[Gta04-owner] Status GTA04 GroupTour

Dr. H. Nikolaus Schaller hns at goldelico.com
Sat Dec 31 10:28:52 CET 2011

Am 31.12.2011 um 04:02 schrieb Thomas Gstädtner:

> On 30.12.2011 15:08, Dr. H. Nikolaus Schaller wrote:
>>> Which leads us to the persitent problem of producing new cases (or adapters
>>> for existing cases). Maybe we can break the problem in two and try to find kits 
>>> for the missing components (antenna, etc.) on one hand and desigining a 3D 
>> For these parts I have some components sitting on my office desk waiting
>> to be evaluated next year ;). Those are some speakers bought from Mouser
>> and I expect that they don't make bigger problems.
>> A minor problem is to find a good source for vibracall motors. Mouser has one
>> in their catalog, but they are sold out for a long time and it appears they are EOL.
>> If someone knows a catalog distributor for such motors, please let us know.
> These guys sell some:
> http://pagermotors.com/Products.php?f_category=Pager
> Other than that only Digikey seems to carry some stock of one model:
> http://search.digikey.com/us/en/products/KHN4NX1RC/P14793CT-ND/2686253

The one from DigiKey is very promising because it looks quite similar to the
one built into the Freerunner! Thanks for the link and part number.

>> The most complex "missing" part is the UMTS antenne. This needs a very careful design
>> so that we do not reduce the reception quality (remember the iPhone 4 issues?).
>> And even worse: if reception is bad, the transmitter has to increase the power
>> which draws the battery empty even faster. So a badly designed antenna has
>> dramatic effects on the overall performance.
>> Fortunately, we have a good RF engineer in our team, but as usual with volunteers
>> development takes a little more time as expected.
>> Technically the idea is to make the antenna as a flexible PCB so we can easily
>> add stubs or change trace widths and lengths at very low experimental cost
>> (e.g. 20-30 EUR for each protoype). Only the measurement tools cost >5000 EUR...
>> This antenna can be bent and stowed into a small slot of the case.
> The company "Round Solutions GmbH & Co. KG" (Aldafunk)  produces and
> sells such antennas, they likely have the equipment to do this properly.
> It is a German company, so I'm sure you could get in touch with them and
> maybe even get a sample, e.g. this model:
> http://www.aldafunk.com/GSM/UMTS-Antenna/Flexible-Adhesive-PCB-Dipole-Antenna-GSM-UTMS::92.html

Yes, this gave us the inspiration. Unfortunately that model is 40x15 mm
which is a little too big. And it has a U.FL connector and we need to connect
differently to the PCB.

But it is exactly the idea we have. And it is not very difficult/expensive to
build such antennas - only the design is quite complex.

A (German) source for geting flexible PCBs is e.g.:


>> And finally, we may need a replacement battery in the future. But we can either
>> use the Nokia BL05 or similar or find another one or it should not be too difficult
>> to get a compatible battery through Alibaba.
> As most high end phones don't come with replaceable batteries anymore,
> it might not be the best idea to bet on a model-specific battery - it is
> nice to have stock, but having underperforming or enormously expensive
> batteries (like the higher-class Nokia ones) doesn't seem like the
> smartest move.
> These guys have a huge selection, might be worth checking out.
> They sell it not only as cells but also as complete packs for easy assembly:
> http://www.ibt-power.com/Battery_packs/Li_Polymer/Lithium_polymer_cells.html

Thanks for all these links!


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