Chances of alternate Pinephone chassis or 3D models?

[diodelass]

do something like goldplating graphene infused filament on on your own chassis

Is... that something that people are doing in their home shops now? If so, I must be pretty behind the times. Last I heard, electroplating required incredibly clean conditions that most people couldn't produce at home, and graphene was still unobtainium for lack of an inexpensive synthesis route.

If I was going to try it I'd probably go for conductive paint, although 3d printing with conductive materials has been done. My reservation is more around the antenna design being good enough for a usable device. It's not impossible, but most of us don't have the required skill to design, test or tune an antenna for good performance. If those who do have the skill could produce a printable design that would be great.

Yeah, I agree. Cellular antennas are tricky. I'm not inexperienced with antenna theory myself - I have a physics background in electrodynamics and a bit of design experience - but the designs we see in smartphones nowadays sure aren't your grandmother's half-wave dipoles. They're nearly incomprehensible even to me, beyond a vague intuition for how they're likely to behave near their resonant frequencies, and I really don't have much of an idea where to start when it comes to actually designing one.

In fairness, it's possible that most RF engineers don't have much more than that, either - I understand many of them are designed probabilistically by genetic algorithms these days.

As for DIYing, I think your best bet might be to try cutting bits of aluminum foil to match the shapes present on the current pinephone chassis as closely as possible, and gluing the results to your 3D-printed version. You could also probably go old-school and just stick a connector on there to attach vertical dipole antennas outside the body, though you might need several of them to cover all the different frequency bands.

or, if you wanted to go really silly, you'd probably do quite well with a log-periodic dipole array, though that would easily get into "oh my gods, what is that" territory for most bystanders. Building your own antennas is a lot of fun, but making them both good and compact is a very involved technical problem.