10KHz – 2MHz Coverage added to SUWS WebSDR

By | May 3, 2015
WebSDR LF - 2MHz Band

DC – 2MHz Waterfall

We’ve added 10KHz – 2MHz receive capability to the SUWS Farnham WebSDR.

You can access the WebSDR at: http://websdr.suws.org.uk/

This frequency band is received by an Active Antenna developed by Martin G8JNJ, which is fed into an R820T2 RTL-SDR running in Direct Sampling mode on the ‘Q’ ADC Input.

The current antenna is a prototype, and is mounted only a few meters up the mast. We are planning to fit a notch filter to reduce intermodulation distortion from the onsite DMR repeater before installing the antenna at the top of the mast, which should significantly reduce electrical noise from the ground and increase sensitivity.

2 thoughts on “10KHz – 2MHz Coverage added to SUWS WebSDR

  1. Dave

    I’m giving your SDR a mention in the LF column in the next Radcom as it’s unusual in the UK for a web SDR to cover 136 and 472kHz.
    Having been involved with the Derby web-SDR (www.1942khz.net) I know how difficult it is to get a quiet receive aerial at a comms site. We eventually went for a flat-top dipole as its lack of a vertical element made it more immune to local noise. The site we are on has kiloWatts of band 2 causing active loops to curl up and die but maybe a Wellbrook or similar would work at your site and could be rotated to minimise the noise?
    Good luck with your interesting project!
    Dave G3YXM

    Reply
    1. Phil M0DNY (SUWS)

      Hi Dave,
      Thanks for giving us the mention!
      Most of the noise we’re encountering is either in the shack directly below the mast, or on the mast itself. It would also be nice to maintain omnidirectional reception.
      Martin G8JNJ has now completed the build of the new Active LF antenna, this contains a Low-Pass filter at 3MHz, as well as notch filters for the broadcast band segments to make the most of the RTL-SDR’s limited dynamic range. This will also be mounted about 20m higher than the existing LF antenna.
      We’ve now just got to find a time to head up there and install it, hopefully should be soon!
      73s,
      Phil M0DNY

      Reply

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