Input frequencies

radioboy75 · Feb 6, 2018

Is there a place where I can find the callsigns for the individual towers on the SD trunked system?

What I'm really looking for is the input frequencies to the various repeaters.

I heard a helicopter using NAC A0 (the South Dakota system) on a 153.XXX frequency. I'm pretty sure, based on the NAC that it was talking into the SD system.

That raised a question in my mind of what are the input frequencies for the voice channels in my area . . .

Anybody know how I could find out?

troymail · Feb 6, 2018

There's lots of info here:

https://www.radioreference.com/apps/db/?sid=2315

in both the "News" section and when you click on the links for the site locations.

You can also do searches in the FCC database.

None (even the FCC data) are likely to be 100% accurate but it helps.

radioboy75 · Feb 6, 2018

Yeah, I've been there. Both places. I did find the frequency in question (153.170) but it is a single frequency on a single callsign, so it wasn't much help in finding any others. However, I am now pretty sure that 153.170 is one of the inputs to the Sioux Falls tower(s). Maybe I'll just take along a scanner next time I visit Sioux Falls and try to find the inputs by searching . . . However that's not much help in finding the other towers' inputs, but it's a start.

WA0CBW · Feb 6, 2018

What was the station class for the frequency? If it was an FX1 ( control station) it would be the input to a repeater.
BB

SCPD · Feb 8, 2018

radioboy75 said:
Is there a place where I can find the callsigns for the individual towers on the SD trunked system?

What I'm really looking for is the input frequencies to the various repeaters.

I heard a helicopter using NAC A0 (the South Dakota system) on a 153.XXX frequency. I'm pretty sure, based on the NAC that it was talking into the SD system.

That raised a question in my mind of what are the input frequencies for the voice channels in my area . . .

Anybody know how I could find out?

NAC A0 on the SD system talk group wise is Animal Industries Board... no helicopter for them. Sanford and Avera out of Sioux Falls fly rotor wing (helicopter) over that part of Iowa all the time so Im sure it was them... Just curious... why are you curious on the input? For a trunking system most people only care about the voice channels and there output. The tower that you would have heard that helicopter on would most likely be the SF simulcast system.. could have been the Beresford tower but it has terrible coverage to the east it seems.

radioboy75 · Aug 3, 2018

Sorry, but I literally just saw this six-month-old message.

You're misunderstanding me. A0 in my message did not refer to a talkgroup.

I was searching the 150-160 MHz band in CONVENTIONAL mode -- so my scanner would not have displayed any talkgroup information. A0 NAC is what shows up when you monitor the SD system in conventional mode -- any talkgroup, any tower -- it doesn't matter.

I'm well aware of what helicopters fly over here. They serve our local hospitals, which are affiliated with them.

As to why I want to know the inputs -- I'm on the fringe of the SD systems over here. But helicopters are high up in the air, so they could use the SD system from here if they wanted to because their altitude gives them better coverage. So if I could monitor the inputs in conventional mode -- even though I couldn't hear the actual tower that they're using, I could still hear what they transmit from the helicopter and get that side of the conversation.

Also, for listening to ground-based vehicles, monitoring the inputs gives you a good idea of how far away a mobile unit is from you. Since car-car FM VHF only works for about 5-7 miles, you know they have to be at least that close to you if you can copy them.

And actually, I pick up Beresford better than any other tower from my location.

Signal strengths as of right now:
Beresford -25 dB
Sioux Falls -32 dB
Wall Lake -34 dB

Rlahey · Aug 3, 2018

radioboy75 said:
Sorry, but I literally just saw this six-month-old message.

You're misunderstanding me. A0 in my message did not refer to a talkgroup.

I was searching the 150-160 MHz band in CONVENTIONAL mode -- so my scanner would not have displayed any talkgroup information. A0 NAC is what shows up when you monitor the SD system in conventional mode -- any talkgroup, any tower -- it doesn't matter.

I'm well aware of what helicopters fly over here. They serve our local hospitals, which are affiliated with them.

As to why I want to know the inputs -- I'm on the fringe of the SD systems over here. But helicopters are high up in the air, so they could use the SD system from here if they wanted to because their altitude gives them better coverage. So if I could monitor the inputs in conventional mode -- even though I couldn't hear the actual tower that they're using, I could still hear what they transmit from the helicopter and get that side of the conversation.

Also, for listening to ground-based vehicles, monitoring the inputs gives you a good idea of how far away a mobile unit is from you. Since car-car FM VHF only works for about 5-7 miles, you know they have to be at least that close to you if you can copy them.

And actually, I pick up Beresford better than any other tower from my location.

Signal strengths as of right now:

Beresford -25 dB

Sioux Falls -32 dB

Wall Lake -34 dB

So if you were listening in conventional mode you shouldn’t hear any traffic on the state system since it is technically digital (still not P25) but I digress. The NAC code really doesn’t play into trunked systems as they don’t use NAC codes..

But anyways yes I agree finding the input frequencies is difficult and frustrating sometimes

Sent from my iPhone using Tapatalk

radioboy75 · Aug 3, 2018

CONVENTIONAL, but DIGITAL.

I was listening on a digital scanner that receives P25 -- just not in trunking mode.

(I know the SD system doesn't meet all the requirements to be a pure P25 system, but I digress)

And the NAC doesn't enter into it for scanner listeners, but every P25(ish) trunking system has a NAC, and I think they use it to keep out interference from other signals on the same frequencies (same as a PL or DPL on an analog repeater)

Rlahey · Aug 3, 2018

Okay I thought you meant analog convetional

and I stole this from another post relating to NAC codes and mixed mode trunking:
3600: For P25 trunked traffic channels the NAC consists of the last two digits of the system ID and the connect tone in the format [AAB] A is the sysid and B is the connect tone.

So kinda a NAC code but not like an astro trunking system

radioboy75 · Aug 8, 2018

I don't know about that. That may be true. All I can tell you is what shoes up on my Homepatrol when I monitor the SD system in conventional digital mode. "A0" always comes up as the NAC. Whether that's the official NAC or just how the Homepatrol displays it, I do not know. But whenever there's traffic on any frequency that is a repeater on the SD system, the Homepatrol shows "A0" for the NAC.

To get into it a little further and go only slightly off-topic, on Minnesota's system, each tower shows a different NAC in conventional digital mode on my Homepatrol. Some of the towers around me are 400, 401, 402, 40D, 40E, etc.

That same code also comes up when I monitor it on my RTL-SDR dongle and DSD+ software.

radioboy75 · Jan 22, 2019

From what I can tell, the inputs seem to be concentrated (in my area at least) in the 153 and 154 MHz area and the 158 and 159 MHz area. Anybody else searching for these? It's kinda fun.

Input frequencies

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