Users may not create topics, posts, or private messages containing or relating to the following material (especially pertaining to Motorola copyrighted software, unless you want Motorola to come along and shut this site down):

  • Listing for sale or trade of, or links to sites offering for sale or trade of, or giving away, Radio
    Service Software (RSS) or Customer Programming Software (CPS)
  • Profanity, pornography, defamation, or slanderous remarks directed towards any individual or entity
  • Commercial advertising (except in the Batboard Vendors forum, as approved by the Admin/Mod Staff)
  • Any other items which may be deemed as offensive

If any topics, posts, or private messages containing or relating to the aforementioned material are brought to the attention of the Admin/Mod Staff, they will be deleted.

Additional FAQ items appear here in Forum Rules. Please review them for posting guidelines and further clarification.

P25 simulcast help

Have a question or information regarding interfacing or interoperating Motorola digital radios with models from other manufacturers? Here's the place to do so.

Moderator: Queue Moderator

New User
Posts: 5
Joined: Tue Feb 03, 2009 6:29 pm

P25 simulcast help

Postby walong » Wed Feb 04, 2009 5:48 pm

Hi all.

After searching the forum, many questions have been answered, and I have gained a whole 'lotta knowledge. But I still need some advice/help. I have experience with Moto, but just analog stuff. So here I go.

My problem: Local PS is on a regional 700/800 Moto trunked P25 system (1a7). My particular county's site is actually a five tower Motorola P25 simulcast system. The simulcast is near impossible to rx using the GRE (other "regular" sites are perfect).

What I'm thinking: After pouring over white papers on P25 theory, etc, and looking over the data structure of a P25 transmission, the best I could come up with is this as a poor-mans solution.

Any P25 800 XTS, setting up as conventional rx, and using the TG #s to "filter" what comes through. I figure 11 voice channels, not too many TGs on system to "filter" through. Kind of similar to scanning for a particular CTCSS tone over many conventional channels, just using the TG info instead. Should be better than just randomly scanning the vc's.

My questions:
1. Is this possible? Is there a way to unmute audio based on TG info in conventional mode?
2. After bringing scan hang time to 0, will the radio scan and check for decode at a fast enough rate to pull this off?
3. Im thinking channel 1's scan list would have the systems voice channels in it's list, but just looking for specific TG info, repeat for ch 2, ch 3 , etc. Am I on the right track?
4. Will I gain anything as far as the simulcast is concerned? Will I be able to adjust for the systems' simulcast?
5. IF this is possible, any specific fw, etc I should look for? I assume an older 3600 radio would still work, as I wouldn't be trying to follow the 9600 trunk. (yes, I know the baud rate deal, just keeping it simple)
6. And last, any pitfalls to watch for would be appreciated. And if it is feasable, any particular flashes I should look for that would be conducive accomplishing this.

Just trying to get ANYTHING to hear this simulcast before moving on to "other" options. Not mission critical, just continuing my hobby.


New User
Posts: 5
Joined: Tue Feb 03, 2009 6:29 pm

Re: P25 simulcast help

Postby walong » Mon Feb 09, 2009 3:44 pm

Ok, maybe I approached this wrong.

First, hello to all. This is a great site, rich with information. I have been refering to this site for years, but just now registered on the forum, and discovered the additional topic-specific forums. Many thanks to the volunteers who keep this site running and provide such a wealth of info.

I did post this in the wrong sub-forum. My apologies.

Let me filter my question as so as not to appear as the "typical" lurker/troll, as I have searched and read the related topics in the (proper) Mot P25 forum:

?- Specifically, can adjustments be made to better recieve what I belive to be LSM in convetional modes, even though I am monitoring a P25 sys? Or are those adjustements only available through the trunking menu?

Thank you ,

User avatar
Posts: 1854
Joined: Tue Jan 13, 2004 7:03 am
What radios do you own?: 2 turntables and a microphone

Re: P25 simulcast help

Postby motorola_otaku » Tue Feb 10, 2009 1:46 pm

Well, part of your question has already been answered. See here.

Regarding the GRE and poor decode of CQPSK simulcast, I think there was thread in the Illinois subforum of Radioreference where some guys up there were having problems decoding a simulcast system and found solutions either in the form of directional antennas pointed at one simulcast tower or trading their GREs for Bearcats. I know I read it, but I can't find it in a search atm.
When exposed to Rapid Fire Growth or Thermal Emergency, two things are lost:
1. Ability to use fine motor skills
2. Presence of mind

User avatar
Posts: 1287
Joined: Tue Dec 10, 2002 10:46 am

Re: P25 simulcast help

Postby Wowbagger » Tue Feb 10, 2009 3:01 pm

That you cannot decode the LSM format is odd, because at symbol time there is no difference between LSM and C4FM. The only difference is that the LSM signal will reach the symbol deviation value (+/- 600 or +/- 1800 Hz) earlier in the symbol time than C4FM, and will leave that value later in symbol time than C4FM. That's the "magic" in LSM: In the face of multiple systems being received, the longer dwell at symbol deviation means you can tolerate a larger flight-time difference between the sites without interference (at the expense of either needing a linear RF power amp or having a larger occupied bandwidth).

Any data slicer that can do C4FM should be able to do LSM *if it was done right*.

Whether the data slicer in question was done right is an open question.
This is my opinion, not Aeroflex's.

I WILL NOT give you proprietary information. I make too much money to jeopardize my job.

I AM NOT the Service department: You want official info, manuals, service info, parts, calibration, etc., contact Aeroflex directly, please.

Posts: 769
Joined: Mon Apr 21, 2003 10:00 pm

Re: P25 simulcast help

Postby MattSR » Wed Aug 04, 2010 1:47 pm

Hi guys, for interest, I came across some good information on demodulating LSM here - the author of that page has cracked the LSM problem wide open for all to see :)

User avatar
Posts: 3087
Joined: Thu Sep 17, 2009 5:00 am

Re: P25 simulcast help

Postby Bill_G » Wed Aug 04, 2010 2:48 pm

Interesting. Thank you.

Return to “Motorola Digital Radio Compatability”

Who is online

Users browsing this forum: No registered users and 1 guest