Brian wrote:

Randy, those figures are not characteristic of modern processors that
use DSP filtering, which is capable of extremely rapid rolloff.

Take a look at http://n2.net/k6sti/speech.jpg . This is a screen shot
of my HP 141T/8553B/8552B spectrum analyzer tuned to a local AM radio
station broadcasting speech. The analysis-filter bandwidth was 300 Hz,
the vertical scale 10 dB/div, and the horizontal scale 5 kHz/div.

Yep and it shows that at around 7.5 it's down 10db - and not symmetrical
at all- I.e. their pushing the positive modulation WAY harder than
negative - which is probably ok for voice - but would sound pretty lame
for music. Their "tilt" would make them "punchy" all right - (make most
listeners punch-drunk - esp. women who (on average) dislike tinny
sounding stuff - and have the ears to hear it.


http://n2.net/k6sti/music.jpg shows a different AM station
broadcasting classical music. The music spectrum is evident, but so is
the brick-wall filtering at 10 kHz. These spectra are typical of what
I observe for AM stations here in Southern California.

So is the -25db roll-off by 7.5khz - this indeed looks like good
conformance to NRSC-1.


If you have a receiver capable of SSB reception,

Yeah - a few - but I also have an Empire NF-105 calibrated RF / Noise
meter that goes from 14Khz to 1000Mhz. It tells me what I need to know.


best regards...
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
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