A few comments inside: Pascal Gosselin píše v Čt 07. 02. 2013 v 08:36 -0500: > Yesterday I was able to confirm that the installation of the Golden > Delicious NavBoard V3 very seriously degrades the performance of GPS > when using the built-in GPS antenna. Getting a 3D fix is taking over 20 > minutes on average using the built-in GPS antenna. When using an > external GPS antenna, the issue goes away and an unaided GPS cold start > can be achieved in about 41 to 44 seconds. > > I suspect that the use of unshielded cabling between the GTA02 is a > likely cause. Being in the Avionics business, I am familiar with the > use of shielded twisted pair wiring, but generally in large 22AWG (will > have to figure out where to source very thin STP cabling). The wires we > use to perform this mod is solid core, probably 30 AWG. In avionics, > when it is desired to keep a signal from radiating outside a cable (such > as Headphone/Microphone wiring), then the shield of only a single side > of the cable is terminated to a good grounding point. When instead it > is desired that the signal inside a cable be protected from EMI/RFI from > the "outside", then the shields on both sides of the cable will be > terminated to ground
We are usually trying to refrain from connecting shileding to ground on both sides as a prevention of grounding loop. > . > > I theorize that only the SCL/SDA would need to be shielded (together in > a shielded twisted pair cable ?), Power and Ground may not need to be > shielded. We have never twisted two differnet signals together. What about cross-talks? The only type of signal we are twisting together are for example positive and negative leg of RS422 bus. Or A429 (you may be familliar with). > This issue seems very similar to the SD Card access/GPS issue of the > earlier GTA02s, so I also wonder if a capacitor fix should be looked at > in this case as well. > > -Pascal > http://www.wi-flight.net/ > Zbynek > > > _______________________________________________ > Openmoko community mailing list > [email protected] > http://lists.openmoko.org/mailman/listinfo/community _______________________________________________ Openmoko community mailing list [email protected] http://lists.openmoko.org/mailman/listinfo/community
