Fleetnet Question (input freq's)

[unusualtech]

Okay here is a question. Sometimes I listen to input frequencies to a specific Fleetnet tower and I hear and see the signal bars.

Now there are times when i am close to the vehicle that I get perfect signal and crystal clear sound just as if i were listening to it on the frequency from the tower.
BUT.. here is the question: Why is it that if I am in between the vehicle and the tower, and the vehicle is far away from me, I can hardly hear what they are saying (i..e too broken ) or not hear anything at all But yet still be able to hear them clear as day on the output tower frequency?
Logically, if their transmission is barely making my radio how is it making it that much further to the fleet net tower that is associated to the input frequencies???

any BMR techs on here that can answer this ? or any one with a definite answer?

thanks in advance

 

[foxtail]

I think they are repeaters. I don't know enough about them, but I'm sure others here do.

 

[davidmc36]

Take look at how high the tower is and how high your antenna is and you have your answer. The transmitting car has a good line of sight to the top of the tower but not to your scanner.

 

[mikewazowski]

You're also comparing a cheapy scanner that covers a lot of frequencies but doesn't excel at receiving any of them with a tuned mega dollar receiver built to receive a small range of frequencies extremely well while rejecting interference.

Your antenna is also a compromise. It receives a wide band of frequencies (once again not excelling at any particular range of frequencies). The tower's antenna is specifically tuned to one band and within that band, a small range of frequencies.

 

[unusualtech]

Okay, well the line of sight thing seems logical.
However I have an antenna tuned to ~141.0000 Mhz -+ 3Mhz (i.e. it is not the stock antenna- I got it for fleet net towers).

So what you are saying is that a line of sight + exceptional receiving of the very specific input frequencies = clear output?

 

[davidmc36]

So what you are saying is that a line of sight + exceptional receiving of the very specific input frequencies = clear output?

Pretty much yes in a nut-shell. You are going to have trees, buildings, etc. in your path but to the transmitting unit but the tower will not.

Plus what mike said about receivers.

 

[unusualtech]

Another question

if a radio in a car is associated with more than one tower what frequecy is it outputing? is it dependent on how close it is to the specific tower (that is to say if it moves from Kitchener to oakville, obviously the input frequencies will be different between the two towers) . so how does the radio deal with this seamless transition in the zone 1 fleetnet area??

 

[mikewazowski]

Radios are only affiliated with the tower that has the strongest signal and it will use the input for that tower.

 

[unusualtech]

Radios are only affiliated with the tower that has the strongest signal and it will use the input for that tower.

Okay, so what is the difference of Affiliating in the manner you described and affiliating in which a TG can be heard over various select towers. i.e. MTO or OPP units that are no where near the selected towers?

 

[mikewazowski]

There's only one type of affiliation that a radio does. It generally finds the tower with the strongest signal and affilates to it.

The system determines which towers to broadcast the talkgroups from based on whether there are any radios affiliated on that talkgroup on that tower.

 

[unusualtech]

There's only one type of affiliation that a radio does. It generally finds the tower with the strongest signal and affilates to it.

The system determines which towers to broadcast the talkgroups from based on whether there are any radios affiliated on that talkgroup on that tower.

Okay what about the BMR techs. I can hear them doing testing far far away.
or the have been other times i have heard certain TG's that are province wide. Is there anyway for the techs to have a certain TG broadcast on all or be able to exclude where the TG broadcast. i.e. Guelph main never gets EMS even though a bus could be right by the tower.

please explain

 

[mikewazowski]

Just because the techs talking are far away, doesn't mean there's not a local tech listening. Keep in mind that the switch which controls Zone 1 is located in Cambridge so the likelihood of a BMR tech being close to Guelph is high.

I don't know which site you're referring too. Site 2 which serves the City of Guelph is setup in such a way that non City of Guelph units will prefer the Woodlawn (Guelph West) site.