Hi,
I wonder if anyone can help.
I am trying to learn about about FM transmitting with the aid of my Raspberry pi.
I currenty have my Raspberry Pi set up and it modulates GPIO4 and produces
an FM signal which I can listen to around my house, using a 20mm long jumper
cable on GPIO4.
Set up by following this tutorial:
https://makezine.com/projects/make-38-cameras-and-av/raspberry-pirate-radio/
I now would like to understand the theory of how to attached a tuned Dipole Antenna
to the Raspberry Pi, and if you would require the use of a BALUN to balance the feed
if using a COAX CABLE.
I have sketch out in the image below how I think the set up would be. This is just
how I assume it would need to be connected and as I have no experience in this field
it may therefore be incorrect.
Also, due to the way the Raspberry Pi modulates the signal and produces harmonics
I will not be creating a working set up, but am more interested on how the theory
of how to get it to work so as to further my knowlege and get a fuller understanding
of how to transmit an FM signal.
A couple of questions that I have relating to how this would be set up are:
1.
Does the downward pointing leg of the Dipole need to be connected to Ground,
if so why does this need to be connected to ground?
If this is the case would it be ok to connect it to the Ground pin on the Raspberry Pi via the
braided outer wire of a Coax Cable.
2.
Would I require a BALUN to balance the feed from the Coax?
If so how which type would be best to use.
I have seen information on using a length of CoaxCable the same length as
1/2 wavelength to balance the feed, but this was shown on a 'Folded' Dipole
(see image below), and not on a standard 'non folded' diplole.
Would it still be possible to do this for a standard Dipole?
If so how would you connect the Coax Cable and the BALUN to the Dipole.
Would it be the same as in the image above where the middle core wire of
the CoaxCable is connected to the top Leg of the Dipole and then the BALUN
length of CoaxCable is soldered to this leg also, with its other end connected to
the bottom leg of the Dipole and all the three braided ends are connected together
(with none of the braid attaching to either the top or bottom leg).
If that is the case, how does it ground? as I assumed that the bottom leg would
require to be attached to a ground.
Any help / explanation would be appreciated.
I wonder if anyone can help.
I am trying to learn about about FM transmitting with the aid of my Raspberry pi.
I currenty have my Raspberry Pi set up and it modulates GPIO4 and produces
an FM signal which I can listen to around my house, using a 20mm long jumper
cable on GPIO4.
Set up by following this tutorial:
https://makezine.com/projects/make-38-cameras-and-av/raspberry-pirate-radio/
I now would like to understand the theory of how to attached a tuned Dipole Antenna
to the Raspberry Pi, and if you would require the use of a BALUN to balance the feed
if using a COAX CABLE.
I have sketch out in the image below how I think the set up would be. This is just
how I assume it would need to be connected and as I have no experience in this field
it may therefore be incorrect.
Also, due to the way the Raspberry Pi modulates the signal and produces harmonics
I will not be creating a working set up, but am more interested on how the theory
of how to get it to work so as to further my knowlege and get a fuller understanding
of how to transmit an FM signal.

A couple of questions that I have relating to how this would be set up are:
1.
Does the downward pointing leg of the Dipole need to be connected to Ground,
if so why does this need to be connected to ground?
If this is the case would it be ok to connect it to the Ground pin on the Raspberry Pi via the
braided outer wire of a Coax Cable.
2.
Would I require a BALUN to balance the feed from the Coax?
If so how which type would be best to use.
I have seen information on using a length of CoaxCable the same length as
1/2 wavelength to balance the feed, but this was shown on a 'Folded' Dipole
(see image below), and not on a standard 'non folded' diplole.

Would it still be possible to do this for a standard Dipole?
If so how would you connect the Coax Cable and the BALUN to the Dipole.
Would it be the same as in the image above where the middle core wire of
the CoaxCable is connected to the top Leg of the Dipole and then the BALUN
length of CoaxCable is soldered to this leg also, with its other end connected to
the bottom leg of the Dipole and all the three braided ends are connected together
(with none of the braid attaching to either the top or bottom leg).
If that is the case, how does it ground? as I assumed that the bottom leg would
require to be attached to a ground.
Any help / explanation would be appreciated.