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Adding a better GPS antenna


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#1 Mnky

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Posted 08 November 2010 - 07:49 AM

I wonder if its possible to add a better GPS antenna to the A81e. Some ideas anyone?Shouldn't be to hard if the GPS chip has a connection for an antenna.

#2 linw

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Posted 10 November 2010 - 02:30 AM

You might want to look here. Wits A81E reviewItems 5 and 6, especially.

#3 Mnky

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Posted 10 November 2010 - 06:02 AM

Thanks. That answers my questions where the GPS is located. Its good to know its on the top already. I like to know if this is some kind of micro connector which connects the antenna to the board? My idea for a external antenna has moved into the direction of an extend able antenna. Since the display kinda blocks the signal. If one could build a "drawer" for the antenna would be great. The cable seems to be long enough to handle it. I imagine the drawer being fully integrated into the case but able to be pulled out on demand to have an unobstructed line of sight to the sky. Alternatively an external antenna port would be nice, but i have no idea how to do that with the internal antenna still connected. Somehow the signal needs to be boosted. i hardly get more than 40+ on satellites. (GPS Test App) and my GPS location error stays above 5 meters.

#4 linw

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Posted 10 November 2010 - 05:28 PM

My SNR is even worse, at 32+.

#5 NorskeDivision

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Posted 10 November 2010 - 09:57 PM

If you have an SNR of 32 I doubt improving the antenna would help much. The problem is the chip or the drivers for it if your signal is already that good. From the tear down images though it does appear to have a small ceramic antenna attached via a little plug, so you should be able to pop out the antenna and replace it, or dissamble the tablet and isolate the antenna from everything else and see if that improves reception. If it does, replacing the antenna might be worth trying, if there's no change than the shot coming is in the chip, which sadly is hard wired onto the board and therefore impossible to replace.

#6 Mnky

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Posted 11 November 2010 - 05:00 AM

anyone want to test thaT? i dont like to disassemble my table in the first 30 days of ownership.I think it will make a difference. When holding the table with the backside towards the sky my signal gets ~3-5 points better compared to having it display up.Putting a better antenna in would make a difference.

#7 linw

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Posted 11 November 2010 - 05:33 PM

Not going to mess with mine! I have another GPS which works well so the A81 GPS was only ever going to be a 'nice to have'.

#8 NorskeDivision

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Posted 11 November 2010 - 06:01 PM

anyone want to test thaT? i dont like to disassemble my table in the first 30 days of ownership.I think it will make a difference. When holding the table with the backside towards the sky my signal gets ~3-5 points better compared to having it display up.Putting a better antenna in would make a difference.

I am going to test it as soon as my tablet arrives. The first thing I do when I get my tablet will be to take it apart. I'm not expecting any improvement in GPS performance but I'll try out a better antenna. I will probably use a bluetooth GPS primarily.

#9 xvinx87

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Posted 12 November 2010 - 09:44 AM

After doing some research, it seems to me the the main issue is the drivers for the gps chip and android. Android apparently does not play nice with GPS, seeing that many other android phones also have GPS issues

#10 Mnky

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Posted 12 November 2010 - 12:57 PM

That might be true, but if i could get the performance of the unobstructed antenna would help alot already. Holding the tablet upside down is just not very comfortable.

#11 NorskeDivision

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Posted 18 November 2010 - 12:12 PM

OK, looks like I won't need to mess with bluetooth GPS. GPS Assist - AndroidIf you really want GPS available at all times, install the above. It keeps the GPS alive at all times so it stops assuming you're off the coast of Gabon. EDIT: I may still try improving the antenna for better reception in buildings. EDIT2: OK, it still assumes that I'm off the coast of Gabon when I start an application that requires GPS, but just for a few seconds at the most. The GPS keep alive service does work, but there seems to be a bug with this tablet where whenever a new application requires GPS, it resets your latitude and longitude to 0,0. If you in the ocean off the corner of Africa south of Nigeria and west of Gabon and own a A81E than you are a lucky man/woman/sea creature because you're GPS will always be right. Otherwise this bug is a pain. Anyone else have their GPS often telling them they are off the coast of Africa?

#12 dmesg

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Posted 18 November 2010 - 12:26 PM

But the lack of a Bluetooth profile for GPS really makes me think the people at Google didn't put a whole lot of time into it.

They don't have to. BT GPS mice are a thing of the past, proper android phones have amazing GPS capabilities. Nexus One, for example, usually gets a fix after 1-2 seconds at most. Of course it knows my coarse location in advance, but it's still amazing - I've never seen such performance from any non-android device. Can you blame Google for not taking into an account some Chinese engineers who have no idea what they are doing?

#13 NorskeDivision

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Posted 18 November 2010 - 01:24 PM

[quote name='dmesg;93719]They don't have to. BT GPS mice are a thing of the past' date=' proper android phones have amazing GPS capabilities. Nexus One, for example, usually gets a fix after 1-2 seconds at most. Of course it knows my coarse location in advance, but it's still amazing - I've never seen such performance from any non-android device. Can you blame Google for not taking into an account some Chinese engineers who have no idea what they are doing?[/QUOTE']Not all Android phones have GPS, and anyway there are various reasons you might want to instead use Bluetooth GPS. My Windows Mobile HTC Ozone usually gets a fix in a few seconds, but it still supports bluetooth GPS. It's a fair point though! Since the GPS works so well on the Nexus one it's pretty clear most (if not all) the problems with GPS on this tablet are not Google's fault. Still though for such a widely deployed platform they ought to support all the major bluetooth profiles.

#14 Nicotine

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Posted 28 November 2010 - 03:55 AM

The GPS problems are nothing to do with Android:) It works about the same under WINCE .The antenna in the A81E is 'active' in that it has a built in amp, so it is possible to replace it with one with higher gain.. It is connected to the board with an IPEX MHFII (U.FL) connector. Digikey sells several active antennas with a short cable already having this connector (the connector is expensive and hard to attach). I bought a couple , and found part #931-1009-ND works very well , although it is thicker than the original. At 24 dB gain, it does improve the signals, but not by as much as I had hoped. Also tried a 30 dB antenna but it wonld not fit in the case. Tried an UF.L to SMC adapter (sold on ########### for adding an external wifi antenna to laptops) so I could add an external antenna, and got a massive improvement. But that kind of defeats the purpose a bit :)I suspect a contributor to the occasional signal problems is poor shielding. Mine has a piece of adhesive backed copper tape (with the backing left on) 'spot' soldered onto the motherboard to cover the soc etc. Pity really considering the pcb is set up to take a proper shielding cage over most of the components. Not much can be done about it though.

#15 Mnky

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Posted 07 December 2010 - 10:39 PM

Awesome info thx. Just have to find these parts in Germany.

#16 Mnky

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Posted 08 December 2010 - 12:53 AM

Do you think its possible to add more shielding? Shouldn't be to hard to get the copper tape and solder it on. But i don't understand how to apply shielding for it to make sense.

#17 Davethesnake

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Posted 08 December 2010 - 06:37 AM

yeah your right the internal antennas are of a micro -connector variety,there a few compatable brands some gold -plated some of them are called "Hirose" of "ufl" you can solder them but its tricky theyre very small and also its better to disconnect the co-ax completely and solder to that as the azimuth pattern will become distorted if you connect to the board,ie because the internal wi-fi uses foil inside the unit as a ground plane,you can just about  get away with soldering a reverse polarity sma connector which you can hook up to an omni-directional antennae,if its not too much of a problem and this will pull in a stronger singal but you migh lose some of its visual sniffing power,well it wouldnt really matter if your after a btter connection any way.
Remember the antannea parameters are probably worked out on paper at the factory at the design stage so distorting the antennae pattern wold probably show weird results,once you sever the co-ax you might find a different or non-existant  result.
The pc kicks out frames on a micro-second foreward basis and seems to send out a probe which is reset by pressing the "enter" key repeatedly,it is pretty difficult trying to visualise this process without specialist laboratory equipment also it is a non reversablee procedure so you cant realy see where the problem is because you cant halt it,and different tries will result in different results.