-power-broadcast-radio-stations#PART15

Quote
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.

Grumpy_Mike

Quote
and I imagine that a similar situation holds true in many other countries

That is where you are wrong.

jremington

#18
Nov 03, 2013, 09:40 pm Last Edit: Nov 03, 2013, 09:44 pm by jremington Reason: 1
As I said, don't be silly.  A very quick check reveals that unlicensed, low powered FM transmitters are also specifically authorized in Australia, New Zealand, Canada and Japan. Agreed, low powered FM-band transmitters do not appear to be allowed in The Netherlands or England, but I didn't bother to look much further. Of course, each hopeful experimenter should consult the regulations of his/her particular country.

Example: Australia:
Quote
Radiocommunications (Low Interference Potential Devices) Class Licence 2000
(1) This Class Licence authorises a person to operate a transmitter included in a class of transmitters mentioned in item in Schedule 1, subject to the following conditions:
(a) the transmitter must be operated:
(i) on a frequency, or within a range of frequencies, mentioned in
the item; and
(ii) at a radiated power that does not exceed the maximum EIRP
mentioned in the item; and
(iii) within the limitations (if any) mentioned in the item;
(b) the transmitter's operation must not cause interference to the operation
of radiocommunications services.
-----------
Schedule 1 Transmitters
Item 21: Wireless audio transmitters and auditory assistance transmitters
Freq: 88-108 Mhz
Max EIRP:  10uW


Example: New Zealand:
Quote
New Zealand residents are allowed to broadcast licence free-of-charge at a maximum of 1 watt EIRP in the FM guardbands from 87.6 to 88.3 and from 106.7 to 107.7 MHz under a General User Radio License (GURL), which is issued by Radio Spectrum Management, managed by the Ministry of Economic Development.

Grumpy_Mike

Not impressed you pick two very sparkly populated countries.
It is not allowed in the whole of Europe, or Russia.
Note that all those regulations say they must not cause interference with others even if they comply to all the other regulations.
Also the range of frequencies is tight, which is impossible to control with the free running crap types of circuits lauded by stupid people in articals like those posted.

UnoDueTre

#20
Nov 03, 2013, 10:59 pm Last Edit: Nov 03, 2013, 11:07 pm by UnoDueTre Reason: 1
IMO, this whole license thing is a bit of a storm in a tea cup.
There are three solutions to this:

1) There are countries that do allow low power transmission in the FM and AM bands.
If you live in one of them great, adhere to the requirements of low power and proceed.

2) Most countries have what is know as "free-bands". These are frequencies set aside for transmissions
without the need for licensing but power restrictions also apply.
These frequencies (or bands) vary from country to country so check first.
Some common ones are 50MHz and 70Mhz (not in all countries though) and are lower then the FM broadcast band
and thus easier to generate.
Cheap receivers are available to pick up these bands (often called weather band or TV sound receivers)

3) Become a radio ham, bit more of a hassle but it does open up more frequency and power options.

EDIT:

The UK does allow low power FM transmissions:

From the Ofcom website:

Quote

Exemptions from licensing

Deregulation is an important aim where this can be done without damage to licensed use. Much radio apparatus is therefore exempted from licensing, including:
   :
   :
e) a wide range of short range devices, including certain low power FM transmitters (sometimes called 'car baby' devices), which wirelessly connect MP3 players and other personal audio devices to radios and in-car entertainment systems.

MLinir

I have built a FM Transmitter with Arduino, It is pretty easy.
Here is the code for the Arduino. after Uploading you put a big Antenna to pin 9.
95,85 MHZ is the best frequency to receive the Signal

//Code
//Tonlaenge
int EF;
int EFZ;
int EA;
int DF;

int np;
int p1;
//Tonhoee
int d;
int e;
int g;
int h;
int a;
int Q;
int R;
int Z;



void setup()
 {
 pinMode(9,OUTPUT);

 }  // end of setup

void loop() {
 EF = 500;
EFZ = 750;
 EA = 250;
DF  = 1000;
np = 80;
p1 = 700;
 
  d = 297;
  e = 330;
  g = 396;
  h = 495;
  a = 440;
  Q = 594;

  R = 660;
  Z = 792;

    delay(p1);
    tone(9,d);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EFZ);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,h);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,a);
    delay(EFZ);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,a);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,h);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,a);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EFZ);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,h);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,Q);
    delay(EF);
    noTone(9);
    delay(np);
   
   
   
//  1 zeilenbruch 
   
    tone(9,R);
    delay(DF);
    noTone(9);
    delay(p1);
   
    tone(9,R);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,Q);
    delay(EFZ);
    noTone(9);
    delay(np);
   
    tone(9,h);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,h);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,a);
    delay(EFZ);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,a);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,h);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,a);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EFZ);
    noTone(9);
    delay(np);
   
    tone(9,e);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,e);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,d);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(DF);
    noTone(9);
    delay(p1);
   
    tone(9,R);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,Q);
    delay(EFZ);
    noTone(9);
    delay(np);
   
    tone(9,h);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,h);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,a);
    delay(EFZ);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,a);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,R);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,Q);
    delay(EFZ);
    noTone(9);
    delay(np);
   
    tone(9,h);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,h);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,Q);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,R);
    delay(DF);
    noTone(9);
    delay(p1);
   
    tone(9,Z);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,Q);
    delay(EFZ);
    noTone(9);
    delay(np);
   
   
   
    tone(9,h);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,h);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,d);
    delay(1/4);
    noTone(9);
    delay(np);
   
    tone(9,a);
    delay(EFZ);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,a);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,h);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,a);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(EFZ);
    noTone(9);
    delay(np);
   
    tone(9,e);
    delay(EA);
    noTone(9);
    delay(np);
   
    tone(9,e);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,d);
    delay(EF);
    noTone(9);
    delay(np);
   
    tone(9,g);
    delay(DF);
    noTone(9);
    delay(np);

}

allanhurst

My goodness!

I've been a professional rf designer for 30+ years.

I hven't looked at the details of the code, but it will put out a square wave , one of it's
harmonics could well be in the fm band together with a whole load of other mush.

ignoring the legalities, (whch I don't recommend)..

buy a synth chip

buy an I-Q modulator  (HP make some good ones)

build or buy a VCO ( mini circuits are reasonably good) or use a colpitts + varicap

design and build a circuit  and a pcb ( a lash-up probably won't work well)

youo can program the synth with the arduino  kit

 now go through the whole approvals process - it isn't easy or cheap

I've done it loads of times from 88 MHz to 30+GHz.

and don't mess up loads of bands

ie don't go there if you don't know what you're doing..........

regards

Allan

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