There are good technical reasons for measuring radiated emissions above 30
MHz and conducted emissions below 30 MHz. The majority of products when
tested with required cabling attached and operating are relatively small
compared wavelengths at frequencies below 30 MHz. Therefore, they are
inefficient radiators of energy below 30 MHz due to very small antennas as
a function of frequency. However, once connected to additional conductors
like the house wiring and PCs and ......, those additional conductors
become good radiators of the "conducted" energy. They become non-intended
antennas. That's why the regulatory world, not just us EMC engineers, do
conducted emissions below 30 MHz and radiated above 30 MHz.
Dave - WØLEV
On Fri, Feb 18, 2022 at 6:01 PM Jim Brown <jim@audiosystemsgroup.com> wrote:
> On 2/18/2022 5:04 AM, Hare, Ed, W1RFI wrote:
> > Actually, Tony, the system installed in your neighbor's house is the
> prototype, so this is not encouraging news. It is interesting that many of
> the systems replaced, including one at a local VHF weak-signal station, has
> significantly reduced the noise.
>
> I'm not at all surprised -- from where I sit, it seems that the EMC
> world is stuck in compliance at VHF/UHF, with little understanding of
> what really matters at HF and below.
>
> 73, Jim K9YC
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>
--
*Dave - WØLEV*
*Just Let Darwin Work*
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