I am building a non-regenerative repeater for several waveforms, one of which is AM voice. I'd like to reduce the IF filter bandwidth from 25 KHz to 10 KHz or less to reduce amplified noise power and ACI.
I've seen filters as narrow as 6 KHz used for AM voice HAM radios. Since voice tends to be with 300 to 3000 Hz, this seems like a reasonable bandwidth and i'm wondering if it has the added benefit of improving distortion since the distortion sidelobes for voice freqs above 2000 Hz or so would be getting some rejection thru the filter.
With digital modulation, filtered sidelobes tend to get regenerated when transmitted, but with AM i'm wondering if filtered distortion sidelobes don't get regenerated. Thanks
Tracy Blackford
Comm and GPS Systems Engineer
I've seen filters as narrow as 6 KHz used for AM voice HAM radios. Since voice tends to be with 300 to 3000 Hz, this seems like a reasonable bandwidth and i'm wondering if it has the added benefit of improving distortion since the distortion sidelobes for voice freqs above 2000 Hz or so would be getting some rejection thru the filter.
With digital modulation, filtered sidelobes tend to get regenerated when transmitted, but with AM i'm wondering if filtered distortion sidelobes don't get regenerated. Thanks
Tracy Blackford
Comm and GPS Systems Engineer