I have a lot of stuff on them. I've only built a few but they do work. They would NOT be even remotely good for a boat however because I have constructed them on foam core, and used materials like copper tape which likely comes off if it gets wet.
Because it uses glue to adhere itself. if we got together we could make much more durable PCB versions.
The spiral antennas are very useful and I have received a ton of interesting signals with mine. there are a lot of different perfectly valid ways to make them, each with its advantages and disavantages.
A number of them were described by Dyson in the 1950s and 1960s. and are easy to reproduce exactly as he made them.
The antenna can be inside of a conductive exterior square, which shorts the outside or not. Both work great. You could cut one out of a square and then use the two pieces you cut out to make another one out of that.
You could actually make one very easily out of just copper tape and graph paper in the same size as the graph paper. Basically, make a two armed square spiral meeting at its center the two arms meeting in a four sqares where they just touch, did you understand what I mean? Ideally your copper tape is fairly thin as is your graph paper size. You make a square archimedian spiral, implement it as a square, To the RF, the square is seen as a meander line, in other words, in a circular projection, a squre is a sine wave, a meander line, does that make sense? A meander line works well to shrink the size of your antenna a bit. You can see what this looks like with some graph paper and a pencil, just make the closest thing to an archimedian spiral you can using straight lines instead of a circle on the graph paper. The important thing being that the space between the arms should be the same as the width of the arms. You could also I suppose make a hybrid design and incrementally increase the width of the tape you used as you went outward. This might produce an antenna much like a lof spiral. But that antenna would likely have irregular discontinuities and wouldnt perform as well for GPS.
You can make archimedian spirals in Inkscape, I am pretty sure. Just make sure it has two arms, not one. You could make a four armed antenna but then you will need a broadband 90 degree hybrid coupler. If depends on how far apart the highest and lowest frequencies you need to receive are.
All GNSS satellites I am aware of have RHCP. Make sure you make an RHCP antenna, not LHCP, otherwise you may have to use it backwards.. I will upload some graphics that could be turned into a pcb or cut out of some conductive material with an xacto knife, and taped in a very halfassed way to some cardboard or something. Using a 4:1 VHF/UHF balun. That works too!
Please read this for an explanation and the math.(Archimedian spiral)
http://erewhon.superkuh.com/library/Electromagnetics/Spiral%20Antenna/Analysis%20of%20Archimedean%20Spiral%20Antenna_%20Chapter%202_%20Caswell.pdfthe equiangular or logarithmic spiral is constructed differently. The angle remains constand and so the width of both arms increases as one moves outwards. The arms of both antennas in the classic design is exactly the same width and the spaces, so a circle should be 50% covered.
At one point, the city of Seattle was going to build a park based on a spiral antenna but it seems, not any more.. One of the tales the late musician, Jimi Hendix used to tell involved some story involving communications from the stars that was to be received with such an antenna, telling the human race where to go?
But only if it was the right polarization. Kind of like what you want to do!
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