Scanning Repeater Input Frequencies - Why would you do it?

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pb_lonny

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In almost all cases, you should program your scanner with the output frequency of a repeater. Since this is the frequency that the repeater is using to rebroadcast all communications and as repeaters with an antenna mounted high up will have much better line of sight to mobiles and portables and cover a much larger area.

When using Close Call mode, you will mostly get hits on the input frequencies of repeaters. This I have found useful for both finding new frequencies in use and also with confirming the user of frequencies, especially on shared repeaters where multiple users are sharing the same frequency but with different CTCSS tones.

As I focus more on traffic analysis (https://en.wikipedia.org/wiki/Traffic_analysis) the content of the message becomes less important than when, where, why and who is using a given frequency. What I have done in the past few weeks is to take a group of the more active frequencies in the Launceston area and program the input frequencies in as below.

72.82500 - ABILITY (TX)
80.15000 - TECS (TX)
80.78570 - LCC (TX)
80.81250 - LCC (TX)
81.53750 - TFS (TX)
81.56250 - AMBO (TX)
157.90000 - BORAL (TX)
158.01250 - TASRAIL (TX)
158.45000 - REDLINE (TX)
158.83750 - TOXFREE (TX)
454.27500 - METRO (TX)
479.42500 - LCC QVM (TX)
479.57500 - LCC PARK (TX)
480.05000 - MARCOMNET (TX)
483.35000 - MARCOMNET (TX)

This limits the radio traffic to only what is physically close to my location. So far my results have been encouraging, a number of times I have been able to visually match what I see (such as trucks from a company who use a shared repeater) with radio traffic on the input frequencies and the matching CTCSS tones.

Over time I will continue to log these results and share them on here and my blog.
 

teufler

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Interesting, and very time consuming I am sure. Here in the states, so many agencies have gone to trunking, its very hard to pick up inputs on 800 mhz. My time is trying to figure out new talk groups, who they are, sometimes checking the unit numbers and comparing to unit numbers that show up on confirmed known talk groups. Equally time consuming, but as scanner listeners, what else we got to do?
 

pb_lonny

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Yes. I also have the input frequencies for my nearest 800MHz EDACS trunking site in a separate bank which I turn on at times but 99% of these are Provoice so not scannable for me.
 

N5XTC

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Interesting, and very time consuming I am sure. Here in the states, so many agencies have gone to trunking, its very hard to pick up inputs on 800 mhz. My time is trying to figure out new talk groups, who they are, sometimes checking the unit numbers and comparing to unit numbers that show up on confirmed known talk groups. Equally time consuming, but as scanner listeners, what else we got to do?
agreed, what else we go to do? lol. for years i had programmed my trunked system by hand and then either looked up the TGs that came in and programmed them OR put in UNID and tried to figure it out myself. was always exciting when a new TG would come in. i guess that is old school anymore as most use software and RR. it does make it a lot easier and quicker. ever see the people who are into battery charging for its own sake? there is a neurotic group. scanners as mere means to drain batteries to recharge them and record the numbers. makes us look normal. lol
 

CrabbyMilton

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I find monitoring the repeater input quite useful. Not just trunked 800 systems but for businesses regardless of frequency. That way if there is something going on nearby, you can monitor that instead of the whole area that the repeater serves.
 

ecps92

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Taxachusetts
YMMV but to answer your input monitoring question.....

a. Some Agencies have the ability to "knock-down" also known as shut off, disable
FDNY calls it a Mixer - the repeater, so only Dispatch can hear the "Sensitive" message
being passed. One of my Local PD's does this regularly - "Code White" , also a near-by
Major Fire Dept has been known to do this, and our Medical Control channels are not
always repeated, but Duplex

b. Identifying the input CTCSS, PL, DPL, NAC, for tracking knowledge.
Helps with interference, image issues
Also agencies have been known to use the input in Simplex mode with Alt Tones.

c. knowing that a unit is near-by

d. YMMV by City/County/State/Country :cool:

In almost all cases, you should program your scanner with the output frequency of a repeater. Since this is the frequency that the repeater is using to rebroadcast all communications and as repeaters with an antenna mounted high up will have much better line of sight to mobiles and portables and cover a much larger area.

When using Close Call mode, you will mostly get hits on the input frequencies of repeaters. This I have found useful for both finding new frequencies in use and also with confirming the user of frequencies, especially on shared repeaters where multiple users are sharing the same frequency but with different CTCSS tones.

As I focus more on traffic analysis (https://en.wikipedia.org/wiki/Traffic_analysis) the content of the message becomes less important than when, where, why and who is using a given frequency. What I have done in the past few weeks is to take a group of the more active frequencies in the Launceston area and program the input frequencies in as below.

72.82500 - ABILITY (TX)
80.15000 - TECS (TX)
80.78570 - LCC (TX)
80.81250 - LCC (TX)
81.53750 - TFS (TX)
81.56250 - AMBO (TX)
157.90000 - BORAL (TX)
158.01250 - TASRAIL (TX)
158.45000 - REDLINE (TX)
158.83750 - TOXFREE (TX)
454.27500 - METRO (TX)
479.42500 - LCC QVM (TX)
479.57500 - LCC PARK (TX)
480.05000 - MARCOMNET (TX)
483.35000 - MARCOMNET (TX)

This limits the radio traffic to only what is physically close to my location. So far my results have been encouraging, a number of times I have been able to visually match what I see (such as trucks from a company who use a shared repeater) with radio traffic on the input frequencies and the matching CTCSS tones.

Over time I will continue to log these results and share them on here and my blog.
 

ofd8001

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Louisville, KY
Every now and then you might see an ageny use a repeater input frequency on a different CTCSS/DCS, etc. as a "discreet" frequency. Since that by-passes the repeater, the average scanner listener won't hear the conversation unless the input frequency is also programmed.
 

wtp

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Port Charlotte FL
why not both ?

i have one main system set with ID search for the new stuff, and many locked out groups.
one system is "open" with no lockouts, so if something happens i can lockout who i want to.
one system is just inputs, for "on the scene" stuff, or a car in the neighborhood.
one is just the outputs and set up as conventioal for a fail soft day, only used once in 10 years.
 

mark432k

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Sioux Falls, SD
Before my old agency went to a trunked system and was using a repeater system, the repeater would be inoperable quite often. We went simplex using the input frequency during these times. Dispatch would relay the messages that we could not hear directly. Plus, as others have eluded earlier, it was a way for us to be sneaky from time to time.

Not a bad idea to at least those input frequencies handy.
 

ecps92

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Taxachusetts
Also [more US, not sure of other countries] but what many folks would consider inputs [+3 Mhz and +5 Mhz for UHF-T/UHF) are also used Simplex manytimes...

Always worth the search of those frequencies

It sure is and I am getting some great results from it ;)
 

majoco

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New Zealand
Not really designed for scanner users, but I always monitor the input frequency of our local repeater when I'm talking with someone - then if I can hear them on the input and he can hear me, we will go to a simplex frequency. I guess most ham rigs just have a pushbutton labelled "Rev" or something to check the input.

Also [more US, not sure of other countries] but what many folks would consider inputs [+3 Mhz and +5 Mhz for UHF-T/UHF) are also used Simplex manytimes.
What does this achieve? You're still blocking the repeater from other users and worse still, you can't hear if anyone distant is trying to get in.
 

KK6ZTE

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Not really designed for scanner users, but I always monitor the input frequency of our local repeater when I'm talking with someone - then if I can hear them on the input and he can hear me, we will go to a simplex frequency. I guess most ham rigs just have a pushbutton labelled "Rev" or something to check the input.



What does this achieve? You're still blocking the repeater from other users and worse still, you can't hear if anyone distant is trying to get in.
Because they aren't always used as a pair. I have more than one customer that uses both channels of their pair as two discreet channels.
 

SCPD

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Virginia
I've seen many use the input with a different tone as simplex aka car to car, talkaround, which depending on programming the radios will use the input as talk around or mobile to mobile. Others will use the repeater rx as car to car or talk around so anyone on repeater will hear the mobiles in talk around. Depends where you go.


YMMV but to answer your input monitoring question.....

a. Some Agencies have the ability to "knock-down" also known as shut off, disable
FDNY calls it a Mixer - the repeater, so only Dispatch can hear the "Sensitive" message
being passed. One of my Local PD's does this regularly - "Code White" , also a near-by
Major Fire Dept has been known to do this, and our Medical Control channels are not
always repeated, but Duplex

b. Identifying the input CTCSS, PL, DPL, NAC, for tracking knowledge.
Helps with interference, image issues
Also agencies have been known to use the input in Simplex mode with Alt Tones.

c. knowing that a unit is near-by

d. YMMV by City/County/State/Country :cool:
 

SCPD

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Virginia
We do this also. The sneaky method. Detectives will be encrypted but will go simplex on the input so dispatch don't hear them if need be. Unfortunately sad but true leaks do arise from dispatch sometimes.


Before my old agency went to a trunked system and was using a repeater system, the repeater would be inoperable quite often. We went simplex using the input frequency during these times. Dispatch would relay the messages that we could not hear directly. Plus, as others have eluded earlier, it was a way for us to be sneaky from time to time.

Not a bad idea to at least those input frequencies handy.
 

KV4BL

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Messages
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Why Monitor Repeater Inputs?

Back in the late 1970's, I lived in one small town and worked in another about 20 miles away as a town cop. The town I lived in was on the Southern fringe of coverage and shared use of that county's Sheriff's Office repeater. Reception of the SO repeater was okay with mobiles and the Motorola ht's used by the town and SO, but not so much with my little xtal controlled Radio Shack pocket scanner. I bought an input frequency crystal and left the delay turned off on that scanner. If I were in a bad reception area, the scanner would frequently skip the repeater channel and monitor closer traffic on the input. I recall attending a Christmas Parade in that town one day and hearing one of that town's cops calling for help in a back lot behind the building I was standing in front of. I was able to run around the block and get to him before others from the SO or his department did. While the troublemakers had made a getaway before I got to him, he was glad for a quick backup, had I been needed. I wouldn't have heard him if just scanning the repeater output.

Until recently when the 800 MHz plague afflicted their comms, as with everyone else, a small city near me was using the input (minus PL/with CS) as a bs channel. This way, they didn't activate their repeater and could hear other traffic on the input if nearby. No doubt, a lot of listeners looked in vain for their "switch over" channel, thinking it was some non-published, secret frequency when it was under their nose all the time.
 

pb_lonny

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Well today this has REALLY paid off.

I was searching the VHF band and came across a signal on the input frequency for a user who I thought had long given up on radio, I had not heard the output frequency for many years. After leaving my radio on this frequency for the afternoon, it appears they have stopped using the repeater and are using the input frequency as simplex.
 

Valeriy

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European Union
In almost all cases, you should program your scanner with the output frequency of a repeater. Since this is the frequency that the repeater is using to rebroadcast all communications and as repeaters with an antenna mounted high up will have much better line of sight to mobiles and portables and cover a much larger area.
That is generally true, but sometimes you can have service vehicles or service personnel with a handheld so close to you that their signal is locally stronger than the repeater's, even in the case they are not so close to trigger a Close Call Hit, so it can be useful having in memory the uplink frequencies as well.

P.S.: when monitoring agencies which use DMR systems, it would be possible to see all their units in the field on a map, but DSD+ doesn't decode all the various standards used to transmit the GPS position, what a pity...
 
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