Radio Wave Experts

Submitted: Saturday, Apr 08, 2006 at 02:23
ThreadID: 32667 Views:1179 Replies:4 FollowUps:4
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Guys I have something strange happening when I drive through a tunnel and I have my Ipod cranking. I use a ITRIP and it works great and I love it but the moment I enter a tunnel it all turns into static? Once I am outside the tunnel it's all good again. I find this very strange and would have thought with the Ipod next to the stereo it won't matter?

Why does this happen?
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Reply By: Member - John - Saturday, Apr 08, 2006 at 02:27

Saturday, Apr 08, 2006 at 02:27
From your name, you must spend too much time in tunnels, stay out of them, problem solved?
John and Jan

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AnswerID: 165737

Follow Up By: Member - Troll 81 (QLD) - Saturday, Apr 08, 2006 at 02:28

Saturday, Apr 08, 2006 at 02:28
LOL...just what I needed a nice laugh

Good one
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Reply By: David from David and Justine Olsen's 4WD Tag-Along - Saturday, Apr 08, 2006 at 05:46

Saturday, Apr 08, 2006 at 05:46
There are a couple of possibilities.

1. There may be something electrical in the tunnels like lighting that interferes.
2. Out of phase reflections of the radio signals off the walls and roof and floor could be effectively cancelling out the signal at th antenna. This is the same problem experienced when someone is too close to you and talking on the UHF but you can;t hear them.
AnswerID: 165746

Follow Up By: Mike Harding - Saturday, Apr 08, 2006 at 10:41

Saturday, Apr 08, 2006 at 10:41
>2. Out of phase reflections of the radio signals off the walls and roof
>and floor could be effectively cancelling out the signal at th antenna.
>This is the same problem experienced when someone is too close to
>you and talking on the UHF but you can;t hear them.

I don't think you should smoke any more of that stuff :)

Mike Harding
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Reply By: Footloose - Saturday, Apr 08, 2006 at 07:25

Saturday, Apr 08, 2006 at 07:25
Davids number 1 is probably close to the mark. There is a lot of unseen stuff going on in (city) tunnels. Lighting, control stuff, speed cameras ...........:)
AnswerID: 165749

Follow Up By: GaryInOz (Vic) - Saturday, Apr 08, 2006 at 15:37

Saturday, Apr 08, 2006 at 15:37
I would agree. Each of the lights in the tunnels are usually about 2 kw each, Most of them being mercury arc types that are reknown for "splattering" rf interference across a wide frequency spectrum. It is simply "drowning out" the Ipod transmitter.
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Reply By: Member - Mike DID - Saturday, Apr 08, 2006 at 10:36

Saturday, Apr 08, 2006 at 10:36
Many tunnels re-transmit Radio signals. These signals can be stronger than from a normal transmitter and this could be blocking your ITRIP signals.

Try a different freqeuncy for the iTRIP.

Mike
AnswerID: 165777

Follow Up By: colinp - Sunday, Apr 09, 2006 at 17:10

Sunday, Apr 09, 2006 at 17:10
The problem will most likely be the retransmission of all the most common local radio signals both AM and FM Broadcast stations. The power and the bandwidth of the retransmissions will be overloading your FM radio. I know this happens in the Melbourne Long Tunnels so probably happens in the others as well.
They retransmit all these signals so they can talk to you with messages while your in the tunnel. I don't know if you have heard this happen, but if there is a holdup or an accident they break into the transmissions and advise you of what is happening.

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