GPS receiver with external antenna?

bes51659 · 01-19-2008, 11:08 AM

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, 12:11 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, 01:13 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, 03:49 PM

Quote: 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, 05:38 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, 02:41 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, 03:42 PM

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

bes51659 · 01-21-2008, 04:08 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, 04:33 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, 08:36 AM

Quote: 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.

-Stomp- · 01-22-2008, 08:42 AM

Ohh... Thinking you was talking about the BMW GPS Reciver not only the OEM antenna :-)

bes51659 · 01-22-2008, 09:30 AM

Laidback:

I think there are levels of DR and that all receivers have som kind of DR.

This unit (Trimble Lassen DR+GPS) require speed, direction (forward/revers) and ignition input and has internal gyro.

For BMW's there might be a difference also from Mk I-II that has this separate receiver and the later NAV computers with integrated receiver so that they have more advanced DR. This BMW receiver (65908385141) lacks that input.

Well, I'm just guessing really.

But it would be great to be able to keep some kind of position even in bigger thunnel systems with lots of exits like "Stockholm Sodra lanken" :-)

---

One more guess about the RXD, RXDN, TXD and TXDN. Soem Trimble devices talk NMEA as well as TSIP (Trimble Standard Interface Protocol)

Laidback · 01-23-2008, 03:20 AM

Quote: Originally Posted by bes51659

Laidback:

This unit (Trimble Lassen DR+GPS) require speed, direction (forward/revers) and ignition input and has internal gyro.

What I was saying was that I'd be surprised if that BMW system didn't include inputs for speed, direction and gyro, but maybe it's doesn't, I don't know. If it doesn't, I wouldn't bother getting the receiver but opt for a DR module or something with the sirf3 chipset.

I understand DR, I have a u-blox - http://www.mp3car.com/vbulletin/gps/...lp-needed.html

Quote: Originally Posted by bes51659

But it would be great to be able to keep some kind of position even in bigger thunnel systems with lots of exits like "Stockholm Sodra lanken" :-)

Yes, it is great

bes51659 · 01-23-2008, 04:14 AM

Mark I and II of BMW does not have DR (in the GPS receiver). If there is one its in the NAV computer which does not help me.

I agree that its not worth while without DR, now that I know that it exist :-) If it hadn't have these technical problems it would have been a cheap way of getting GPS receiver with connection for external antenna.

At the moment I am trying to find a distributor for "Trimble Lassen DR+GPS" in Sweden and hopefully its not to expensive.

Thanks for the thread pointer! I will read it through carefully.

bes51659 · 01-23-2008, 01:15 PM

Oj

Heavy reading. I'm exhaused. So I want DR, and what it destills down to as far as I understand is the following:

There is a GPS receiver board RCB-4H at €105

And a possibly newer u-blox unit EVK-5H at €150

There is also a complete kit AEK-4R with gyro at €500 (!!!) which I suspect is built around the RCB-4H?

There is also the Lassen DR+GPS eval kit that I have not yet found a source and price for.

Unfortunately I cannot be able to find the Murata (or any other for that matter) gyro.
Q1-> Is it old?

----

There seems to be a number of pcb's made in the comunity to glue the kit together, but I have not seen one offering to sell one!

And apart from that in this new world that opens up to me there are active and passive antennas. I guess it is just a matter of preamp or not and both should work, only active is better?

----

As this obviously been done before, please spoon feed me:
Q2-> What should I buy from whom? (I do not mind building some glue electronics)

Q3-> Is the best option to get a good grip in the wallet and purchase the AEK-4R?

BR, B-O