
The RadioInstigator: A $150 Signals Intelligence Platform - crankylinuxuser
https://www.rtl-sdr.com/the-radioinstigator-a-150-signals-intelligence-platform-consisting-of-a-raspberry-pi-rpitx-2-4-ghz-crazyradio-and-an-rtl-sdr/
======
amingilani
Wait, an antenna connected to the GPIO pin on a RaspberryPi for transmissions?
Correct me if I'm wrong, but doesn't the Pi output square waves, that would
cause harmonics if transmitted?

~~~
SuperNinjaCat
There was an old RPi project released a while ago (PiRadio I think?) which
simply involved attaching a jump lead to GPIO pin 4 which allowed the
transmission of FM radio signals.

It worked on the principal that the Pi had a stupidly powerful clock and thus
could be used as a transmitter.

I did a little experiment where I hooked it up to a yagi antenna and asked my
dad to set his cars radio to the frequency I set the software to transmit on
and drive around the block to test the distance.

Not only did it work well but I think I heard someone listening to the radio
in their home near mine open their front door and yell out "who ever is doing
that could you please stop it!" as it was interfering/jamming what they were
listening to.

I'm definitely checking this project out though, thanks for posting.

~~~
3xblah
"There was an old RPi project..."

Is this it?

[http://icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry...](http://icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry_Pi_Into_an_FM_Transmitter)

~~~
SuperNinjaCat
That link looks very familiar but I remember getting the idea from this
article first:

[https://makezine.com/projects/raspberry-pirate-
radio/](https://makezine.com/projects/raspberry-pirate-radio/)

Using this disk image for the RPi:

[http://cdn.makezine.com/make/pifm/PiRadio.zip](http://cdn.makezine.com/make/pifm/PiRadio.zip)

(good times)

EDIT: That link was definitely part of what I was researching at the time (as
it is linked in the project article I posted and I remember reading about the
limitations regarding stereo output, as well as the line "Most radio receivers
want a signal to be an odd multiple of 0.1 MHz to work properly").

