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How can I reduce HF noise over the USB cable?

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  • peeraxel
    My old motherboard has died (KV2 Lite), that s why I use a new PC (ECS A740GM-M). But it causes very strong noise on my Perseus, the sort typical for power
    Message 1 of 6 , May 3, 2010
      My old motherboard has died (KV2 Lite), that's why I use a new PC (ECS A740GM-M). But it causes very strong noise on my Perseus, the sort typical for power supplies. It is very strong around 480 KHz (up to -40 dB), still bad around 1600 KHz (-60 dB) in the evening. The noise clusters are constanttly drifing downwards, a few KHz every minute.
      Funnily the noise is weaker when the overall signal level is weaker, too. But it is definitely caused by the PC. When I use my laptop (HP6715s) with the Perseus at the same place, the noise has only -82 dB at 480 KHz which would be more or less acceptable. And when I switch off the PC, the noise is gone. I use the laptop with the accu. When I use its power supply, it causes other noise clusters, but weak enough to get along with that.

      By the way I use the ALA1530S as an antenna. It is outside, more than 10m away from the computers.

      So using the laptop with the same setup, the noise is much weaker. So where does it come into the Perseus? It can only be the USB cable. I'm using the one supplied with the Perseus, with HF reduction (the thick part close to the PC connector).

      Now should I exchange the power supply? I can't use the old one, the connectors are different. Which one would do it? Are there any solutions for the USB cable? And has anyone in the group experienced similar problems?

      Thanks in advance for your help.
    • Jurgen Bartels
      ... Disconnect the antenna and put a 50 ohm termination at the input terminal. Is the noise still present? If not then your antenna picks it up, probably
      Message 2 of 6 , May 3, 2010
        > So using the laptop with the same setup, the noise is much weaker. So where
        > does it come into the Perseus? It can only be the USB cable. I'm using the one

        Disconnect the antenna and put a 50 ohm termination at the input terminal.
        Is the noise still present?

        If not then your antenna picks it up, probably because the feed line carries it
        to it


        Jurgen Bartels Suellwarden, N. Germany
        11-element 45-87MHz antenna horz.
        TV: Winradio G305 / Fly2000 + video noise filter & variable IF BW
        FM: 15.11 horz Ant. Downconverter + Perseus + Speclab as WFM demod.
        http://dx.3sdesign.de/tv_offset_list.htm
        http://dx.3sdesign.de/station_list.htm

        http://fewo.3sdesign.de - Vacation home: DX right at the Northsea coast
      • Roelof Bakker
        Hello Axel, ... So using the laptop with the same setup, the noise is much weaker. So where does it come into the Perseus?
        Message 3 of 6 , May 3, 2010
          Hello Axel,

          >>>
          So using the laptop with the same setup, the noise is much weaker. So
          where does it come into the Perseus?
          <<<

          Noise is a complicated issue, but in this case my guess is that it is
          received either on the shield of the coax feedline of the ALA1530 or on
          the ALA1530 itself. A building can act as a Faraday Cage for the electric
          field. However the ALA1530 is receiving the magnetic field, so even
          mounted 10 metre from your house, noise pick up from within the house can
          still be order.

          You can try to rotate the ALA1530 and observe if the strength of the noise
          signal changes.
          It pays off to buy a quality PC power supply if possible.

          I hope this helps,

          Best regards,
          Roelof Bakker, pa0rdt
        • Mauno Ritola
          Hi Peer-Axel, do you hear it on other rxs, too? I had noise on many parts of MW from the motherboard of my new computer, and it was also heard on my AR7030,
          Message 4 of 6 , May 3, 2010
            Hi Peer-Axel,
            do you hear it on other rxs, too? I had noise on many parts of MW from
            the motherboard of my new computer, and it was also heard on my AR7030,
            but only when Perseus software was running and only with the new
            computer. I tried additional sound cards; no help. I was planning to
            replace the motherboard, but as the last trick trick I tested all the
            USB connectors. All the rear connectors had to noise at the same level,
            BUT the ones in front were practically noise-free! If that had not
            helped, there would still have been the possibility to put chokes on the
            USB wires inside the computer or to replace them with shielded ones.

            Mauno

            3.5.2010 11:30, peeraxel kirjoitti:
            >
            > My old motherboard has died (KV2 Lite), that's why I use a new PC (ECS
            > A740GM-M). But it causes very strong noise on my Perseus, the sort
            > typical for power supplies. It is very strong around 480 KHz (up to
            > -40 dB), still bad around 1600 KHz (-60 dB) in the evening. The noise
            > clusters are constanttly drifing downwards, a few KHz every minute.
            > Funnily the noise is weaker when the overall signal level is weaker,
            > too. But it is definitely caused by the PC. When I use my laptop
            > (HP6715s) with the Perseus at the same place, the noise has only -82
            > dB at 480 KHz which would be more or less acceptable. And when I
            > switch off the PC, the noise is gone. I use the laptop with the accu.
            > When I use its power supply, it causes other noise clusters, but weak
            > enough to get along with that.
            >
            > By the way I use the ALA1530S as an antenna. It is outside, more than
            > 10m away from the computers.
            >
            > So using the laptop with the same setup, the noise is much weaker. So
            > where does it come into the Perseus? It can only be the USB cable. I'm
            > using the one supplied with the Perseus, with HF reduction (the thick
            > part close to the PC connector).
            >
            > Now should I exchange the power supply? I can't use the old one, the
            > connectors are different. Which one would do it? Are there any
            > solutions for the USB cable? And has anyone in the group experienced
            > similar problems?
            >
            > Thanks in advance for your help.
            >
            >
          • Huw
            Putting a few turns of all the the cables to Perseus through ferrite cores also helps a lot.
            Message 5 of 6 , May 3, 2010
              Putting a few turns of all the the cables to Perseus through ferrite cores also helps a lot.

              --- In perseus_SDR@yahoogroups.com, Mauno Ritola <Mauno.Ritola@...> wrote:
              >
              > Hi Peer-Axel,
              > do you hear it on other rxs, too? I had noise on many parts of MW from
              > the motherboard of my new computer, and it was also heard on my AR7030,
              > but only when Perseus software was running and only with the new
              > computer. I tried additional sound cards; no help. I was planning to
              > replace the motherboard, but as the last trick trick I tested all the
              > USB connectors. All the rear connectors had to noise at the same level,
              > BUT the ones in front were practically noise-free! If that had not
              > helped, there would still have been the possibility to put chokes on the
              > USB wires inside the computer or to replace them with shielded ones.
              >
              > Mauno
              >
              > 3.5.2010 11:30, peeraxel kirjoitti:
              > >
              > > My old motherboard has died (KV2 Lite), that's why I use a new PC (ECS
              > > A740GM-M). But it causes very strong noise on my Perseus, the sort
              > > typical for power supplies. It is very strong around 480 KHz (up to
              > > -40 dB), still bad around 1600 KHz (-60 dB) in the evening. The noise
              > > clusters are constanttly drifing downwards, a few KHz every minute.
              > > Funnily the noise is weaker when the overall signal level is weaker,
              > > too. But it is definitely caused by the PC. When I use my laptop
              > > (HP6715s) with the Perseus at the same place, the noise has only -82
              > > dB at 480 KHz which would be more or less acceptable. And when I
              > > switch off the PC, the noise is gone. I use the laptop with the accu.
              > > When I use its power supply, it causes other noise clusters, but weak
              > > enough to get along with that.
              > >
              > > By the way I use the ALA1530S as an antenna. It is outside, more than
              > > 10m away from the computers.
              > >
              > > So using the laptop with the same setup, the noise is much weaker. So
              > > where does it come into the Perseus? It can only be the USB cable. I'm
              > > using the one supplied with the Perseus, with HF reduction (the thick
              > > part close to the PC connector).
              > >
              > > Now should I exchange the power supply? I can't use the old one, the
              > > connectors are different. Which one would do it? Are there any
              > > solutions for the USB cable? And has anyone in the group experienced
              > > similar problems?
              > >
              > > Thanks in advance for your help.
              > >
              > >
              >
            • Mauno Ritola
              Yes, it does. I forgot to mention that I already had antenna cable etc. equipped with proper chokes. The noise occured with only that particular computer, only
              Message 6 of 6 , May 3, 2010
                Yes, it does. I forgot to mention that I already had antenna cable etc.
                equipped with proper chokes. The noise occured with only that particular
                computer, only at certain parts of MW and even with it only when Perseus
                software was running.

                3.5.2010 14:37, Huw kirjoitti:
                >
                > Putting a few turns of all the the cables to Perseus through ferrite
                > cores also helps a lot.
                >
                > --- In perseus_SDR@yahoogroups.com
                > <mailto:perseus_SDR%40yahoogroups.com>, Mauno Ritola
                > <Mauno.Ritola@...> wrote:
                > >
                > > Hi Peer-Axel,
                > > do you hear it on other rxs, too? I had noise on many parts of MW from
                > > the motherboard of my new computer, and it was also heard on my AR7030,
                > > but only when Perseus software was running and only with the new
                > > computer. I tried additional sound cards; no help. I was planning to
                > > replace the motherboard, but as the last trick trick I tested all the
                > > USB connectors. All the rear connectors had to noise at the same level,
                > > BUT the ones in front were practically noise-free! If that had not
                > > helped, there would still have been the possibility to put chokes on
                > the
                > > USB wires inside the computer or to replace them with shielded ones.
                > >
                > > Mauno
                > >
                > > 3.5.2010 11:30, peeraxel kirjoitti:
                > > >
                > > > My old motherboard has died (KV2 Lite), that's why I use a new PC
                > (ECS
                > > > A740GM-M). But it causes very strong noise on my Perseus, the sort
                > > > typical for power supplies. It is very strong around 480 KHz (up to
                > > > -40 dB), still bad around 1600 KHz (-60 dB) in the evening. The noise
                > > > clusters are constanttly drifing downwards, a few KHz every minute.
                > > > Funnily the noise is weaker when the overall signal level is weaker,
                > > > too. But it is definitely caused by the PC. When I use my laptop
                > > > (HP6715s) with the Perseus at the same place, the noise has only -82
                > > > dB at 480 KHz which would be more or less acceptable. And when I
                > > > switch off the PC, the noise is gone. I use the laptop with the accu.
                > > > When I use its power supply, it causes other noise clusters, but weak
                > > > enough to get along with that.
                > > >
                > > > By the way I use the ALA1530S as an antenna. It is outside, more than
                > > > 10m away from the computers.
                > > >
                > > > So using the laptop with the same setup, the noise is much weaker. So
                > > > where does it come into the Perseus? It can only be the USB cable.
                > I'm
                > > > using the one supplied with the Perseus, with HF reduction (the thick
                > > > part close to the PC connector).
                > > >
                > > > Now should I exchange the power supply? I can't use the old one, the
                > > > connectors are different. Which one would do it? Are there any
                > > > solutions for the USB cable? And has anyone in the group experienced
                > > > similar problems?
                > > >
                > > > Thanks in advance for your help.
                > > >
                > > >
                > >
                >
                >
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