Re: Interference from PC?
- --- In email@example.com, Bill Tracey <kd5tfd@a...> wrote:
> ...the gunk you see near the center frequency with or w/o hardwarenoise
> attached is an artifact of the signal processing architecture, and
> near DC on the audio input (ie 60 hz hum,. etc)...Exactly, and this is one tough sucker to get rid of.
The soundcard is one of the most vulnerable spots for letting in
spurious signals. Most soundards get around the problem by rolling off
the frequency response below 100Hz or so.
Rolling off is not the same as eliminating, however, and when you can
mix the residual spurious signals up into the center of the passband,
they're conspicuous weak signals just like anything else would be.
It is possible through DSP magic to subtract out the gunk, but you pay
for it with a higher MDS. Preferable on the whole to use a better
When I operate on the low bands (40M thru 160M) I have to turn off my
PC's. In fact I sometimes have had to unplug them completely, as the
power supply isn't completely off when the On/Off switch is in the Off
I found the problem to be caused by the computer's switching power
supply. In fact I lost a power supply in one of my computers recenly,
and replaced it with a better grade supply, and then was happy to find
that the noise from that computer was gone.
Try unplugging your computer completely and see if that quiets things
--- In firstname.lastname@example.org, "observer35" <rein0zn@i...> wrote:
> Hi all,
> Just new to the group.
> Does anybody experience interference from the PC on 40 meters?
> What about noise and garbage on the 5 V USB line?
> 73 Rein W6/PA0ZN