Comment on Series coax stub capacitors for more precise loop antenna tuning
fullsquare@awful.systems 6 days agothe thing with using aluminum tape is that you can get away with very small thickness, because current flows only in top tens of micrometers depending on band. you can just roll up, say, 5cm wide, 0.5mm thick aluminum tape and have riveted or maybe brazed short length of 2mm thick bar to the ends for connecting capacitor. the problem is with mechanical stability of this setup, which is why you see pipes and thicker bars, bicycle rims etc
with braid you get a lot of contacts between wires, and i’m not sure that resistance of them would be low unless tire is fully inflated. maybe you can put short U-turn within loop at end opposite of capacitor and have adjustable shorting bar there. adjustable capacitor is more common by far, because if you can adjust it widely enough, you can get to different bands
einfach_orangensaft@sh.itjust.works 6 days ago
Good point with the copper sulfide, that wasnt on my mind at all, if i try ill put a protective layer between the braid and the tire rubber
Yeah i heared about the skin effect in aluminum being much shallower than in copper negating the better conductivity of copper, but i didnt found aluminum braids.
On the point of braids, i was thinking that would probably work well since the shielding in coax is also copper braid and many loops are made out of coax, but big diameter coax cant be folded as good due to the core, so i was thinking…maybe just use the shielding and no core at all.
You are right with the dipole, that would probably be the most sane solution. But i cant get the idea of a inflatable loop out of my head now…
fullsquare@awful.systems 5 days ago
Skin depth is larger in aluminum but not enough to balance out its lower conductivity, copper is better material taking all into account, in practice both are good. If opposite was true we’d use lead or zinc for conductors. There are satellite microwave parts made out of aluminium (low weight) coated sequentially with zinc (bonding layer), copper (better conductivity), thin layer of silver (even better conductivity) and then gold (actually not thick enough to contribute, this one is for corrosion protection)