General Scanner/Radio Questions

BroadOne

Member
Joined
Apr 19, 2023
Messages
38
Hopefully this is an appropriate place for this. Basically this is just a bunch of stuff I haven't been able to understand. My knowledge of this field with radio/frequencies is limited to the FCC Technician License as well as basic researching with help from people here helping me to find a vehicle mount/scanner setup. So very basic ground-level knowledge. I personally use a scanner setup (SDS-100).

Also for all of these, genuinely anything would help, like if you say absolutely nothing and just post a link and be like "figure it out" I will 100% do that lol. I don't expect essay level replies although I don't mind reading, I'd appreciate even just a general push in the right direction, I have no problem studying/researching, just don't really know where to look for some of this.

So for these questions:

1. I see TGIDs but no individual frequencies listed in various software. From what I understand, TGIDs are a lot of frequencies or units, all interacting together. So if Fire 1, Fire 2, and Fire 3 are all operating within one area, I suppose TGIDs are used to make categorizing groups easier? I guess I don't understand the point? Is it just to say "Ok this group of people, these units, are using these frequencies, and they're all part of a group".

2.
As I mentioned, I see sometimes TGIDs are listed without frequencies individually. I'm guessing that one way to separate it and figure it out is by listening to a programmed TGID, and paying attention to which frequency is used, and making note of it.

3. I noticed some units or frequencies have different frequencies, which is confusing to me. Like Tone A and Tone B and they'll be assigned supposedly to the same emission source, but why are they two different frequencies, and why Tone A and B, and what are the "tones" supposed to mean.

Example: Medic 1 - Ambulance Tone A > 584.8 Hz Tone B > 651.9 Hz . I also see "Fire Tone Out". I've not done a lot of research into this, maybe it's related?

4. As well as, along this area of topic, I see that different transmissions have a VHF frequency, and then a UHF frequency. I see it a lot with aircraft communications. Why two? The only explanation I can think of, is so different receivers can hear. Not sure.

5. Next is encryption. Very confusing for me. From my area (Okaloosa County, Florida), FHP, Fish and Wildlife, some select departments, and some select Emergency Services, are labelled "DE". L, unlucky. But I've also seen people say "You can't listen to SLERS". However, I see people claim "Here's the SLERS frequencies" and it works. And then there's EDACS, Provoice, DMR. So Statewide Law Enforcement System. So SLERS is NOT an encryption, rather, a system right? Which means Provoice, EDACS, DMR, are all separate encryptions?

6. Also I've successfully found and listened to channels from like 100-300-700. However, when it comes to 850+, I have many many many programmed, but never hear anything. I'm wondering if maybe these are the sets of encrypted channels as I beehive I was told these are common for "public safety" and such. But as far as I know, higher frequencies have shorter waves, which means less range right? So maybe these radios are out of range? My SDS-100 should be able to detect those though. As well as, even if I can't listen to encrypted channels, I'm guessing the radio will still pick them up, it'll just sound like static. (For reference I do have DMR/Provoice unlocking)

7. Next I learned that repeaters can be linked or in a system. How far can repeaters carry a signal. And is there degradation over distance, time. As well as, is there a max distance for repeaters? Can I talk to someone in a different state without a proper antenna setup worth hundreds/thousands etc. Like imagine I'm only able to head near a repeater, and use a simple transmitting-capable handheld. As long as I can get that signal to that repeater, I can send it along the series until it reaches the person right?

8. Additional sub-question, would it be possible to use sky-wave to bounce an HF signal off the ionosphere to a repeater and have the repeater carry to a station. This would eliminate the need for multiple repeaters right? Or maybe using a satellite for uplink and downlink. Seems like there's multiple ways to send a message to someone in this hobby. "Multiple ways to skin a cat" as they say?

So yeah, that's pretty much the questions I have that I don't really know where to look to learn or understand. Anything is appreciated.
 

hiegtx

Mentor
Premium Subscriber
Joined
May 8, 2004
Messages
11,268
Location
Dallas, TX
So for these questions:

1. I see TGIDs but no individual frequencies listed in various software. From what I understand, TGIDs are a lot of frequencies or units, all interacting together. So if Fire 1, Fire 2, and Fire 3 are all operating within one area, I suppose TGIDs are used to make categorizing groups easier? I guess I don't understand the point? Is it just to say "Ok this group of people, these units, are using these frequencies, and they're all part of a group".
Talkgroups are used on trunked systems. The frequencies are listed for the sites. Read this article on trunking, which should help illustrate how the frequencies & talkgroups are used.

2. As I mentioned, I see sometimes TGIDs are listed without frequencies individually. I'm guessing that one way to separate it and figure it out is by listening to a programmed TGID, and paying attention to which frequency is used, and making note of it.

This Wiki article covers most of what you are asking in these two items.

3. I noticed some units or frequencies have different frequencies, which is confusing to me. Like Tone A and Tone B and they'll be assigned supposedly to the same emission source, but why are they two different frequencies, and why Tone A and B, and what are the "tones" supposed to mean.

Example: Medic 1 - Ambulance Tone A > 584.8 Hz Tone B > 651.9 Hz . I also see "Fire Tone Out". I've not done a lot of research into this, maybe it's related?
The tones you mention here sound like that's the tones used to page out fire and/or EMS units. Those audible tones are specific to the station, or unit. In some cases, those are used to alert volunteer firefighters that they need to respond to an incident.

See this:

4. As well as, along this area of topic, I see that different transmissions have a VHF frequency, and then a UHF frequency. I see it a lot with aircraft communications. Why two? The only explanation I can think of, is so different receivers can hear. Not sure.
Different frequencies have different uses & properties. Vhf signals are good for longer range, but they do not penetrate a building as well as higher frequencies. These days, most, though not all, agencies are using 700 & 800MHz frequencies in a trunked system. If the system is properly constructed, they penetrate buildings better, so that crews can maintain contact with other units. At [resent, my city (Dallas, TX) is in the process of converting from using Uhf frequencies in a conventional system (not trunked) to a large trunked system, using 700 & 800Mhz frequencies.

5. Next is encryption. Very confusing for me. From my area (Okaloosa County, Florida), FHP, Fish and Wildlife, some select departments, and some select Emergency Services, are labelled "DE". L, unlucky. But I've also seen people say "You can't listen to SLERS". However, I see people claim "Here's the SLERS frequencies" and it works. And then there's EDACS, Provoice, DMR. So Statewide Law Enforcement System. So SLERS is NOT an encryption, rather, a system right? Which means Provoice, EDACS, DMR, are all separate encryptions?
DMR and EDACS are emission codes and in some cases are used in describing specific trunked systems, not encryption. Provoice is a type of digital transmission on an EDACS system, such as SLERS. Provoice cannot be received on most scanners, but newer Uniden models can get the Provoice upgrade, and they can listen to those calls that are not encrypted. I see a number of talkgroups on SLERS in your county (Okaloosa) that are Provoice, but not encrypted. Look at the Mode column on the systems. On EDACS systems, a D means it is Provoice. If it was also encrypted, you would see a letter E beside the D. A capital E means that talkgroup is always encrypted. If, instead, its a lower case e, then encryption is used only part of the time. For the times encryption is not in use, you can hear the radio traffic. But once it flips to encryption, you will be unable to monitor.

6. Also I've successfully found and listened to channels from like 100-300-700. However, when it comes to 850+, I have many many many programmed, but never hear anything. I'm wondering if maybe these are the sets of encrypted channels as I beehive I was told these are common for "public safety" and such. But as far as I know, higher frequencies have shorter waves, which means less range right? So maybe these radios are out of range? My SDS-100 should be able to detect those though. As well as, even if I can't listen to encrypted channels, I'm guessing the radio will still pick them up, it'll just sound like static. (For reference I do have DMR/Provoice unlocking)
Again, look for the E in a database listing. That will tell you if encryption has reported. Generally speaking, the higher the frequency, the less the range might be. Of course, range is also dependent on other factors, such as the transmit power used, the way the antennas are set up, and how high they are positioned. A transmitter and antenna placed on a tower on top of a hill or mountain will have longer range than one mounted low, just on the top of a building. In most cases, Uniden scanners will automatically skip encrypted transmissions. Even if you listened, you;d hear an unintelligible strung of sounds that sound like R2D2 on steroids.

7. Next I learned that repeaters can be linked or in a system. How far can repeaters carry a signal. And is there degradation over distance, time. As well as, is there a max distance for repeaters? Can I talk to someone in a different state without a proper antenna setup worth hundreds/thousands etc. Like imagine I'm only able to head near a repeater, and use a simple transmitting-capable handheld. As long as I can get that signal to that repeater, I can send it along the series until it reaches the person right?
I suppose, if the system was set up correctly, something like that might work, but in most cases, systems are designed to cover a specific area, There might be transmitter sites at the distant location, but in most cases, those sites are not directly linked to the one in your area.

8. Additional sub-question, would it be possible to use sky-wave to bounce an HF signal off the ionosphere to a repeater and have the repeater carry to a station. This would eliminate the need for multiple repeaters right? Or maybe using a satellite for uplink and downlink. Seems like there's multiple ways to send a message to someone in this hobby. "Multiple ways to skin a cat" as they say?
That's getting into areas that I don't deal with. There is a specific forum dealing with HF & other similar topics.
Also see this: Skip / Tropospheric Ducting Forum

There is also a forum dedicated to issues involving space communications.
 

mmckenna

I ♥ Ø
Joined
Jul 27, 2005
Messages
24,383
Location
I am a lineman for the county.
I'll take a swing at some of these...

Hopefully this is an appropriate place for this. Basically this is just a bunch of stuff I haven't been able to understand. My knowledge of this field with radio/frequencies is limited to the FCC Technician License as well as basic researching with help from people here helping me to find a vehicle mount/scanner setup. So very basic ground-level knowledge. I personally use a scanner setup (SDS-100).

Also for all of these, genuinely anything would help, like if you say absolutely nothing and just post a link and be like "figure it out" I will 100% do that lol. I don't expect essay level replies although I don't mind reading, I'd appreciate even just a general push in the right direction, I have no problem studying/researching, just don't really know where to look for some of this.

So for these questions:

1. I see TGIDs but no individual frequencies listed in various software. From what I understand, TGIDs are a lot of frequencies or units, all interacting together. So if Fire 1, Fire 2, and Fire 3 are all operating within one area, I suppose TGIDs are used to make categorizing groups easier? I guess I don't understand the point? Is it just to say "Ok this group of people, these units, are using these frequencies, and they're all part of a group".

TGID is a Talk group ID. This is specifically to do with trunking systems.

Think of trunked radio system like a telephone system. The telephone system might have 100 telephones connected to it, but only 10 trunks to the outside world. This because at any given time, most people are not using their phone. There's no need to have each phone directly connected to a trunk 100% of the time. It's expensive and wasteful.
Same applies to radio systems. In a big city/county, there may be 100 departments that all need radio service. Might be PD, Fire, EMS, public works, roads, dog catcher, garbage pickup, etc. But like the phone system, those guys are not using the radio 100% of the time. Most of the time the radio is quiet. Each department in the county having their own radio frequency/repeater would be wasteful, especially considering that most of the time they are not getting used.
So, the solution is (like a phone system) to build a trunked radio system where there may be 100's of talk groups, each one assigned to a different group of users, but maybe only 10 actual repeaters.
When a person with a radio needs to talk to their respective group, they key up, the radio transmits some data that says "Hey, Bob's radio wants to use the system and talk to all the garbage trucks". The trunked radio system says "OK, here, use repeater #7, no ones using that". The radio system sends a message out to all the radios and says "Hey, if you are listening to the garbage truck talk group, switch your receiver over to channel #7, Bob wants to talk". This data stream is all handled without the user being involved, the radios just do what the trunked system tells them to do. So the TGID or TalkGroup ID isn't a set frequency or repeater. It's just a resource programmed into the radio that is assigned for a specific group of users. When that group needs to talk, the trunked radio system assigns them a repeater to use. When they are done talking, that repeater is released (like a telephone trunk) and another group can use it to make a call.

It's all about sharing resources so there is less waste. In large systems, it is cheaper than having dedicated repeaters for each group of users.
The TGID is a virtual channel that isn't assigned to any specific repeater until it actually needs to be used.

2. As I mentioned, I see sometimes TGIDs are listed without frequencies individually. I'm guessing that one way to separate it and figure it out is by listening to a programmed TGID, and paying attention to which frequency is used, and making note of it.

That's what a trunked radio will do, or a scanner that will monitor a trunked radio system. It listens to the data stream and can be programmed to recognize specific talk groups and then jump to which ever frequency the trunked radio system assigns for it to use.

3. I noticed some units or frequencies have different frequencies, which is confusing to me. Like Tone A and Tone B and they'll be assigned supposedly to the same emission source, but why are they two different frequencies, and why Tone A and B, and what are the "tones" supposed to mean.

These are not radio frequencies. They are audio frequencies. In the olden days, that's how pagers worked. The pager would listen on the paging system radio frequency for those specific two audio tones. When it heard the right ones, it would open up the receiver so the person carrying the pager would hear the radio traffic directed at them. When it heard radio traffic that didn't have the correct audio tone frequencies, it would ignore the radio traffic.
Great for old radio pagers. Those sorts of pagers are still used in some applications, like hospitals, but not so much in the general public.
Where that sort of two tone paging is heavily used is for fire department radio systems. Each station, or even specific asset, can be assigned a specific set of two tones. When the dispatcher wants to send out that specific asset, their dispatch terminal can send out the correct two audio tones over the radio. The radio at the fire station, the hand held radio carried by the fire fighter/emt, or the radio on the truck, will hear those two tones and make the radio play a tone to get the users attention. They then hear the dispatcher telling them where to go and what to do (as dispatchers like to do…).

If you want to hear this in action, go watch and episode of the 1970s era TV show "Emergency!". It's used heavily in the radio dispatches to the station.

Example: Medic 1 - Ambulance Tone A > 584.8 Hz Tone B > 651.9 Hz . I also see "Fire Tone Out". I've not done a lot of research into this, maybe it's related?

Yep, see above. Or, wander over to the Youtubes and watch this:

4. As well as, along this area of topic, I see that different transmissions have a VHF frequency, and then a UHF frequency. I see it a lot with aircraft communications. Why two? The only explanation I can think of, is so different receivers can hear. Not sure.

It's just different resources. Some aircraft only have VHF radios. Some have VHF and UHF. You'll see the military uses a lot of UHF air radio.
There are some on here that specialize in listening to air band radio traffic and can probably explain it better than I can….

5. Next is encryption. Very confusing for me. From my area (Okaloosa County, Florida), FHP, Fish and Wildlife, some select departments, and some select Emergency Services, are labelled "DE". L, unlucky. But I've also seen people say "You can't listen to SLERS". However, I see people claim "Here's the SLERS frequencies" and it works. And then there's EDACS, Provoice, DMR. So Statewide Law Enforcement System. So SLERS is NOT an encryption, rather, a system right? Which means Provoice, EDACS, DMR, are all separate encryptions?

SLERS is a radio system.
Encryption is something that can be done on a per-talk group basis, a per radio basis, or a system wide basis. Just depends on how the system is set up and what the usage case is. SLERS may have some talk groups that are not encrypted, and you would be able to hear those if you had your scanner set up correctly.

If a talk group or other radio resource is encrypted, you usually cannot hear the radio traffic.

6. Also I've successfully found and listened to channels from like 100-300-700. However, when it comes to 850+, I have many many many programmed, but never hear anything. I'm wondering if maybe these are the sets of encrypted channels as I beehive I was told these are common for "public safety" and such. But as far as I know, higher frequencies have shorter waves, which means less range right? So maybe these radios are out of range? My SDS-100 should be able to detect those though. As well as, even if I can't listen to encrypted channels, I'm guessing the radio will still pick them up, it'll just sound like static. (For reference I do have DMR/Provoice unlocking)

Depends on exactly what frequencies you are talking about.

Yes, 800MHz would have a shorter wavelength that lower frequencies. That can result in less range in some applications. On the other side of the coin, higher frequencies will often penetrate buildings much better.

As for hearing encrypted traffic, no, you won't be able to hear what they are saying. Some scanners will just block out the noise since it annoys most people. Some radios will pass it and you'll just hear an unpleasant noise. Might sound like static. Might sound like buzzing, might sound like garbled speech.

7. Next I learned that repeaters can be linked or in a system. How far can repeaters carry a signal. And is there degradation over distance, time. As well as, is there a max distance for repeaters? Can I talk to someone in a different state without a proper antenna setup worth hundreds/thousands etc. Like imagine I'm only able to head near a repeater, and use a simple transmitting-capable handheld. As long as I can get that signal to that repeater, I can send it along the series until it reaches the person right?

The range of the repeater over RF will depend on location, location and of course, location. Don't forget about the location. The altitude of the repeater will impact range. Higher repeaters can "see" further than a lower level one. Power output plays a bit of a role in range, but not as much as many people think. Antenna design will impact range.

As for linking multiple repeaters together, it depends on how it is done.
Repeaters can be linked via radios on different bands that connect the sites together.
Repeaters can be linked via phone lines (not dial up phones, but a dedicated circuit from the phone company.
Microwave can be used to link radio sites.
Fiber optic cable can be used to link radio sites.
Some even use satellite links or even cellular links to connect sites.
But, likely what you are talking about is linking repeaters over the internet. A lot of amateur radio and some GMRS repeaters use Internet Protocol linking to tie repeaters together into large networks. There isn't really a limit on the distance the link can be. It is easy enough to link repeaters all over the world and let individuals with a small hand held radio to easily talk around the globe.

8. Additional sub-question, would it be possible to use sky-wave to bounce an HF signal off the ionosphere to a repeater and have the repeater carry to a station. This would eliminate the need for multiple repeaters right? Or maybe using a satellite for uplink and downlink. Seems like there's multiple ways to send a message to someone in this hobby. "Multiple ways to skin a cat" as they say?

Yep, see above.
HF radio can be used, but it's not very common. The signal quality can be iffy. The link can easily be degraded and drop out. Yes, it can be done, but it's not very common. There are systems that will do this. There are HF radios that will allow a link to a local VHF or UHF radio to create a quick setup system like this for emergency use.

So yeah, that's pretty much the questions I have that I don't really know where to look to learn or understand. Anything is appreciated.

It's a whole industry. A whole field of study. A whole hobby. A whole career.
You won't find all those answers easily in a short amount of time. I've been working in the industry 30 years now, and I am constantly having to learn new subjects.
Best thing to do is ask questions, learn, and decide where your interests lead you.
 

BroadOne

Member
Joined
Apr 19, 2023
Messages
38
Appreciate the responses. So after reading what's here, along with the articles and videos linked:

So TGIDs, I've been thinking about it wrong then, it's less about the users and more about the system. It's not people saying "hey lets all use frequency x" it's the system saying "you're going to use these frequencies because they're not being used right now". And it happens instantly, automatically. Which means that a TGID speaking from a scanner perspective is more of a way to ride the current. Like a vehicle, a bus that constantly travels, in order to hear conversations on that bus, you have to be on the bus. But it's constantly moving. So a TGID allows you to ride the waves, ride that bus with the group basically if I understand right.

Tones are not frequencies, they're literally specific audio tones. It's like a header of information that the system reads and says "Ok this following message needs to go to Station A and all corresponding radios" if I understood that right.

And everything else seems more clear in general. And went through and double checked the database against the scanner import I did to make sure I didn't have any known encrypted channels, as well as tried to find some known Tone Out signals and program those into the scanner. I'll test it in the near future. I really appreciate it, thanks again.
 

mmckenna

I ♥ Ø
Joined
Jul 27, 2005
Messages
24,383
Location
I am a lineman for the county.
Appreciate the responses. So after reading what's here, along with the articles and videos linked:

So TGIDs, I've been thinking about it wrong then, it's less about the users and more about the system. It's not people saying "hey lets all use frequency x" it's the system saying "you're going to use these frequencies because they're not being used right now". And it happens instantly, automatically. Which means that a TGID speaking from a scanner perspective is more of a way to ride the current. Like a vehicle, a bus that constantly travels, in order to hear conversations on that bus, you have to be on the bus. But it's constantly moving. So a TGID allows you to ride the waves, ride that bus with the group basically if I understand right.

Yes, essentially.
Each radio can have a lot of talk groups in them. The talk group ID will be given a name, like "Police Primary" that the user will see on the screen.
All the stuff that happens with the actual data stream is transparent to the end user, they don't know anything about what is going on with their radio, just that they can talk to Bob when they want to.
The radio system itself calls the shots, it's the one that assigns a frequency for the radios to use.
All this happens over a 'control channel' which is how the radio and radio system talk to each other.
The control channel is just a data stream, and will sound like raw data if you set your scanner on that frequency.

It's all about sharing a limited number of resources (talk paths/radio frequencies) with a large amount of users.

Tones are not frequencies, they're literally specific audio tones. It's like a header of information that the system reads and says "Ok this following message needs to go to Station A and all corresponding radios" if I understood that right.

Yes. It is a very simplistic selective calling/alerting tool. "Back in the day" it used mechanically vibrating reeds to sense the audio tones. Modern radios do it all electronically. It is old and simple, but if set up correctly, its reliable and works well.

And everything else seems more clear in general. And went through and double checked the database against the scanner import I did to make sure I didn't have any known encrypted channels, as well as tried to find some known Tone Out signals and program those into the scanner. I'll test it in the near future. I really appreciate it, thanks again.
 

BroadOne

Member
Joined
Apr 19, 2023
Messages
38
The control channel is just a data stream, and will sound like raw data if you set your scanner on that frequency.
I appreciate it, and this part of what you said actually answered another question I forgot I had lol. I thought that control channels were a main channel or something, but that received a copy or duplicate of what's happening on the primary/secondary channels. Don't ask me why I thought that, I honestly don't know. But I had a primary programmed as well as a control channel. And when the primary would switch over, I'd just hear static or what sounded like a garbled transmission. I thought it might've been encryption but the primary wasn't encrypted so I was confused. But if the control channel is only raw data, then this probably explains that.
 

mmckenna

I ♥ Ø
Joined
Jul 27, 2005
Messages
24,383
Location
I am a lineman for the county.
Control channels on most trunking protocols runs the data stream 24/7 constantly. You'd hear a constant data stream.
Some systems will periodically 'roll' the frequency that is used by the control channel between the available frequencies. Not all systems do this, but some will.
 
Top