EMRFD Message Archive 9253

Message Date From Subject
9253 2013-10-15 07:37:43 Ashhar Farhan Fm transmitter for a repeater
Nbfm generates infinite sidebands. Thus, their broadband noise too
will be high. Does it make sense to generate nbfm at a lower
frequency, pass it through a 15 khz filter and then upconvert?
The aim is to reduce receiver desensing. A high Performance receiver
will be used.
- farhan

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9262 2013-10-18 01:57:53 ha5rxz Re: Fm transmitter for a repeater

You may find the following document to be of use:


The interesting stuff starts at page 16 where they say:

In practice, the spectrum of an FM signal is not infinite. The sideband amplitudes become negligibly small beyond a certain frequency offset from the carrier, depending on the magnitude of β. We can determine the bandwidth required for low distortion transmissi