GSM antenna problems - Pipo P9 3G

[ivia]

Hi all,

I've been having hard times making the WiFi of my beloved Pipo work. After sending the tablet to the official support several times, now wifi works (they added an additional antenna) but I have no data connection through gsm network.

So, I've tried to figure out what of the mainboard's connection belongs to the gsm antenna (I've the wifi ones located) but I'd like to know which the GSM antenna connection is.

Any help (pics would be great) to identify the GSM antenna will be greatly appreciated.

Thank you very much

[giouncino]

New pipo models...
old problems still present...

This happened on M6 and M9 too.

It's really strange that Pipo doesn't learn from their errors.

Where is the Quality control??

If you send a pictures of the back of the tablet (without metal cover) I can help you identifying the various antennas.

[ivia]

Thank you very much giouncino, I really appreciate it.

I'll send the pics right after going back from work this afternoon. I've identify four connectors (If I remember well) with 4 identical antennas connected to 3 of them. I assume that one is for wifi, (the official support staff added a seccond antenna here last time I sent the tablet back to them) another for bluetooth, and a last one for the GSM.

I have now 2 antennas attached to the 3rd connector, and thus this is the one for the Wifi. But I'm not sure which one (first or second one) is the GSM connector.

BR

EDIT: Pic attached

[ivia]

Picture uploaded, posting to refresh the notification, thanks again

[giouncino]

buetooth and wifi generally shares the same antenna (because they both use 2.4Ghz)
one is for GPS (the simpliest one, it's only a dipole on tablets)
one is for GSM (generally the bigger one and more complex antenna)

I need a picture of the antennas to help you indenfying which antennas are, soldering point on the mainboard is not useful because I don't have P9 tablet!

To help you further, generally 3G antenna is close to the connector on the mainboard, to reduce EMI noise

[ivia]

P9 comes with "generic" antennas, as I've been told by support (don't know if it's true or not), and as you'll see once I take the pic, all the antennas looks the same. Are of the same size and type (except for the original wifi located at one corner, the same that the M9 have), so I'm afraid the type of antennas won't help us to identify the GSM one Btw, I'll open the tab and upload the pics within a few hours (g2g now).

Thanks again

[giouncino]

P9 comes with "generic" antennas, as I've been told by support (don't know if it's true or not), and as you'll see once I take the pic, all the antennas looks the same. Are of the same size and type (except for the original wifi located at one corner, the same that the M9 have), so I'm afraid the type of antennas won't help us to identify the GSM one Btw, I'll open the tab and upload the pics within a few hours (g2g now).

Thanks again

This is simply impossible: geometry of the antennas MUST be different, taking into account that GPS/Wifi and 3G works on VERY different frequencies:

GPS: 1535Mhz

WiFi/Bluetooth: 2.4Ghz

3G: 1900/2100Mhz

So if they have the same antennas with wrong dimensions they cannot work.

Antennas must be optimized on Lambda/2 or Lambda/4 to work correctly....

[ivia]

I understand the point related to the frecuency and obviously it must be as you said, but looking at the antennas, they all look the same, they look the same than the pic posted below (didn't had time to take the pic of my own tab, I'll upload it today as soon as I arrive home):

[giouncino]

this one seems to me a simple dipole generally used for GPS antenna

[ivia]

Finally

Those are pics of my P93G. There you can see the antennas A-B-C and the connections of the mainboard. There we go:

Antenna A is connected to connection 1
Antenna B is connected to connection 3
Antenna C is connected to connection 2

In the mainboard picture, you can see the original antenna I disconnected once reived from support due the Wifi signal was lowered around -20/-30 dBms ( I assume the chipset is not preparred to "power" 2 antennas) and the Wifi received signal goes back to normal again.

As I can see now I've open tha tab again, there are 2 antennas that looks the same to me, and a third one thinner than the other "C". "A" and "B" looks the same.

In any case, I've not been able to solve the GSM connection problem, so if you can help me identify the GSM one, I'll reconnect this antenna again to check if it's a welding/conenction issue

Thanks again

Edited: 4K res pics, may take some secs to load

A antenna: http://i.imgur.com/wAOoD1U.jpg
B-C antenna: http://i.imgur.com/KvJXBQR.jpg
MB connections: http://i.imgur.com/y28danV.jpg

[giouncino]

Antenna C is the GPS one, so don't touch it.

[giouncino]

Antenna A and B seems identical, but to be sure you may try to unglue them and see the antenna geometry printed under the tape.

Original antenna on mainboard picture if I remember well is a wifi antenna (same used on M9pro as shown here: http://freaktab.com/filedata/fetch?i...4&d=1439629966), sensitivity problem is probably due to a short circuit somewhere in coax cable.

Take a look here too:

http://freaktab.com/forum/tablet-support-android/pipo-tablets/8977-pipo-m9-pro-wifi-antenna-modification-instructions

[giouncino]

Chip AP6476 in mainboard picture is responsible for GPS, WiFi and Bluetooth, so again connection 2 and 3 should be for GPS and Wifi and connection 1 could be the GSM one