Argument AGAINST allowing encrypted comms for PD's, SWAT, etc

[Tallpine]

#1 Repeater tower can be configured to handle encrypted or not encrypted frequencies.

#2 All radios must have the same encrypted key or keys to be on a secured network.

#3 If the cops have encrypted radio they would need a non secured radio for, firefights , EMT's , and air recover if, they are not on the same network.
  

So the repeater would have to handle 2 incoming frequencies and 2 outgoing frequencies to support both encrypted and non-encrypted 

[Neemi]

There are too many "laws" on the books for John Q Public to self police itself.

I'd also be worried about some folks' (mis)interpretaion of the laws on the books - and their attempt to enforce the laws as they read them.  Sure, it might not hold up in court, but it would still put a strain on whoever they arrest and has to show up at court.

[Frank Castle]

So the repeater would have to handle 2 incoming frequencies and 2 outgoing frequencies to support both encrypted and non-encrypted

Yes!

[Doggy Daddy]

So, the retired guy doing 55 in the fast lane to keep you from speeding... now he's going to be in your rearview mirror with his Harbor Freight flashing lights?   

[Tallpine]

Quote
So the repeater would have to handle 2 incoming frequencies and 2 outgoing frequencies to support both encrypted and non-encrypted

Yes!

Our county comm guy can barely keep what we have operational.  He is also the chief of EMS.

Main thing that I want to keep track of is when they start chasing somebody through our neighbohood.  Sheriff Woody likes to play Roy Rodgers, except the guy they're chasing doesn't always follow the script. 

I maintain a pretty high level of security all the time anyway (doors locked and sidearm plus rifles handy), but honestly our local LE is more of a hazard to public safety than any kind of protection. 

[Ron]

Our county comm guy can barely keep what we have operational.  He is also the chief of EMS.

Main thing that I want to keep track of is when they start chasing somebody through our neighbohood.  Sheriff Woody likes to play Roy Rodgers, except the guy they're chasing doesn't always follow the script. 

I maintain a pretty high level of security all the time anyway (doors locked and sidearm plus rifles handy), but honestly our local LE is more of a hazard to public safety than any kind of protection. 

Maybe the dept should send him off to a big city for proper training. A couple weeks of training in a big city dept like the LA Police Dept should help 

[Tallpine]

Maybe the dept should send him off to a big city for proper training. A couple weeks of training in a big city dept like the LA Police Dept should help 

Yeah, but who would drive the ambulance 

 

[Frank Castle]

If the local LEO's, are using a non-encrypted radio , you should be able to pick them up with a good scanner. I could take a little while to find the right frequencies. My buddy found the MP frequencies on post with his scanner.   

But you need to remember one thing.....

We are talking about line-sight comm, if the bad guys goes into a heavy wooded area or in a valley comm can get sketchy . Just like a cell phone.

[Tallpine]

If the local LEO's, are using a non-encrypted radio , you should be able to pick them up with a good scanner. I could take a little while to find the right frequencies. My buddy found the MP frequencies on post with his scanner.   

But you need to remember one thing.....

We are talking about line-sight comm, if the bad guys goes into a heavy wooded area or in a valley comm can get sketchy . Just like a cell phone.

Are you talking to me?

I have a VFD pager which monitors our repeater channel.   

I also have a 2-way portable radio, but you can't use it when it is in the charger because of static. 

Our old Radio Shack scanner just up and died last year.

[RocketMan]

So the repeater would have to handle 2 incoming frequencies and 2 outgoing frequencies to support both encrypted and non-encrypted  

No.  The repeater is just repeating the RF audio from the radios in the field, encrypted or not.

eta: correction necessary due to adult beverage consumption

[Tallpine]

No.  The repeater is just repeating the RF audio from the radios in the field, encrypted or not.

eta: correction necessary due to adult beverage consumption

Yes!

Now we have two conflicting opinions. 

But I don't understand how dispatch could receive both encrypted and non-encrypted on the same frequency

[AmbulanceDriver]

No.  The repeater is just repeating the RF audio from the radios in the field, encrypted or not.

eta: correction necessary due to adult beverage consumption

Minor correction here....  You were right the first time... Repeaters work by using paired frequencies, and they retransmit RF.   One pair if it's simplex (only one person can talk at a time), two pairs if it's duplex (works like a telephone).  It's easiest to explain with the simplex - the incoming transmission is received on frequency X, then rebroadcast on frequency X+Y, where Y is the offset, a predetermined shift in the frequency (depending on the frequency range that the radios operate on).  So if the radio is running at 825MHz, with an offset of 25MHz, then the incoming transmission would be rebroadcast at 850MHz (on a + offset) or 800MHz (for a - offset).  Whether it's a +/- offset is also determined by the system, and the radios are programmed accordingly.  

A full duplex system works slightly differently.  In reference to the base station, there's a "talk" frequency and a "listen" frequency (these are reversed in the field radios).  The repeater works exactly the same, but with a total of 4 frequencies instead of 2.

[RocketMan]

Actually, a standard repeater does use paired frequencies, but it does not mix and retransmit the actual RF of the incoming signal.  It receives on the input frequency, fully demodulates that incoming signal, then uses the resulting audio or data to modulate the outgoing RF at the new offset frequency.  A repeater has a separate receiver deck (sometimes more than one, remoted and linked) and a separate transmitter deck, although usually in the same case, that allows them to operate in this full duplex mode.
Repeaters are often linked into multiple systems to cover larger areas.  These linked systems can even be cross banded.
The offset frequency differs based on the service, whether it's land mobile or amateur radio or something else.

[Tallpine]

Minor correction here....  You were right the first time... Repeaters work by using paired frequencies, and they retransmit RF.   One pair if it's simplex (only one person can talk at a time), two pairs if it's duplex (works like a telephone).  It's easiest to explain with the simplex - the incoming transmission is received on frequency X, then rebroadcast on frequency X+Y, where Y is the offset, a predetermined shift in the frequency (depending on the frequency range that the radios operate on).  So if the radio is running at 825MHz, with an offset of 25MHz, then the incoming transmission would be rebroadcast at 850MHz (on a + offset) or 800MHz (for a - offset).  Whether it's a +/- offset is also determined by the system, and the radios are programmed accordingly.  

A full duplex system works slightly differently.  In reference to the base station, there's a "talk" frequency and a "listen" frequency (these are reversed in the field radios).  The repeater works exactly the same, but with a total of 4 frequencies instead of 2.

What they call "simplex" around here is a non-repeated frequency: tx and rx frequency is the same.

Usually, that is our "tactical" or mobile-to-mobile channel used for comm on an incident.  The state owns multiple of these channels which means that different divisions or different incidents can have their own channel with little overlap to other incidents because of limited range.

When we want to talk to the county dispatch (or a neighboring county), we have to use the repeated channel but for incident operations you want to keep the repeater clear for other traffic.

Anyway, the whole point being (again!) that our county has a base channel (non-repeated) for LE that is encrypted now, which only covers the county seat and nearby.  Anywhere else in the county (2500 sq mi and mostly mountains), LE has to use the non-encrypted repeaters which are also used by fire, EMS, road crews, school buses, etc.

[RoadKingLarry]

Now we have two conflicting opinions. 

But I don't understand how dispatch could receive both encrypted and non-encrypted on the same frequency

It isn't the frequency that is encrypted it is the information carried on the frequency. The encryption/decryption occurs at the sending and receiving ends .

Talk  -encrypt - IF - RF -transmit/receive - RF - IF -decrypt - listen.

[Tallpine]

It isn't the frequency that is encrypted it is the information carried on the frequency. The encryption/decryption occurs at the sending and receiving ends .

Talk  -encrypt - IF - RF -transmit/receive - RF - IF -decrypt - listen.

But how would the dispatch radio know whether or not to decrypt the rx signal if it is used for both 

[RoadKingLarry]

Getting a little out of my field of experience and it's been more than 20 years since I've worked with RF equipment but it doesn't seem like it would be to hard to do with digital equipment. Receiver detects a signal, it can detect if it's encrypted by the signal, along the lines of an IP header perhaps.

[Tallpine]

Getting a little out of my field of experience and it's been more than 20 years since I've worked with RF equipment but it doesn't seem like it would be to hard to do with digital equipment. Receiver detects a signal, it can detect if it's encrypted by the signal, along the lines of an IP header perhaps.

I don't think they're ever going digital in our county.

They still haven't switched over to narrow band yet.

Plus, the damn digital doesn't work too well anyway.  The neighboring county switched over a couple years ago and can't hardly hear anything anymore.