Receiving hits from a tower that is nowhere near me

Okay, first I'll start with the fact that I may be absolutely confused about how it works in the first place.

I have a BCD396XT set up to scan both the local PD/FD in my city and the Nebraska State Patrol which runs on the Nebraska State Radio System trunked P25 system.

Now in FreeSCAN I have two sites set up, North Platte and York.

Pretty frequently, it will show that I am receiving stuff from York even though it is 180 miles from m.e

On Wednesday when they do the state ROC calls, I'll pick up the D-ROC call which comes out of my city but it will always say York on my scanner instead of North Platte.

Is there any reason it's showing a lot of stuff coming off of York?

1 (1) 081 (51) York York 154.42250 154.77750a 155.51250a 156.14250c
1 (1) 053 (35) North Platte Lincoln 155.43000 155.64000 155.89500a 156.13500c

Looks like the two control channels are right next to each other frequency-wise. It could be that the scanner is picking up the off-frequency data. It could also be a combination of that along with the possibility that your scanner is off frequency itself by a little.

I would program the two as different systems so you aren't even trying to scan the site that is 100 miles away from you.

Assign quick keys to the sites and disable the York site.

It can be explained in one word, Affiliation

An important concept to understand with networked systems is affiliation. Affiliation is what happens when a specific subscriber's radio is using a specific site to communicate with the trunked system; it "checks in", and this causes talkgroup traffic for the talkgroup to which that radio is "tuned" to appear on that particular site/tower.

Trunking Basics 3.1 - Affiliation

W8RMH said:

It can be explained in one word, Affiliation

An important concept to understand with networked systems is affiliation. Affiliation is what happens when a specific subscriber's radio is using a specific site to communicate with the trunked system; it "checks in", and this causes talkgroup traffic for the talkgroup to which that radio is "tuned" to appear on that particular site/tower.

Trunking Basics 3.1 - Affiliation

Click to expand...

So if I removed the York site from my scanner, I wouldn't get any hits from radios that are "checking in" to that tower?

Thanks for help, I'm fairly new to scanning, I've had my scanner for awhile, I'm just not getting around to wanting to have a good grasp on how they function.

You can lockout the talkgroups you don't want to hear and still monitor the site. You will still get the affiliations on your local site even if you remove the York site.

W8RMH said:

It can be explained in one word, Affiliation

An important concept to understand with networked systems is affiliation. Affiliation is what happens when a specific subscriber's radio is using a specific site to communicate with the trunked system; it "checks in", and this causes talkgroup traffic for the talkgroup to which that radio is "tuned" to appear on that particular site/tower.

Trunking Basics 3.1 - Affiliation

Click to expand...

But that would have nothing to do with the scanner appearing to tune to a site 100 miles away. The scanner, when tuning to a TG that is used 100 miles away and carried on a local site will show the local site. (unless the programming is erred in some way and a TG is programmed to be Site X which it should never be)

Voyager said:

But that would have nothing to do with the scanner appearing to tune to a site 100 miles away. The scanner, when tuning to a TG that is used 100 miles away and carried on a local site will show the local site. (unless the programming is erred in some way and a TG is programmed to be Site X which it should never be)

Click to expand...

You are missing the way affiliation works from the radio system system point of view. It has little or nothing to do with the scanner programming. If I have a radio A, with agency A that normally affiliates with tower A, and carry that unit with me to a neighboring county (B), on a regional or statewide network, if the radio has the permission to do so, it will affiliate with tower B, which now begins broadcasting all of the traffic from tower A and agency A for me to hear, and allows me to talk back to users on tower A via microwave or fiber backhaul. The traffic will display from whatever agency or TG radio A is usually affiliated with as that is where the traffic is coming from for purposes of the .

This is a huge concern on the user and system side of things for heavily loaded sites because for example if a tower that normally serves Minneapolis has a user (EMS for example) transport a patient to Rochester MN, the traffic from Metro comms could easily overwhelm the system in Rochester.

n0esc said:

You are missing the way affiliation works from the radio system system point of view. It has little or nothing to do with the scanner programming. If I have a radio A, with agency A that normally affiliates with tower A, and carry that unit with me to a neighboring county (B), on a regional or statewide network, if the radio has the permission to do so, it will affiliate with tower B, which now begins broadcasting all of the traffic from tower A and agency A for me to hear, and allows me to talk back to users on tower A via microwave or fiber backhaul. The traffic will display from whatever agency or TG radio A is usually affiliated with as that is where the traffic is coming from for purposes of the .

Click to expand...

First, I know exactly how affiliation works. And affiliation has nothing to do with receiving a site 100 miles away on a scanner on an RF channel.

Yes, you will hear a TG that is used 100 miles away if a unit is affiliated on a local site, but you will hear it on the local site, not on the one that is out of range.

The the odds are overwhelmingly large that you were hearing the distant traffic broadcast from a local site due to affiliation, rather than actually hearing traffic from the distant site directly.

Scanners don't differentiate between sites. If two or more sites in a system all share a common frequency (as a potential control channel), the radio will show "that site" on the screen when listening to a closer site using the same frequency as its own control channel. As an example, 771.59375 is a control channel for a trunked site quite near to me, named Radnor. It's also a control channel for a site about 60 miles distant, named Longview. If I allow that distant site to be scanned by my scanner, it will say I'm "on" the Longview site, even though I am very obviously hearing Radnor. Scanners do not pay attention to the site number that the site broadcasts (or at least don't seem to - I can't profess to know what the code actually looks like inside the radio). If it gets a signal on frequency xyz and the system ID and protocol type match, it'll find a match for frequency xyz in your programming and show it to you.

Now, I don't know how this is happening in the OP's particular case, since none of the frequencies seem to be identical (or even close enough) such that he would be receiving it on "the other" site. Unless 156.1425 and 156.135 are close enough that the radio is picking up the signal when tuned that far off center.

Jay911 said:

Now, I don't know how this is happening in the OP's particular case, since none of the frequencies seem to be identical (or even close enough) such that he would be receiving it on "the other" site. Unless 156.1425 and 156.325 are close enough that the radio is picking up the signal when tuned that far off center.

Click to expand...

Good point, and one I made in post #2. But, look again - the two control channels are 7.5 kHz apart. Although I suspect you made a typo in "156.325" and meant 156.135, as I'm sure you know that. If the scanner is say 2.5 kHz off frequency (not unheard of), it might be picking up the local site on the distant site's frequency.

Regardless, it is very unlikely that he is actually picking up the site 100 miles away. (again, not impossible, but unlikely)

Programming could also be an issue here. Depending on how the system was programmed into Freescan. But I think that affiliation is what is happening here. Zeroxysm did not explain clearly how this “stuff” is showing up. Is the actual display showing this or is it the police units in the field calling out the tower names. Here in Wisconsin the state patrol calls out their badge number and the closest tower name. The radio traffic is pushed out to many or all towers in an area. This is how my Grandpa thinks he can pick up State Police from over 150 miles away. He is actually hearing the radio traffic from the tower 2 miles from his house, not 150 miles away.
I would guess that the ROC calling channels may be statewide or regional talk groups. So they would be affiliated with several or all towers since they are calling talk groups.

I think that Zeroxysm needs to maybe group the talk groups into separate groups then to add quick keys to site and groups. FreeScan User Guide - The RadioReference Wiki

You should not be always scanning a tower that is out of range. Wastes resources of the scanner. Set up site quick keys to turn sites on and off.