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low energy bulb [ie folded fluorescent] as noise generator.

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  • gw8lxo
    After suffering interference from mains powered low energy bulbs - I thought perhaps this bug could be turned into a feature . I have seen several people
    Message 1 of 1 , Jul 28, 2007
      After suffering interference from mains powered low energy bulbs - I
      thought perhaps this "bug" could be turned into a "feature".

      I have seen several people struggle trying to debug their softrock
      without much in the way of test equipment. This may or may not help!

      The low energy bulbs, sold as replacements for incandescent lights are
      folded flouorescents which generate high levels of broadband noise.

      After a bit of fiddling I can easily generate S9+ signals with 5 turns
      of insulated wire wrapped around the bulb. Best results are with the
      turns closer to the base.

      I used "bulbs" 11W and a 20W rating the results were similar and
      fairly consistant across three brands, from cheapo to expensive.

      Noise levels dropped slightly from 80M to 40M on the same softrock.

      I hope there is no need to spell this out but - it is vital for your
      own safety - and your softrocks, that no mains voltages or conductors
      carry same be exposed or have any chance of coming into contact with
      you or your softrock. Use insulated wire for the coil around the bulb!
      Some bulbs get hot in use, so watch out for melting insulation! Dont
      do these tests wet, always brush your teeth, dont swear in public...

      A Caveat, you need to be careful hich SDR software you use for testing:

      Rocky will show an S9 reading on the signal level meter - but shows
      hardly any rise in the noise floor.

      M0KGK and Power SDR will show an increase in noise floor on the
      display of 40-50db. My setup also showed at least two pronounced
      humps/spikes within the 96k spectrum from the bulb.

      I wonder if an S9 signal level is sufficient to help debug a miswired
      input transformer?

      I am sure higher levels could be obtained with more efficient coupling
      to the bulb. [This based on my experience with the radiation from the
      shack wiring with the bulbs installed....!]

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