Naked Science Forum

General Science => General Science => Topic started by: neilep on 04/03/2007 20:06:52

Title: In A Tunnel Radio Signals
Post by: neilep on 04/03/2007 20:06:52: Dearest Peeps Who Know Things That I Do Not !!

How come my Sat Nav Works in a tunnel but my car radio does not ?

(except in some cases my car radio does !!..why's that then ?)...sorry for the contradiction...but in most cases my car radio does not..
Title: In A Tunnel Radio Signals
Post by: eric l on 04/03/2007 20:18:25: I would not know about satelite navigation in this matter, but I know that more and more tunnels are equiped wit a system that transmits radio signals, in order that drivers may receive traffic information by radio even in a tunnel. But do not ask me how this system works for relaying the signals (I suppose they must relay different frequencies and all that).
Title: In A Tunnel Radio Signals
Post by: Karen W. on 04/03/2007 20:20:46: HAVE NO CLUE OTHER then perhaps your car radio antenna is not as elaborate and strong enough to pick up a signal. I would think because of the nature of the satelite navigation system, that the antenna must be way more powerful and designed to be more of and emergency aid then a radio. So it would be required to be able to reach signals in the most remote location Yes? I think it might be the nature of the power of your antenna! But I am no expert. seems the navagation system would be more complex as far as an antenna!
Title: In A Tunnel Radio Signals
Post by: neilep on 04/03/2007 20:21:07: Quote from: eric l on 04/03/2007 20:18:25
I would not know about satelite navigation in this matter, but I know that more and more tunnels are equiped wit a system that transmits radio signals, in order that drivers may receive traffic information by radio even in a tunnel. But do not ask me how this system works for relaying the signals (I suppose they must relay different frequencies and all that).

AHA !!...so that's why ?....Thank you Eric !

Lets hope a passing Sat-Nav-In-Tunnel expert passes by to complete the solution.

Thank you again.
Title: In A Tunnel Radio Signals
Post by: Karen W. on 04/03/2007 20:23:33: How did you do that! You beat me!
Title: In A Tunnel Radio Signals
Post by: Soul Surfer on 04/03/2007 23:45:38: Your sat nav does not work in the tunnel. It is less likely to work than your FM car radio in difficult conditions even heavy tree cover can stop it working. What is probably happening, is that you are not in the tunnel long enough for it to complain because sat nav systems are quite clever and expect to be continually losing and regaining signals (they need at least 3 and preferebly 4 for full 3d navigation and have around 12 channels of which around 6 - 8 are usually available) if they lose signals they keep extrapolating your journey based on the direction and speed you were going whan they lost the signal and wait up to half a minute before they complain that they have lost the signal. On the other hand your FM car radio is immediate, if the signal goes no reception.
Title: In A Tunnel Radio Signals
Post by: neilep on 05/03/2007 14:59:36: THANK YOU IAN,

I was always under the illusion that my Sat Nav was working but now I understand otherwise.

Regards

Neil
Title: In A Tunnel Radio Signals
Post by: daveshorts on 06/03/2007 13:51:05: Yes it could be assuming that you keep going at the same speed.

I guess the way to test it would be to get a hand held version, walk into a tunnel, and then turn around and go back out the way you came, and see what it makes of it. I was going to suggest you did this with your car, but then I thought better of it.
Title: In A Tunnel Radio Signals
Post by: neilep on 06/03/2007 15:29:30: Thank you Dave......as a firm believer in.....No !!...you're right..this is one experiment I am not compelled to study !
Title: In A Tunnel Radio Signals
Post by: Karen W. on 06/03/2007 15:39:59: LOL!! Yes Do Be careful Sir!