[8525, TyTN, MDA Vario II, JasJam Software Upgradin] jpogge:
A quick exercise in reverse engineering

Hi, I have been reviewing the many pages of this forum to get up to speed, I am looking to buy either a Hermes or Trinity, but feel I may be of some help. I have over 15 years experience as a DSP / RF design engineer, and have worked on several GPS, CDMA network switches and one of the original design team members of the wideband OFDM 802.11 A project back in 1998, we demonstrated the first 108 MB/s links at the SuperComm show in Atlanta.

To start with, many of the nmea strings I have seen posted are being interpreted incorrectly, GSPV is the message header for Satillites in view, but the first field is not the number of satelites but rather the number of contiguous messages to be posted, I .E.

$GPGSV,1,1,00*79\r\n

Should be read as 1 Message, this is message number 1, no satellites in view , * 79 is the checksum.

$GPGGA, :,,,,,0,,,,,,,,*66\r\n

The 0 is sixth field which is the satelitesquality indicator which is here rated invalid

GPGSA, A,1,,,, :,,,,,,,,,,,,*32\r\nNMEA

The first A is auto track mode, the 1 indicates fix is not available, the empty fiends should be the satelite ID's

The good news is that you have sucessfully awakened the supposedly "non existant GPS" , the bad news is that this is indicative of either a bad signal or very weak signal. IMHO, and I can back it up.

I have carefully gone over the photos from the FCC filing for the hermes and there is definitely hope.

At this point I had trouble downloading any Trinity mother board photos, if any one can provide me with a link this would be helpful.

Below is a series of items that made me investigate further.

1) Qualcomm is very protective of their IP, and an actual data sheet would be helpful. the pages provided are sales brochures and as I have nothing else I will use those.

The RTR6250 ?? the brouchure calls this an RFR, is the RF front end that reputedly has the GPS. The listed sensitivity of this GPS radio is -155dbm that means that it can grab data sufficiently if the signal is approc=ximately 3.89X10-9 volts, thats 4 billionths of a volt. It should have a seperate antennae for the GPS, this is because the GSM requires both a transmit and receive diplexer( the brouchure erroneously calls this a duplexer as well)

2) the best info is from teh FCC filing photos,

referencing the FFC doc, provided, there is a page 12, (pdf 7 of 22) the picture of the whole mother board shows clearly the four coplanar wave guides toward the right side of the page into the diplexer antennae switch. The actual diplexer antenae interface is on the other side of the board. see close up photo top picture page 10 upper photo. The smaller black square just outside the shield can are samsung GSM transmit receive switches, Im downloading data sheets. The traces surrounded by the ground plane are also the coplanar wave guides I mentioned. Better view on the bottom of page 9, (pdf 4 of 22)

If you follow the trace to the Actual GSM antenna page. It continues up to the external SMB connector, gold jack just below the antennae matching network (the collection of resistors and caps near the gold pinch connector see page Top of page 9, (pdf 4 of 22)) just below that is the blue tooth antenna and chip set, and the coplanar wave guide, with a smaller snap miniature, possible smb type p connector.

A simular RF connector is on the wave guide to the 802.11 WLAN antennae.

As a test engineer this is expected, when these units are tested a series of fingers from the ATE (automatic test unit) touch all of those gold solid circles throughout both sides of the mother board. During development and test it is imperative to have a direct connection to your radio test set up that creates known data grams and patterns with controlled signal strength and quality. This way it removes the variables in testing and keeps the software / hardware engineers from chasing ghosts caused by a goofy signal while trying to develope the system.

So we have a test RF jack for the Bluetooth, the GSM made into an additional external port, and the WIlan chip set,

What I want to know is what is the RF jack directly to the right of the RTR 6250 qualcomm chip with the 1500MHz (possibly SAW flter) just north of the little shield can shown clearly on pages 11 (PDF 6 0f 22) the bottom of page 12 (PDF 7 0f 22) nearthe top right. The coplanar wave guide trace terminates in the silver square with the black center I.E. the RF antennae connector and proceeds to the small shield can along the top side.

Further examination of page 14 (pdf 14 of 22) shows a close up of this area, According to the brocure there is a Pre GPS LNA( low noise amp), and a second GPS LNA, the reason for this being seperated externaly is for the design engineer to build a matching network or secondary filter, to correct for any changes in the RF signal due to layot and interference from other circuits. The brochure indicates the signal from the antenna enters a band pass filter, into the pre GPS LNA exits the chip again and is connected into the second GPS LNA, a further examination shows what we are looking for, A wider trace assuming the Rodgers 4350 standard 1/2 ounce PCB multilayer material necessary for high frequency 1 GHz + design we should see a .018" to .022" trace to keep the impedence of the exit and reentry points with the matching network near 50 Ohms. This is clearly evident in this photo top of page 14, look near the small dot in the corner of the RTR6250 chip, the pins are connected skiping a pin between, possibly grounds connections in between as this will reduce noise, a very common design technique. three inputs from the filter and a single rentry of the circuit on pin 56 near the dot. A closer inspection of the small shield can shows a SAW filter as this is normal in such device as I can find this my first WAG so I would appreciate if someone with an actual unit, could get more info off this filter, the black square in the small can. Either way I wager a large pint against my being wrong. In the lower right corner I can clearly see the mystery 4th RF antenna jack.

Lastly on the speculation that the GSM and GPS antennae are the same since the trinity docs point to the same location, Please could some one send me a link to these I didnt come across them during the 200 + pages I read over the last few days.

The GPS satelites are in a planar grouping of 6 orbits very nearly 12,600 miles above the user. If you had a device the size of your hand, and wanted to connect to a signal 12,600miles away you better have an antenna that can see in a fairly narrow field of view. no side lobes. This is the prime function of a patch antennas used in most GPS, I have seen some strip line antennaes but they suck... so I would be willing to bet that a small connector with AMP or molex teflon miniature coaxial cable is plugged into a smal patch antennae and mounted in the plastic top that has the GMS dual strip in the photo. The actual antena is the rounded metal blade on the top.

If any body has a trinity and is willing to pop open the case and check if this RF jack has anything plugged into it. At this point I have convinced myself that the Hermes has no antenna, not to worry I have found some suppliers of a 12mm square patch, it could be super glued into the top plastic assembly, could some one let me know what the diameter of the jack is so an adapter can be matched. A not so easy up grade, however look at FCC photo the bottom of page 11 (PDF 6 of 22) the connectr is visible without a complete disassembly, it is however on the front of the board , the same side as the LCD....

I rambled a bit, sorry for the core dump, I will continue to investigate to make sure, I did endevour not to speculate, as I checked some of my common supliers datasheets and what I wrote is accurate,IMHO it would however fill several pages to support, I'll see if I can put a zip file/ rar together later with the important bits.