OT: LED Light Bulbs

[Elecraft mailing list]

    Hi.

    A lot of the LED QRM issues, are caused by the PSU, or "Electronic
    Ballast" dropping into a discontinuous conduction mode within it's SMPS
    when low voltage halogen lamps are substituted with LED types.  Change
    the "Ballast" or re-fit enough Halogen types to keep it happy (and quiet!)

  It's also worth noting, that the EMC regs for unwanted emissions from
    electrical/electronic equipment, is designed to protect Broadcast
    services, where signal levels are often several 10's of dB greater than
    those that we are interested in.

  So, it is quite possible for a fully approved gadget to pass all the
    required emissions tests, and still create mayhem on HF in particular.
    Also, in the EMC world, for commercial products (sold to the likes of
    us) it is assumed that nothing "radiates" directly from itself, as it is
    too small a fraction of a wavelength, so only conducted tests are done,
    and on artificially loaded leads and cables.

        Of course, add such things as long speaker leads, other gadgets, and you
    have a situation where a collection of fully approved pieces of (for
    example) domestic cable/satellite TV equipment, where each on it's own
    is fine, when used together cause trouble.
   
    It's what happens when committees create test spec's.    That and
    commercial pressure to go the TCF route (Technical Construction File)
    where a technical appraisal is done on the design, resulting in a
    statement that it is believed no problem will ensue, and again, the
    product itself is never tested in practice.  Cost saving pure and simple.
   
    Then you also get creative installers who adapt and modify things,
    causing trouble, for example using unscreened leads between a variable
    frequency drive inverter, and the motor it powers, purely because
    screened power cable is expensive.  Or, they don't correctly ground the
    shield rendering it useless.
   
    Similarly, some of the modern LED based traffic signals, should have
    screened cables, but don't, purely because of the cost of replacing the
    old cabling with new.
   
    And we haven't even touched VDSL and G.Fast used for broadband
    connections from fibre enabled cabinets, and the noise they can produce,
    or in house Power Line Networking.
   
    Have Fun.
   
    Dave G0WBX.

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