Technical Experts on PG County

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bmyos

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A question to all RR radio technical experts reading and listening to MD - PG County:

I recently programmed all PG County police frequencies into my PSR 800 and tried listening from DC. In doing so, I have been surprised at how few transmissions I receive from PG and decided to read up on RR about PG frequencies (since 100% of my problems have been user error) - to double check my frequency selections. I came across some info that was well above my technical expertise - hence this thread.

Using the mindless programming offered by the PSR 800, I have selected pretty much all of the 'police' options from the library. Despite all of the frequencies, I mostly (99%) receive the District IV (J/K) transmissions only. I would expect to hear more transmissions from District I (A/B) and District III (G/H), given the close proximity of these locations from DC.

Did I read correctly that PG Police are using Project 25 Motorola X2-TDMA (I say that not really knowing what it means, mind you)? Is this at all contributing to my lack of transmissions as I read this system evades a lot of scanners? Or, are the towers for Districts I & III out of range for a 800mhz rubber ducky in DC?

I don't rule out user error, but any insight that can be provided on my lack of transmissions from PG would be helpful - especially from you technical gurus.

I have been told there is never a lack of action in PG county. =)

Thanks for the help.
 

c5corvette

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If you have a PSR-800 and are using the library as it comes, you should hear Prince George's if you are in range. Add a wildcard if you can. Mine works fine when in Prince George's.

I think you may not be in range of the system. Typically with a handheld scanner and rubber deck antenna, you need to be withing the proximity of the county or system (there are some exceptions in the NCR, but I tend to need an outdoor antena to get reception of neighboring county trunk systems.)
 

WA3RTH

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Exactly what frequencies did you program into the PSR-800? If they were 490 Mhz frequencies, that would explain why you are not hearing anything. If you used the RR library to load the PG System 25 Trunking System (700 Mhz) channels, then you should be picking up most if not all of the districts. I live in the Bowie area and I can pickup the northside (District 1 - A/B) units with no problem at all on my PSR-800.

You can hear when the District 1 units are transmitting by using the RR live audio of those units at this link:
http://www.radioreference.com/apps/audio/?action=wp&feedId=8651
 
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chief34a

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Probably 90% of your problem is the fact that the PSR-800 sensitivity is crap. You have to be in PG for the thing to work most of the time or less than a mile outside of the county.If you are trying to listen from downtown you could be dealing with building shading or a multitude of problems that reduce coverage. Kinda depends on where you are in DC as to what kind of problems you may be dealing with.
 

The_B_Chief

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I have also heard that the sensitivity is not very good in the PSR-800. If it helps any, the APX6500 portables (issued by the county) do not work on the PG County Zones once you get out of PG County. They hang in there for a little while but go "OUT OF RANGE" fairly quick.
 

ka3jjz

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While the lack of sensitivity on the 800 is an issue, has anyone tried a better antenna on it?

And on another note - perhaps chief34a can answer this one - is the PG trunk configured so that it concentrates its coverage within the county, and keeps the coverage out of the county restricted? I'm thinking of systems like Philadelphia where that is exactly what they did. If you go too far out of Philadelphia I am told the signal drops like the proverbial rock, depending on where you are...

best regards..Mike
 

troymail

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LSM -

It's the same problem we're seeing with Baltimore City even though BCity is not TDMA

The post by B_CHIEF above tells us alot.....we got very similar reports about Motorola radio reception dropping out once leaving Baltimore City several months ago....
 

ocguard

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Many of the "new" public safety bands (like portions of the UHF T-Band and the 700mhz band) have very stringent rules regarding confining the system's signal to the intended coverage area. This is even true now for 800mhz. With the high demand for 800mhz frequency pairs, and potential interference between UHF-T and 700mhz with nearby co-channel TV providers, systems have to be "tightened down."

For instance, Baltimore County built it's 800mhz system in 1986. Very few agencies were using 800mhz so there was little demand and frequency re-use was over great distances. So they built tall towers (300' and 600') and put the unidirectional transmit antennas all the way at the top and cranked up the power. Now, Baltimore County is overhauling and upgrading. Transmit antennas are typically between the 75' and 130' marks, are almost all directional, and the power is turned as low as it can effectively go. This means that tower sites are more than doubled, and simulcast multi-path is a huge issue. Welcome to 2011.
 

chief34a

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The PG system was built prior to the new rules so all the antennas are omnidirectional. Of course all the towers are in the county so that naturally concentrates the power within the county but there is plenty coverage outside of the county. I have not had any problems outside of PG in my travels in Montgomery, Howard, Anne Arundel, Calvert and Charles. I have used my portable as far south as Mechanicsville in St. Mary's on the C zone with no problems. We do know of a few spots outside of the county that there are problems with coverage but the bottom line is if you are responding outside of the county, then you should be on the system of the county that you are responding to, not PG. Unfortunely, that doesn't help the hobiest that is trying to listen to PG from outside of the county. Some my have to resort to a yagi on the roof to listen. Hopefully now that TDMA has become a accepted standard, more scanner manufactures will be producing some quality radios with good specs.
 

The_B_Chief

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Ok so now I’m curious. I have been doing some experimenting with my portable. It seems that on some days the system drops out about 2 and half miles outside the county. Now on other days I can access the system a good 10-15 miles past the county line. I’m watching this to see if there are any coincidences as far as day of the week, time of day, and system demand. I will add that I'm using the same radio in the same locations.
 

troymail

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Ok so now I’m curious. I have been doing some experimenting with my portable. It seems that on some days the system drops out about 2 and half miles outside the county. Now on other days I can access the system a good 10-15 miles past the county line. I’m watching this to see if there are any coincidences as far as day of the week, time of day, and system demand. I will add that I'm using the same radio in the same locations.
On the scanner receiving side, I've noticed for a long time that some frequencies on trunked system aren't as good as some others (remember, every time your hear something it's probably transmitting on a different system frequency than it was a minute ago - not always of course but generally) -- and I've seen this on the PG system also. Not sure if that has anything to do with it -- or weather/atmospherics - or the fact that the system/talkgroup is currently in FDMA vs. TDMA because of the presence/lack of a FDMA subscriber.

Last week I had an opportunity to listen to some PG talkgroups on a AA County portable from inside the Odenton fire station. It was receiving pretty well (I didn't attempt a transmit). However, I've noticed that one of the really good reception spots outside PG county is along Route 32 just west of Route 175.... so this may have just been because the Odenton station is very close to that spot.
 

ocguard

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There is a new VHF channel listed in the DB as station alerting. Does anyone know what alerting protocol is used?
 
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