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Re: [linrad] Quietening computer noise

Hi Richard,

I haven't seen it directly mentioned here yet, so it might be worth mentioning.
You did not say what you are using for an antenna.
Be very careful that the PC does not become part of that antenna.
If you just use a simple wire connected to the RX, your PC is sure to
be part of your ground plane and will generate noise. I am not so sure
that double sheilded coax is needed at HF, but it is important that
the antenna be remotely located and have its own local independant
ground, depending on antenna type. None of my outdoor HF antennas
pick up RFI from the PC.

73, Jim Shaffer, WB9UWA.

On 2 May 2004 at 20:58, Richard Hosking wrote:

> Dear all
> I have managed to recieve signals on HF using two SBL-1 mixers driven
> by a quadrature LO (AD9854) and a couple of low noise opamps (NE5534).
> Linrad runs in direct conversion I/Q mode. The main limiting factor at
> present is noise from both computer and monitor. The sound card is bog
> standard and the machine is a PII 400 MHz running RH9, but with only
> 64MB of RAM
> Questions
> The max filter bandwidth appears to be about 2 KHz on SSB, and
> narrower on AM  - if I try to make it wider nothing happens. Is this
> due to RAM and processor limitations?
> How to get rid of that computer noise? ( I have made no attempt
> whatever so far)
> Thanks in advance
> Richard