Police, FIre EMS - Shift from FM to Narrow Band FM in Massachusetts?

[aeromarine]

I was under the impression that police and fire agencies across the state had to shift to NFM a while back. However, in looking at the Radio Reference Frequency Database, it still shows many towns to be using FM. Is that correct or are the RR files out of date?

I ask because I'd like to update my ICOM scanner and Baofeng radios. Given the large numbe of frequencies I have in my datafiles for Mass it's not really practical (or easy) to verify each town individually, though in a pinch, that may be what I have to do. So, I was hoping others may have dealt with this issue already and can give me advice based on their experience.

Please comment if you have any suggestions. Thanks!!!

 

[Uzi2]

If you put the frequencies in your radios, with or without the narrow band option, they'll still work.

The narrow banding was done to limit the deviation of the wider band FM signals and provide more space in between the existing assigned frequencies, thereby allowing more stations per given amount of spectrum.
A wide band FM signal sounds better, but if the transmitting station is using NFM (narrow band FM) that is all you will hear on your receiver/2way. The narrow band modulation doesn't have the fidelity of wide band FM but it will be intelligible.
They both use the same center frequency.

 

[ToddDubya]

If your radio is expecting wide and someone transmits narrow, it'll sound quieter. They're not using as much deviation as the receiver expects. I assume the reverse may cause distortion. But to be honest I can't say I've ever tried it to see if it makes a appreciable difference.

 

[s&w3913]

The database maybe wasn't updated to reflect NFM. Also on low-band frequencies 30-48 mhz use FM still. I still think a powerful low band mobile simplex with a full size antenna will get you out on a mobile radio. Which is why Holland and Wales Police still use 44.740. However, your ability to use a low band only portable is diminished the antenna is huge, the range limited. Most have crossband VHF or UHF vehicle repeaters that link back to the mobile low band simplex radio.

 

[Uzi2]

The database maybe wasn't updated to reflect NFM. Also on low-band frequencies 30-48 mhz use FM still. I still think a powerful low band mobile simplex with a full size antenna will get you out on a mobile radio. Which is why Holland and Wales Police still use 44.740. However, your ability to use a low band only portable is diminished the antenna is huge, the range limited. Most have crossband VHF or UHF vehicle repeaters that link back to the mobile low band simplex radio.

All low band VHF, High band VHF and UHF public safety radios operate in the FM mode, either wide band or narrow band. Some use "companding" in conjunction with narrow band FM, others don't.

Low band VHF works better in hilly terrain because it is less line of sight dependent and the radio waves bend around geographical obstacles. "Huygen's Principle".

The higher you go in frequency, the more direct line of sight dependent the signals become and that is why there is a condition known as "RF shading". VHF and UHF signals can be blocked or severely diminished (shaded) by terrain and groups of large buildings. This is why repeaters are usually located in a spot with a long visual horizon.

When dealing with microwave frequencies, they are extremely line of sight dependent and the antenna horns must be looking directly at the aperture of the other antenna or the signal just goes by the receiving antenna.

 

[UJay]

My town just switched to p25 digital. Old scanners and Icoms won't work with the digital solutions the towns are moving to.

App 'Scanner Radio' handles it.

 

[Roscoe]

My town just switched to p25 digital. Old scanners and Icoms won't work with the digital solutions the towns are moving to.

App 'Scanner Radio' handles it.

Can the fancy bearcat scanners decode it ? Its not encrypted I don't think.

 

[Talon3]

Can the fancy bearcat scanners decode it ? Its not encrypted I don't think.

Yes a new p25 capable scanner tunes in p25 crystal clear. I have the uniden bcd15x works great at p25 reception.

 

[flippinfleck]

My town just switched to p25 digital. Old scanners and Icoms won't work with the digital solutions the towns are moving to.

App 'Scanner Radio' handles it.

That's just someone with a capable scanner or radio that streams it over the internet. Sometimes it is a sanctioned stream that is done by an employee.

 

[appraiser]

kind of like www.liveATC.net


They are always looking for people near airports to set up a scanner and feed them via the interwebs