Hi There are a lot of 3D printers out there that happily print ABS ….
Bob > On Oct 15, 2019, at 10:17 AM, Attila Kinali <[email protected]> wrote: > > On Fri, 6 Sep 2019 10:07:29 -0700 > Nick Sayer via time-nuts <[email protected]> wrote: > >> I’m late to the party, but my go-to antenna is the Gilsson marine antenna. >> If >> it has a downside, it’s that it has a flat top instead of a cone. I’ve got >> one mounted outside at our vacation home near Lake Tahoe, so we’ll see >> whether snow loading becomes a problem shortly. The fix would presumably >> just >> be a 3D printed plastic gnome’s cap, though even that might not be useful if >> we get snow like we did last year. > > I don't recommend 3D printing. The materials used for 3D printing > are quite hygrophile, ie suck up a lot of humidity. This will give > you varations in the refraction index of the cover depending on > the air humidity. > > Instead use some thin plastic sheet and thermoform it. > ABS is a good candidate for ease of thermoforming, with reasonable > RF performance. PTFE would be better (almost ideal) in terms of > RF performance, but is quite a bit more difficult to thermoform. > Though, considering how cheap PTFE sheets are, I would probably > try it anyways. > > BTW: an indication of what the cover does on the phase center > can be found in [1] > > Attila Kinali > > [1] "The Effect of Antenna Covers On GPS Baseline Solutions", > by Braun, Stephens, Ruud, Meertens, 1997 > https://kb.unavco.org/kb/article.php?id=185 > > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neal Stephenson > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
