Shark Fin Antenna Purpose?

Hello all, I'm new to this thread so if there is a better place for me to post this, please let me know.

I'm replacing the stock shark fin antenna with a combo mount so I can have a clean antenna mount for my ham/GMRS radios. My combo mount has 2 cables attached, one for my radios and the other allegedly for the GPS.

The OEM antenna has 3 cables attached to it (see pictures) and the best I can tell is that they are for the SiriusXM and emergency communication system because those are the two things that do not work when I disconnect the antenna. The navigation continues to work fine so I am assuming that the GPS antenna is mounted elsewhere on the vehicle.

I have attached pictures of the shark fin unit disassembled so anyone that has knowledge of which cable does which function is greatly appreciated.



I feel fairly confident to which component is connected to which pin, but I do not know what any of the components are.

Thank you

 

GPS antenna is under the dash

 

Maybe the connection to the head unit is, but not the antenna. The antenna itself is external because the GPS signal is line of sight.

 

I'd check TW

https://www.tacomaworld.com/threads...shark-fin-with-a-oem-satellite-stubby.552228/

https://www.google.com/search?q=tac...HUZTO4cQrQIoBHoECBcQBQ&biw=1440&bih=779&dpr=2

 

Hmmm.

 

OOPS, my GPS antenna is not OEM. I have a Kenwood head unit.

Sorry for the disinfo...

 

Hmmm... is right. I would not have thought that because GPS is line of sight due to it's frequency...

I might have to bow the knee and defer to the Captain!

 

To be honest, I just posted a pick from a 2010 wiring diagram. I combed through the diagram using the search term “antenna” and found several references, but in the diagram they are just labeled “antenna” with no further description or wire colors. Which is why I posted that image with the very non-committal “Hmm,” which translates into “I may be right but I don’t know I’m right.” So don’t dirty your trousers. ;-)

 

There are at least two G

I think it's close enough to the windshield to get good signal, but even without that, most modern GPS units work well in poor propagation environments because their processing can handle multipath signals.

 

Thanks for consideration of my trousers - all clean for now!

@backpacker maybe I should stop thinking about aircraft, because that is what I do... For a vehicle that doesn't fly, a windshield just might be good enough. But in my pea brain, a windshield is still external.

You guys are awesome!!

 

On a related note: I once rented a car in Europe in which my Garmin GPS would get no signal. It was explained to me that the windshield was “metallized”. An oxide layer of some kind was in the lamination with the idea of reducing UV. Fortunately I was able to find (with the help if my Belgian nephew, who spoke Flemish) an external GPS antenna that attached to the roof magnetically. I don’t know of any modern GPS receivers that have the external antenna port.

 

Yeah, that does happen. I'm not sure about consumer GPS handhelds, but pretty much any modern electronic test equipment has GPS antenna inputs, especially for 1PPS.

ETA: The metallized window thing still applies to a handful of vehicles on the US market, which is why you can still get external toll transponders in NJ.

 

Thanks for confirming; that's what I was thinking. Now to figure out what the shark fin is for???

 

Satellite radio and DCM (the latter uses a mobile telephone chipset).

 

Is there a legitimate need for the telephone chipset since we all have mobile phones these days? Is it just for the emergency call system?

 

It serves a number of purposes. Besides emergency calls, it handles over-the-air SW updates and (for those that choose it) assisted navigation and on-board WiFi. It also provides vehicle health and status information to Toyota and their licensees. There are numerous threads on disabling it for those that are so inclined.

 

The over the air software updates include map updates, I believe. For those of us who have disabled our DCMs I’ve yet to see a workaround.

 

Here’s what’s in the shark fin, courtesy of @Old Red. It varies by model and model year:
https://www.4runners.com/threads/ho...-the-5th-gen-4runner.20628/page-4#post-255976