"FM Center Indicator"

[shortride]

While reviewing the R7100 Instruction Manual and familiarizing myself with the definitions of the display, I find indicator No. 47 "FM Center Indicator" on the lower left of the display on page 5 of the manual a little confusing. As the description explains, I understand what the symbol is and what it means but what does the "FM" in the title of the paragraph stand for? The center of a received signal can be displayed on any one of the modes with the except of USB and LSB. Normally FM stands for frequency modulated but in this case I don't think so.

 

[dkf435]

The center tunning indicator only works when in the FMN,FM and WFM modes. Also as the radio ages sometimes this indicator will be off and things may need to be realigned. When the AFC control is turned on it will automaticallly tune the radio to the center of the carrier.

David Kb7uns

 

[shortride]

The center tunning indicator only works when in the FMN,FM and WFM modes. Also as the radio ages sometimes this indicator will be off and things may need to be realigned. When the AFC control is turned on it will automaticallly tune the radio to the center of the carrier.

David Kb7uns

Thanks but I evidently didn't ask the question correctly.

What does the "FM" mean or stand for in the title?

 

[Squad10]

FM = Frequency Modulation

(Pg 39) R7100 Selectivity:

FM-N (N=Narrow) More than 6.0 kHz/ - 6dB
FM More than 15 kHz/ - 6dB
WFM (W=Wide) More than 150 kHz/ - 6dB

Frequency modulation - Simple English Wikipedia, the free encyclopedia

RF Receiver Sensitivity :: Radio-Electronics.Com

Radio Receiver Selectivity :: Radio-Electronics.Com

 

[n5ims]

The "FM Center Indicator" is basically a tuning aid to help you correctly tune the station correctly. For example a station is broadcasting on 146.940 MHz. You're tuning around and pick it up on 146.935 MHz and it sounds OK, but not great. Your indicator will instruct you to keep tuning up in frequency to the correct frequency. You tune it up, but a bit too far to 146.945 MHz so now the indicator should instruct you to tune down in frequency. You then land on 146.940 MHz and the indicator should show you're exactly on frequency for that signal.

The "center" part is because FM works by varying the signal's frequency as a way to modulate the signal (it isn't all that wide of a swing, but it's there - just how wide depends on the FMN for a narrow swing, FM for a moderate swing, and WFM for a wide swing in frequency). For the clearest signal, you should "center" your radio's tuning on the "center" of the transmitter's frequency swing so both the above and below center movements are identical.