FDMA 1 Frederick County

[md_p97]

Hi Guys,

Lately, I have heard Frederick County Fire and Rescue units responding into Montgomery County via mutual aid, and being told to respond on channel "FDMA 1."

This is not a listed talk group in the database, nor do I hear any comms when I open the trunked bank up, nor on the 154.2800.

Can anyone provide insight on this for me?

Also, Frederick Co had, in the past, been openning up the talk group to Frederick City (digital, encrypted) for the Sheriff's Dept to respond to urgent calls. When the action was over, the talkgroup was turned off. However, for just about the entire month of January I was able to monitor the city via the talk group. Does anyone know if this was some kind of test, or had they simply forgot to deactivate the talkgroup for 30 days?

Paul

 

[ericcarlson]

"FDMA1" is a talkgroup on the Montgomery County system, this is probably what they were referring to:
http://www.radioreference.com/modules.php?name=TRSDB&sid=2142

-Eric

 

[Admin0140434]

eric is right, Frederick County (like almost EVERY COUNTY in this state) has the ability to switch to another county's system to allow comms between the two counties.

 

[md_p97]

well, I kinda thought that, but Montgomery County uses a 860mhz digital trunk system, while Fred Co is a 860 mhz analog trunk system.

Did Montgomery County supply all neighboring fire stations outside the county line with digital radios? That seems like an awful lot of extra radios to me.

Paul

 

[2gigch1]

From the Montgomery Co Info Page

Copied from the Montgomery Co RR Info Page:

Fire & Rescue - Interoperability Talkgroups

DEC HEX Mode Display Description
5840 16d D 5B PGFIR Prince George's County Channel 2 Patch
5872 16f D 5A PGEMS Prince George's County Channel 1 Patch
5904 171 D 5C PG4/6 Prince George's County Channel 4/6 Patch (Dispatcher Selectable)
49168 c01 A FDMA1 Analog Mutual Aid Patch
49200 c03 A FDMA2 Analog Mutual Aid Patch
49232 c05 A FDMA3 Analog Mutual Aid Patch
49264 c07 A FDMA4 Analog Mutual Aid Patch

Note FDMA1 is an analog patch on Montgomery Co's system. Their system can handle both analog and digital radios. A Frederick County radio can easily be programmed to transmit on Montgomery County's system, they just can't hear 98% of the stuff on their system. No doubt the 'patch' is tied in with whatever talkgroup Montgomery County needs Frederick County on at the time and the translations analog/digital happen back at the comm center. Thus a Frederick County Engine responding to a house fire switches to FDMA1, which the comm center ties to 7 Kilo so they operate seamlessly.

A side effect would be that analog trunking scanners, set on FDMA1, would be able to hear the entire incident since the digital talkgroup must be translated to analog and retransmitted on FDMA1 for the benefit of the Frederick County unit.

Remember, apco25 / digital has little or nothing to do with the trunking aspect of the system, that's old technology. Digital is about voice modualtion.

- Side note; I too have noticed the wide open use of the Frederick City patch. I sure hope it doesn't go away anytime soon. I have not heard anything that would appear to comprimise operations, just the usual stuff one hears in a more urban environment.

If anything it probably helps the sheriffs and state police; I notice they monitor each other's transmissions quite a bit since their duties overlap so much. Countless times I've heard a sheriff announce a traffic stop and moments later the state police dispatcher alerts a trooper to the fact with no apparent mutual aid requested. Seems to be a good mutiagency symbiotic relationship that the city may be trying to take advantage of.

 

[md_p97]

2Gig...

I understand how the two channels could be tied together, by both systems.....What I don't understand is How the Fred Co units are communicating. There is NO talkgroup listed for FDMA1...and when I "open" the bank in my pro-97, no comms are being heard or any new talkgroup appears. So is this a conventional frequency? and if so, what is the conventional frequency? The counties are using 154.2800 (dispatch to dispatch) to notify each other, so what freq are the Fred Co units using?

Also, I stopped hearing the Fred City comms about a week ago.

Paul

 

[Llwellyn]

When the FC unit switches their radio to their setting for FDMA1, they switch to MC TG 49168 in Analog mode. MC's comm center then patches the incident talkgroup to that analog talkgroup. The FC unit is no longer operating on the FC trunk, but on the MC one. If you want to listen to that traffic, you need to program the MC trunk and those TG's that are listed as analog patches, then monitor the MC trunk during an incident when FDMA channels are in use. I'm sure they are not permanent patches.

 

[2gigch1]

Beat me to it -

Monitor the Montgomery sytem, not Frederick's. A couple years ago I had the use of a digital radio to monitor Baltimore City before digital scanners came out. That radio also had Baltimore County, Anne Arundel and Carroll County in it. All these radios can easily work on multiple jurisdictions.

Bummer about the city patch.

 

[md_p97]

Thanks guys....I've programmed into my pro-97 ALL 20 of Mont Co's 800 mhz frequencies, set them and the bank to MOT, and added the 4 analog talkgroups. We'll see what happens.

Paul

 

[md_p97]

Well who'd have thunk it.....about 2pm today, right after leaving the Home Depot store (which is fast becoming my favorite scanner support parts store) my pro-97 lights up on the FDMA 1 talkgroup I plugged in this morning.....Mont Co and Fred Co on a working brush fire near White's Ferry...imagine my surprise when a second call went out for a shed fire in the same 1st due area and FDMA 2 lit up.... :lol:

I know that the brush fire was working on Mont Co 7G, but didn't hear the call go out for the shed on FDMA 2.

Anyway, thanks guys...since anything large in my area always involves a Fred Co Company reponding, I'll be able to listen in!

Paul

 

[4909]

I started hearing Frederick City PD around the same time on that TG. It was great! I didn't want to say anything for fear it would go away....and sure enough, it has. I've never been able to figure out why FPD didn't/doesn't piggyback onto the county system anyway. Ah, well, it was good while it lasted. I'm hoping it comes back up sometime soon.