Question about psp and "opensky"

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rrbum

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I am trying to understand this system. I would appreciate if anyone could help me with a few questions.
I guess what I am trying to figure out is if, when a patrol car is on the network and on duty is it constantly connected (similar to a cellphone call) or does it behave like a standard two-way radio system?
Basically I am curious as to what frequencies are eminating from the unit at any given time. For instance, if a patrol car comes within range of my antenna is there any way to pick it up. I understand that the modulated information is unobtainable but is there a carrier which can be detected and cause a scanner to stop on that frequency?
Thanks in advance to anyone that understands what I mean and can clear this up for me.
 

n3obl

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opensky uses freqs in the 851-854 range. The system is a cellular like system. There will never be a scanner made to monitor even without the encryption as ma-com patented the technology and will never license it to scanner mfg's

Frank
 

K3HY

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If you monitor only the input frequencies, shouldn't you hear a data burst coming from any kind of unit that is very close?
 

W2SJW

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Possibly yes, but the system works very much like a cell system - there are two frequencies per tower, and the constant data stream you hear on the one active channel of the two is the full-time bi-directional way that voice & data flow into & out of the system.

It's not like other system's control channels (that tell the radio what frequency to go to)...
 

fourthhorseman

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so it uses the 2 channels,so are they operating like ports on a computer/lan-wlan connection?..ports being individual users?
 

W2SJW

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No. From what I understand, the second channel will come on-line based on traffic load.

With the system running in it's normally-designed 4:1 TDMA mode, those 2 frequencies can support 8 simultaneous conversations.
 

69Z28

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Open Sky is a proprietary type system.

I believe that each car and each officer is given a log in name and number.
When the log in - all calls directed at them are transmitted either phone - audio or digital data - the computer screen mounted on the dash.

They do have two car to car frequencies which are just digital and 850 something mhz, along with 2 lower band - 155 - 157 mhz frequencies - narrow band.
With the equipment in the car, it also operates a cell phone which they carry, along with the local police and fire and ambulance, county control - ( 450 - 460 mhz ) ( 155 - 157 Mhz )

The neat thing about it is - the broadcasts between the dispatcher can be sent directly to the one car and no one else can hear it, or it can be sent as a general broadcast to all cars in the area.

A car in Pittsburgh can talk to a car in Philadelphia PA because of the way it is linked.

It is possible to hear the car to car traffic, you just have to have a digital scanner and be at the right place at the right time.
The 850 mhz signal only travels a mile or so - in my neighborhood - so unless you are right on top of it, you would never hear it.

There are handheld two way radios - Motorola - which can receive Open Sky - if it is set up to receive it.
The thing about it is - you have to find someone who is a Motorola technician / tower technician - that can set it up.

There is nothing in this world that you cannot listen to - because somewhere in this world, someone has to have access to this technology in order to maintain it.
The problem is - with all the digital data being used, there is not much phone traffic anymore.
It is all dispatched via the computer.

When the information is dispatched, it gives the names and the addresses and even a map showing the officer how to get there from where they are at.

The system knows where the car is at at all times.

Before 911 - the intention was to make some monitors which could be used by the newspapers etc - to monitor the frequencies.
After 911 - forget it.

Harris EDACS P5450 P5400 P-25 Upgradable | eBay

I sent a email to a friend of mine who is a Motorola Tech about this handheld and got no reply.
 

n3obl

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I call BS on a motorola handheld being able to receive opensky. Harris will never license the opensky protocol to motorola. Ive seen PSP troopers carrying MACOM portables P7100 series. Some users have the older portables that look like kenwood tk-x90 series radios with top display.


Im currently sitting at my work with a DOH control station sitting behind me. Every so often I hear activity on one of the PEMA channels.
 

ocguard

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I call BS on a motorola handheld being able to receive opensky. Harris will never license the opensky protocol to motorola. Ive seen PSP troopers carrying MACOM portables P7100 series. Some users have the older portables that look like kenwood tk-x90 series radios with top display.


Im currently sitting at my work with a DOH control station sitting behind me. Every so often I hear activity on one of the PEMA channels.
Correct. The only time a Motorola radio would be communicating with an OpenSky radio would be in a conventional mode, either analog or P25. Most of the newer OpenSky platforms (such as the P7100 mentioned) can also operate in P25 conventional. There is no Motorola radio that can operate in the OpenSky protocol.

I'm not sure what 69Z28 means about equipment in the car and a cellphone that they carry. The portable radios on the OpenSky system depend heavily on the vehicle repeater to connect to the network, as the system itself is only designed for mobile coverage (and mobile coverage isn't even that good). So the portable radio networks with the higher-powered mobile vehicular repeater (known in OpenSky lingo as a VTAC), then connects to the network. PSP used vehicle repeaters (or mobile extenders) for portable radio use on the VHF system heavily too. The only time a portable on the OpenSky system could connect directly to the network (without using the VTAC) would be if the radio was extremely close to a cell site.

While OpenSky may in fact have the ability to operate in full-duplex mode (where both parties can talk and listen at the same time -- similar to a telephone), the portable and mobile radios used by PSP, to the best of my knowledge, do not have this capability.

And because of the very limited network capacity at each cell site, unit-to-unit private calls are very limited. The majority of calls for PSP and PennDOT are group calls, just like on a standard dispatch system.
 
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