[8525, TyTN, MDA Vario II, JasJam Software Upgradin] jpogge:
I started to build an active antenna until we discovered HTC shut this section down,literaly, in the end we decided a good $75 BT receiver with Sirf III and WAAS was the answer, to us it was an engineering exercise, this is why we posted the "cons". At the end of the day, I want to use my phone not prove to anyone what I already know.;) , having designed several GPS systems in the past, I too was looking for a quick fix.....it would have been cool to get GPS working, but the risk was very high at this point if the mods are made, The phone would be vibration sensitive and may brick if one of the connections fatiqued, also as I have posted , it would not be a mod anyone could try. Which is what we set out to do.

But here is what you will need, the NDA on qualcomm is thourough and they mean business, Ive heard they have more lawyers than engineers, and I need to protect my sources which were of a professional courtesy, so I wont betray them to a public source. However sleuth has posted the correct pin outs,

The circuit requires an antenna with gain of approx 30 db, insertion loss < 5db, several commercially available, google for an ceramic antennae for some small footprint devices. The antenna will need a matching network to insure 50 Ohms to the first LNA, a simple LC network will suffice, resonance should be at 1575 MHz with a pass band -3db of +/-10 MHz. I would give you the values but it has to be matched to the antenna you pick. the output of the qualcomm LNA goes directly into a matching BPF typically a SAW filter, It looks like trinity uses a passive filter, but this can only be made with SMT components that have a vey high Q and the self resonance must be at least 3 GHz to insure that they will not interfere with the extremely small input power levels in the GPS band. Murata Erie is a good source for passives. I used a SAW, in my design. The output of which can have a differential balun (transformer) built in or you will have to provide one, check Laird technologies, or EPCOS, as a supplier. If you use an external LNA, make sure that the outpput cannot exceed +15 db as this will definitely damage the device, also if you use the available BIAS voltage the current draw must not exceed 2mA, my hats off to Qualcomm on their excellent use of low power. Using another power source, you will find that 2.5, 1.8 and 1.2 are most common, care should be taken not create a path for coupling in noise,particularly digital noise, this LNA is VERY sensitive. Most likely a filter on what ever you choose will also be necessary. Traces will have to be kept short and have a match to the 50 Ohms, care should be taken not to couple any energy into the surrounding circuits by using long unshielded wires. If the distance is greater than 2.5" then you risk creating a resonant pathway and the wires will act as an antennae for the surrounding RF. particularly the higher frequencies and the BT/WIFI. Hitachi Inc makes micro coax, 50 ohms, to 4 GHz < 0.25mm dia. They sampled me 2 ft. Laird makes thin RF absorbing material, like tape, you may have to place some of this near the matching network. The antenna must not have a ground directly below it as this can adversly effect its sensitivity. The trinity uses a smaller GSM to make room for the GPS antenna, The Hermes has a GSM which takes up most if not all of the plastic holder st the top. The output of the SAW BPF/ Balun combo should be differential and input to the two mixer pins, the P and N designations are +/-.

The pins have to be lifted and float above the board, another problem we saw but did not discuss as it would have been an extra bucket of water thrown on this party is that the material used in the pins is not mechanically stable, that is , it does not anticipate having a weight exerted on them, even two wires floating in space so excess vibration from normal use, combined with the fatique exhibited by simply heating and lifting the pins makes them suseptable to breakage. These are .10 mm wide .2 mm long metal alloy pins, you are bending them beyond their designed shape and adding a dynamic component to the end like a lever. if they break you brick... As the resulting floating inputs on the mixer will probably(very likely according to the documents I saw,) take out the RFR6250 chip entirely, not necessarily at once , but the GSM is in danger if this happens.

Not trivial, not easy, and IMHO not worth the cost of the phone,

Good luck,