SDS200 Optimization for scanning a single system

[jonwienke]

Affiliation and talkgroup provisioning has nothing to do with whether the site is simulcast or not.

 

[slayer816]

Affiliation and talkgroup provisioning has nothing to do with whether the site is simulcast or not.

True. The previous poster was probably listing the side effects of side holds in response to my post glorifying it. Which was correct; you will only pick up talkgroups that are active on that one site and no more. The OP will have to balance all that together to decide how to monitor.

 

[drdispatch]

Affiliation and talkgroup provisioning has nothing to do with whether the site is simulcast or not.

But if it's NOT simulcast, and you are held on a site and there is no user radio that's on TG 1234 affiliated with that site, you will not hear any traffic on TG 1234. You would need to monitor the other sites in the area which would potentially carry traffic on that talkgroup. At least that's the way it works on Motorola P25 systems like the State of Michigan's. This was covered in our MPSCS user & instructor training.

I was merely cautioning the use of site hold.

 

[jonwienke]

But if it's NOT simulcast, and you are held on a site and there is no user radio that's on TG 1234 affiliated with that site, you will not hear any traffic on TG 1234. You would need to monitor the other sites in the area which would potentially carry traffic on that talkgroup. At least that's the way it works on Motorola P25 systems like the State of Michigan's. This was covered in our MPSCS user & instructor training.

I was merely cautioning the use of site hold.

Simulcast has zero relevance to which talkgroups are provisioned on a site/cell, and whether they are broadcast full-time, or only when a talkgroup user affiliates. That is dictated by the system settings for the talkgroup, and has nothing to do with whether a site is simulcast or a single transmitter. If you were told otherwise, you were told wrong.

Also, when something is broadcast on multiple frequencies (e.g. a dispatch talkgroup on a trunked system patched to an analog frequency for legacy 2-tone pager compatibility, or on multiple system sites/cells), that is multicast, not simulcast. Simulcast is multiple transmitters broadcasting the same signal on the same frequency at the same time. Multicast is multiple transmitters broadcasting on different frequencies at the same time.

If you hold on a site/cell, you will only hear traffic broadcast by that site/cell, regardless of whether it is a single-transmitter site, or a multi-transmitter simulcast cell. You'll miss less traffic on that site/cell by holding, at the cost of missing 100% of what isn't broadcast there.

You need to log what talkgroups are broadcast by each site for a while to know if a site hold is a good idea. If everything you want to hear can be found on a single site, then holding on that site is your best option. But if not, it's the worst.

 

[sfb88]

Jon, a followup question to your explanation. In a simulcast system since the transmitters are broadcasting the same signal at the same time, would all towers and sites broadcast all talkgroups regardless of where a user affiliates?

 

[AvidHiker]

Seems this thread is a little mixed up now and I'm getting more confused.

It would be helpful if we could return to the source of the current discussion, which is the first paragraph of post #9, questioning the OP's approach to optimizing their scanner. Some of that didn't seem right to me and I was attempting to get clarification but we've meandered a bit since.

Jon, a followup question to your explanation. In a simulcast system since the transmitters are broadcasting the same signal at the same time, would all towers and sites broadcast all talkgroups regardless of where a user affiliates?

Here's some of that terminology again - an individual "simulcast" in my local P25 system (NJICS) typically consists of 3 or more towers (which form a cell as I understand it), all broadcasting the same stuff. These simulcast cells are basically organized by county, and everything operating in a particular county can always be found on their simulcast (IOW, "site hold" works well if you're only interested TGs from that county). As mentioned, sometimes additional TGs will appear on my county simulcast, presumably because one or more radios from a different part of the system (e.g., the county next door) have affiliated, so I can sometimes listen in on things happening in additional towns (I can't typically get reliable reception on that county's simulcast, so I'm not missing anything by omitting it anyway, and the radio would absolutely be wasting time attempting to scan it).

 

[jonwienke]

Jon, a followup question to your explanation. In a simulcast system since the transmitters are broadcasting the same signal at the same time, would all towers and sites broadcast all talkgroups regardless of where a user affiliates?

All transmitters in a simulcast cell broadcast the exact same traffic on the same set of frequencies at the same time. But whether a given cell carries a talkgroup from another area is totally at the discretion of the system administrators.

 

[slayer816]

Seems this thread is a little mixed up now and I'm getting more confused.

It would be helpful if we could return to the source of the current discussion, which is the first paragraph of post #9, questioning the OP's approach to optimizing their scanner. Some of that didn't seem right to me and I was attempting to get clarification but we've meandered a bit since.


Here's some of that terminology again - an individual "simulcast" in my local P25 system (NJICS) typically consists of 3 or more towers (which form a cell as I understand it), all broadcasting the same stuff. These simulcast cells are basically organized by county, and everything operating in a particular county can always be found on their simulcast (IOW, "site hold" works well if you're only interested TGs from that county). As mentioned, sometimes additional TGs will appear on my county simulcast, presumably because one or more radios from a different part of the system (e.g., the county next door) have affiliated, so I can sometimes listen in on things happening in additional towns (I can't typically get reliable reception on that county's simulcast, so I'm not missing anything by omitting it anyway, and the radio would absolutely be wasting time attempting to scan it).

A little of that was my fault, sorry! I was trying to explain there's a difference between simulcast "sites" and standalone "sites" (both of which are programmed identically in the radio regardless of if there's one tower broadcasting or several). A proper understanding of which will help one have better programming and thus a better monitoring experience. It's slightly related to what TG's you can pick up depending on how you run the "sites" (site hold or some other option) depending on your location and the specific system.

All of which are related to "optimizing for scanning a single system" in my opinion. Even if it is two items under discussion simultaneously. Really wanted to make a simulcast joke on that last statement but I will refrain.

 

[drdispatch]

Simulcast has zero relevance to which talkgroups are provisioned on a site/cell, and whether they are broadcast full-time, or only when a talkgroup user affiliates. That is dictated by the system settings for the talkgroup, and has nothing to do with whether a site is simulcast or a single transmitter. If you were told otherwise, you were told wrong.

I didn't say that it did.

Also, when something is broadcast on multiple frequencies (e.g. a dispatch talkgroup on a trunked system patched to an analog frequency for legacy 2-tone pager compatibility, or on multiple system sites/cells), that is multicast, not simulcast. Simulcast is multiple transmitters broadcasting the same signal on the same frequency at the same time. Multicast is multiple transmitters broadcasting on different frequencies at the same time.

True. But that really isn't relevant to the discussion at hand.