So I've been following this guide on how to build a LoRa Radio tracker. When speaking about the antenna used, he says that he adds "radials".
Solder a 17.3cm bit of guitar wire in place for the DRF1278F antenna, this is a ¼ wave at 434Mhz. Before the tracker is actually launched, cut two bits of guitar wire 34.6cm long and fit these as radials in the holes provided either side of the centre pin of the antenna connector.
I've done a bit of research and I sort of get the general picture of what they are for, however there are rather a lot of holes next to the antenna, so I have not quite understood if the radials should be connected to the main antenna or not (maybe they are supposed to just be there or something).
So when I make my own antenna, should it look like Picture 1 or picture 2?
I'm very sorry, I know how stupid this question must sound, but I really have no clue...
Also: What diameter would you recommend for the antenna wire used?
bestanamnetnogonsin:
Ok I think i finally got it. Should it look like on the picture below? So the radials are attached to the antenna?
One last question: What wire would you recommend for antennas? (what diameter?)
The radials are not attached to the antenna wire, itself. They are attached to the ground connection closest to where the antenna wire is connected. The antenna wire is only 1/2 of what is necessary to radiate. the other 1/2 will be the circuit board and associated electronics and wire, unless you provide another path for the RF energy. The radial wires provide that path.
Any single conductor bare wire stiff enough to hold it's shape will work for you.
Those instructions were specifically written to assembe a tracker using one of my boards, they were not intended to be a generic set of instructions for making HAB tracker or 1/4 wave antennas and radials.
If you had one of the boards in front of you it would be clear that the radials go in the (grounded) holes in the pads next to the centre pin connected to the devices antenna pin.
The wire used is normally Ernie BAll Custom Gauge 13 for the UHF antenna, and maybe Custom Gauge 9 for the shorter GPS antenna. The holes in the boards are sized to allow this, thicker wire might not fit.
The radials have a significant effect in improving antenna efficiency.
Those instructions were specifically written to assembe a tracker using one of my boards, they were not intended to be a generic set of instructions for making HAB tracker or 1/4 wave antennas and radials.
Yes I know, and it would have been great to use one of your boards. They really seem excellent for high altitude balloons. However due to a number of reasons, I'm unable to use one for this particular project.
The radials are not attached to the antenna wire, itself. They are attached to the ground connection closest to where the antenna wire is connected.
Ok, great. in that case I guess I'll just connect it them to GND?
By the way: As it would be a bit unpractical to have the antenna directly by the side of the arduino, I wonder: Is there a way to get it further away? For example with a cable like this. Or would the cable act as an antenna itself and ruin my signal?
Paul_KD7HB:
Any single conductor bare wire stiff enough to hold it's shape will work for you.
Paul
There's a trick for making copper wire much stiffer - if you have some mains cable (the sort that
goes into the walls, single strand), strip off a length plenty long enough, fix one end in a vice, wrap
tie the other end round a stout bar and pull it until the wire stretches significantly (it may snap even).
This work-hardens the copper making it much less soft and suitable for antenna wires. It also increases
the resistance of the wire somewhat (which is why electrical copper is soft and annealed).
But this modifies the impedance and the radiation pattern, so the radials are often bent down.
Ok, will try to incorporate this. What about the angle between the radials themselves? I guess 90° is best for 4 radials?
Also: Is there a way to get the antenna further away from the shield itself? For example with an extension cable or so? But then again: Wouldn't the extension cable act as an antenna?
