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[Taxi_Driver]

Two transmitters roughly outputing the same output power situated a few miles apart....

TX A is 166.65 MHz
TX B is 166.625 MHz

Is that miles apart in world of frequencies or could they interfere with each other? say TX A is tx'ing to RX  A but TX B is in the middle??

Ta muchly

[MR MISTER]

Radio transmitter experts? Yer wha? 

[Kevin Wood]

Depends what they're transmitting, but guessing it's PMR. 25KHz channel separation should be fine for a normal FM voice channel if the deviation is kept under control and the receivers have the appropriate filters fitted. 12.5KHz is quite workable in most cases. If you're VERY close to the adjacent channel transmitter you might get some interference but I wouldn't expect widespread problems.

[Taxi_Driver]

Radio transmitter experts? Yer wha? 

Well, i know your not 

But i know theres a few on here....that would know 

[MR MISTER]

Radio transmitter experts? Yer wha? 

Well, i know your not 

But i know theres a few on here....that would know 

There's only ever a few on here full stop these days. Perhaps a 'radio transmitter expert' will be on in a week or two.

[Taxi_Driver]

Depends what they're transmitting, but guessing it's PMR. 25KHz channel separation should be fine for a normal FM voice channel if the deviation is kept under control and the receivers have the appropriate filters fitted. 12.5KHz is quite workable in most cases. If you're VERY close to the adjacent channel transmitter you might get some interference but I wouldn't expect widespread problems.

Voice and data......those frequencies happen to be the frequency that my company and another cab firm tx on......some days its murder to get a job sent to you....how it basically works is office sends the job (in data) to my data unit.....i get the job, but to make sure i have got it.....my data unit then transmits back to say its got it.....this seems to fail on a regular basis (not just me).....then what happens is the computer office decides i havent got the job and then sends me a job cancelled message and tries to transmit the job to another car......very frustrating......

[Taxi_Driver]

Radio transmitter experts? Yer wha? 

Well, i know your not 

But i know theres a few on here....that would know 

There's only ever a few on here full stop these days. Perhaps a 'radio transmitter expert' will be on in a week or two.

Ermmm Mr Wood is on  One of the experts i had in mind    

[I_want_an_Omega]

That's only 5khz apart - so could be an issue. I'm surprised that they were granted a licence that close to another user that close - in RF terms.

Is there not a mobile data "app" that can be used in this day and age?

[Taxi_Driver]

That's only 5khz apart - so could be an issue. I'm surprised that they were granted a licence that close to another user that close - in RF terms.

Is there not a mobile data "app" that can be used in this day and age?

As Kevin guessed its PMR, dont think you need a licence for that freq range 

And yes there are mobile data applications around.....but whose mobile network do you trust not to go down  and at the cost implications as well....if monitoring on data that our system does....data would be constantly sent and received....

[zirk]

Two transmitters roughly outputing the same output power situated a few miles apart....

TX A is 166.65 MHz
TX B is 166.625 MHz

Is that miles apart in world of frequencies or could they interfere with each other? say TX A is tx'ing to RX  A but TX B is in the middle??

Ta muchly

Assuming its current equipment and really not old stuff that someone's found in the shed it will be fine, even if they were transmitting from the same room.

There 2 channels apart, theres another channel in the middle of them, ie, 166.6250, 166.6375 and 166.6500, current comercial legal spec is 12.5 KHz Channel Spacing with 2.5 KHz deviation, Older stuff (really old now) was 25 KHz spacing with 5 Khz, Newer allocations are now normally 6.25 KHz spaced but are normally then 6.25 KHz off set so they full in line with current spec's until they decide to narrow it again.

Amature bands tend to be the older 25 KHz channel spacing, Air Band can differ and Military Bands, well they can do pretty much what they wont to. 

[Kevin Wood]

Do you have any problems with voice communication between mobiles and base or is it just data that's causing a problem?

Do all cars have the same problem or is it just you?

[zirk]

And yes it is PMR and you do need a Licence. those frequencies belong to the older Message Handling Operators like Aircall and Securicor prior to Cellular and are now allocated as Packet Data Channels for PMR use. 

[Taxi_Driver]

Do you have any problems with voice communication between mobiles and base or is it just data that's causing a problem?

Do all cars have the same problem or is it just you?

Voice is usually ok....its the data the problem....what tends to happen (if the base operator hasnt gone out for a ciggie) job gets sent....i receive it..my data unit doesnt seems to send a valid response....comp sends me job cancelled msg.....base op notices and calls me on voice telling me to move my car....i reply i seen the job....just 'end it' .....that means cancel it on the comp....so it wont keep trying to send it out to other cars.....not just me either.....happens to all the drivers

Maybe just crap tx from the cars.......but thought i ask the question about the closeness in freq's with another comp....

[Kevin Wood]

So, is it the case that the data isn't getting through when the signal is perfectly OK for voice comms?

If so, I wonder if the radio is over / under deviating when sending data?

Sounds like it'd be better to rely on a smartphone app and internet connectivity in this day and age than squirting data down your PMR link, though.

[zirk]

what frequencies are you Voice channels?,  Ive seen this before if there VHF High Band (167 - 172 Mhz), a couple of factors, sorry need to be a bit Tech'y here, but your Voice Tx Power will probably be 25 Watts and the Data TX more like 5 or 10 Watts as the RA seem to think FSk (Didital type signalling) goes further than Anolog, it does'nt its the other way round.

The other thing that can happen is the newer Data Channel allocations (159 - 166 Mhz) can be TX and RX reversed away from each other meaning if the Installer has combined the Base station up the same Aerial the antenna is out of spec for the Data Transmitter.

How many Aerials do you have for each Base Station and how many Aerials on the Cab?