Wanted: N900
 

I am looking for a n900, not necessarily in working condition.
I can get access to a machine that can scan the parts to get a digital model of it. So I will be able to design a body in metal for the N900.

Re: Wanted: N900
 

You may want to see this:
http://talk.maemo.org/showthread.php?t=83928
Maybe it would be more productive to join forces? My project for it is quite advanced. Coincidentally, access to 3D scanner is the thing I'm currently lacking, and it was slowing down progress quite a much (needed to re-design everything manually).

/Estel

Re: Wanted: N900
 

it interesting to see more people getting involved in creating metal bodiy for N900. Can you people show us a preview of what you are people are making ?

Re: Wanted: N900
 

150§ in indian rs?? If that antneea thing gona increase range count me in:)

Re: Wanted: N900
 

Yeah, mettal housing will shield all forms of radiation so external antenae are pretty much a must.

Re: Wanted: N900
 

you mean to they would used just to claim the lost raditaion back:eek:

Re: Wanted: N900
 

Yes.

10 chars

Re: Wanted: N900
 

I have been following your project from the beginning and am aware that you were measuring the device up. One of the first thing I was going to do is share the scanned images with you ;)

But my first design is different than yours. I am trying to make one with keyboard below screen, thinner device with place for 2 batteries side by side.

I'll probably also make one normal, just like N900, but with lesser volume and maybe full USB.

No not necessarily. I'll have a cutout with plastic at the place of antennae, just like iPad.

I don't have a preview yet. I'll start next week. This week I still have exams :(
But I do need a device first to be scanned in! I use my own as a daily driver.

Re: Wanted: N900
 

Thanks a lot :) Yea, I, of course, remember you from there - was unsure if you may have forget about it (as I'm so slow to deliver :o :()

Ah, that kind of beast. Well, the more choices, the better :)



In case of GSM radio, it causes - sadly - quite a lot of directionality (for other types, like WiFi, too, but not as much, due to lower operating range as a whole, and higher frequency). This is, probably, reason why N950 sucks so much @ signal strength compared to N900 - even despite clever helical antennas design (similar to helicals found in early mobile phones). I'm sure they aimed at getting circular polarized waves - ideal for devices, which should work no matter of position/angle toward base stations - but, due to limited space and reflectors (metal parts behind and between), it seems to produce either vertically or horizontally polarized one. This result in super signal when aiming device at "correct" angle, and 80% worse, when changing it just a 40 degrees (both numbers made up, to give and idea of what I'm talking about).

Consider, that iPad is designed to work with WiFi, not GSM/3G - especially the former will get affected.

Heck, I had quite a experience with designing antennas, but after starting body replacement project, I feel like I've studied for master thesis in antennas theory. (Damn, even during checking something for this every post, I found myself spending ~4 hours of constant reading, because I noticed interesting information in one article that may affect work on project, then followed link after link...)

And even now, I know just a tiny fraction of how those things (should) work - I'm absolutely amazed by talent of antenna's design pioneers, especially those, who did it in pre-personal computer era... What they achieved using just trial and error and manual calculations is AMAZING - you could literally spend a lifetime, just tweaking one design for one purpose (and sometimes, they invented quite a few).

Summing it up, maintaining non-worse signal for metal body replacement - of any shape - is a, sorry for word, "b|tch" of a task (mostly responsible for my delays in delivering hardware awesomeness to thirsty "masses" ;) ). Don't underestimate it - personally, I'm, sometimes, cursing myself for not promising wooden replacement (which, depending on type of wood used, may be much more elegant than metallic one, without practical differences in heat dissipation), instead of metal one. I plan to keep working on it for some time in hope for getting decent reference implementation for metal-body N900 - but, if it keep failing, I'll do a survey around per-orderers, if they would accept wooden variant, instead.

/Estel

Re: Wanted: N900
 

Wow Estel, you really seem to be very knowledgeable about this subject. Thank you for all the information. I think I'll consult with you when I get to the design-antenna part ;)

Do you thing it would work if I put the antennae on the outside of the structural metal body? That the antennae only on one side have the metal?

Re: Wanted: N900
 

It would surely help, but then, having all antennas close to each other isn't very good, due to unpredictable results of so-called radiation coupling. It may, or may not be severe, depending on random conditions - hard/impossible to predict, so they're put on different sides of device - basically, as far from each other-, as possible/feasible - for a purpose. Note, that even N950 put them to both sides (thus complicating body design, due to two plastic parts above antenna, instead of one).

Coupling mentioned above would happen no matter how many antennas are actively used at the same time. But, there is other possible problem - active interference, when using radios simultaneously. Thankfully, we're rarely using both 3G and WiFi transmission at the same time (3G is closer frequency to WiFi, while GSM/2G is far away, much lower), but to minimize it, users would need to get habit of switching to 2G-only, while on WiFi. I do it intuitively for battery saving purposes, but for some it may be PITA to remember.

Now, it is possible that you may just scratch all of above, as you would never encounter any problems in real life. sadly, no other way to test, than doing prototype and test-driving it (and adjust in case of failure, then re-do prototype, then test drive again... and again...). Despite advancements on antenna design simulators, such complicated array of antennas and feeds so close together - with half of feeds hardware properties unknown/closed - is simply uncomputable.

That's why guys designing mobiles are doing it first, together with whole board project. We meet existing design, trying to put it in different "box", (and/or using antenna replacements) changing layout, etc - it's *much* more complicated than some would think.

Funny enough, the design that should work in *all* cases, would be to add stick-type antenna, like in those early days mobiles:

http://pesatalk.com/wp-content/uploa...e_timeline.png

Putting antenna outside "hull", far away from noises, interferences, heat, etc, clear 99,99% of problems.

/Estel

Re: Wanted: N900
 

Yes, those were the days, Motorola v60, Ericsson R320, Treo 650. With the antenna sticking out. Easy to locate the upside of the phone while taking the phone out of the pocket. No death grip :)

How about keeping the antennae at the same place and building the metal case around it?
The antennae are on the outside so it really should not matter right?

Re: Wanted: N900
 

Then, we're back at point one ;)

Cover- which must/should be connected with N900 ground plane - will cancel signals when N900 would face base station by side. Of course, in real life, where signals bounce xyz times from everything, it won't cause 0 signal - it just be much worse than it should (aka N950).

Note, that N950 was designed from the beginning to be metallic, and they had *everything* they might need to make it work right - still, it fail to work as it should. Who knows, if it isn't main reason, why N9 is polycarbonate. (or any other funny-named thing, which means "plastic")

/Estel