GPS receiver with external antenna?

**bes51659** · 01-19-2008, 12:08 PM

I have been trying to find a USB GPS receiver with connector for external antenna. No success.

The reason for this is that I've got a GPS antenna on my car roof in a sharkfin.

On ebay I found a BMW part but it is not USB, and if it is NMEA it is probably thunneled in BMW protocol IBus.

BMW-TRIMBLE-GPS-RECEIVER

system overview

Pointers appreciated!

B-O

**DarquePervert** · 01-19-2008, 01:11 PM

Search the forums for OEM GPS. You'll find what you're looking for.
Most of the GPS receivers we use (like my BU-353) are like a small puck and require no external antenna. They output NMEA-fomatted data, which is merely one "language" of the raw GPS data.

Chances are that sharkfin is merely an antenna that connects to a receiver somewhere else in the car.
The store here sells a Hirschman multi-function antenna that includes a GPS antenna designed to be connected to an OEM-style receiver.

**bes51659** · 01-19-2008, 02:13 PM

Thanks Perv, I did search "OEM GPS" but I only found this for $100 and it comes without casing. I was hoping for something that looked like any GPS puck but with a connector. And maybe half the price :-)

"OEM GPS" gave a lot of hits, so maybe I've missed one?

Sharkfin is indeed only the antenna. Combined with radio and tv antenna (and in some cases cellular antenna I think). I beleive that most BMW Nav system has the receiver internally in the NAV computer with the exception of this part. I have no clue if it is RS232 or IBus (electrically), NMEA or something propriatry to BMW (protocol). If some one know's please tell me. They are only $45 on Ebay.

**DarquePervert** · 01-19-2008, 04:49 PM

Originally Posted by bes51659

Thanks Perv, I did search "OEM GPS" but I only found this for $100 and it comes without casing. I was hoping for something that looked like any GPS puck but with a connector. And maybe half the price :-)

I don't see that happening.
Maybe on EBay...

**bes51659** · 01-19-2008, 06:38 PM

I found the pinout of the BMW GPS receiver. I post it since I think it could be of interest not only for BMW owners but for all wwanting external GPS antenna.

I do not get much smarter from it though... If not GPS_RXDN is "neutral/gnd" or maybe a balanced connection... And what is PPS?...

Getting tempted to buy one and try it out...

And its assembly where you also can see the antenna connection.

**bes51659** · 01-21-2008, 03:41 AM

I've just been informed that PPS is pulse per second and is a method of synchronisation. Standard GPS technology. This makes it even more likely that BMW used standard components.

I qualified quess is also that TXD, TXDN, RXD, and RXDN is RS422 talking NMEA. 5V point to point balanced com. If so a simple RS422 to RS232 (or USB) converter can be used. Could be verified with oscilloscop first, and then hyperterminal (with electrical interface).

Can anyone confirm this? Is anyone at all interested?

**-Stomp-** · 01-21-2008, 04:42 PM

Look's interesting, but what chip does it use Sirf III? Where have you got your Shark antenna?

**bes51659** · 01-21-2008, 05:08 PM

I do not know what chip it uses. Does it matter? The shark antenna is OEM.

I'm trying to buy one receiver at the moment, but main ebay seller wants $56 for shipping and will declare acctual value which will add $30 in tax in customs and does not accept paypal... :-(

**bes51659** · 01-22-2008, 05:33 AM

I found that sirf III is a great device in wikipedia :-)
Since the design is maybe 8 years old I doubt very much that the ship is a Sirf III.

But talking perfomance I think what I really want is this...

What I want is the kit with usb cable. Love the dead reconing. I hope it is not an arm and a leg. Anyone used it?

**Laidback** · 01-22-2008, 09:36 AM

Originally Posted by bes51659

I found that sirf III is a great device in wikipedia :-)
Since the design is maybe 8 years old I doubt very much that the ship is a Sirf III.

But talking perfomance I think what I really want is this...

What I want is the kit with usb cable. Love the dead reconing. I hope it is not an arm and a leg. Anyone used it?

I'd be surprised if the BMW system is not DR.