FMN Questions ??

[Tracker44]

Hello, I have read about FMN types of signals . I tried to find out more information about what FMN is , but the information is a little sketchy . They seem to want to focus in on FM signals , which the FM part of FMN may be that ????
I understand about FM-AM-SSB radio signals.
What is FMN and is it necessary to enter it into the scanner to receive a signal ????
If so how is that done, maybe like the NAC ???? Useing ARC500 software.
I am useing a Radio Shack Pro 651 scanner with ARC500 software.
TNX again ------Tracker44

 

[mmckenna]

FM = Frequency Modulation.
FMN = Frequency Modulation Narrow.

Basically the hobby way of saying narrow band FM. 12.5KHz bandwidth/2.5KHz deviation.

When you are talking about scanners and LMR radio, FM usually refers to 25KHz bandwidth frequency modulation. FMN usually refers to 12.5KHz bandwidth frequency modulation.

Not a huge deal if it isn't set up right, you'll still hear something. Listening with a wide band FM receiver to a narrow band signal will result in low audio. Listening with a narrow band FM receiver to a wide band signal will often result in distorted audio. It'll sound better if you have it set correctly.

In most parts of the VHF and UHF LMR bands, narrow band (NFM) has been mandatory in the USA since January 01, 2013. VHF Low and some 800MHz systems are wide band FM.

 

[ecps92]

Experiment with your local signals
Try them in both FM and FMN

I've got local Repeaters/Agencies that have gone FMN aka Narrowband FM that still sound better in FM than FMN, also with the Pro651 as you find with is better, experiment with the "AudioBoost" to compensate for the lower audio that FMN brings. YMMV as the audio levels will vary based on who the RF Tech at the department was

Hello, I have read about FMN types of signals . I tried to find out more information about what FMN is , but the information is a little sketchy . They seem to want to focus in on FM signals , which the FM part of FMN may be that ????
I understand about FM-AM-SSB radio signals.
What is FMN and is it necessary to enter it into the scanner to receive a signal ????
If so how is that done, maybe like the NAC ???? Useing ARC500 software.
I am useing a Radio Shack Pro 651 scanner with ARC500 software.
TNX again ------Tracker44

 

[QDP2012]

Hello, I have read about FMN types of signals . I tried to find out more information about what FMN is , but the information is a little sketchy . They seem to want to focus in on FM signals , which the FM part of FMN may be that ????
I understand about FM-AM-SSB radio signals.
What is FMN...?

I'm sure the experts on here can give a better answer than I can. As a quick-answer to the question about FM, here are a couple of links that might help:

• Radio Reference Wiki: Modulation Methods
  This page explains a little more about Modulation. The information about FM, NFM, etc. is near the bottom of the article.
  
  
• Wikipedia: Frequency Modulation
  This article is more in-depth. The calculus math might be more than you are wanting right now, but near the top of the article is an animated graphic which shows the relation between AM and FM wave-patterns.

...is it necessary to enter it into the scanner to receive a signal ????...

Yes, in-general, your scanner should have the correct modulation setting for you to hear the radio-traffic.
When you look in the RR Database at a list of conventional frequencies, you will see the correct modulation settings in the "Mode" column. (Random Example: RRDB: Dallas Texas)

...If so how is that done, maybe like the NAC ???? Useing ARC500 software.
I am useing a Radio Shack Pro 651 scanner with ARC500 software.

To adjust a Conventional Frequency's Modulation setting in ARC500,

• Open ARC500
• Open your data file.
• Enable Expert Mode (Click Menu "View", and choose option "Expert".)
• In the left column, click on "Conventional".
• In the right main window, navigate to the row that contains the frequency of interest.
• On that row, navigate to the cell in the "Mode" column.
• Double-click on that cell. This will display a pull-down arrow.
• Click the pull-down arrow to display a list of modes available.
• Choose the desired/correct mode.
• Navigate away from the cell.
• At this point, you have successfully adjusted the Modulation Mode for the frequency on that row.

Hope this helps,

 

[Tracker44]

TNX every one for the great information, that explains alot , I guess I should have known that , but there are still things about scanning and useing the software I run across every day that I am not sure about , but we are working on that .
The Audio Boost is something that I always set to on, and the scanner stays in the Expert Mode. So I guess I have that covered.
I will start paying alot of attention to the right mode if that is something that is given. Something that is very important to me is ounce you know what the Mode is, the proper way to enter it into the scanner with the software.
I believe QDP2012 covered that and TNX a bunch for the great detail.
I would really be in a mess sometimes if not for the great help here in the RR forum.
TNX again and have a Great 4th of July.
Tracker44