Maryland FIRST 700mhz TRS

[ResQguy]

Originally Posted by doctordave

I wonder what came about of the plans to establish some standardized aviation "guard" channels on 700mhz in Maryland? Haven't heard anything further on this. When this was proposed a few years back, as a means of simplifying air-ground coordination, there were some FCC hurdles to overcome.....maybe this is tabled for now.

How did you miss it? Granted back in August: Maryland Air-To-Ground Waiver Request | FCC.gov

[doctordave]

Thanks for that update, ResQ.....nice to see that it was worked out. There sure will be a lot of conventional 700mhz freqs for agencies to choose from - when you combine the proposed aviation guard freqs and the numerous nationwide/standardized 700mhz freqs.....not to mention the continued use of existing 800mhz mutual aid freqs.

[doctordave]

I've received some additional reports of the 700 system coming in very clearly within Chestertown limits(Kent). Quite a bit of traffic from the MdTA PD Bay Bridge units on the Kent system.....perhaps someone in Kent has selected that TG - forcing affiliation....or maybe the MdTA units are sometimes switching over to the Kent zone in their radio (the Rock Hall tower isn't far away in air miles from the bridge).

Just plugged in the various standardized/nationwide 700 MHZ repeater/simplex mutual aid freqs (see the link a few posting back). Very curious to see if these will be utilized in analog mode with a 156.7 tone (much like the 8CALL/8TAC freqs and RINS freqs) - or if they'll be in digital mode. Anyone hearing testing on these channels as yet?

[troymail]

Originally Posted by doctordave

...perhaps someone in Kent has selected that TG - forcing affiliation....

I assumed this was the case while sitting in Chestertown and seeing some radios affiliate. Wondered if there was some playing or training going on. I didn't hear any voice so people are probably just curious.

...or maybe the MdTA units are sometimes switching over to the Kent zone in their radio (the Rock Hall tower isn't far away in air miles from the bridge).

Guess this somewhat depends on programming. I would have assumed I would see them affiliating on Pro96Com but the only TGs listed/that I saw were the 128xx tgids.

Oddly, and on a related not, I was watching Pro96Com last night on the Anne Arundel site and I was really surprised how many radios were affiliating -- some as expected on the Bay Bridge talkgroup but many others on the tunnel and Key/Port talkgroups. Key/port I can understand but the tunnel ones are a real surprise.

Just plugged in the various standardized/nationwide 700 MHZ repeater/simplex mutual aid freqs (see the link a few posting back). Very curious to see if these will be utilized in analog mode with a 156.7 tone (much like the 8CALL/8TAC freqs and RINS freqs) - or if they'll be in digital mode. Anyone hearing testing on these channels as yet?

I'll add these tonight and start monitoring. I loaded the Air2Grd frequencies as conventional last week but haven't heard anything (testing) yet. I wondered it these are going to be used as full channels vs. 2-slot (if that even makes sense).

[doctordave]

Troy,

Where did you find the specific freqs designated for 700mhz air-ground communication?

[troymail]

Originally Posted by doctordave

Troy,

Where did you find the specific freqs designated for 700mhz air-ground communication?

Google is fun.... here's one:

http://doit.maryland.gov/interoperab...uestWaiver.pdf

I found another one that contains a table with freqs and descriptions of each... I need to find it again....

[FiveAlarmPhotography]

Originally Posted by troymail

Oddly, and on a related not, I was watching Pro96Com last night on the Anne Arundel site and I was really surprised how many radios were affiliating -- some as expected on the Bay Bridge talkgroup but many others on the tunnel and Key/Port talkgroups. Key/port I can understand but the tunnel ones are a real surprise.

It was probably due to this. Every local jurisdiction was there (Balt City FD, Anne Arundel PD & FD, MDTA, and I think MSP also).

2 Dead After Wrong-Way Crash On I-695 « CBS Baltimore

[troymail]

Originally Posted by FiveAlarmPhotography

It was probably due to this. Every local jurisdiction was there (Balt City FD, Anne Arundel PD & FD, MDTA, and I think MSP also).

2 Dead After Wrong-Way Crash On I-695 « CBS Baltimore

Good thought but no -- I was watching between 4-8pm....

[doctordave]

Yes, Troy......I'd read that petition some time ago - just wasn't 100% clear if the proposed freq plan had been appoved in full & without any modifications at all. I've not stumbled upon anything else more recent/definitive.

[troymail]

Originally Posted by doctordave

Yes, Troy......I'd read that petition some time ago - just wasn't 100% clear if the proposed freq plan had been appoved in full & without any modifications at all. I've not stumbled upon anything else more recent/definitive.

Agree -- but since it doesn't cost me anything additional I went ahead and programmed 'em up... nothing so far but I really wasn't expecting anything for now.... a long shot....

[doctordave]

Certainly worth plugging them in. It is interesting that the petition text did reference use of a 293 NAC - -and suggested that this is what is typically utilized on ALL 700mhz nationwide interop channels.....so perhaps we have our answer of the analog/156.7 tone vs digital mode for these.

[doctordave]

I've confirmed that FIRST users will have most of the 700mhz standardized/nationwide freqs available in their radios - - and have submitted them for our MD database under "common freqs" - - - - -and I've also included the specific air-ground freqs that were cited MD's petition to the FCC. If anyone learns that one or more of the air-ground freqs included in the petition was changed during the FCC review, please advise so we can amend the DB accordingly.

[maus92]

Originally Posted by troymail

Google is fun.... here's one:

http://doit.maryland.gov/interoperab...uestWaiver.pdf

I found another one that contains a table with freqs and descriptions of each... I need to find it again....

Post #7 in this thread has a .ppt with tables and A-G freqs - not sure if it's what you were thinking about.

C.

[troymail]

Originally Posted by maus92

Post #7 in this thread has a .ppt with tables and A-G freqs - not sure if it's what you were thinking about.

C.

That's the one I was thinking of..... thanks.

[dpcain]

In regards that affiliation you're seeing Troy, I have noticed that the BC site comes in very weak and barely readable on the scanner from when I exit FMT all the way southbound on 95 from there, while the AA site comes in STRONG. Given that MDTAP FMT patrols all the way to 195 pretty frequently, it's not therefore too surprising that their units south of the tunnel would affiliate with the AA site.

Just to clarify (so do correct me if I'm completely off), from my understanding of these systems as a once-upon-a-time user of a multisite system, unless a TG is locked to a specific site it is handled in 'roam'- aka the user does not consciously switch to a new tower and site, but the radio automatically affiliates with the new site as a user moves from one site's area to another and the signal strengths flip. This in theory (though again possibly me talking out the wrong end) makes the Kent affiliations make a lot more sense- this would indicate that transmission strength to and from there is simply a lot higher, likely due to a pretty stark lack of obstructions as the signal comes across the Bay.

[troymail]

Originally Posted by dpcain

In regards that affiliation you're seeing Troy, I have noticed that the BC site comes in very weak and barely readable on the scanner from when I exit FMT all the way southbound on 95 from there, while the AA site comes in STRONG. Given that MDTAP FMT patrols all the way to 195 pretty frequently, it's not therefore too surprising that their units south of the tunnel would affiliate with the AA site.

Yeah - that's odd but it's also the CQPSK issue because I believe the Baltimore site has a tower on Bush St just off I-95 @ Russell St/Rt 295. The next closest tower (I think) is at BWI but I also believe this is tower on the AA site. However, I do not know for certain since not much of this is recorded on the fcc.gov website.

I seem to have an easier time receiving the Baltimore site from my house and I live south of BWI airport.

I've been wondering if the towers go into low power transmit mode if they don't sense radios affiliated within their range....that would explain some things I'm seeing but it's pure speculation.

Just to clarify (so do correct me if I'm completely off), from my understanding of these systems as a once-upon-a-time user of a multisite system, unless a TG is locked to a specific site it is handled in 'roam'- aka the user does not consciously switch to a new tower and site, but the radio automatically affiliates with the new site as a user moves from one site's area to another and the signal strengths flip. This in theory (though again possibly me talking out the wrong end) makes the Kent affiliations make a lot more sense- this would indicate that transmission strength to and from there is simply a lot higher, likely due to a pretty stark lack of obstructions as the signal comes across the Bay.

That is my understanding as well. If a user is on a talkgroup and it isn't limited to a specific site, it transfers to the next site just like a cell phone -effectively "extending" the coverage to another site (it's really interesting listening to activity in Cecil County all the way down here in Anne Arundel) Therefore, you could easily hear a talkgroup on a site temporarily and then wonder why it disappeared as quickly as it showed up (like MdTA BWI did the first week it went live and hasn't been heard since)

I'd expect that possibly the Kent users would be limited to the Kent site and if they run across into another County, they would switch over to that County's system on their radio (that's the way the radios in AA County have worked for years). On the other hand - State talkgroups may not be as limited. Again - more speculation.

As always - time will tell.....maybe.

[EyeSpy]

So listening in my office and my drive in, seems I am not picking up the FiRST from just inside the Baltimore Co line down to White Marsh. As I get close to Harford, I jump on that tower, but zilch in White Marsh. I will have to let it run all day tomorrow and see while not listening to Baltimore Co... but when I had turned the County off... it was very silent compared to once I hit Harford...

Sent from my DROID3 using Tapatalk 2

[troymail]

Originally Posted by EyeSpy

So listening in my office and my drive in, seems I am not picking up the FiRST from just inside the Baltimore Co line down to White Marsh. As I get close to Harford, I jump on that tower, but zilch in White Marsh. I will have to let it run all day tomorrow and see while not listening to Baltimore Co... but when I had turned the County off... it was very silent compared to once I hit Harford...

Sent from my DROID3 using Tapatalk 2

Maybe just timing? At times, McHenry, Port/Key and MSP JFK are very "chatty" but other times there is quite a bit of silence. What's really important is - are you locking onto the Baltimore site?

On the drive, browse to the wildcard object on the Baltimore site (if you have sites programmed as "Stand-alone") and HOLD on that wildcard object. While driving do you maintain a solid [T] indicating you are receiving and holding on the control channel?

[dcr_inc]

If no radios are in the area of the tower for the talkgroup you are listening to, you won't hear anything.. It's called SmartZone..

[EyeSpy]

Troy, I did in Harford County. So far - nada in Baltimore County. And my office is just off of I-95 where I have JFK and MdTA all the time. Not getting locked on the control channel. Not sure where the tower is on this side (I am off of exit 67 - Rt.43)... I have tried two different antennas and same thing happened today as previous - signal dropped coming further into Balto Co.. I was getting a few hits on hills from Harford but zero on Baltimore here.

I did check all of the freqs and I have all that are listed in RR... No hits in 2 hours here doesn't happen since there are plenty of accidents and traffic stops in this area.