Washington, DC - D.C. emergency radio communication system shuts down

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jks19714

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Hard to believe that the entire city's communications is totally dependent on one site. I don't suppose they ever have lightning in DC either?

Stuck on stupid (SOS)!

john
 

box23

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Hard to believe that the entire city's communications is totally dependent on one site. I don't suppose they ever have lightning in DC either?
Fist of all, looking at the system information in the database, and the FCC's database, there are two separate simulcast sites consisting of 11 sub-sites that make up the system. 10 of these sub-sites have co-located 460 MHz and 850 MHz equipment for the two simulcasts used by law enforcement and fire & EMS, respectively. The 850 MHz fire & EMS simulcast has an 11th sub-site at a separate location.

So your first comment is incorrect as there are 11 separate physical site locations. Since these locations are sub-sites of the simulcast sites, if one tower happens to fail, for any number of reasons that include your possible lightning strike, the coverage will only be degraded where that sub-site alone provides coverage. If a radio is located within the coverage footprint of the remaining sub-sites, then the user would not know anything is wrong.

Secondly, the report does not mention what caused the failure and explicitly states "No cause could be determined for the sudden halt in radio transmissions..." It also doesn't explain in more detail what actually happened as told by the radio users such as the radios entering Fail Soft or any other modes, or alerting in any manner.

Also, unless the system was built without any grounding or other protection against lightning, which you seem to be implying, lightning would have to make its way to certain high value components to bring down the entire system. And as b7spectra referred to the system and radios should have went into Fail Soft mode which would still allow limited used of the radios. As I mentioned before though, this was not explained in the article.

Now I admit that I don't know everything about this system, and for all I know it may not even have a Fail Soft mode or could even be programmed differently than a "normal" Motorola trunking system, but barring that, it seems your comments may have been misplaced.
 

jks19714

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Not so fast.

If it is anything like some other P25 systems from that era that I'm familiar with, they have a centralized controller. I've seen a number of them "kick the bucket" and leave entire systems in "site trunking". And if you need 11 sites (or more) in a system due to geography or desire for portable coverage, you'll find yourself having to dispatch from local firehouse/precincts - it can be a REAL problem if you don't have a plan.

john
 

box23

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Not so fast.

If it is anything like some other P25 systems from that era that I'm familiar with, they have a centralized controller. I've seen a number of them "kick the bucket" and leave entire systems in "site trunking". And if you need 11 sites (or more) in a system due to geography or desire for portable coverage, you'll find yourself having to dispatch from local firehouse/precincts - it can be a REAL problem if you don't have a plan.
Oh yes, I agree. Even if the system failed "properly" it would cause big problems. That is the one inherent problem in Motorola trunking systems that there is only the one central controller. However, there should be a backup at the same location in case the primary one fails, although it could be subject to the same conditions which could cause it to fail also.

Now that I read your previous post I see that I took it out of context. Sorry about that.
 
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N_Jay

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And the engine on my push mower never fails to start.:roll::roll:

Of course maybe you have never heard of a VHF or UHF TRS.:twisted:
 

a29zuk

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And the engine on my push mower never fails to start.:roll::roll:

Of course maybe you have never heard of a VHF or UHF TRS.:twisted:
For which we keep the old mower, which still runs, out in the shed in case the newer one doesn't want to start and is repaired.
 
N

N_Jay

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For which we keep the old mower, which still runs, out in the shed in case the newer one doesn't want to start and is repaired.
If it makes you feel good.

You will find that;
1) The old mower, not unused for several years is too rusty to actually work
2) The blades were dull when you put it away, and with time and being moved around are probably worse now.
3) After several years of a power mower you are more likely to buy a new one before actually trying to cut the entire lawn with the push mower.

But, if it makes you feel good. keep it.

(Above analogy applies to radio systems also)
 

a29zuk

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If it makes you feel good.

You will find that;
1) The old mower, not unused for several years is too rusty to actually work
2) The blades were dull when you put it away, and with time and being moved around are probably worse now.
3) After several years of a power mower you are more likely to buy a new one before actually trying to cut the entire lawn with the push mower.

But, if it makes you feel good. keep it.

(Above analogy applies to radio systems also)
????????
Just speaking from personal experience. It has nothing to do with feeling good.
1.The old mower, gets started once a month in the summer to assure that it runs.
2. Have a bench grinder in the garage to keep all lawn mower blades sharp.
3. Both mowers are push mowers. I mow the entire lawn with my push mower. Walking is good for everyone.
 

ResQguy

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How often did you ever hear of a VHF or UHF system failing compared to a TRS?
Most of the places that don't have enough work to require more than that level of communication haven't developed internet connections or even pony express yet, maybe thats why you don't hear it. Or perhaps they have been around long enough to have enough conventional infrastructure and frequency allocation to support their operations (NYC)?
 

RADIOGUY2002

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Simple

This is so simple, its called redundancies for failures. I'm pretty sure their eoc's and anyone that maintains the radio system was immediately put on notification to get it back up. Granted it would be a giant pain in the a** to have them revert to system that's conventional in what ever mode they operate on, its pretty easy to make it work of if the infrastructure is there. If their are elven sub sites I'm pretty sure a 800 mhz repeater can be pulled for trunking mode to conventional mode or their are few 800mhz conventional repeaters floating around to hook up to a feed line. We are unaware of the back ups in play here and what the specific node (radio) does in a failure without speaking with a administrator representative.

If you build a system right,

You think of what could go wrong and you come up with alternatives. Even if the radio sits on a shelf it still can become a resource at a time of need. A little thought process can go a long way when playing with technology.
 

freqhopping

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The FD 800mhz system has five locations. FCC Callsign KNJA391 Details
The MPD 460mhz system has six locations FCC Callsign WPYM761 Details
Three of the locations have both.

The FD system was patched into the Montgomery Co system, but there were some issues with signal strength according to the radio techs I was listening to and they working on using the Arlington Co system, or Alexandria if necessary, to make it work better.

One article I read reports officials saying it took 30 minutes before the MPD backup, i.e. failsoft, was operating. Though when I tuned in at 7:50pm, more than 30 minutes past 7:15, it wasn't working. I got busy listening to radio techs and such, but it wasn't until about 8:50pm that I noticed the MPD system operating in failsoft mode.
 

kc0vgj

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A simple 800 or 900 Mhz system With only the basic PTT and ID system is all your need, Me I personaly perferd the Convetional System Not Trunking
 

kc0vgj

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oh ya.. and I forgot to say... Keep the data terrminal MDT or laptop computer system on a seperated system. this way there not connected to the voice system. If one fail the other will work.
 

ResQguy

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The FD 800mhz system has five locations. FCC Callsign KNJA391 Details
The MPD 460mhz system has six locations FCC Callsign WPYM761 Details
Three of the locations have both.
The FD system was patched into the Montgomery Co system, but there were some issues with signal strength according to the radio techs I was listening to and they working on using the Arlington Co system, or Alexandria if necessary, to make it work better.
Somebody should check the RR / FCC tower data. Both systems have 10 colocated sites. Also, the DCFD system could not be patched to anything while it was down. The users merely selected a different zone in the subscribers.
 
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