Taxi radios

i m sorry if this is the wrong place but here’s my problem.i work for a taxi company,all the radios are Motorola gm340.
we have a system where the driver keys his mic and his number is displayed on the computer in the office.we have 2 channels.we can also enter a drivers number into the software on the computer to call a drivers radio.sounds like a phone ringing.and doesn’t knock of till he keys the mic.
now the problem is someone has hacked into our radios.
whoever it is can imitate drivers one point he could only block the base station,but now he can actually transmit to other drivers radios.
the main channel is channel one so last night i got every driver to switch to channel 2,it seems he couldn’t use channel 2,i m back in a night later and now he can use both channels.
anyone have any idea what we can do.

[Moderator Note: I moved it from General Discussion to Business discussion. All is well :)]

Just some suggestions:

  1. Make out a report to whatever governing body that oversees communications for whatever country that you are operating in. If it were the US, I’d say FCC, but since this is a Europe-based radio I don’t know the particular agency for your country as you were non-specific.
  2. Contact the radio shop or company that installed your radios- the dispatching company may have to change frequencies and/or privacy codes for the radios.
  3. Contact the local authorities regarding this communication violation- they may be able to investigate as to who may have been recently fired from the taxi company and/or someone who may have a grudge against the company.
    Good luck!

thanks for your reply.
1 comreg,it think,they can come out and hook up to the system,but he blocks the radio at all different times,day and night.which they don’t like.
2 we have changed over to a second frequency,took him all of a few hours to get on to change it again,each radio has to go back to the shop,which would be a nightmare.
3 they would ask us if we where having a laugh.

thanks for your reply.

sorry for bumping but i m all out of ideas.
communication officer has been out and cant do a tap,they don’t even understand how a radio company works.

he now has the ability to stun each drivers radio,something that could only be done from the office.
11 hours straight tonight he has been blocking us.
we can now hear different taxi company’s coming across our radios.
any other suggestions would be greatly appreciated.


Hey Mark, sounds like you got a real fool here…but a fool who knows what he’s doing. Since you are using the GM340 by Motorola I can make a couple presumptions:
Your radios use a signalling protocol called MDC1200, developed by Motorola which enables data to be sent over the air along with voice. The ID feature you mention is common in fleets or squads to identify what “unit” is talking. When you “page” a taxi’s radio you are also using MDC1200 signalling, or 2-tone/5-tone signalling, to alert just one user’s radio in the whole fleet of taxis. Your first problem (which can’t neccessarily be solved quickly) is that most upper-tier Motorola radios and some software programs can decode your signalling and see what “numbers” your taxis are assigned. Your radio fool is then just mimicking what you do through your dispatch computer by using a radio or computer to mess with your fleet.

Let’s rewind a little bit… In this day and age it is actually pretty easy to track down a user’s frequency and CTCSS/DCS code using a conventional scanner. I’m sure that wasn’t hard for him. You can make it “harder” for him by using a different CTCSS/DCS code on transmit and receive (assuming you are using a repeater). This will make it a little more difficult to track your “input” frequency on the repeater because he would have to be within range of an individual taxi to pick up its transmitting signal, not the repeaters powerful output signal. The other option which is costly would be to slowly migrate to digital communications. You can keep the same frequencies but you have to amend your FCC license to show digital operation. In a digital system you can enable and disable what users have access to your system similar to MAC address filtering in your home router. The repeater would deny this fool’s transmissions because his radio would not be “approved” by the system as an authorized user.

For now, I don’t think changing just your frequency will stop this guy. He’s proven that he knows the technology and has the equipment to interfere with your you. Before spending money on re-coordinating or revamping your system I would look at methods to raise your defense level against hackers like this fool.

Mark, where are you located? In the US?

we are currently changing frequency and changing the the 5 tone code which is what i think your saying.
could this person be mobile?
changing to digital at the moment? I m not sure we could afford it.
and i’m in Ireland.

thanks for your responce.

whoever is changing the frequencies request to have the input and output on the repeater pair with different CTCSS/DCS codes. That will delay anybody hacking the system again.

Mobile? Possibly… do you operate with a repeater or are you just communicating taxi-to-taxi? I doubt he would be mobile as it would be WAY too much work to constantly be following your taxis just to mess around on your frequency.

Not sure about the repeater,I’ll find out in the morning I’m in at 7.taxis can’t communicate with each other.only with the base station.

we don’t use a repeater we transmit from our own mast.
the CTCSS/DCS codes have been changed.

Gee, I’m seeing the second recommendation that I posted back in early December…may work until the person figures out the new frequency and codes (if he or she has a whole lot of time on their hands)… much better to cut off the head of the snake, in other words find out who is doing this and prosecute them to stop all this nonsense…it has to be costing the drivers a lot of money in lost revenue…good luck!

sorry guys just an update,nothing has changed,radios still been blocked,frequencies where changed.that didn’t last long,it turns out its happening to 3 other companys around the area.Were starting to think someone is paying this person to mess us up.
we are looking into another system just using a mobile phone,but it costs so it won’t happen for awhile yet.
Comreg,Irelands regulator, don’t seem to know what they are doing,well they don’t know how to catch him.same difference.
looks like i’ll have to put up with it for awhile.

Thanks for all your help.