Yaesu VX-7R modes (NFM vs. WFM)

[KC0KBC]

I just discovered something that I don't understand. I've had the radio programmed for some time with all my local repeaters as well as some other stuff just for monitoring, and it has always worked well. Tonight I realized that my memories were all set up with the mode set to NFM (narrow FM). Since the 2m and 70cm Amateur bands are FM (wide FM - not narrowbanded), I thought, "why have I had this wrong all this time?" and proceeded to change them all to WFM. When set to WFM, I just get noise on nearly every frequency no matter how high I set the squelch level, and I don't seem to be able to hit even nearby repeaters. Changing them all back to NFM puts it back in working order.

Doesn't this seem backwards?

 

[AK9R]

No. It's a matter of terminology. Wide FM, according to the Yaesu VX-7 manual (page 26), is for receiving broadcast FM stations. Narrow FM is for 2-way voice radio communications.

 

[KC0KBC]

Ah, thank you sir. Nice of them to come up with their own definition of what is otherwise a generally accepted standard.

 

[AK9R]

An FM broadcast signal is 200 kHz wide. I would call that Wide FM.

FM two-way communications started out at 60 kHz wide. Then 30 kHz became the standard and it was "narrow FM". Then 15/25 kHz became the standard and it was "narrow FM". Now we have 7.5/12.5 kHz being used in land mobile radio and it's called "narrow FM".

Since the VX-7 is designed to receive and transmit amateur radio and receive FM broadcast, their arbitrary designations of Wide FM vs. Narrow FM make sense in the context of what the radio was designed for.

Describing a signal as simply "wide" or "narrow" is very ambiguous, in my opinion. Without stating exactly what bandwidth "wide" or "narrow" mean, you really don't know what they mean.