No, Carson's rule is occupied bandwidth = 2*(deviation + maximum modulating frequency)
For 5 KHz deviation and 3 KHz highest modulating frequency, bandwidth is 16 KHz. For 4.5 KHz and 3 KHz, it's 15 KHz, not 13. Jack K8ZOA Lyle Johnson wrote: >> Typical FM bandwidth is 5Khz, so the DSP really needs to be changed as >> in its current state the K3 is chopping off 1Khz of received signal in >> FM, or 20% of the bandwidth. >> > > There is more than one FM standard in use in Amateur radio around the > globe. In some parts of the U.S., 2 meter channels are on 20 kHz > spacing, some are on 15 kHz spacing. In some parts of the world, > channels are 12.5 kHz apart, or moving towards 12.5 kHz spacing. > > The rule of thumb for FM signals is that the bandwidth is (2 * > deviation) + Fmod where Fmod is the highest audio frequency. This is an > oversimplification, but serves to illustrate the idea. > > In the K3 we have a 13 kHz wide IF filter. By limiting deviation to 4.5 > kHz and Fmod to 3 kHz, we occupy about 12 kHz. > > If we allowed 5 kHz audio and 5 kHz deviation, we'd occupy 15 kHz. Such > operation leaves no room for frequency error or adjacent channel > rejection in a 15 kHz channel region. > > By limiting the audio response to about 3 kHz, we ensure that we are > compatible with existing channels and will be compatible with future > narrower channels. > > In the case of AM, we will be increasing the upper audio frequency response. > > 73, > > Lyle KK7P > > > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > > _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
