using walkie talkie on SMRT trains


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firefly99

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Jun 6, 2007
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I have been using Motorola T4503 walkie talkie (3km range) when out shopping with my buddies. In general, they work well in most part of Singapore. Even on the SMRT train platform, as in from one end to the other end of the platform.

However, when we board the same train, first and last carriage, the walkie talkie set would not be able to establish the radio link. Do not think it is an issue with the range, since the moment both of us step out of the train carriage, radio link is reestablished.

We had tried using other more powerful walkie talkie sets with the same results.

Anyone had this experience or know what is the cause ?

Please advise. Thanks.
 

Canew

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#3
Probably because there are more obstacles (train carriage, people, etc.) in between the 2 sets when you guys are inside the train. When the sets are at the platform, the path between the 2 sets has less obstacles.
 

Astin

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#5
Probably because there are more obstacles (train carriage, people, etc.) in between the 2 sets when you guys are inside the train. When the sets are at the platform, the path between the 2 sets has less obstacles.
Radio frequency, no need line of sight.
 

Canew

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#6
Radio frequency, no need line of sight.
Bro Astin, I am no expert, but what I've read, there is a line of sight consideration even for radio frequency.

Here is an explanation from Wikipedia: http://en.wikipedia.org/wiki/Line_of_sight
"Radio signals, like all electromagnetic radiation, travel in straight lines."

Another statement: http://en.wikipedia.org/wiki/Non-line-of-sight_propagation
"Many types of radio transmissions depend, to varying degrees, on line of sight between the transmitter and receiver. Obstacles that commonly cause Non Line Of Sight conditions include buildings, trees, hills, mountains, and, in some cases, high voltage electric power lines. Some of these obstructions reflect certain radio frequencies, while some simply absorb or garble the signals; but, in either case, they limit the use of many types of radio transmissions."
 

Astin

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#7
Bro Astin, I am no expert, but what I've read, there is a line of sight consideration even for radio frequency.

Here is an explanation from Wikipedia: http://en.wikipedia.org/wiki/Line_of_sight
"Radio signals, like all electromagnetic radiation, travel in straight lines."
Maybe we can ask those security officers in shopping centres, they should know better...
 

firefly99

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Jun 6, 2007
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#8
We are want to test the range of walkie talkie and determine if we can depend more on walkie talkie and avoid the airtime charges of mobile phone.

Very often when out and about with buddies, there are lots of unnecessary phone calls as in
a) are you here yet
b) I am here, what is your exact location
c) etc...

In theory, the range is determine the line of sight. If both walkie talkie are not in line of sight, the signal would either be distorted or very weak. But this is not the case when inside the train carriage because the link is totally silence. Both party cannot hear each other at all, which is very weird.
 

J-Chan

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Sep 21, 2005
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#9
got a theory of my own, maybe the high voltage rails that power the train caused some interference of some kind?
 

Prismatic

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#10
There is line of sight considerations for radio signals too. The reason why radio signals appears not to require line of sight is that radio waves can bounce off surfaces. Everytime it bounces off something, the signal becomes weaker.

My guess is that it could be the material that the train carriages are made off? Maybe there's some radio insulation or something to prevent interference with the electric components on the train?
(Though I think I've seen those SBSTransit guys carrying walkie talkies on the NE line.)
 

Canew

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#11
Maybe we can ask those security officers in shopping centres, they should know better...
I myself is using a walkie talkie (using the GRID network). When I am at certain areas (eg. middle of the a building) where I am unable to get a signal. I need to walk to the edge of the building in order to re-acquire the signal.
 

jtb

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May 9, 2006
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#12
This set of talkies has a low transmission range at lower power and agreed it will never work. Try another high power version maybe more than 1Watts, you will receive the transmission. Nothing to do with interference but the quality of the set itself.


I have been using Motorola T4503 walkie talkie (3km range) when out shopping with my buddies. In general, they work well in most part of Singapore. Even on the SMRT train platform, as in from one end to the other end of the platform.

However, when we board the same train, first and last carriage, the walkie talkie set would not be able to establish the radio link. Do not think it is an issue with the range, since the moment both of us step out of the train carriage, radio link is reestablished.

We had tried using other more powerful walkie talkie sets with the same results.

Anyone had this experience or know what is the cause ?

Please advise. Thanks.
 

yk200

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Jun 19, 2006
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#13
Could it be the electromagnet that came out from the train? :dunno:

I used to worked very near MRT track (below it) and everytime when the train pass by, my monitor color will start changing (slightly), due to the electromagnet (cause by train movement on the track).
 

jtb

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#14
yes, monitor will be affected. shield it with alu-alloy or switch to LCD


Could it be the electromagnet that came out from the train? :dunno:

I used to worked very near MRT track (below it) and everytime when the train pass by, my monitor color will start changing (slightly), due to the electromagnet (cause by train movement on the track).
 

zac08

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Feb 21, 2005
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#16
Walkie talkies uses radio frequency, normally shortwave.

They travel in a sine curve and will be affected by electronics, barriers and also by large groups of humans. It normally works better in open ground/
 

waileong

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#18
The quoted range for walkie talkies are optimistic, and are valid only in open terrain. In an urban environment, the range is reduced signficantly. Google to understand more.
 

Jan 14, 2005
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#20
Metals, re-inforced concretes, etc, greatly reduce the range of radio signals. It is not surprising that the metal MRT carriages blocked the transmission.

BC
 

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