[Odin the Wanderer]

Nice thread bro, I am going to get my HAM licence in February

[ฬєรlєч]

Just ordered my Raspberry PI the B 512MB version, gonna try this as soon as i get it :)

[slober]

How do you send to a range for example 106.1 - 106.5? Great tut thanks

you can't send on multiple frequencys at the same time it would be to hard for the pi and it just isn't possible hardware wise also the code isn't meant to do that.

in theory it is possible if you use a normal audio output and wire it through a fm transmitter or fm transmitters in your case tuned to the diffrent frequencies

Nice thread bro, I am going to get my HAM licence in February

HAM is nice i have my (basic ON3)license since last year march ^^
but don't have the money for buying a proffesional installation due to srict euope regulations and taxes :s

allowd to send on at 10w for everything lower then 24890KHz and 50w for the other ones:
Spoiler (Click to View)
1810 – 1875 kHz
3500 – 3800 kHz
7000 – 7100 kHz
10100 – 10150 kHz
14000 – 14350 kHz
18068 – 18168 kHz
21000 – 21450 kHz
50 – 52 MHz
144 – 146 MHz
430 – 440 MHz

Just ordered my Raspberry PI the B 512MB version, gonna try this as soon as i get it :)

nice, it's really worth the money i'm hoping to use the transmitter in the future as a FM file transmitter estimated speed 9600bits a second max :) thats euh 1200bytes and euh aprox. 1.2Kb/s using a prof antenna and amplifier estimated range 10KM ^^

[RuffledUp]

Seeing as the pi is creating square waves then broadcasting that directly without any filter present on the transmitter, won't this cause harmonic interference across other frequencies in the sidebands? Which would be a bad thing. :D

[slober]

Seeing as the pi is creating square waves then broadcasting that directly without any filter present on the transmitter, won't this cause harmonic interference across other frequencies in the sidebands? Which would be a bad thing. :D

You'll get interference --> You shouldn't even be transmitting on some of these bands (1-250MHz) without having a proper HAM license

Due to its weak output power interference isn't a really big deal most of the people don't have a 1/4 dipole (75cm @ 100MHz) so the range is further limited of course it can cause problems.
the power output is around 10mW

Some interesting links about legality:

1. http://raspberrypi.stackexchange.com/que...m-legality
   
2. http://www.raspberrypi.org/forums/viewto...63&t=72766
   

[RuffledUp]

Still, without a filter even if you were broadcasting on say 100Mhz because of the square wave and harmonic resonance you could possibly be broadcasting on say 50Mhz and 150Mhz or something like that. In reality you would probably find a signal anywhere across the frequency range.

[slober]

Still, without a filter even if you were broadcasting on say 100Mhz because of the square wave and harmonic resonance you could possibly be broadcasting on say 50Mhz and 150Mhz or something like that. In reality you would probably find a signal anywhere across the frequency range.

I didn't encounter any noticeable interference while using the PiFM library
Of course without a filter and good equipment it's impossible to send a clean signal out

The Raspberry PI isn't a (V)HF transmitter and it's definitely not designed to be one.

This doesn't mean that the project is (...). I would say that it's capable of doing some really interesting things. An introduction to the world of amateur radio.

Of course if you are interested in the world of Amateur radio and electronics in general you could make your own filter circuit for a predefined frequency. This would require some research, electronic skills, parts and patience

[DaKnOb]

Something not mentioned here but really important, despite the low power, picking up an antenna that is suitable for this purpose will help not get your Pi into trouble. Static can gather in an out of range antenna and destroy your "transmitter" (the GPIO pin). Despite the extremely low power (I think LPDs run at 10mW), there's still the danger..