DE, NJ, PA, NY Linked Fed System

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naSTI

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Okay from my vantage point (location and excellent antenna height) I get to receive stations from all four states. I've recently come across a chain of linked P25 systems that are running full-time DES-OFB. The transmissions come *very* seldom.

I get all of the following systems synchronously repeating the same traffic:

167.4375
167.4625
167.5875
171.6125
172.1125
172.7625

All using NAC $207. This NAC code is used by no other agencies I'm aware of, which leads me to believe it's likely a shared crime info network above and beyond FIO, which is more e-ops and tac based. I know some of the freqs are well-known, old-time FBI freqs and others seem to be new NTIA allocs.

There are a couple more freqs I suspect are participants in the network I have yet confirmed, so I have not listed them. I receive these stations varying from S1 to +40db over. Using a log I know they are scattered through-out Philly, Allentown, Atlantic City, Trenton, NYC and possibly in DE/MD.

Anyone have any idea what agency(ies) this might be?

naSTI
 

ecps92

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The 167's are FBI, so the assumption is the rest of them are also FBI.

The common theme with many of the FBI Networks were to use ONE Input to
multiple Outputs for the Repeaters.[Back in the CTCSS/DVP Days] This allowed units to trip multiple repeaters, which many have confused with LINKED Repeaters or Patched Repeaters for years.

ie: 164.1500 was the input for many year for all the New Hampshire Repeaters

Okay from my vantage point (location and excellent antenna height) I get to receive stations from all four states. I've recently come across a chain of linked P25 systems that are running full-time DES-OFB. The transmissions come *very* seldom.

I get all of the following systems synchronously repeating the same traffic:

167.4375
167.4625
167.5875
171.6125
172.1125
172.7625

All using NAC $207. This NAC code is used by no other agencies I'm aware of, which leads me to believe it's likely a shared crime info network above and beyond FIO, which is more e-ops and tac based. I know some of the freqs are well-known, old-time FBI freqs and others seem to be new NTIA allocs.

There are a couple more freqs I suspect are participants in the network I have yet confirmed, so I have not listed them. I receive these stations varying from S1 to +40db over. Using a log I know they are scattered through-out Philly, Allentown, Atlantic City, Trenton, NYC and possibly in DE/MD.

Anyone have any idea what agency(ies) this might be?

naSTI
 

HM1529

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The 167's are FBI, so the assumption is the rest of them are also FBI.

The common theme with many of the FBI Networks were to use ONE Input to
multiple Outputs for the Repeaters.[Back in the CTCSS/DVP Days] This allowed units to trip multiple repeaters, which many have confused with LINKED Repeaters or Patched Repeaters for years.

ie: 164.1500 was the input for many year for all the New Hampshire Repeaters
I wouldn't expect this to be an FBI net. The geographic area mentioned is covered by four different FBI Field Offices (Philly, Baltimore, Newark, and NYC). All of these offices have their own channel plans and are operating mixed analog and digital repeaters as they migrate. The digital repeaters have been noted with NAC's of 167.
 

Gilligan

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The common theme with many of the FBI Networks were to use ONE Input to multiple Outputs for the Repeaters.[Back in the CTCSS/DVP Days] This allowed units to trip multiple repeaters, which many have confused with LINKED Repeaters or Patched Repeaters for years.

ie: 164.1500 was the input for many year for all the New Hampshire Repeaters
Do you have any more information on this? I am trying to figure out why they would have set it up as such. It's easy to see why you'd want different inputs keying different repeaters all with one common output. But why have one common input keying several different repeaters? So each unit would just tune in their local repeater? Something just doesn't make sense to me about it. Please help me to understand the concept, as I am very interested in how these kinds of networks function. There are similar ideas often times w/ forest and parks networks. Thanks.
 

APX8000

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Many federal repeater networks use one input and several different repeater outputs (old INS, now ICE for example). The input frequency is on a voter, which sends the best signal through. All the repeaters are linked, so as the repeater with the best signal keys up, the link frequency also keys up all the other repeaters at the same time on all the other frequencies.

If the repeaters were on the same frequency, you would need to simulcast the transmitters at the EXACT same time, which requires ALOT more equipment, testing, etc.

With the above setup using different repeater outputs, the person in the field uses a "voting scan" option in their radio. So, even though he may be able to hear two of the repeaters from his location, his radio will scan and lock on to the repeater with the strongest signal. As this person travels from state to state, area to area, etc., they don't even need to change channels...the voting scan will change the channel for them.

You could also not use voting scan, and just tune directly into the repeater with the best output signal.
 
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ecps92

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Best of luck hunting.
I've seen the FBI 167.9 Hz migrated to the 167 Nac
many agencies did the same thing to make an easy
translation, however many others FBI Field Offices
did use different NAC's :(

I wouldn't expect this to be an FBI net. The geographic area mentioned is covered by four different FBI Field Offices (Philly, Baltimore, Newark, and NYC). All of these offices have their own channel plans and are operating mixed analog and digital repeaters as they migrate. The digital repeaters have been noted with NAC's of 167.
 

ecps92

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As someone else suggested, Voter Sites, but nope, not what I have experienced in New England.

One Input, Multiple Outputs


this allowed units to travel a Region [southern NH vs northern NH] and only hear the traffic
for the input channel. Works well here in New England with all the Hilltops


Do you have any more information on this? I am trying to figure out why they would have set it up as such. It's easy to see why you'd want different inputs keying different repeaters all with one common output. But why have one common input keying several different repeaters? So each unit would just tune in their local repeater? Something just doesn't make sense to me about it. Please help me to understand the concept, as I am very interested in how these kinds of networks function. There are similar ideas often times w/ forest and parks networks. Thanks.
 

Gilligan

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So w/ FBI for example, do they link the repeaters w/ microwave or UHF? I would assume they would be fairly directional links, cause I've never heard FBI on UHF.
 

ecps92

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In the past few years, it appears they have moved to Land-Line" to trip the various Repeater from the Dispatch Point, altho a few UHF [406-420] channels still exisit in New England and even NY [just outside NYC]

The linking of Repeaters [New England] is not really linking. It's One Channel input with Multiple Outputs.
Depending on where the Radio is, and Port vs Mobile they might trip One, Two, Three or more of the repeaters. Depends on Wattage, Terrain etc.



So w/ FBI for example, do they link the repeaters w/ microwave or UHF? I would assume they would be fairly directional links, cause I've never heard FBI on UHF.
 

naSTI

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I wouldn't expect this to be an FBI net. The geographic area mentioned is covered by four different FBI Field Offices (Philly, Baltimore, Newark, and NYC). All of these offices have their own channel plans and are operating mixed analog and digital repeaters as they migrate. The digital repeaters have been noted with NAC's of 167.
I partially agree with your statement. Would it stand to reason this may be an intra-office network and not a day-to-day field network (Channels A1..D10)?

naSTI
 

Gilligan

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The linking of Repeaters [New England] is not really linking. It's One Channel input with Multiple Outputs. Depending on where the Radio is, and Port vs Mobile they might trip One, Two, Three or more of the repeaters. Depends on Wattage, Terrain etc.
This appears to be the way that the Oklahoma FBI repeaters are currently set up. What I usually do is set up my scan list for the weakest repeaters first. That way, when the transmissions cut in and out, I can hear if they are going out over the closer repeaters as well.

I still do not understand the idea of setting up repeaters in this way, however. It appears that most (if not all) Oklahoma FBI regional dispatch repeaters are using a common input of 164.425 MHz.

Consider this scenario: Three local repeaters in the OKC and surrounding areas are on 170.950, 167.2375, and 167.3875. If a field agent is travelling through the metro, he may key up all three repeaters at the same time. Those last two (2375 & 3875) are not for the OKC metro but for outside the metro (somewhere). So if they belong to a field office in a nearby county, then that guy has to listen to all these OKC agents keying up his repeater with a weak, unreadable signal.

Let me add that I do not think these repeaters are linked in any way at all (landline, network, etc).

I thought I heard Stillwater guys talking to Enid guys because of sharing the same input (they may have been keying up each other's repeaters). But outside of wanting to key up multiple repeaters, doesn't this method drive the agents nuts when they hear distant transmissions making it into their local repeaters?
 

zerg901

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My guess is that the FBI radio systems are primarily set up for wide area surveillance operations. With the scanning/voting receiver in the cars (as was mentioned earlier), the agents can travel over wide areas without changing channels.

If Enid OK agents are causing interference to Stillwater agents, I suspect that the FBI would give each group of agents a separate system. Perhaps 1 dedicated repeater in each community, or a group of dedicated repeaters in each community (each with a different input freq no doubt).

http://www.fbi.gov/contact/fo/territory.htm - This URL shows that 1 FBI Field Office covers all of Oklahoma. Maybe all of the nets in Oklahoma are statewide.

Maybe the FBI has the capability to split a statewide net into 2 or 3 separate regional nets if they are running multiple surveillances at the same time.

And to throw one more rinkle into the situation, I thought that the FBI purchased radios within the last 10 years that use GPS to automatically switch the radio to the correct / best repeater for any given location.

Peter Sz
 

SOFA_KING

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You can see into several states, but you may be hearing a system in only one state or wide area. I have never heard of a system that covers several states or known agency areas. Those sound like D of J pool freqs to me, but it could be any one of them. Maybe Marsh by the upper freqs, but could also be "B of I" by the lower. Two of the lowers were confirmed analog "B of I" in my database at one time when I lived up there. RA's used many freqs in the upper portion. The NAC is interesting as it doesn't follow what others are reporting.

I was BIG into searching and database recording this stuff in upstate NY and NYC area in the late 90's and the S. FL area from 92 to 97, and 99 to just a couple of years ago. Things are changing here in FL. As agencies are moving to digital, and some old systems have either moved or are combined. I have a lot to catch up on. I came here looking for advice on a possible new scanner that has NAC. (I could use some advise here...help me out!) Is it only GRE at this point? If so...how good is it? Software for logging NAC hits???

What I do know is that the "B of I" did go P25 here not long ago, and it looks like the system channels did change. They are doing P25 multi-cast on different channels in different areas just as they have always done (A1, A2, A3...). Here in S. FL they had core freqs in the main 167 portion, and then rural RA freqs outside usually up in 168 area and above. They also used to use UHF fixed links here in FL and in NY, but I work at tower sites and T1 equipment carries the encrypted link data now here in FL. What I have also found over the years is that there is a pool of freqs that "D of J" agencies use at their choosing in different areas of the country. What may be "B of I" in one area could be "Marsh" or "I and NS" in another. The PL tones and protocals, as well as radio system design (OTAR or other unique features like MDC1200) would confirm who was who, as well as the rare call sign usually only now using the callsign numbers (ie 300) without letters.

A few years ago my database freq list was nearly full and VERY accurate! I created 1000 channel scan lists and I was just listening to empty channels with software PL tracking looking for ANYTHING new or unknown. We get a lot of tropo openings here in FL, so I really raked em in. I got tapped out with nothing new to discover! The "SS" was the first to go P25 here. No channel changes I could see. Then "AT & F" went, and although they are still on the main channel, I do not know if they have changed others. The old "Marsh" analog went dead a couple of years ago. Some big P25 RPTR is now active on one of the old inputs in the Miami area (170.7500), so that might be them, however and I have not heard much else. I'm sure they're on some other channels as well, but I got too busy at work to continue the hobby. Someone "in the know" mentioned they use "the new D of J system", so that may be it. And what about "D of HS"? Where are they?

I'm getting interested again with all these new changes, but I need better equipment. With the "B of I" now P25, I would like to set up a new software controled system that can capture NAC, PL, DPL, and do the "fill the blanks" type of database thing again. No doubt, things have changed and I need to look at new possible freqs. "Cust" is still analog, but for how long? I don't hear any trunking control channels other than the old UHF stuff up around the Cape. Maybe I should look around more here on this forum and see what I'm missing.

BTW - When comparing info that other people have reported, I find so many errors that I can't believe some people can be so far off. A lot of it is VERY old data that had errors to begin with. These obvious errors keep getting passed onto other lists, and some of it is SO wrong that I discount the whole list. The business of cross user/task force freqs is not to be considdered IMO. What you need to focus on is WHO built the system you are listening to. Who hosts it? And understanding the system is key. I know first hand that cross-agency is always going on. Who cares? You just need to tie the systems together. This hobby is fun when you get it right and understand the systems and how they work. Getting mobile to mobile simplex freqs tied to a system is tough when not on a known output, but that is where NAC and PL come in handy as well as formats and ID's. ;) That is the hard part, but what a feeling when you "got 'em all". :) Then you use one scanner to listen to the "knowns" and another to listen to the "empties". :D
 
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