RJ45 cable

Comments

• smg

  March 20

  Cat5e and Cat6e by their wiring standards are low noise. The wiring standards, such as TIA/EIA-568 and ISO/IEC 11801, provide guidelines on electromagnetic interference (EMI) and radio frequency (RF) noise emissions for Cat5e and Cat6 cables

  Any good quality cable should be low noise. You can use shielded for even better noise reduction.

  The amount of RF noise emitted depends on the frequency of the signals transmitted. As network speeds increase, the operating frequency of the cable increases, which can result in higher emissions if not properly controlled.

  • Cat5e
    • Max Frequency: 100 MHz
    • Typical Use: Up to 1 Gbps
    • RF Emissions Considerations: Lower emissions than Cat6, but less effective at high speeds due to less stringent twist and shielding standards.
  • Cat6
    • Max Frequency: 250 MHz
    • Typical Use: Up to 10 Gbps (short runs)
    • RF Emissions Considerations: Tighter twists reduce emissions compared to Cat5e. Higher speed operation (10GBASE-T) increases potential for noise.
  • Cat6a
    • Max Frequency: 500 MHz
    • Typical Use: 10 Gbps
    • RF Emissions Considerations: Even better twist rate and shielding, significantly reducing RF emissions.

  The reason the Kiwi is set to 100Mbit is its very low noise

  Network Speed and Noise Emission Relationship

  • 100 Mbps (Fast Ethernet): Very low RF emissions. Cat5e and Cat6 behave similarly.
  • 1 Gbps (Gigabit Ethernet): Moderate RF emissions, but still well-managed in UTP (unshielded twisted pair) due to proper balancing.
  • 10 Gbps (10GBASE-T on Cat6): Operates at 500 MHz, which increases the risk of RF emissions and crosstalk, making shielding more critical.

  Decent quality networking will also help. Cheap switches will likely produce a lot of noise.

  Have your kiwi as far away from your networking equipment as possible.......

  Most (domestic in particular) network equipment is also notorious for creating a lot of unwanted nasty QRM from unshielded network components (common with all the cheap plastic routers, switches, and access points floating around.) - even your neighbours equipment if close by will cause you issues

  Why These Things Are So Noisy

  • Switching Power Supplies – Most routers and switches use SMPS (switch-mode power supplies), which are notorious for spewing RF noise, especially in the HF bands. If you've got a dodgy power brick, it'll dump harmonics all over the place.
  • Ethernet Cables Acting as Antennas – Unshielded twisted pair (UTP) cables are basically long antennas radiating whatever high-frequency signals they're carrying. Gigabit Ethernet is particularly bad for this.
  • Clock Noise & Data Switching – Inside every router or switch, you've got clock generators and high-speed data signals that leak RF like crazy if there’s no proper shielding.
  • Wi-Fi Interference – Some Wi-Fi APs leak spurious emissions that can mess with receivers, especially if they’re running on cheap, poorly filtered hardware.

  How This Wrecks Your Radio Listening

  • HF bands (3-30 MHz) get hit with broadband hash, clicking, and whining sounds from SMPS and Ethernet noise.
  • VHF/UHF (30 MHz - 3 GHz) picks up mixing products, spurious signals, and desensitisation from nearby Wi-Fi gear.
  • Mains power can carry interference too—noisy power supplies can dump RF back into your house wiring and make everything worse.

  How to Fix It (or at Least Reduce It)

  • Swap out noisy SMPS for a linear power supply if possible.
  • Use shielded Ethernet (STP/FTP) and ground it properly—ferrite chokes help too.
  • Stick ferrites on power cables and Ethernet leads—snap-ons are easy to use.
  • Move your router, switch, or AP as far away from your SDR or antenna as possible.
  • If you’re running Powerline Ethernet, get rid of it! Those things are absolute RF garbage.

  try tuning around 100-300 kHz (or where you might see the biggest noise spurs) while unplugging your network gear one by one. You’ll probably hear the biggest offenders loud and clear.

  Hope that helps—keen to hear what you find!
• G8JNJ

  March 20

  Generally speaking, you are better off using WiFi if you can get it to work.

  Unscreened twisted pair is often better than screened twisted pair, as it doesn't provide an additional ground path.

  I tend to wrap my Ethernet cables with about 12 turns, through FT240-31 ferrite cores, to help minimise any remaining imbalance, as the terminating components in the network connectors may not be particularly effective at MF and HF frequencies.

  I also reduce the KiWi Ethernet speed in the admin page, as I find that it works OK at the lower rate, and Ethernet "spurs" on the upper frequencies are reduced.

  As mentioned in another thread, don't ever use Ethernet over mains power line adaptors, as these badly pollute the spectrum, and I suffer from several at my home location, even though they are nearly a km away from my antenna.

  PoE can also be problematic, due to the DC-DC convertors used in the power supplies and terminating equipment.

  Good luck,

  Martin