London Bus change over to DMR

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London Bus change over to DMR

Postby Metradio » Sun Nov 04, 2018 3:16 pm

Testing of the London Bus DMR Network has started. From where I live I am receiving DMR in the clear from them on 139.66875MHz, this has been receivable for the last 3 weeks or so. Eventualy the system will be encrypted.
Their current MPT1327 and the new DMR Tier III system use the frequencies between 139.500 and 140.500MHz..

Mike

http://www.landmobile.co.uk/news/tait-tfl-bus-transport-for-london-dmr-tier-iii-contract-award/
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Re: London Bus change over to DMR

Postby PDC760 » Mon Nov 05, 2018 5:02 pm

Where did the information that it will be encrypted come from?

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Re: London Bus change over to DMR

Postby Metradio » Mon Nov 05, 2018 5:51 pm

PDC760 wrote:Where did the information that it will be encrypted come from?


The TFL invitation to tender....

The tender focuses on addressing the capacity issues with the current system and scaling with the forecasted growth of TfL’s bus network over the next 10 years and its implications for call volumes (the current system handles an average of 62,000 calls per day, rising to more than 74,000 during major events or disruption). The successful bidder must reuse many of the existing system’s asset, significantly improve voice quality, provide encryption security and bring functionality improvements.


From: http://www.landmobile.co.uk/news/tfl-launches-massive-radio-system-tender/

Mike
Connect Systems CS750 and CS800, Hytera PD-365, Motorola DP4600.
Raspberry Pi 2 and DV4Mini HotSpot.
AOR AR-DV1 Digital Voice Receiver / eSPY on ARD.
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Re: London Bus change over to DMR

Postby GalaxianFive » Wed Nov 14, 2018 6:00 pm

Very disappointed to see that the London bus network is going digital as I enjoy listening to the buses when I am visiting relatives in Dartford and Gravesend as I used to live in Thamesmead 20 years ago. Looks like I won't be able to listen much longer as I have a Uninden 125XLT and cannot afford a digital scanner.
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Re: London Bus change over to DMR

Postby Minus1 » Thu Nov 15, 2018 10:13 am

"provide encryption security" is very different from "use encryption security'.
Many companies have some talkgroups encrypted, whilst others are not.
It is thus obvious that there is an overhead to encryption, and companies avoid it if they can.

Sometimes encryption is not specifically used for security reasons. The USAF at Fairford for example do not encrypt the tower talkgroup, because it carries the same audio transmitted in AM on the UHF Airband. Encrypting it would help a hacker to break the encryption.
I reserve the right to ignore people who have made no attempt to the read the manual, and expect others to do it for them.
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Re: London Bus change over to DMR

Postby Metradio » Thu Nov 15, 2018 11:33 am

Only time will tell...

Mike
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Re: London Bus change over to DMR

Postby Metradio » Wed Nov 21, 2018 4:13 pm

Minus1 wrote:"provide encryption security" is very different from "use encryption security'......

You are quite right, we will have to see what happens..

Mike
Connect Systems CS750 and CS800, Hytera PD-365, Motorola DP4600.
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Re: London Bus change over to DMR

Postby Alfie » Tue Nov 27, 2018 5:18 pm

it would be a shame to see them go encrypted and totally unnecessary imho and not worth the voice degradation
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Re: London Bus change over to DMR

Postby bigboyblue » Tue Nov 27, 2018 10:52 pm

Alfie wrote:it would be a shame to see them go encrypted and totally unnecessary imho and not worth the voice degradation


Where has this idea of voice degradation come from ?

Encryption used to (when trbo first came out) affect voice payload, but not any more unless you use some sort of aes-256 style encryption.

On Motorola kit, basic doesn't affect, and enhanced you can not hear the difference to the naked ear
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Re: London Bus change over to DMR

Postby Alfie » Tue Nov 27, 2018 11:26 pm

voice degradation is a fact with enhanced encryption which is admitted and acknowledged by users, experts and Motorola themselves

Basic is not so noticeable but still has its issues which you can look into

everyone who has used mototrbo/dmr knows what i mean when i say dalek as in the common bad decode it has and this happens more even at a basic enc level at the same range with encode delay and much further at advanced level with added delay. without enc dmr will turn robotic and unintelligible where analogue would still be weak but readable. adding basic enc adds this and a delay and with enhanced enc this is a lot more.

i am not a radio engineer but i can tell you we have had an intense check on our systems. we have an internet linked dmr system and on some far out units enc has been disabled. they can talk and hear on our normal enc channels as they have the enc code programed but they transmit in clear as using enc is less unintelligible. this has been real tested by the radio engineers so i know it to be true as it has been advised and adopted by my workplace on those grounds.
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