gta02-core and external GPS antenna

Steve Mosher steve at
Sat May 30 20:22:32 CEST 2009

Werner Almesberger wrote:
> Steve Mosher wrote:
>> Question: are you considering folding in the A8 changes? and the 1024 fix?
>> beware on the A8 microphone as it requires an annoying case mod. doable,
>> but annoying.
> I definitely want the audio changes, yes, even beyond GTA02v8.
> I.e., amplifier removal. I hope Joerg will have a look when we
> get to the audio design and see if we missed anything.
> The new EMI-hardened microphone sounds good, but I wonder if we
> actually need it, if the existing buzz fix already solves all
> issues without introducing new ones. Component availability may
> also be an issue, perhaps even the deciding factor.
   Agreed.  does your design include the beads to prevent the RF from 
getting into the mixer?
   I believe this is one of the differences between A7 and A8. A7 ( i 
was told) is a bandaid on the
  output after the mixer, A8 ( i understood) fixed the root cause and 
had ferrite beads added.
  Joerg will know. Preventing the RF from getting into the mixer is much 
better ( wired mic for
  example is believed to cause buzz even in an A7?? )  If you haven't 
heard an A8 it was,
for me, quite a pronounced improvement. Overall the S/N was perceptably 
better. Andy
 may be a better source of information than I am. That said, the 
improved mic would require
 that annoying little case mod.. not to bad for a DIY, but in mass pro 
it would not be a good
> The #1024 fix would be easy to implement. Instead of adding
> another ceramic capacitor, we could just use a sufficiently
> large low-ESR tantalum cap, so the layout wouldn't even have to
> change.
> The main problem with GSM at the moment is how we get the
> design. The entire GSM side is non-public, schematics and
> layout. I don't think Openmoko would have much of an issue with
> releasing all this, but these things are under NDA with TI, so
> TI would have to agree as well. We can knock on TI's door, but
> I'm a little afraid they would have to recall people from
> retirement to even know what that Calyoso thing is we're
> talking about.
> I'm also not sure if those NDAs are with Openmoko directly or
> via FIC. Wolfgang probably knows.
  Ya check with Wolfy.
> An alternative would be if gta02-core could somehow license the
> design from Openmoko and drop it in in a non-public way. Since
> this would be the last gleaming of the whole Calypso complex
> anyway, I wouldn't worry too much about the freedom aspects per
> se. However, this would complicate handling the layout files on
> the gta02-core side.
 I'm looking at those issues.  It's probably best if you create some 
kind of legal
 entity. Postmoko. 
> External GPS antenna connector removal seems to do more good
> than harm. By simplifying the circuit and maybe cleaning up
> some of the signals (I find the lack of filters on TX/RX a bit
> irritating), we may very well recover a dB or two, making the
> internal antenna almost as good as the external one.
 Ya,  I never saw any substatiated numbers on the gain from the external 
  there are of course reports of improved performance. It would be 
  to see what you get by simplifying the circuit.
> - Werner

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