[Elecraft] K3 KFL3B-FM Change?

[David Woolley]

> In the telephone world, equipment allows out to 4Kc.
> That was considered optimal for intelligibility vs bandwidth. 
>
The telephone network bandwidth is 3.1kHz (300 to 3400Hz).  4kHz was the 
analogue bearer channel separation, and allows for realistic shape 
factors on the channel filters.  On digital signals, the 8kHz sampling 
rate allows the use of realistic anti-aliasing filters when the audio 
bandwidth is 3.1kHz.


> For swl use, 16Kc is not unreasonable for people with good ears, that gives
> 8Kc 

The channel spacing for SW broadcast stations is 5kHz,  although I 
suspect they are are allowed to overlap each other.  I'm sure there are 
standards for this, but I suspect a well maintained transmitter is 
limited to a similar audio bandwidth as the telephone system, or less. I 
would think that one would normally expect to be received with a filter 
that was well down the skirt at 10kHz, so as to suppress the adjacent 
carriers.  Propaganda stations and commercial ones in a poorly regulated 
environment might well transmit more bandwidth.  (Medium and long wave 
transmissions use 9kHz channel spacing.)

-- 
David Woolley
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