Loading ...
Sorry, an error occurred while loading the content.

On using CW Skimmer with the SDR-IQ wideband

Expand Messages
  • w2rf
    Hi All, If you have a SDR-IQ you know what a great receiver it is. Now there is a new version of SpectraVue, available at
    Message 1 of 1 , Feb 24 4:02 PM
    • 0 Attachment
      Hi All,

      If you have a SDR-IQ you know what a great receiver it is. Now there
      is a new version of SpectraVue, available at

      http://www.moetronix.com/svdownload.htm

      that can connect to CW Skimmer in wide bandwidths. In order to enable
      direct I/Q output, simply uncheck demod and press Start. Next you need
      to route that I/Q signal to CW Skimmer.

      I have concentrated on 50, 100, and 190khz, and routing the I/Q signal
      rather than through a soundcard, which has some problems, through a
      VAC "virtual cable", which works much better. Here's why.

      The exact sample rate output from the SDR-IQ and from SpectraVue at
      each of these settings, along with the corresponding CW Skimmer
      setting is:

      SDR-IQ CW
      indicated actual Skimmer
      --------- --------- -------
      50khz 55,554hz 48khz
      100khz 111,108hz 96khz
      190khz 196,073hz 192khz

      Note that the frequency expected by CW Skimmer is slightly different
      than the output of SpectraVue. It is possible to use VAC automatic
      resampling to correct this. Simply piping the signal from SpectraVue
      to CW Skimmer through a virtual cable with the SR range set
      appropriately will give a reasonably good result.

      However if you look closely at the CW Skimmer waterfall display there
      may be artifacts such as weak images of signals repeated above or
      below the actual frequency. This is because the resampler in VAC is
      designed for the audio spectrum, and is introducing harmonics when
      wideband I/Q signals are converted.

      In order to overcome the distortion introduced by the VAC resampler
      Alex VE3NEA has developed a custom filter designed specifically for
      this purpose. I have been testing it here with excellent results. I
      believe his plan is to introduce this capability in the next version
      of CW Skimmer.

      But in the mean time plug up some VAC cables and enjoy!

      73 Ed W2RF
    Your message has been successfully submitted and would be delivered to recipients shortly.