BC125AT: Programming question for Uniden BC125AT regarding tone settings and modulation.

[corneileous]

Hey guys, I’ve done a little searching here on the subject but I’m still unsure and confused on what the best settings are when it comes to modulation- auto, am, nfm and fm and as far as in the tone section, what the scanner will do if I set the CTCSS/DCS to off, search, no tone, ctcss frequency or dcs.

Like for example for my local sheriff, the mode on this site’s page for Oklahoma frequencies says it’s FMN which is FM narrow, if I’m not mistaken so would it be better for that channel’s modulation on my scanner to be set to auto or NFM which I believe is the same thing as FMN? For the tone on the same channel, it’s 151.4 PL so is it better to set the tone on my scanner to CTCSS 151.4Hz, off, search or no tone? In other words, how will my scanner scan this frequency based on both the tone settings and the modulation settings? Thanks.

 

[sallen07]

Yes, "FMN" in the database is "NFM" on your scanner. If you know a frequency is narrow-banded you are better off setting the correct modulation.

If you set the PL tone, you won't hear anything on that frequency other than the agency you want to hear. If you leave the tone off (or set it to search) then if someone else is using that frequency within range you'll hear them too. Chances are that won't happen, but most people set the CTCSS or DCS tones if they know them.

 

[corneileous]

Yes, "FMN" in the database is "NFM" on your scanner. If you know a frequency is narrow-banded you are better off setting the correct modulation.

So what if you don’t know if a frequency is narrow-banded and you’re just going off what the information says on the site?

But I guess most importantly, is there really any change that’s noticeable if I leave the modulation set to auto as opposed to matching the programming to what it says on the website to my scanner?

If you set the PL tone, you won't hear anything on that frequency other than the agency you want to hear. If you leave the tone off (or set it to search) then if someone else is using that frequency within range you'll hear them too.

So what you’re saying, at least to what I think you’re saying, anyways, only the people that are transmitting from a radio that has that same tone programmed into their radio is what I will hear, correct? And that like, say for example, a fire department or EMS person wants to talk to an officer on that officer’s frequency, I most likely wouldn’t hear that person because they might not have that tone programmed into their radio? I guess I’m just still not quite understanding how that works that would determine what I would hear if somebody outside that agency keys up on that frequency and I have that frequency’s tone programmed into my scanner.

But to add to that, what’s the difference in leaving the tone set to off as opposed to search?

Chances are that won't happen, but most people set the CTCSS or DCS tones if they know them.

But what do you mean chances are that won’t happen and OK, I get it that most people would program in the tones if they knew what they are, I’m just trying to figure out what the best would be for me having them programmed in or not because I still don’t quite understand what I would be gaining or losing while having that tone programmed in or not.

Sorry to be naïve about this but I’m still used to an old scanner that didn’t give you these kind of options when you go programming the frequencies into it… Lol.

 

[sallen07]

So what if you don’t know if a frequency is narrow-banded and you’re just going off what the information says on the site?

That's how you know.

Almost all public safety (except for VHF Lo) is narrow banded in the US.

But I guess most importantly, is there really any change that’s noticeable if I leave the modulation set to auto as opposed to matching the programming to what it says on the website to my scanner?

It may "pick" the wrong one. If you listen to a NFM signal using FM the audio will be low.

So what you’re saying, at least to what I think you’re saying, anyways, only the people that are transmitting from a radio that has that same tone programmed into their radio is what I will hear, correct? And that like, say for example, a fire department or EMS person wants to talk to an officer on that officer’s frequency, I most likely wouldn’t hear that person because they might not have that tone programmed into their radio? I guess I’m just still not quite understanding how that works that would determine what I would hear if somebody outside that agency keys up on that frequency and I have that frequency’s tone programmed into my scanner.

In almost all cases, if you are listening to public safety you are listening to a repeater. So you aren't listening to the transmission from the individual radios, you are listening to the re-broadcast of that traffic through a repeater. The CTCSS or DCS tone you are programming into your scanner is the one sent by the repeater.

If there is another repeater (for example) 50 miles away it will be using a different tone.

But to add to that, what’s the difference in leaving the tone set to off as opposed to search?

If you set the scanner to search for the tone it will display it. So you can program it in.

But what do you mean chances are that won’t happen and OK, I get it that most people would program in the tones if they knew what they are, I’m just trying to figure out what the best would be for me having them programmed in or not because I still don’t quite understand what I would be gaining or losing while having that tone programmed in or not.

Sorry to be naïve about this but I’m still used to an old scanner that didn’t give you these kind of options when you go programming the frequencies into it… Lol.

Understood.

Actually the bigger advantage of using tones is that the squelch will not open unless the scanner detects the tone. That way you can set the squelch lower and not have the squelch open if the frequency is noisy.

 

[corneileous]

That's how you know.

Almost all public safety (except for VHF Lo) is narrow banded in the US.

It may "pick" the wrong one. If you listen to a NFM signal using FM the audio will be low.

Oh OK so being that my scanner when it stops on a channel, it tells you what the modulation is set to but the only way to know if it accidentally set the wrong modulation is you’d have to know what it truly is to see that it wouldn’t be right which kind of makes me think it would be better to just go ahead and set the frequency to the proper modulation.

In almost all cases, if you are listening to public safety you are listening to a repeater. So you aren't listening to the transmission from the individual radios, you are listening to the re-broadcast of that traffic through a repeater. The CTCSS or DCS tone you are programming into your scanner is the one sent by the repeater.

If there is another repeater (for example) 50 miles away it will be using a different tone.

If you set the scanner to search for the tone it will display it. So you can program it in.

Understood.

Actually the bigger advantage of using tones is that the squelch will not open unless the scanner detects the tone. That way you can set the squelch lower and not have the squelch open if the frequency is noisy.

So then what would you do if you have frequencies that use a tone and some that don’t? The reason why I ask is because if I’m understanding you correctly about setting the squelch to a certain level, because of the tone that that might affect the other frequencies that don’t use a tone, depending on where the squelch was set for the channels that do have a tone.