PG police?

[bikerdan]

I haven't been using my scanner for a few months. I don't get the PG Co. police any more. Did they change freq?
Forgive me if this had been talked about before.

 

[ka3jjz]

Yes they have largely moved over to the new 700/800 mhz system which is pretty much unmonitorable, unless someone forgets to hit the switch (hi). Use the search tools and you'll learn all about it

best regards...Mike

 

[ka3jjz]

Along those same lines, is it time now to modify the PG county police, sheriff and park police frequencies in the database? Do they still come up monitorable from time to time (in which case the deprecated tag would be appropriate) or are they now dead (in which case they should be dropped)?

best regards..Mike

 

[Dewey]

Along those same lines, is it time now to modify the PG county police, sheriff and park police frequencies in the database? Do they still come up monitorable from time to time (in which case the deprecated tag would be appropriate) or are they now dead (in which case they should be dropped)?

best regards..Mike

I wouldn't call them dropped. Looking over my bcTool directory,

- Channel 3 is still CW id'ing as late as this morning.
- Channel 5 had a bunch of dead carry key ups yesterday and this morning.
- Channel 7 is still CW id'ing as late as this morning.

There could be even more activity. This is just what I have when the scanner "passes through" that system.

Dewey

 

[troymail]

Yes they have largely moved over to the new 700/800 mhz system which is pretty much unmonitorable, unless someone forgets to hit the switch (hi). Use the search tools and you'll learn all about it

best regards...Mike

Actually -- the way the new PG system works -- most conversations on this system are the new TDMA MOTOROLA format where they insert two 6.25 khz channels (talkgroups) in the space of what is normally a single 12.5 khz FDMA channel (talkgroup).

The system automatically detects when a radio that is not capable of using the smaller 6.25 khz channel becomes active on a talkgroup -- When this happens, all radios start using a full 12.5 khz FDMA channel. Once all FDMA radios leave the talkgroup, the system automatically goes back to using the new 6.25 khz channel.

There was a quite a bit of police activity today in Takoma Park on the PG/Montgomery County border (Police: Suspect killed after bank robbery - wtop.com) and I think this resulted in quite a bit of FDMA activity on the PG system today that could be monitored.

See page 5 of this white paper: http://www.motorola.com/web/Busines...hase_2_Standards_White_Paper.pdf?pubid=987654

 

[ka3jjz]

The operative question here - and it's likely we won't know the answer - is why would they switch back to Phase 1 when staying in Phase 2 would have been more secure, and more efficient for the system (as I understand it, when a Phase 2 system down switches like this, there's a cost in efficiency...) unless not everyone has a pre-phase 2 compatible radio yet...

best regards..Mike

 

[troymail]

The operative question here - and it's likely we won't know the answer - is why would they switch back to Phase 1 when staying in Phase 2 would have been more secure, and more efficient for the system (as I understand it, when a Phase 2 system down switches like this, there's a cost in efficiency...) unless not everyone has a pre-phase 2 compatible radio yet...

best regards..Mike

Certainly a cost in efficiency -- when a talkgroup falls back to FDMA, it's essentially tying up TWO potentially channels from the TDMA system.

However, the obvious reason for automatically falling back is to maintain interoperability (i.e. Montgomery County police using FDMA radios can still switch over onto the new TDMA PG system and communicate even though they don't have TDMA capable radios.).

 

[ResQguy]

Certainly a cost in efficiency -- when a talkgroup falls back to FDMA, it's essentially tying up TWO potentially channels from the TDMA system.

And that is why the system is configured to use FDMA exclusively on certain talkgroups, as well as TDMA exclusively on others, and DDM on the ones left over. Careful planning was done to minimize or prevent busy bonks due to M/A radios affiliating. Of course, all the 700 voice channels will be forced to TDMA full time (or whatever it becomes to achieve 6.25KHz eff) in 2017, but that's a long way off. All the non phase-2 radios should be in landfills or beer cans by then.

 

[troymail]

...all the 700 voice channels will be forced to TDMA full time ...

700 voice channels?

 

[ResQguy]

700 voice channels?

700 megahertz not quantity

 

[troymail]

700 megahertz not quantity

Doh!

Now it makes sense.

 

[dpm797]

Right now only Motorola APX 7000 portables and the associated APX Mobile will do TDMA. If you have a Motorola XTS 5000 that affiliates with the system the TG dynamically changes to FDMA.

 

[lawman349]

Actually, the talkgroups in PG do not automatically revert to FDMA. They are manually selected to go to FDMA by the dispatcher when mutual aid requires interoperability.

 

[troymail]

There may be some activity tonight that can be heard: UMd. plans to channel fans' spirit after Duke game - wtop.com

 

[funpack]

Help I can not pickup PG Police I Have a Uniden BCD 396T Need help with frequencies

 

[Dewey]

Help I can not pickup PG Police I Have a Uniden BCD 396T Need help with frequencies

Have you even bothered to read this thread before adding to it??? Look at the first two posts.