Conventional P25 Programming

[tweiss3]

I have some XG-100 (both portable and mobiles). I have noticed a few things that seem odd, and I'm looking for clarification (under appropriate license usage).

P25 conventional programming, simplex use. I have a system, and assign a TG list to the system, but don't assign a TG, it appears to pull the first TG in the list on the screen, and lets me "change TG", but it doesn't seem to transmit on that TG, simply as "1" i.e. none. Is that normal? Do I have to assign the talkgroup to the frequency in order

Secondly, the encryption/clear switch doesn't seem to work under any scenario. I noticed that encryption is off all the time unless I assign a global encryption key to the system, then its on all the time. Cycling through TG does change which key is used, if a key is assigned to that TG. Is this related to the above "none" TG.

Am I missing something? I'm sure I am missing some best programming practices.

 

[BMDaug]

I’ve never tried to change TGs on a conventional channel. I always program duplicate channels with different assigned TGs for each channel. I really don’t even like using multiple TGs on a single conventional frequency, because most users don’t really pay attention enough to see if another TG is using the channel before keying up.

There’s an option in digital voice options that controls the encryption mode. On Unity radios, I’ve had success using autoselect, while older radios seem to interpret that as ‘only respond encrypted if the received transmission was encrypted’.

I think your main issue is with your group set though… are you assigning a key number and checking the ‘encrypted’ box for each of your TGs? Each group should have a name, a group id, should be set encrypted, use system, with a key number set. Then check transmit, receive, calls, and scan (if you want the TG to be scanned).

Then, in your set, assign the group set, and define the TGID for each channel. If everything works, you should be able to set the Sq mode to ‘sel’, which is the most complete use of the P25 standard, allowing you to use individual calling and TGs to the greatest extent.

-B

 

[tweiss3]

Thanks for the input. It was the digital voice options that made it so the switch worked. I still don't understand why the system has to have an encryption key assigned for encryption to work at all.

In reading further into the help, I understand what it is doing with TG now. I just wanted a way to switch the key on the fly, not necessarily use multiple talk groups to select different groups of people. I understand that TG 1 is equivalent to NONE, or not assigning a TG. I did find that it doesn't like having more than one TG1 in the list (ignores others). I just need to understand how/why in order to program equally across other brands.

 

[BMDaug]

Right on… the way the Harris radios work, they will receive if they have the right key. It doesn’t matter if the key is assigned to a particular TG. If the radios have the same key set, they can communicate on a TG, even if one radio has key 1 associated with that TG and the other radio has key 2 associated. I believe the system key is just a default. As long as you assign different keys to each TG, switching TGs will change the key used for TX. I’ve never had the system key matter… perhaps that key would be used for system registration? I have nine Harris radios, and they all work perfectly together with iCall, AES, etc., so perhaps I haven’t had to explore the implementation as deeply as someone who needs compatibility between multiple manufacturers.

-B