Re: Noise band around the centre frequency
- Hi Rob,
I too had problems with feedback from input to output using a SB Live
24 PCI card. I worked round it by using the onboard AC97 sound for
output, rather than by finding a proper fix :-)
73, Neil G4BRK
--- In firstname.lastname@example.org, "Rob Campbell" <gm6oqn@...> wrote:
> I've seen a few comments about the noise around the centre frequency
> and would like to add my experiences.
> While I was testing my SR6 at work I had the output connected to the
> audio-in socket on the back of my keyboard and a pair of small
> headphones on the audio-out. In other words, the I/Q signals from
> the SR and the PC audio out were bundled together in the keyboard
> cable (odd but useful HP arrangement). I could see the usual spike
> at the centre frequency but with no input signal from the rf signal
> generator, when I increased the volume on the headphones (they've
> got their own in-line control) the noise band also increased!
> I can't see any reason for this other than crosstalk between the I/Q
> and audio-out signals. To put it another way, careful screening and
> routing of the audio signals should minimise crosstalk and help keep
> the noise band to a low level.
> I wonder if this is why some sound cards behave better than others
> in this respect - manufacturers paying close attention to signal
> routing to keep crosstalk down.
> Rob GM6OQN