Encryption affect range (NXDN)?

[Samotak]

I've just figured out how to enable encryption on my NX-220 radios. Will be using them in NXDN conventional mode. Will encryption affect range at all? Or will useable range be the same whether or not encryption is enabled?

I'm guessing that there will be no difference.

Cheers,
John

 

[kayn1n32008]

I've just figured out how to enable encryption on my NX-220 radios. Will be using them in NXDN conventional mode. Will encryption affect range at all? Or will useable range be the same whether or not encryption is enabled?



I'm guessing that there will be no difference.



Cheers,

John

I have not used encryption on my Nx700 or NX-200, but I would expect to see no range degradation. It is simply altering an already digital signal. It's not like the old days of DVP, which did suffer from range and audio degrading.

 

[mmckenna]

I'm using both encrypted talk groups and non-encrypted talk groups on an 800MHz NexEdge trunking system. NX-900 mobiles and NX-410 portables. Zero difference in coverage. The encryption just rearranges the 0's and 1's of the digital signal.

 

[Samotak]

kayn1n32008 and mmckenna, thanks much. That's what I was thinking and hoping it would be.

Cheers,
John

 

[MSS-Dave]

No difference encrypt on or off but you may find a bit better performance overall if you run very narrow if you aren't now.

Sent from my SAMSUNG-SGH-I337 using Tapatalk

 

[RayAir]

I'm using both encrypted talk groups and non-encrypted talk groups on an 800MHz NexEdge trunking system. NX-900 mobiles and NX-410 portables. Zero difference in coverage. The encryption just rearranges the 0's and 1's of the digital signal.

My question has to do with nxdn 15 bit scrambling and the issue I discovered only pertains to basic privacy schemes.

If you have a system with a few TG's and you enable them all with 15 bit scramble, but you want one of the TG s to have a unique scramble key to prevent users on the other groups from hearing the conversation, is there any chance the keys would be similar and allow partial decoding?

I'll have to test this myself, because i ran into this setting up a Hytera system with Hytera basic privacy.
If the key doesn't have at least 4-5 different digits than another key, you will get a partial decode.

I see NXDN loads registers with the key data and generates a PN sequence for scrambling.

Do each of the 32,000+ keys differ enough to prevent partial decoding?

 

[Samotak]

No difference encrypt on or off but you may find a bit better performance overall if you run very narrow if you aren't now.

Sent from my SAMSUNG-SGH-I337 using Tapatalk

I've got a couple of channels programmed in very narrow and others in narrow. Thanks for the tip, MSS-Dave, I'll have to check that out. So far I've only been able to program both analog and digital channels and just yesterday got the encryption working. I've got lots to learn.

Cheers,
John

 

[mmckenna]

My question has to do with nxdn 15 bit scrambling and the issue I discovered only pertains to basic privacy schemes.

If you have a system with a few TG's and you enable them all with 15 bit scramble, but you want one of the TG s to have a unique scramble key to prevent users on the other groups from hearing the conversation, is there any chance the keys would be similar and allow partial decoding?

....

Do each of the 32,000+ keys differ enough to prevent partial decoding?

Yes, even having the key data one digit off doesn't result in a decode. The key has to be exact.

You can also set the "Encryption Type" under the Encryption tab to either Type 1 or Type 2.
Type 1 will unmute the radio audio for any traffic, even if it's encrypted and the receiving radio doesn't have the correct code. It'll receive encrypted or encrypted traffic however if the code isn't in the radio, all you'll hear is garbage.
Type 2 will mute the receive audio if the received signal is encrypted and the radio doesn't have the right code. The green LED will light since it's receiving, but the encrypted audio won't make it to the speaker.

 

[kayn1n32008]

No difference encrypt on or off but you may find a bit better performance overall if you run very narrow if you aren't now.

Sent from my SAMSUNG-SGH-I337 using Tapatalk

Agreed. Unless you are running a system that needs data capability, go with very narrow NXDN.

 

[Samotak]

Any difference in sound quality between 12.5kHz bandwidth and 6.25kHz bandwidth? Maybe not for voice but I believe that if we are talking about analog FM bandwidth and with a figure like 6.25, you wouldn't be able to transmit and receive an 8kHz tone. When it comes to bandwidth for a digital signal, I don't know how that translates to what kind of tones can be used.

Yes, a bit off topic but thought I'd ask here instead of starting another thread.

Cheers,
John

 

[kayn1n32008]

Any difference in sound quality between 12.5kHz bandwidth and 6.25kHz bandwidth?

No difference in audio quality.

Maybe not for voice but I believe that if we are talking about analog FM bandwidth and with a figure like 6.25, you wouldn't be able to transmit and receive an 8kHz tone. When it comes to bandwidth for a digital signal, I don't know how that translates to what kind of tones can be used.

Yes, a bit off topic but thought I'd ask here instead of starting another thread.

Cheers,
John

6.25KHz is too narrow for analogue voice. If a ever there is a requirement to go to that channel size, then it will have to be digital only.

 

[mmckenna]

Any difference in sound quality between 12.5kHz bandwidth and 6.25kHz bandwidth? Maybe not for voice but I believe that if we are talking about analog FM bandwidth and with a figure like 6.25, you wouldn't be able to transmit and receive an 8kHz tone. When it comes to bandwidth for a digital signal, I don't know how that translates to what kind of tones can be used.

Yes, a bit off topic but thought I'd ask here instead of starting another thread.

Cheers,
John

For FM analog 2 way radio, 12.5KHz is the logical limit for useable voice traffic.
6.25KHz NXDN digital is about 4.8Kb/s, which will do human voice just fine.
12.5KHz NXDN digital is about 9.6Kb/s.

I couldn't really tell any difference between the two. I set up our trunked system to use 12.5KHz NXDN since the need for running some slow speed data was a possibility. If I was setting it up from scratch again, and finding that my end users don't have much interest in data, I'd go with the 6.25KHz.

 

[Samotak]

Thanks, mmckenna. Sounds like either setting for NXDN will work fine for voice audio. I appreciate your sharing of your thoughts (and everyone else's too).

Cheers,
John

 

[kayn1n32008]

Sounds like either setting for NXDN will work fine for voice audio.

I use very narrow NXDN on simplex with a friend. It works very well, audio quality is better than DMR, at least using NX-700 mobiles.

You may find that very narrow NXDN voice will give you a bit better range than narrow NXDN, and much better coverage than analogue narrowband.

 

[Samotak]

I need to go out and do some experimenting now that I've got my radios programmed and have both analog and NXDN channels set up. It's been a little challenging learning how to use KPG-141DN but it's nice to have a community here where one can get help.

Cheers,
John

 

[kayn1n32008]

To make things easier, find the edge of analogue coverage, then switch to digital.

 

[jonwienke]

The same is true of DMR--no noticeable difference between encrypted digital and unencrypted digital.

 

[Samotak]

To make things easier, find the edge of analogue coverage, then switch to digital.

Will do. Makes sense.

I hope to find the time soon to check this out. Work and family "stuff" can get in the way. But work and family are good to have

Cheers,
John