Hello Brian. Yes, I have 2 bulkhead mounted filters; one for the screened room & one for the control room. However; I think the fundamental frequency of the noise may be in the KHz or 10s of KHz range.
Regards; Ian From: Kunde, Brian [mailto:brian_ku...@lecotc.com] Sent: 26 April 2018 14:12 To: McBurney, Ian <ian.mcbur...@allen-heath.com>; EMC-PSTC@LISTSERV.IEEE.ORG Subject: RE: Mains Conducted rf emissions measurements Ian, Does your screen room have massive line filters on the AC mains coming in? This would be a requirement I believe. Brian From: McBurney, Ian [mailto:ian.mcbur...@allen-heath.com] Sent: Thursday, April 26, 2018 9:08 AM To: Kunde, Brian; EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: RE: Mains Conducted rf emissions measurements Hello Brian. If I power the LISN from the wall socket with no load connected, the emissions measurements are high. If I switch off the wall socket, (double pole switch) but leave the LISN supply cable plugged in the wall socket the emissions drop considerably. It is unfortunate that the measurement chamber is within a busy air conditioned R&D building but it is a screened room. Regards; Ian From: Kunde, Brian [mailto:brian_ku...@lecotc.com] Sent: 26 April 2018 13:38 To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] Mains Conducted rf emissions measurements Ian, First, are you sure the noise if coming from your AC Mains? If you are using line filters, you need to get some kick butt filters that will give you good attenuation down to at least 10khz. Second, are you sure the signals you are seeing between 150kHz and 400kHz are real? Zero in on one of the signals and do a linearity check. This is done by taking a reading, then add attenuation such as a 6 dB attenuator to the input, and take another reading, which should be 6 dB less. If not, the problem might be a signal much lower in frequency which is throwing off the input stage of your receiver/spectrum analyzer. Check the AC Mains powering your analyzer. It might be the source of your problem. Hope you figure it out. The Other Brian From: McBurney, Ian [mailto:ian.mcbur...@allen-heath.com] Sent: Thursday, April 26, 2018 6:33 AM To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: [BULK] [PSES] Mains Conducted rf emissions measurements Importance: Low Dear Colleagues. I am setting up a mains conducted rf emissions measuring system and am experiencing excessive mains noise when connecting the LISN to the 240V wall socket. The noise affects my measurements between 150kHz to 400KHz. Beyond that and up to 30MHz I am satisfied. Is there a way of filtering out this noise. I have tried various EMI mains filter modules but none appear to attenuate enough at that frequency band. They are very good at attenuating frequencies beyond 1MHz. I have tried inserting an isolation transformer before the LISN but this appears to distort the measurements. Can anyone recommend a solution? Many thanks in advance. Ian McBurney Lead Compliance Engineer. Allen & Heath Ltd. 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