MD Dept. of Transportation

[TinEar]

I'm trying to get a clearer picture of their frequencies and channel numbers. The info in the database is not complete and has a couple of minor discrepancies.

The police at BWI airport use channel 8 (453.9) and channel 9 which is 453.8. Then we come to the Baltimore Port and various bridges and tunnels.
Channel 1 is 453.1 and the controller there is McHenry. One guy from there announced he's going to channel 6 which turned out to be the 453.575 (PL167.9) frequency. Are the other versions of 453.575 with different PL tones different channels? How does the operator select which 453.575 he wants? Or does he not get to select any of them and just gets the one that's associated with his duties?
We've got PL167.9 which is Port of Baltimore and Key Bridge. This one we know is channel 6 to the guys that work McHenry 453.1
We've got PL127.3 which is Bay Bridge.
We've got PL173.8 which is Hatem Bridge.

I'm looking for the rest of the channel numbers and their associated freqs. There is also the question of whether the BWI channels 8 and 9 are in the same sequence with the guys at the bridges and ports.

 

[fourwd1]

Not sure about now, but on the Bay Bridge they used to use .100 in one direction and .575 in the other (ie eastbound or westbound). Diff PL's from other users of those freqs. I'd have to check my data at home for specifics.

 

[Spleen]

Their license still has 453.475 listed...could that be the missing channel?

 

[ka3jjz]

Their license still has 453.475 listed...could that be the missing channel?

Unless they use it for mobiles or a tac channel (possible), nope. I've had that freq on al morning with RecAll and nary a peep.

73s Mike

 

[Spleen]

Nope, nothing here either. At that power and location, if they were using it, they should be blowing me out of the chair...perhaps they're sharing with MDOT at some point? The airport freqs are licensed as MDOT Aviation, the Fort McHenry freqs as MD Transportation Authority....not that for a minute I would believe such a sharing arrangement would be a conscious attempt at interoperability....

 

[Spleen]

And what's better, looking for that stuff led me to the frequencies they use down at the football stadium, which are listed under the MD State Lottery Agency...

Perhaps someone could check these out Sunday afternoon when the Giants are in town before I bother submitting them:

453.15
453.325
453.375
453.55
453.875
453.95
458.15
458.225
458.375
458.55
458.875
458.95

 

[Dewey]

I don't know if this helps, but I did notice that no one else has posted this freq... on the Harry W. Nice Bridge, they use 453.975 / 127.3.

 

[TinEar]

Thanks Dewey. I should have mentioned that one too but simply forgot about it when I posted the rest of them. That .975 freq is obviously one of the missing channels numbers.

I still have that basic question about whether the 453.575 freq is considered three different channels in their radios depending on the three PL tones used there or do they have a way to select a particular PL tone within the same channel structure? That's one of the keys to solving the channel plan.

 

[ka3jjz]

Thanks Dewey. I should have mentioned that one too but simply forgot about it when I posted the rest of them. That .975 freq is obviously one of the missing channels numbers.

I still have that basic question about whether the 453.575 freq is considered three different channels in their radios depending on the three PL tones used there or do they have a way to select a particular PL tone within the same channel structure? That's one of the keys to solving the channel plan.

It might very well be; sounds like its time to use those multiple search ranges that the Unidens have and start scanning ranges.
One channel that's not been mentioned yet is one I found not long ago; 453.1375 (127.3) is a garage, maintenance and courtesy van frequency at BWI.
Just exclude the freqs you know; anything else that comes up, say in the 453 thru 454mhz range is a potential target.

73s Mike

 

[TinEar]

Yes, but even with that method of searching, I still won't know if 453.575 is just channel six no matter which PL tone is used, or whether 453.575 and the three PL tones are channels 4, 5 and 6 (or 5,6,7 - but you get the idea), depending on the PL tone, for instance. That's my biggest problem right now since I don't know how an officer that wants to change from Key Bridge to Bay Bridge does it. Does he select a separate channel to change the PL tone? Or does he have a way to stay right there on channel 6 and just change the PL tone. I'm thinking it almost has to be separate channels.

 

[Admin0140434]

I don't know how an officer that wants to change from Key Bridge to Bay Bridge does it. Does he select a separate channel to change the PL tone? Or does he have a way to stay right there on channel 6 and just change the PL tone?

ill clear up this mess (a little). they have to switch channels. there is no way an officer can "select" a PL tone for the frequency he/she is on. so for an officer to change from Key Bridge to Bay Bridge, he simply changes to the channel on his/her radio.

 

[ka3jjz]

Yes, but even with that method of searching, I still won't know if 453.575 is just channel six no matter which PL tone is used, or whether 453.575 and the three PL tones are channels 4, 5 and 6 (or 5,6,7 - but you get the idea), depending on the PL tone, for instance. That's my biggest problem right now since I don't know how an officer that wants to change from Key Bridge to Bay Bridge does it. Does he select a separate channel to change the PL tone? Or does he have a way to stay right there on channel 6 and just change the PL tone. I'm thinking it almost has to be separate channels.

Yeah, and I don't know of too many manufacturers that sell external tone decoders; that way, with a discrim tap, when the frequency hits - even during a search - the PL would be detected.
Well insofar as changing PLs and staying on the same frequency, ham HTs have had this ability for years; I can't see why the commercial/professional market wouldn't also have this ability. For ease of use and speed, it probably is programmed with a different channel number. Too bad I don't know any MTA personnel.....

73s Mike

 

[Dispatcher308]

Ok folks look at it this way we have six frequencies on the DOT page for the MDTA and we have 8&9 on the BWI page so somehow we have all but 1 frequency so wee will have to find out the Channel designators for those and also try to find the 7th frequency. it is going to take a little time but we will eventually get it.

 

[Spleen]

ka3jjz said:

Well insofar as changing PLs and staying on the same frequency, ham HTs have had this ability for years; I can't see why the commercial/professional market wouldn't also have this ability.

That's all you're doing when you change the "Interference Eliminator Code" in a Talkabout, you're just changing the CTCSS setting. Poor innocent radio buyers think it's some sort of sweet way of adding channels...