GMRS and FRS Compatability

[Don WQXJ891/NI6A]

Per another message thread, a possible problem was identified where GMRS radios set at wide-width FM (WFM) mode and FRS radios set at narrow-width FM (NFM) modes may be incompatible.

In my own experience, I have not found a problem, although NFM FRS radios may sound a bit "tinny" when the receiver is set to wide-band. Likewise, it is possible that a WFM GMRS radios' audio may sound distorted and over-deviated to a FRS NFM receivers.

In regard to weak signal use, Richard brought up a salient point; i.e., that in NFM communications where the power is concentrated in approximately half the spectrum width, the signal is more punchy, while as much as a 3dB gain in the signal may be achieved. If that is the case, what is the advantage of WFM other than perhaps better audio fidelity? Other technical factors could be involved such as width related signal to noise (S/N) ratios, IF filter design, RF detectors, Demodulators, etc. This could be a highly technical investigation, but nothing is better than obtaining hard data in the field especially under fringe conditions. See: https://www.pericle.com/wp-content/uploads/UC-Apr-2010-Narrowband.pdf

If you have a GMRS radio that can be programmed to both NFM and WFM a comparison at both ends with a partner could easily be obtained, but it will be unique to the way those two radios implement NFM and WFM I imagine.

Those who have experimented with WFM/NFM cross-talk please share your evidence.

Thanks and 73,

Don