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Old 02-16-2013, 3:44 PM
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Default NFM vs FM

Hello all,

This to me I think is a fairly simple question that I do not know the answer to. I have two icom 880h radios and absolutely love them. I'm messing with the programming for the first time in a while seeing as how i just moved across the country. I have a few questions about NFM and FM.

1. When it comes to simplex/repeated 2m/440 frequencies I have always kept to FM due to the face it takes less power to transmit the same range/clarity than at NFM. But, I always assumed that for the running step programming, it was mainly a VFO thing (ie scrolling through frequencies). However in my programming software, it has a tuning step field per memory channel. Does it matter what's in that field?

2. I also have some local fire/pd channels programmed in seperate banks as rx only. There are a few agencies that had switched to NFM. Does my receive capability change between setting the radio from NFM to FM or is it a TX thing. Also does the running step apply when listening on one of these frequencies.

Sorry, but Id like to have these radios programmed right the first time for optimal RX/TX(when applicable) than to have to reprogram everything.
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Old 02-16-2013, 3:45 PM
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Default NFM vs FM

Running should be tuning.
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Old 02-16-2013, 4:44 PM
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From the 880 specs...
Max. frequency deviation 5.0/2.5 kHz (FM, wide/narrow)
....to my mind they are both NFM compared to the VHF FM broadcast band deviation of +/-75kHz.
I would expect most users and repeaters are set up for the 5kHz deviation - I haven't heard anybody here using 2.5kHz but then all you would notice is that the audio volume is low. The transmitter power output and hence battery useage won't change - you're only wobbling a carrier up and down in frequency, not amplitude as in SSB or AM.
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Old 02-16-2013, 5:53 PM
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That 'step' is mainly for how far the VFO changes in receive. If you have the larger 'step' then entering a frequency that's slightly 'off' will result in the radio 'converting' it to the nearest 'step' division. So it's sort of a 'finer' tuning of the VFO. Make sense? That has nothing to do with the transmitted signal being 'wide' or narrow'. The 'step' function only applies to the receiver.
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Old 02-16-2013, 7:15 PM
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Ham Radio should be FM and Not NFM. Public Safety and Business could be both FM and NFM
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Old 02-16-2013, 8:14 PM
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dupe. self delete

Last edited by rapidcharger; 02-16-2013 at 8:17 PM..
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Old 02-16-2013, 8:16 PM
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I think you're confusing tuning steps with deviation. It's a common point of confusion.
When possible, I set my tuning steps to 2.5khz. Most ham rigs won't do 2.5 tuning steps but it enables you to receive more frequencies, an increasing number of which are public safety or business splinters. It will make your radio take long to scan or tune manually but you'll be able to tune more accurately and tune into frequencies like 146.4525.
Most ham rigs will only go to 5khz steps. So with 5khz steps you'd be able to tune 146.450 and 146.455 but not 146.4525. Thats not all that useful in the ham band but if you like to listen to other radio services or 900mhz ham, it is.

As for FM vs. NFM, that depends on what the repeater is set up for. All business and public safety should now be narrow because of the mandate. That doesn't mean all are but all should be. The ham band didn't have a narrowbanding mandate and practically none of it is NFM.
If you RX a wideband signal and your radio is set to narrow, the received audio will be low.
If you TX in narrowband on a ham rerpeater set up for wide your audio will sound low to everyone else.

Welcome to the hobby. This will all start to make sense before long.
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