I have been experimenting with the K3's synchronous AM feature
and was wondering about why I am hearing a background "roar"
whenever I tune in an AM broadcast station that is running
HD. The "roar" is not something supersonic, but is heard right through
the audio that runs from 30Hz to 5kHz. I am a broadcast engineer dealing
with AM transmitters, and am familiar with the AM HD transmission techniques.
The HD sidebands are located approximately 6 to 17 kHz removed from the
carrier, are about 20db down from the carrier, and when detected on an AM
envelope detector, are heard as a "hiss". I was thinking that if the K3's
bandwidth was narrowed
to less than 6 kHz, using both the 6 kHz roofing filter and
the DSP filtering, the digital HD sidebands would simply be
unheard since they would fall outside of the bandwidth of
the receiver. Using the K3 in standard AM mode, thats just
what happens, you hear no "roar" underlying the detected audio.
However when switched to either synchronous
mode or USB or LSB in SSB mode, those HD sidebands appear to
be causing that "roar" in the detected audio. That also got me
to wondering what effects other spurious signals near an AM
(or SSB) signal would be audible or detectable as "noise" or
any other artifact in the detected audio. Has anyone else
found this to be happening on their K3's in synchronous AM or
SSB modes?
Ted W8IXY
_AMFMTV@AOL.com_ (mailto:
[hidden email])
______________________________________________________________
Elecraft mailing list
Home:
http://mailman.qth.net/mailman/listinfo/elecraftHelp:
http://mailman.qth.net/mmfaq.htmPost: mailto:
[hidden email]
This list hosted by:
http://www.qsl.netPlease help support this email list:
http://www.qsl.net/donate.html
Locked
