SDS100/SDS200: police scanner and technical functionality

[OPTreadstone]

Hello, I am currently about to buy a police scanner sds100 uniden and what i am looking for exactly is to detect the presence of law enforcement officials nearby by only picking the signal (such between 1 and 5 mile away) but i am not 100 percent sure if this device can only pick cell tower repeaters , and unfortunately I cannot find enough information about it. Does anybody here can help me tell me if this device fits for my technical purposes?

 

[dave3825]

what i am looking for exactly is to detect the presence of law enforcement officials nearby by only picking the signal (such between 1 and 5 mile away)

Hmmm, may we ask why you need to detect the presence of police close to you?

 

[nessnet]

That is not how it works.
LE (law enforcement) uses sites (towers) that both dispatch and the officers out in the field use to communicate.
They cover a much wider area then you are looking for.
Depending on the system and it's configuration - many miles more than 1 to 5...

There is something called close call, but I seriously doubt it'd be reliable enough for you.

Then, depending on where you are at - there is encryption. You will hear nothing no matter how far or close they are.

Now, if you want a scanner to hear what is going on in your county or city, that is another story (unless encrypted).

 

[mmckenna]

Hello, I am currently about to buy a police scanner sds100 uniden and what i am looking for exactly is to detect the presence of law enforcement officials nearby by only picking the signal (such between 1 and 5 mile away) but i am not 100 percent sure if this device can only pick cell tower repeaters , and unfortunately I cannot find enough information about it. Does anybody here can help me tell me if this device fits for my technical purposes?

It's not going to work that way in most cases.

The days of a single frequency system are well behind us. While some still do use radios that way, it's getting more and more uncommon.

Most public safety systems are going to use repeaters, so you'd need to know the frequency the hand held and mobile radios transmit on, not the output of the repeater. That information is not hard to find. But the range is going to vary based transmitter output power, antenna, topography, buildings, interference, etc.

To make it even more complicated, trunked radio systems used in most large cities, will use any number of frequencies for the radios, the exact frequency used by the portable or mobile radios will be based off what the trunked radio systems tells it to use.

It would be difficult to have anything reliable like this.

And I think others may be under the impression you have some nefarious reason for wanting to know where law enforcement radios are. I'm not going to make that judgement. But it might help your case if you explained why you wanted this capability.

 

[jtwalker]

The concept of a “repeater” or more likely a “trunked radio system site” and a police officer being 1-5 miles away are in conflict with one another. You can use close call to pick up signals close to you, but it’s probably going to be more like < 0.5 mile radius of the radio that is transmitting.

 

[wtp]

i use trunked input freqs all the time and used repeater inputs years ago.
you don't hear the base, but you get the local stuff.

 

[n1chu]

Listen to the inputs and run the attenuator option.

I’m not concerned with nefarious intentions in this instance… the police have other forms of communicating when they suspect they are being monitored. A perfect example of this is the catalytic converter thefts… I hear nothing regarding police activity (with the exception of a citizen wanting to report after-the-fact the theft of a converter where an officer is dispatched for report writing.) My guess is everything else is via cell phone or MDT’s.

 

[Whiskey3JMC]

Welcome to the forums @OPTreadstone. It would help if you stated the agency(ies) City/State you intend on monitoring. You're certain they aren't encrypted? You can certainly monitor input frequencies but: 1.) a unit needs to be in extreme close proximity to you, maybe a few blocks at the most? for your scanner to get a hit & 2.) You won't hear dispatch's (or units further away) reply until you monitor the output frequency(ies)

 

[hill]

You would basically need two scanners one programmed to the input frequencies for the close units and one to receive the distance unit's plus dispatch.

I listened to the inputs many years ago before trunk tracking scanners came out just to monitor a local event with hearing the whole county. Worked well, but all were in a very small area.

 

[GROL]

Radio frequency propagation can be very unpredictable. Depending on an infinite number of factors of too many to easily list, a 100 miliwatt signal could potentially be received farther than a 100 watt signal under various conditions. In order to be able to detect the presence of anyone using a two way radio, it is necessary to severly limit the sensitivity of a receiver, such that the signal would be within maybe a few hundred feet of you in order to limit it from detecting things miles from you without using a directional antenna, and even then reflected signals can defeat a directional antenna. Trying to use a scanner to detect the location of anyone using a two way radio is a futile effort. Even signal triangulation can be problematic.

 

[GROL]

Listen to the inputs and run the attenuator option.

I’m not concerned with nefarious intentions in this instance… the police have other forms of communicating when they suspect they are being monitored. A perfect example of this is the catalytic converter thefts… I hear nothing regarding police activity (with the exception of a citizen wanting to report after-the-fact the theft of a converter where an officer is dispatched for report writing.) My guess is everything else is via cell phone or MDT’s.

Law enforcement make extensive use of cell phones when doing surveillance.

 

[nessnet]

Some of the warrant/major crimes taskforces out here use ESChat, which is a PTT over cellular application.

That is until they switch over to PSERN, the new P25II system latter this year- and encrypt.

:-(

 

[Randyk4661]

Listen to the inputs and run the attenuator option.

I’m not concerned with nefarious intentions in this instance… the police have other forms of communicating when they suspect they are being monitored. A perfect example of this is the catalytic converter thefts… I hear nothing regarding police activity (with the exception of a citizen wanting to report after-the-fact the theft of a converter where an officer is dispatched for report writing.) My guess is everything else is via cell phone or MDT’s.

I would use the inputs to the repeaters as well, HOWEVER remember if they aren't talking on the radio, it's not going to help you when they are hiding behind the billboard waiting to catch speeders. The SDS100 mutes the audio on encrypted traffic so you may still not hear anything.

 

[mmckenna]

The issue with listening to trunked system repeater inputs:
There are other users on most of those systems.
You have no idea what site they may end up on.

It's not going to be simple.

 

[Randyk4661]

The issue with listening to trunked system repeater inputs:
There are other users on most of those systems.
You have no idea what site they may end up on.

It's not going to be simple.

Exactly.
If the poster is experienced then he might have a chance. If he isn't, there will be a used SDS100 for sale soon.

 

[PD47JD]

Hmmm, may we ask why you need to detect the presence of police close to you?

I suspect he fears the Eye is on him.

 

[nessnet]

If you want to know if there is a cop "hiding behind a billboard", get a V1 with JBV1 or an R7/8.

Scanners, basically. will not do what you want.
Most 21st century LE uses trunking, even in many rural areas now.
Trunking makes knowing what the channel grants are a necessity, to follow any radio traffic (or know what freq a cop is using at that moment).
Thus, you are always monitoring an area, not your immediate vicinity.

It's just how it works nowadays.

BTW, if "trunking" is a foreign term to you - ask.
It is basic to understanding how modern public service radio system works.
(Unless you are out in the boonies and they still use conventional....)

 

[PD47JD]

Listen to the inputs and run the attenuator option.

I’m not concerned with nefarious intentions in this instance… the police have other forms of communicating when they suspect they are being monitored. A perfect example of this is the catalytic converter thefts… I hear nothing regarding police activity (with the exception of a citizen wanting to report after-the-fact the theft of a converter where an officer is dispatched for report writing.) My guess is everything else is via cell phone or MDT’s.

In New Haven equipment is borrowed from FBI Regional Tech Support (New Haven field office).

 

[nessnet]

In New Haven equipment is borrowed from FBI Regional Tech Support (New Haven field office).

WSP (State Patrol) uses 3 systems, depending on the district here.
One of them they 'piggyback on' is JIWN, which is the Fed's 170Mhz P25II system.
(FBI, DHS, CBP, USCG, etc, etc...).
Lots of DEs in RR, however, WSP still is in the clear.

 

[Boilermaker]

what i am looking for exactly is to detect the presence of law enforcement officials nearby by only picking the signal

Try this: The Police Detector Detects Police Cars