BCDx36HP: WFM Channel Width?

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jonwienke

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NFM is 12.5KHz.
FM is 25KHz.
FMB is 100KHz.
What is WFM?
 

mancow

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I assumed FMB and WFM are the same. The FMB is just noting a service category that uses FMW.
 

jonwienke

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Then why are they separate modulation tags, rather than service type tags?
 

dlwtrunked

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NFM is 12.5KHz.
FM is 25KHz.
FMB is 100KHz.
What is WFM?
First of all, do not confuse step size and band-width. They are not the same thing. What you give above are most often step sizes (and are not the only ones, as 8.33 kHz is the new one coming for aero; and smaller sizes that above are also now in use). Regarding bandwidth, receivesr have a selection but often that selection does not exactly match the ones in actual use by the transmiting stations. As an example, of reality: The FM broadcast band in the US actually uses a 200 kHz step size (88.1, 88.3, etc.) but using a receiver with a 100 kHz step size will not miss anything and makes it more compatible with other parts of the world. The "bandwidth" of an FM broadcast station is actually somewhat complicated. I suggest reading https://en.wikipedia.org/wiki/Frequency_deviation and Bandwidth needed for FM broadcasting. And of course, HD (which in this case stands for Hybid (not High) Definition has digital sidebands making a much wider signal (but when receiving analogue, we tune narrower to ignore them).
 

majoco

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Wide FM - maximum deviation of a broadcast FM transmitter is +/- 75kHz so the receiver needs a bandwidth of 150kHzor more. To add a 'safety factor' adjacent transmitters are spaced at 200kHz intervals as there used to be a sub-carrier at 85kHz with a low deviation signal on it for 'lift music' subscribers. Fortunately FM has a "capture effect" in that the receiver tends to 'lock on' to the strongest signal ignoring an interfering adjacent one.
 

SteveC0625

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NFM is 12.5KHz.
FM is 25KHz.
FMB is 100KHz.
What is WFM?
When I got in the radio manufacturing industry in 1969, marine channel spacing was 50 KHz steps. That was the old original block of 156 MHz channels. The Part 90 spectrum was much the same.

Part 90 has been "narrowbanded" several times since then. Depending on where in time one looks what was narrowband then is viewed as wideband now. What is NFM today will be looked at as FM or even WFM somewhere down the line.

Check your scanner's operator's manual to see if they apply these terms to any channel spacing mode.
 

jonwienke

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Check your scanner's operator's manual to see if they apply these terms to any channel spacing mode.
That was the first place I looked. None of the modes are actually defined. Most of the modes I was able to figure out based on my knowledge and experience with radio stuff, but there isn't anything concrete in the manual I can point to to form a conclusion for WFM. I'm guessing it's something wider than FM but not necessarily as wide as broadcast stereo FM. But that is a guess, and I'd prefer to find out from someone who actually knows.
 

jonwienke

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First of all, do not confuse step size and band-width.
I'm aware of that. Actual bandwidth used is always slightly less than nominal channel width (at least at non-negligible power levels) to prevent bleedover from one channel to the next. But that doesn't tell me how Uniden is defining their modulation type labels. As has been pointed out, yesteryear's "narrowband" is tomorrow's "wideband", and therefore the precise channel width designated by "WFM" is a bit vague.
 

jonwienke

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Thank you, that was exactly what I was looking for.
 
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