Taxi frequency help

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Taxi frequency help

Postby Schloff » Tue Apr 04, 2017 10:44 pm

Hi
You'll have to bare with as in fairly new to Amateur Radio.

I have picked up a local taxi company, I can hear the operator but not the drivers. i know they stop the drivers from hearing each other using CTCSS but surely I should be able to hear all traffic is i have no tones enabled. I have checked the WTR and these are the only frequencies they use.

TX: 164.5875 MHz
RX: 160.0875 MHz

Is this normal or am I doing something stupid?

Thanks in advance
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Re: Taxi frequency help

Postby m0lsx » Tue Apr 04, 2017 10:53 pm

No one can hear each other, not due to the lack of CTCSS, but as the drivers are not being relayed as part of the main transmitter. It is like the old Police system. You could hear the control only, unless talk through was enabled.
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Re: Taxi frequency help

Postby Schloff » Tue Apr 04, 2017 10:57 pm

Ahhhh!

Thankyou.
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Re: Taxi frequency help

Postby m0lsx » Tue Apr 04, 2017 11:04 pm

Do you know where the Taxi office is? If so does it have a antenna on the roof that gives it a radio link to the repeater? That would give you the drivers input to the Taxi office.
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Re: Taxi frequency help

Postby Schloff » Tue Apr 04, 2017 11:34 pm

yeah it's just shy of a mile and there is an antenna that is visible on the roof. How would I set about doing that? Would it be just like programming a regular repeater?
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Re: Taxi frequency help

Postby G4RMT » Wed Apr 05, 2017 8:03 am

What Alan means is that very often taxi company offices are not in the most ideal place, so they use a system where the repeater the taxi drivers use is a dual unit - somewhere at a radio site in a good place, and it is this that you are hearing. However, some then use another radio to send back what the drivers say to the office, and another to relay the message from the office out to the drivers. This will use two other frequencies, so if you can find those, you have access to the driver's responses. To check this, you can use OFCOM's WTR - you can search for the frequency in your area that you can hear and it will tell you where it is. If this is not the office, the WTR might also reveal what radio licence is linked to that address and if you are lucky, the frequencies. Keep in mind that the link between the high big radio site and the office is likely to be a beam antenna - so depending on where you are, you might not be in the beam. On top of all this, they could be using a telephone (leased line) link to the office, or even an IP broadband link if it's modern, because it is often cheaper!

If this makes no sense, try following this.

Office sends to the distant repeater on freq 1
distant repeater sends this to drivers on freq 2
driver responds to distant repeater on freq 3
distant repeater responds to office on freq 4

You are listening to freq 2, you need to also listen on freq 4

A repeater that links the things it hears back out again is using what is called 'talkthrough'. For many years OFCOM, and the Home Office before them frowned on this system - and it had to be specifically approved. Taxi drivers rarely need to speak to each other, and it encourages chit chat, so taxi systems usually do not use it. Some do have the facility to turn it on, but certainly around here I have never heard it.
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Re: Taxi frequency help

Postby Minus1 » Wed Apr 05, 2017 8:08 am

Schloff wrote:Hi
You'll have to bare with


Why? This isn't a naturist forum.

"bear with me" :rolleyes:

Mobile transmissions are less powerful, and vehicles may be blocked by hills and buildings.
Base stations are high on a building, or even on a hill, so can be heard much more widely.
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Re: Taxi frequency help

Postby mickydt » Sun Apr 23, 2017 1:03 pm

most taxis operate on duplex frequencies which is why you cannot hear the cabs talking back.

if you find the taxi base on a frequency then simply add or subtract 4.800 to the frequency you find which will then give you the cabs talking back.

the same applies to cabs add or subtract 4.800 to the frequency to give you the base frequency.
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Re: Taxi frequency help

Postby Metradio » Sun Apr 23, 2017 6:03 pm

mickydt wrote:most taxis operate on duplex frequencies which is why you cannot hear the cabs talking back.

if you find the taxi base on a frequency then simply add or subtract 4.800 to the frequency you find which will then give you the cabs talking back.

the same applies to cabs add or subtract 4.800 to the frequency to give you the base frequency.


Unless they are using UHF, then it could be all sorts of splits dependent on frequencies..

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Re: Taxi frequency help

Postby Wiggy » Mon Apr 24, 2017 5:09 pm

Shouldnt the freqs be...
TX - 164.5875
RX - 169.3875
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