N900 with poor aerial connection. Anyone with hardware experience still on this forum?
 

Hi,

I have an N900 which is well out of warranty at this stage. It has developed signal problems in the last week or so and I have identified that the problems are being caused by a bad aerial connection. I know this as I'm using NetMon to measure signal strength. This can jump from -96db on 2G to a reasonable signal on 3G, just by pressing the top right corner of the screen tight (which feels loose).

Where exactly is the aerial on the N900? Is is on the screen part? I'm hoping that the connection from the screen to the main board is loose, as it came loose before and was causing display issues, this was very easy to fix.

Any experts around?

James

Re: N900 with poor aerial connection. Anyone with hardward experience still on this forum?
 

From the legend that bought you the injection drivers...

http://david.gnedt.eu/blog/wp-conten..._locations.jpg

To get to it you need to open up the WHOLE N900. It is fairly easy though. It is only 6 phillips screws and 2 T5 torx screws. The antenna has a 'spring leaf' on it that presses against a pad on the main PCB, just bend it out a bit.

While you are in there you can quickly solder your USB port down as well so it can never break. Search for the the USB thread by the TMO supe legend dr_frost_dk.

Re: N900 with poor aerial connection. Anyone with hardward experience still on this forum?
 

I'm glad your reference has matched my diagnosis. At least it could well be a simple bad connection. Have you heard of this before?

Thanks for the quick reply.

James

Re: N900 with poor aerial connection. Anyone with hardward experience still on this forum?
 

No never. However there is always a first time for everything!

Re: N900 with poor aerial connection. Anyone with hardward experience still on this forum?
 

PROBLEM SOLVED, AND BETTER SIGNAL THAN EVER!

I thought I'd take the time to write this down in detail.

Right, my N900 was stolen about three months ago and this one is actually a replacement I've gotten from Ebay.

It has been fine up until this week, probably just a knock that made it worse, here's how:

In the picture below, where screw one is located, is where I had found pressing the screen was making it better. I turned the phone over to open it up, and the screw was actually MISSING. I removed screw two (I don't have a replacement) and placed it in screw ones' slot. Not only do I now have full reception, but I'm getting 3.5G in places where I could only get 2G. I'm assuming screw one actually holds the antenna together internally, and without this the antenna was bobbing about, causing the random reception problems.

http://i.imgur.com/cTrsU.png


Thanks guys!

James

Re: N900 with poor aerial connection. Anyone with hardware experience still on this forum?
 

Amazing! One screw can change everything. Interesting solution for more or less usual problem.

Re: N900 with poor aerial connection. Anyone with hardware experience still on this forum?
 

Just checked my screws...
All there
looks like you can actualy fix stuff by screwing up!

Re: N900 with poor aerial connection. Anyone with hardware experience still on this forum?
 

:D That should be marked as NSFC (Not Safe For Commuting) - causes real "laugh of loud", that is quite hard to explain to fellow passengers ;)

---

Thanks for sharing info with us - very interesting. Also, do You know that N900 got internally ready-to-use micro-sockets for external antenna connecting? Preparing output for them into modified mugen-cover is on my (quite long) list for things that I should do one day ;)

Using that, one can boost cellular and wifi. We already got antenna for bluetooth (it's same module as FM receiver, so connecting correct wavelength antenna into headphones jack = external antenna for bluetooth), so only thing remaining is FMTX. I wonder, how hard it would be to solder another micro-socket for it's external antenna ;)

/Estel

// Edit
As for bluetooth, it's pity, that we haven't got any sniffing software. Tests performed long time ago proved, that hardware sold at high $$$ "for hacking" is just matter of firmware included - transmitted correctly to 5$ generic consumer bluetooth dongle, it worked exactly as it should. Maybe one day, someone will create such thing, like our wifi injection ;)

Re: N900 with poor aerial connection. Anyone with hardware experience still on this forum?
 

"As for bluetooth, it's pity, that we haven't got any sniffing software."

Someone made an app for eavesdropping, listening on others bluetooth headset devices. Not sure if that's what you meant.

Re: N900 with poor aerial connection. Anyone with hardware experience still on this forum?
 

Can I have the name of this app please? For educational purposes of course. I played with this stuff on a laptop with a bluetooth dongle before and it was quite interesting.

Re: N900 with poor aerial connection. Anyone with hardware experience still on this forum?
 

This is very common. All those mobile broadband sticks (the ones made by Huewei) all have a connection for an external antenna on board.

Re: N900 with poor aerial connection. Anyone with hardware experience still on this forum?
 

Carwhisperer, next time google it!
Not sure if it works on the n900, it might, i've installed maemo4 bins and it works (stella- atari2600 emulator)
http://talk.maemo.org/showthread.php?t=20780

info here:
http://zitstif.no-ip.org/?p=377

Re: N900 with poor aerial connection. Anyone with hardware experience still on this forum?
 

The little connectors on the N900 PCB are hirose u.fl if you're referring to test points. I personally doubt they would be the same type of connector that you would find with a mobile broadband stick. These hirose u.fl connectors have far less connect/disconnect cycles before they become faulty compared to generally any other antenna connector.

As for getting something that is equivalent to bluetooth monitoring in the early days, you needed cambridge silicon radio non-ROM chipset. That with a commercial sniffer program (which can only now be found on sites that leak them) that offers the firmwares along with a bit of linux knowhow can turn a fairly cheap bluetooth dongle into a commercial bluetooth sniffer. Unfortunately N900 is equipped with broadcrap (ahem, broadcom rather) bluetooth chipset which is most likely incapable of doing that.

With USB hostmode these days I'm sure one can still get by with a decent USB bluetooth device (something like aircable for instance) and might be able to do some bluetooth pentesting. Otherwise there is that option of building/buying ubertooth.

Re: N900 with poor aerial connection. Anyone with hardware experience still on this forum?
 

Interesting, I have one of the CSR DBT120 'RAM' dongles. What is the name of this 'commercial software' tux?

Re: N900 with poor aerial connection. Anyone with hardware experience still on this forum?
 

tuxsavvy, thanks for this valuable and very informative post.

As for Hirose U.FL, they're indeed ones I'm referring to. This page:
http://wiki.maemo.org/N900_Hardware_Hacking
...contains invaluable info about possible solutions and commonly available adapters, that one can use for connecting (see "external antennas" part). There is also note about FMTX contact pad (*not* H. U.FL), and it seems it's just connected by spring-like "clip".

This page seems to confirm that (clip for FMTX):
http://wiki.maemo.org/N900_FM_radio_transmitter

Overall, it's possible to - relatively easy - extend range of GSM, GPS and WiFi/Bluetooth (same frequency range = same connection pad). If I'm not wrong here, Bluetooth should be also connectable via headphone jack, due to it sharing same chip as FM radio (with antenna shared with headphone jack). Of course, that would require specially crafted DIY connector with jack plug.

As for Hirose U.FL, it's commonly used in mini-pcie cards, found in notebooks/netbooks/UMPC/some bigger tablets. So, cables for them, are - novadays - also quite common, so instead of buying adapter, one can craft one (with due care, cause it need to be shielded correctly - such thin cables are capable of catching interferences).

To be honest, it's so (relatively) easy, that I'm 100% sure I'll do it one day - only one thing that I need it's time ;) Mugen Cover (that I use daily, alongside DIY dual-scud battery) got enough room for all adapters, so no need to werar&tear H U.FL.

/Estel

Re: N900 with poor aerial connection. Anyone with hardware experience still on this forum?
 

Frontline Bluetooth Sniffer (v5.6.9.0). If you want, I still have a copy on my computer. I also even have the DFU files as well (firmware updates iinm for CSR non-ROM based chipset). Let me know in PM if you want them as new posts about N9 keeps flooding the active topics bar and preventing me from seeing topics like these :). In other words I'm losing track.

Estel: heh no worries. Yeah I wrote up the external antenna mod part of that hardware hacking wiki page with help from SpeedEvil (not sure on his tmo username) and joerg_rw.

Its a bit of a shame that the FM transmitter was a spring like clip, had it been a hirose u.fl connector in place one can have some more `fun'.

Re: N900 with poor aerial connection. Anyone with hardware experience still on this forum?