reception ?

[Roy99664]

I have a friend that works for the D.O.T. on the radio mounted in his truck, he can flip a switch and choose the station he wants to talk to. Be it Nome, Kodiak, Anchorage, Soldotna, etc. all from the yard in Seward. My question is, how does this work? Does flipping the dial direct the transmission to different repeaters or something? Why doesn't my scanner pick up transmissions from all these places? I have heard the Seward DOT talking to Kodiak DOT claear as a bell. I've even heard radio tests of the ALMR emergency system from as far away as Oregon. Why aren't we constantly picking up signals from these places?

Thanks in advance

 

[kikito]

Well, at the risk of oversimplifying:

The ALMR system, just like most radio systems out there is comprised of many sites or repeaters that can and are interconnected by one or more ways like telephone lines, microwave links, fiber optics, Internet, satellite, etc. In the case of the example you provided, the person's radio talking in Seward will be affiliated to the nearest or best reception site the radio can find at the moment they transmit. His transmission on the specific talkgroup he's using will ONLY be transmitted on the sites that have radios afilliated to it AND are also tuned to the same TG. So the person's radio in Kodiak affiliated to a site and tuned to the same talkgroup will be able to hear the transmission from Seward BUT so will someone in Fairbanks or for that matter anywhere in the state that's also tuned in to the same TG. The way the system knows how to properly route the radio traffic is by way of a centralized computer that serves as the "traffic referee".

So in other words, if the two people talking on that specific TG or channel are the only ones talking on it, the transmission will only be transmitted on those two sites or repeaters that the said radios are affiliated to (One in Seward and one in Kodiak) and you will have to be within reception of either site to hear it because it won't be transmitted system wide or statewide.

Of course, with that said, then you can throw in many variables depending on how the radios, the system and TGs are setup and you might have TGs that are transmitted area wide when used or TGs or radios that are only allowed on certain sites or geographical area and so on.

And that's the "oversimplified" explanation! LOL

 

[Roy99664]

Well, at the risk of oversimplifying:

The ALMR system, just like most radio systems out there is comprised of many sites or repeaters that can and are interconnected by one or more ways like telephone lines, microwave links, fiber optics, Internet, satellite, etc. In the case of the example you provided, the person's radio talking in Seward will be affiliated to the nearest or best reception site the radio can find at the moment they transmit. His transmission on the specific talkgroup he's using will ONLY be transmitted on the sites that have radios afilliated to it AND are also tuned to the same TG. So the person's radio in Kodiak affiliated to a site and tuned to the same talkgroup will be able to hear the transmission from Seward BUT so will someone in Fairbanks or for that matter anywhere in the state that's also tuned in to the same TG. The way the system knows how to properly route the radio traffic is by way of a centralized computer that serves as the "traffic referee".

So in other words, if the two people talking on that specific TG or channel are the only ones talking on it, the transmission will only be transmitted on those two sites or repeaters that the said radios are affiliated to (One in Seward and one in Kodiak) and you will have to be within reception of either site to hear it because it won't be transmitted system wide or statewide.

Of course, with that said, then you can throw in many variables depending on how the radios, the system and TGs are setup and you might have TGs that are transmitted area wide when used or TGs or radios that are only allowed on certain sites or geographical area and so on.

And that's the "oversimplified" explanation! LOL

Thanks. Over simplication is good! It has to be simple for me to grasp it
.
I think I got it.

The only traffic our scanners will pick up is off of a repeater that is relatively close, and then only if someone is directing traffic to that repeater by selecting a frequency assigned to an agency in the Seward area. That about it?

 

[kikito]

The only traffic our scanners will pick up is off of a repeater that is relatively close, and then only if someone is directing traffic to that repeater by selecting a frequency assigned to an agency in the Seward area. That about it?

That's it in a nutshell.


The actual radios on the system obviously do not have that limitation. They work just like a cellphone as they move around getting handed off from site to site and it's intended traffic sent to it. So in theory, as long as they have reception of at least one nearby site, the same radio can continue talking throughout the state on the same TG, for example.

Going back to scanners, you could program all the active control channels your scanner can receive wherever you are at the moment and that would expand somewhat on what you could receive. Most late model scanners allow you to program a lot of frequencies associated with the same system and it'll check and track each one, looking for any traffic as long as it can receive the signal reliably.

 

[Roy99664]

Thanks
I think I have a somewhat clear understanding of the basics.

We already went through the RR list of the ALMR system and picked out every control channel freq. listed, and programmed them in our scanners. So, theoretically we have done the correct thing to enable us to recieve all the traffic that is available to our scanners. Correct? ( not counting analog and local systems)

 

[kikito]

So, theoretically we have done the correct thing to enable us to recieve all the traffic that is available to our scanners. Correct? ( not counting analog and local systems)

Yep, you got it! What you did it's also good for when you're driving around and you lose reception on some sites but new/different ones pop up as far as signal reception.

 

[Roy99664]

Thanks for you time and patience. It helped erase the thought that I may be missing a lot of the action by not knowing what I was doing.