differences between digital and analog trunking

chrisw8189 · Sep 17, 2018

I am trying to understand digital vs. analog trunking systems.

Doesn't trunking have to be digital?

Don't both require a computer to route traffic?

How does an analog receiver know what channel to switch to?

How is it possible for a system such as Motorola SmartZone to be Analog AND Digital? Why are speeds such as 3600 or 9600 bps important? Is that because when signals are transmitted in 9600bps you need a radio that has enough processing power to process that signal efficiently? Shouldn’t something capable of 9600 bps be able to handle 3600 bps?

Why are Motorola radios so proprietary? Aren’t they transmitting on the same frequencies any other radio can transmit on? What prevents use from hearing a SmartZone system transmission if we have the frequency on our scanner?

Is it possible to just program old Motorola radios to receive trunking frequencies like a scanner so you hear everything?

ecps92 · Sep 18, 2018

There are plenty of NON Digital Trunking systems out there, so No to the first Question.

Questions 2/3 are similar - [talking Motorola right now] the system has a dedicated Control channel that the two-way radio and/or scanner monitor, as the TG's become active they are assigned the Voice Channel

You might want to read/browse the Wiki
Trunked Radio Systems - The RadioReference Wiki
Lots of Good information for FREE

chrisw8189 said:
I am trying to understand digital vs. analog trunking systems.

Doesn't trunking have to be digital?

Don't both require a computer to route traffic?

How does an analog receiver know what channel to switch to?

How is it possible for a system such as Motorola SmartZone to be Analog AND Digital? Why are speeds such as 3600 or 9600 bps important? Is that because when signals are transmitted in 9600bps you need a radio that has enough processing power to process that signal efficiently? Shouldn’t something capable of 9600 bps be able to handle 3600 bps?

Why are Motorola radios so proprietary? Aren’t they transmitting on the same frequencies any other radio can transmit on? What prevents use from hearing a SmartZone system transmission if we have the frequency on our scanner?

Is it possible to just program old Motorola radios to receive trunking frequencies like a scanner so you hear everything?

buddrousa · Sep 18, 2018

A google search came up with your answer.
https://en.wikipedia.org/wiki/Trunked_radio_system

chrisw8189 · Sep 18, 2018

Thank you.

But how does from what I understand an analog system using a control channel to pass instructions to the microcomputers, isn't that digital why don't we call that digital? What's the alternative to that?

zz0468 · Sep 18, 2018

chrisw8189 said:
Thank you.

But how does from what I understand an analog system using a control channel to pass instructions to the microcomputers, isn't that digital why don't we call that digital? What's the alternative to that?

The designation of analog or digital refers only to the modulation methods used for the voice paths. "Digital" systems sample and convert the voice to a stream of ones and zeros. Analog keeps it in its original analog waveform.

slicerwizard · Sep 18, 2018

chrisw8189 said:
Why are Motorola radios so proprietary?

It's called vendor lock in. Been going on for decades.

marksmith · Sep 18, 2018

Analog trunking systems transmit digital control channel content over analog transmission method, and yes a computer is used.

But all the voice (and control channel transmissions) are over analog.

Mark
SDS100/536/436/ws1095/996p2/996xt/325p2/396xt/psr800/396t/HP-1/HP-2 & others

chrisw8189 · Sep 18, 2018

Sorry to drag this on but I think this will clear it up for me..

All trunking systems use a digital control channel which tells the receiver where to listen depending on the TGID,

Some trunking systems use analog voice and some use digital voice.

Anything that can receive a specific frequency can hear any analog transmissions on that frequency if it knows where to listen, It sounds like "vendor lock in" occurs by some receivers not being able to receive or decode those digital instructions on that control channel, but in theory if it knew where to listen could actually hear it.

That being said with P25 standards, these radio regardless of vendor have an open source set of instructions all vendors follow to determine what channels to listen on via the control channel. The reason P25 and digital can be encrypted is not because radios can't hear it, but they don't have the software to decode it? Is this correct?

DJ11DLN · Sep 18, 2018

chrisw8189 said:
Sorry to drag this on but I think this will clear it up for me..

All trunking systems use a digital control channel which tells the receiver where to listen depending on the TGID,

Some trunking systems use analog voice and some use digital voice.

Anything that can receive a specific frequency can hear any analog transmissions on that frequency if it knows where to listen, It sounds like "vendor lock in" occurs by some receivers not being able to receive or decode those digital instructions on that control channel, but in theory if it knew where to listen could actually hear it.

That being said with P25 standards, these radio regardless of vendor have an open source set of instructions all vendors follow to determine what channels to listen on via the control channel. The reason P25 and digital can be encrypted is not because radios can't hear it, but they don't have the software to decode it? Is this correct?

You are on the right track, mostly. A radio with the ability to decrypt an encrypted signal still cannot decrypt it if if hasn't had the proper key loaded. And while the theory behind P25 is to have a common standard, all of the vendors tend to add custom features to their P25 systems which mostly won't work, at least properly, with competitor's gear.

And that last is "vendor lock-in." Want it to work right, stick with whatever vendor built out the system. And yes that can suck very much bad sometimes.

SteveSimpkin · Sep 18, 2018

chrisw8189 said:
Sorry to drag this on but I think this will clear it up for me..
That being said with P25 standards, these radio regardless of vendor have an open source set of instructions all vendors follow to determine what channels to listen on via the control channel. The reason P25 and digital can be encrypted is not because radios can't hear it, but they don't have the software to decode it? Is this correct?

Not exactly. In a nutshell, encryption works by having software take the digital voice bitstream and mathematically scramble it (encrypt) using a numeric "key". On the receiving end the radio must have the correct decryption software *AND* this same "key" to unscramble (decrypt) the audio. These encryption "keys" are carefully controlled and are typically not seen by people. They are loaded into the radios using a Keyloader device or service or via Over-the-air rekeying (OTAR).
https://www.taitradioacademy.com/topic/introduction-to-p25-encryption-1/

krokus · Sep 19, 2018

chrisw8189 said:
That being said with P25 standards, these radio regardless of vendor have an open source set of instructions all vendors follow to determine what channels to listen on via the control channel. The reason P25 and digital can be encrypted is not because radios can't hear it, but they don't have the software to decode it? Is this correct?

P25 is a modulation standard, like FM or AM. That is utilized with the trunking protocols.

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slicerwizard · Sep 19, 2018

chrisw8189 said:
Some trunking systems use analog voice and some use digital voice.

And some support both.

differences between digital and analog trunking

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