What does Dec/Hex mean?

[wtp]

i sent a PM to you that reads better.

 

[n5ims]

Most Scanners use HEX for the SysID and NAC, not Decimal

True, but they go as is into scanner or radio. The OP questioned the difference between the database columns DEC and HEX and as I indicated they're both the same and you only enter one or the other depending on your scanner/radio of choice.

 

[gmclam]

Ah I see. So where I'm at they use a simulcast and the uniden SDS100 handles that the best? As in if one unit transmits to dispatch then another they will go by which ever is first? For example E14 says "E 14 to dispatch" then E15 at the same time/frequency says "E15 to dispatch" they would have E14 go first then cast E15? Sorry if it's confusing

Trunking, of any kind, is a computer driven system that assigns a frequency (from the pool) for each transmission. An entire conversion could be assigned the same frequency over and over, or each separate transmission assigned a different frequency. Trunk tracking scanners handle this for us.

With a simulcast system, signals arrive at the receiver from multiple locations "simultaneously". The signals will vary (slightly) in strength and generally will not arrive at absolutely the same time. Older receivers, including the BCD996P2 can't handle this. Unfortunately the only scanner radios out there that do is the SDS-100 hand-held and SDS-200 base model.

If you are going to be stationary, there are ways to mitigate the effects of simulcast. Some people are using SDR dongles on a PC as their receiver.

Since you're asking about a hand-held model, I suspect you're going to be mobile. You will run into simulcast issues. The result is garbled stuff and not receiving a transmission at all. For some, and considering the expense, this is apparently tolerable. When my county went simulcast it drove me crazy listening on older receivers and I was amazed at the difference using an SDS-100 made.

 

[Jeremy1873]

Trunking, of any kind, is a computer driven system that assigns a frequency (from the pool) for each transmission. An entire conversion could be assigned the same frequency over and over, or each separate transmission assigned a different frequency. Trunk tracking scanners handle this for us.

With a simulcast system, signals arrive at the receiver from multiple locations "simultaneously". The signals will vary (slightly) in strength and generally will not arrive at absolutely the same time. Older receivers, including the BCD996P2 can't handle this. Unfortunately the only scanner radios out there that do is the SDS-100 hand-held and SDS-200 base model.

If you are going to be stationary, there are ways to mitigate the effects of simulcast. Some people are using SDR dongles on a PC as their receiver.

Since you're asking about a hand-held model, I suspect you're going to be mobile. You will run into simulcast issues. The result is garbled stuff and not receiving a transmission at all. For some, and considering the expense, this is apparently tolerable. When my county went simulcast it drove me crazy listening on older receivers and I was amazed at the difference using an SDS-100 made.

So you recommend the SDS100? I’m still confused on simulcast but to summarize Trunking It’s a pool of frequencies for a large amount of users and when a user needs to talk they talk on a available channel but I’m confused. Because I thought a decimal channel was just a regular frequency channel basically so you input the decimal and talk on it, why would they move to an available/idle channel.

 

[Mike_G_D]

You are confusing two different concepts. Frequencies are not talk groups but both can be considered as "channels" from higher perspectives and depending on what part of the system you want to focus on. Very important - keep this in mind!

Trunking is a way to use a relatively small number of available radio frequencies to be used in such a manner that allows a compartively larger number of distinct user groups to have their own "channels" of communication without assigning them to one exclusive specific radio frequency (that never changes, as in "conventional" radio systems).

And, outside of the user choosing which talk group to use on their radio (which can be labeled as a "channel" and is often thought of as such by end-users and non-technical users and is not an inaccurate description anyway), the actual assigning of a radio frequency to the voice path when needed is done by computers. Computers in the user radios talk to computers at the trunking sites who, in turn, talk to master computers at higher system levels, and on and on depending on the complexity and size of the system. Those computers switch the radios involved in the conversation to the same frequencies and the whole process is transparent to the user (or supposed to be). Outside of the trunking control channel (the path that the computers mainly use when "talking" to each other and allways revert to listening to when idle) no one frequency is dedicated to a specific user group. That is where the talk groups come into play.

The talk group is a "code", which can be represented in either hexadecimal or decimal format (most professional radios use the former, "HEX", while most consumer scanners default to the latter, "DEC"). This "code" is kept track of by those computers mentioned earlier so the system "knows" you are a user member of a group assigned that code and therefore you should be getting any voice traffic assigned to that group code regardless of whatever actual physical level radio frequency is used in the process and that, should you desire to transmit by pressing the PTT button you get immediately assigned an available radio frequency and the radios of all other users listening that have that same assigned code get told by the master site controller to go to that frequency to "hear you".

Simulcast distortion refers to a physical radio path issue (and it can be encountered on both conventional and trunked radio systems) - transmitting the same content from different locations (but still locations with signal coverage that often overlaps each other) on the same frequency. Normally, this would be an undesireable "bad thing" in conventional radio usage because you would get distortion problems. However, if you can exactly time the radio waves in synchronicity with each other, in theory, you can keep the distortion down to a level that makes the system work well for the end users within a certain area it is designed for. It's done with extremely accurate synchronized timing using a master clock signal that all involved sites sync from and using very carefully aligned antennas that keep their reception and transmission patterns within a desired area. Analog systems that use this sound decent when everything is "in phase" but can sound distorted when things go out of phase (which gets really bad once you go outside of the designed for coverage area). In digital systems, it is important to keep the "bits" "clean" and they can get "scrambled" when the simulcast sync is corrupted. The issue (for non-system subscriber listeners, like "scanner users") is that, the receiver design in most consumer scanners cannot handle digital simulcast signals very well (even when in the desired designed for area of coverage) while professional (and some few higher cost consumer grade equipment) work fine with it.

That's a super simplistic introductory broad description of the two concepts - I left out A LOT! But I don't know your level of technical expertise and tried to keep it as simple as I could to start with.

-Mike

 

[Jeremy1873]

You are confusing two different concepts. Frequencies are not talk groups but both can be considered as "channels" from higher perspectives and depending on what part of the system you want to focus on. Very important - keep this in mind!

Trunking is a way to use a relatively small number of available radio frequencies to be used in such a manner that allows a compartively larger number of distinct user groups to have their own "channels" of communication without assigning them to one exclusive specific radio frequency (that never changes, as in "conventional" radio systems).

And, outside of the user choosing which talk group to use on their radio (which can be labeled as a "channel" and is often thought of as such by end-users and non-technical users and is not an inaccurate description anyway), the actual assigning of a radio frequency to the voice path when needed is done by computers. Computers in the user radios talk to computers at the trunking sites who, in turn, talk to master computers at higher system levels, and on and on depending on the complexity and size of the system. Those computers switch the radios involved in the conversation to the same frequencies and the whole process is transparent to the user (or supposed to be). Outside of the trunking control channel (the path that the computers mainly use when "talking" to each other and allways revert to listening to when idle) no one frequency is dedicated to a specific user group. That is where the talk groups come into play.

The talk group is a "code", which can be represented in either hexadecimal or decimal format (most professional radios use the former, "HEX", while most consumer scanners default to the latter, "DEC"). This "code" is kept track of by those computers mentioned earlier so the system "knows" you are a user member of a group assigned that code and therefore you should be getting any voice traffic assigned to that group code regardless of whatever actual physical level radio frequency is used in the process and that, should you desire to transmit by pressing the PTT button you get immediately assigned an available radio frequency and the radios of all other users listening that have that same assigned code get told by the master site controller to go to that frequency to "hear you".

Simulcast distortion refers to a physical radio path issue (and it can be encountered on both conventional and trunked radio systems) - transmitting the same content from different locations (but still locations with signal coverage that often overlaps each other) on the same frequency. Normally, this would be an undesireable "bad thing" in conventional radio usage because you would get distortion problems. However, if you can exactly time the radio waves in synchronicity with each other, in theory, you can keep the distortion down to a level that makes the system work well for the end users within a certain area it is designed for. It's done with extremely accurate synchronized timing using a master clock signal that all involved sites sync from and using very carefully aligned antennas that keep their reception and transmission patterns within a desired area. Analog systems that use this sound decent when everything is "in phase" but can sound distorted when things go out of phase (which gets really bad once you go outside of the designed for coverage area). In digital systems, it is important to keep the "bits" "clean" and they can get "scrambled" when the simulcast sync is corrupted. The issue (for non-system subscriber listeners, like "scanner users") is that, the receiver design in most consumer scanners cannot handle digital simulcast signals very well (even when in the desired designed for area of coverage) while professional (and some few higher cost consumer grade equipment) work fine with it.

That's a super simplistic introductory broad description of the two concepts - I left out A LOT! But I don't know your level of technical expertise and tried to keep it as simple as I could to start with.

-Mike

Hey. I just first want to start off and say this was actually very very helpful although I still do have questions. I'll ask them and if you're confused on any question I asked please let me know so I can try and explain it better.

Question #1:
So these are the definitions I saw and came up with.
Definitions: Conventional radios operate on fixed channels and each user group is permanently assigned a fixed frequency or a set of frequencies.
Trunking: Trunked radios use several channels or frequencies, and allows those channels to be shared by a large number of users, in multiple talkgroups, without their conversations interfering with each other.

So
Is trunking to not interfere each other on the same "channel" for example let's say Engine 1 transmits and at the same time Engine 2 transmits on the same channel, instead of interfering it would block out?

2. If two units are on two different frequencies they wouldn't be able to interfere with each other so what's the point of trunking?

Question #2

Your whole third paragraph really confused me. The paragraph that starts "And, outside". I'd really appreciate it if you can explain it more

Question #3

What is a master computer?

Question #4

My summary was once you press the PPT button you're assigned (as in move) an available frequency. And All units on that code will be assigned to the channel to hear the transmission.

So my question really is let's say the Medical Command channel is decimal 729 right, once you press the PTT you'd talk on the 729 code/medical command channel right? So what does it mean when you mean they go to an automatic idle channel? Like if let's say E2 was transmitting on the medical command channel/DEC729 and then E4 needs to transmit will they still be on the same channel 729 or moved to an idle?

Again your paragraph's were very helpful and i really appreciate you taking the time to tell me the information.

 

[RMason]

There is some good reading on trunked systems here

Trunked Radio Systems - The RadioReference Wiki

wiki.radioreference.com

You may want to start here:

https://wiki.radioreference.com/images/c/c7/Trunking_description.pdf

 

[gmclam]

...Is trunking to not interfere each other on the same "channel" for example let's say Engine 1 transmits and at the same time Engine 2 transmits on the same channel, instead of interfering it would block out?

People tend to use the terms "channel" and "frequency" interchangeably, they are not (unless you're discussing Conventional Channels). In a trunked system, channels are virtual and it's less confusing if they're referred to as talkgroups.

On a trunked system, when a user presses the transmit button, it's really a "request" to the control computer. I don't want to get too deep here, but the user may want to talk on a talkgroup or directly to another user. If a second user tries to transmit on the same talkgroup while the first user is transmitting, the request is not granted.

2. If two units are on two different frequencies they wouldn't be able to interfere with each other so what's the point of trunking?

I'm not sure if you are asking about two separate conversations, one conversation on the same "channel" or duplex operation where two frequencies are involved in the same conversation (which is how the CHP is set up).

My department wants to have 100 channels. Yeah it is large. In the days where we only had Conventional Channels, that would require at least 100 frequencies (in praticality it would be more than 100). I can now employ a trunked system with oh let's say 5 frequencies. One would be the control channel and that leaves 4 frequencies for simultaneous "voice". The 100 channels are virtual. Most of the time the voice channels are actually idle. You can have more than 4 simultaneous conversations, but no more than 4 people would be transmitting at the same time. If more is needed, add more frequencies.

What is a master computer?

Casual observers might consider a trunked radio system to be a radio; while it uses radio frequencies, it's really an over-the-air computer system. A "master computer" receives requests from users (which could be considered as terminals) and makes them happen. It's not just pressing the talk button, it's also things like changing channels -- errrr -- talkgroups.

My summary was once you press the PPT button you're assigned (as in move) an available frequency. And All units on that code will be assigned to the channel to hear the transmission.

PTT = Push To Talk. Radios are more like computer terminals and are "logged in". The master computer knows who is logged in and what "channel" they are on.

So my question really is let's say the Medical Command channel is decimal 729 right, once you press the PTT you'd talk on the 729 code/medical command channel right? So what does it mean when you mean they go to an automatic idle channel? Like if let's say E2 was transmitting on the medical command channel/DEC729 and then E4 needs to transmit will they still be on the same channel 729 or moved to an idle?

Each radio is affiliated with a channel (or could be just logged in to receive private calls). When a user changes channels, it informs the computer to affiliate it with another talkgroup.

 

[Jeremy1873]

People tend to use the terms "channel" and "frequency" interchangeably, they are not (unless you're discussing Conventional Channels). In a trunked system, channels are virtual and it's less confusing if they're referred to as talkgroups.

On a trunked system, when a user presses the transmit button, it's really a "request" to the control computer. I don't want to get too deep here, but the user may want to talk on a talkgroup or directly to another user. If a second user tries to transmit on the same talkgroup while the first user is transmitting, the request is not granted.

I'm not sure if you are asking about two separate conversations, one conversation on the same "channel" or duplex operation where two frequencies are involved in the same conversation (which is how the CHP is set up).

My department wants to have 100 channels. Yeah it is large. In the days where we only had Conventional Channels, that would require at least 100 frequencies (in praticality it would be more than 100). I can now employ a trunked system with oh let's say 5 frequencies. One would be the control channel and that leaves 4 frequencies for simultaneous "voice". The 100 channels are virtual. Most of the time the voice channels are actually idle. You can have more than 4 simultaneous conversations, but no more than 4 people would be transmitting at the same time. If more is needed, add more frequencies.

Casual observers might consider a trunked radio system to be a radio; while it uses radio frequencies, it's really an over-the-air computer system. A "master computer" receives requests from users (which could be considered as terminals) and makes them happen. It's not just pressing the talk button, it's also things like changing channels -- errrr -- talkgroups.

PTT = Push To Talk. Radios are more like computer terminals and are "logged in". The master computer knows who is logged in and what "channel" they are on.

Each radio is affiliated with a channel (or could be just logged in to receive private calls). When a user changes channels, it informs the computer to affiliate it with another talkgroup.

I’m kinda understanding but of course i still have questions.

My summary about a trunked system is let’s say E1 is transmitting something to dispatch on the talk group then at the same time E2 transmits instead of interfering with E1 it will cancel or block E2 right?

And to clarify a talk group is just a channel right? Like is a decimal talkgroup it’s own channel for example
729 is it’s only channel and 719 is it’s only channel like frequencies 556.267 is it’s own channel and 157.562 that is it’s own channel?

 

[gmclam]

My summary about a trunked system is let’s say E1 is transmitting something to dispatch on the talk group then at the same time E2 transmits instead of interfering with E1 it will cancel or block E2 right?

If E2 tries to talk on the same talkgroup that E1 is already on, it is likely E2's radio will be NOT given a channel grant (inhibiting E2's ability to talk at that time on that same talkgroup).

And to clarify a talk group is just a channel right?

Yes, a virtual channel.

Like is a decimal talkgroup it’s own channel for example 729 is it’s only channel and 719 is it’s only channel like frequencies 556.267 is it’s own channel and 157.562 that is it’s own channel?

Yes.

 

[nd5y]

On a trunked system only one user at a time can talk on a talkgroup. The system prevents all other transmissions on that talkgroup. If another user keys up they get a busy tone and their radio won't transmit and interfere with the transmission in progress.

 

[Jeremy1873]

On a trunked system only one user at a time can talk on a talkgroup. The system prevents all other transmissions on that talkgroup. If another user keys up they get a busy tone and their radio won't transmit and interfere with the transmission in progress.

So a trunk system doesn’t allow interference while a regular frequency or conventional does? (Is conventional/frequency the same thing?) What’s a talkgroup. Someone said it’s just 2 user in the same department is that correct?

 

[chrismol1]

So a trunk system doesn’t allow interference while a regular frequency or conventional does? (Is conventional/frequency the same thing?) What’s a talkgroup. Someone said it’s just 2 user in the same department is that correct?

Interference as in two user talking over each other? No, whoever gets the voice grant first wins and the other users get bonked
Did you read this?
https://wiki.radioreference.com/images/c/c7/Trunking_description.pdf

 

[Jeremy1873]

If E2 tries to talk on the same talkgroup that E1 is already on, it is likely E2's radio will be NOT given a channel grant (inhibiting E2's ability to talk at that time on that same talkgroup).

Yes, a virtual channel.

Yes.

If decimals are there own frequency and lets say E1 is transmitting on 729 then E2 tries to transmit on 729 why would they switch channels? You said " E2's radio will be NOT given a channel grant" but if they're already connected on the 729 decimal channel or talkgroup why would they need to switch if that makes sense

 

[Jeremy1873]

Interference as in two user talking over each other? No, whoever gets the voice grant first wins and the other users get bonked
Did you read this?
https://wiki.radioreference.com/images/c/c7/Trunking_description.pdf

Yes I got that now. it's just this guy said "Talk group-. Two or more individuals from the same department, agency or activity (PD dispatch, FD dispatch, TAC one, etc)." So that would mean two firefighters on Tac one right? So that's why i asked a talkgroup is just 2 user in the same department is that correct?

 

[RMason]

Talk Groups identify channels within the system.

Here are some sample police Talk Groups from a system in your area.

San Diego City 800MHz Trunking System, San Diego, California

San Diego City 800MHz Trunking System Profile

www.radioreference.com

 

[Jeremy1873]

Talk Groups identify channels within the system.

Here are some sample police Talk Groups from a system in your area.

San Diego City 800MHz Trunking System, San Diego, California

San Diego City 800MHz Trunking System Profile

www.radioreference.com

View attachment 109642

If a talkgroup is a bunch of channels with the system such as DEC 208 and 272 then if you look at the picture why wouldn’t those frequencies be a “talkgroup”. I’m pretty I got it wrong, but just want to understand the difference between them.

 

[RMason]

The Wildland Fire Operations you show are a CONVENTIONAL system. In the conventional system, a separate frequency is dedicated for each group of users (channel).

Talk Groups are used in TRUNKED systems. In a TRUNKED system, a larger number of users/groups share a smaller number of frequencies. Each time a member of a talkgroup starts to transmit, a central computer assigns all members of that talkgroup to an available frequency. Unlike a conventional system, each frequency/channel is not dedicated to any particular group of users. Instead, a pool of frequencies is shared among a larger number of users. In a typical trunked system, frequencies may be shared among police and fire departments, utilities, buses, dog catchers, etc. It is very unlikely that all users in each agency will transmit at the same time, so the trunked system can get by with fewer frequencies than users. Users in a trunked radio system are organized into groups known as talk groups. A large agency like a police department may have numerous talk-groups organized similarly to the channels in a conventional system.

Above is derived from:

Radio Scanner Guide - Part 3A: Monitoring Trunked Systems - Police, Fire, Medical, & Business

A guide to selecting Radio Scanners; divides both new and used radio scanners into 6 categories, based on their specifications and features - e.g. analog trunking scanners, digital trunking scanners, etc; provides specifications on each model

radio-scanner-guide.com

 

[RMason]

Here is an illustration that might help:

In the below snapshot from a system in my area, you can see 3 TalkGroups from different agencies are broadcasting in a Trunked System:

1) TG-4029 (FtCollins PD 1) has been assigned to 852.675 (voice channel)​

2) TG-9150 (LarimerCO SO1) has been assigned to 853.050 (voice channel)​

3) TG-2451 (CSP Troop 3A) has been assigned to 851.850 (voice channel)​

The control channel is 853.8875.

 

[chrismol1]

Yes I got that now. it's just this guy said "Talk group-. Two or more individuals from the same department, agency or activity (PD dispatch, FD dispatch, TAC one, etc)." So that would mean two firefighters on Tac one right? So that's why i asked a talkgroup is just 2 user in the same department is that correct?

yea, could be 2 or more users, could be a paging only channel, could be a dispatcher talking a unit, really anyone who needs to talk. In the most simple way and I'm sure you already heard this in different ways. The deal is since trunking is a pool of frequencies which the computer system selects the next available free freq from the pool, there needs to be a way to distinguish the voices or else everytime someone presses the mic it would be like scanning all the frequencies hearing everything. So a talkgroups individual hexadecimal address becomes what was once individual frequencies and separate the voices on all the freqs so you only hear the voices you want to hear in your same group(talkgroup)