Advancing amateur radio since 1913

vision values governance teamwork

Emerging EMC Threats

of Great Britain

Advancing amateur radio since 1913

Radio Society

Dr David Lauder G0SNO

Dr John Rogers, M0JAV

11/10/2014 1

Advancing amateur radio since 1913

What do we mean by “Emerging Threats” ? •  Green Energy

– Solar PV – Wind Farms – LED Lighting

•  Communications – Broadband – xDSL – PLT

•  Others – SMPSU’s USB chargers – Wireless Charging – next investigation

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Advancing amateur radio since 1913

Solar PV Characteristics •  Cause / Reports

– Grid-tied Inverter converts DC from panels to AC (synchronous to Grid)

– Optimisers (switching DC-DC converters) may be fitted to individual panels

•  Spectra / Sounds – Typically peaks at intervals of ~50 kHz

modulated with100Hz buzz – Some recent solar PV systems appear to

use Dithered Clocks which spread inverter harmonics over a wider bandwidth

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37

10 3

No emissions

problems

resolved

RSGB Survey

Advancing amateur radio since 1913

Solar PV Spectra

•  Mitigation –  DC cables should be run as closely spaced pairs –  Clip-on ferrites may be required on DC cables –  May be necessary to change inverter or optimisers

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Broad band emissions up to 40dB above typical back-ground noise level on 10.1 – 10.15 MHz band

Advancing amateur radio since 1913

Wind Farms •  Some wind farms radiate QRM at up to S9 + 30 dB across the

1.81 - 2MHz band •  Pulse modulated with relatively low duty cycle but peak field

strengths of over 40dB(µV/m) at a distance of 3km. •  Only seen so far on wind farms that are built on low-lying fen land,

1 - 2 metres above mean sea level

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Advancing amateur radio since 1913

Noise near Althorpe windfarm

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Advancing amateur radio since 1913

Windfarm noise G3VBS

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Advancing amateur radio since 1913

Noise near Windfarm Goole

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Advancing amateur radio since 1913

LED Lighting

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LED driver Conducted emission (QP) with Cy1 fitted

LED driver Conducted emission (QP) with Cy1 missing

EN 55015 limit (QP)

0.15 300.5 50.15 300.5 5

•  Some LED drivers fail conducted emission limits below 1 – 2 MHz by up to 40 dB (red and blue traces)

•  Missing Class ‘Y’ capacitors can increase emissions at 3 – 30 MHz by up to 25 dB (red trace)

Advancing amateur radio since 1913

FTTC based VDSL2 •  Usage of up/downstream bands depends on distance from

cabinet - attenuation increases with frequency

•  System uses frequencies with acceptable S/N => reducing use of higher bands further from cabinet

•  Upstream signals stronger than downstream at user, but upstream power is backed off to minimise crosstalk

•  VDSL is active all the time users modem is powered up •  Few reports of VDSL RFI even with coverage of 66% •  Most reported cases are from someone else's VDSL

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U1  

0.138 3.75 5.2 8.5 12 14 17.664

D2   D3  U2  D1  

f (MHz)

Plan  998ADE17  U0  

0.025

Advancing amateur radio since 1913

VDSL2 – distance from cabinet

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10% premises U1/U2 & D1/D2/D3

25% premises U1 & D1 / D2

50% premises U1/U2 & D1 / D2

15% premises U0 & D1

km

Normally no problem when underground cables used for final drop

Think Broadband

Advancing amateur radio since 1913

U1 @ QTH M0JAV 1km from cabinet

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Detect by f of band edges

Looks and sounds like

a raised noise floor

Advancing amateur radio since 1913

U2 @ QTH G3JWI 500m from cabinet

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Advancing amateur radio since 1913

D1 near Coventry

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3.71 MHz bandedge

Noise across 40m band

Advancing amateur radio since 1913

VDSL during Training

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Carriers 4kHz apart

Carriers across upstream and downstream bands

Advancing amateur radio since 1913

Transmitting can cause retraining

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Advancing amateur radio since 1913

Open circuit λ/4 wave stub on modem line

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System does not use frequencies near λ/4 wave stub avoiding

radiation

Advancing amateur radio since 1913

Ongoing investigations •  Working with BT to understand the issues better

–  Investigating modes of radiation and variations in near field patterns, including effect of in house extensions

– Fault conditions can cause lower broadband speeds and increase radiation in all our interests to resolve problems

–  Investigating mitigation for cases suffering interference – Trying different common mode filter designs – Broadband accelerator can reduce U2 emissions

•  Self Install launched may see more mismatches as no centralised splitter and/or distributed microfilters

11/10/2014 18

Advancing amateur radio since 1913

PLT - update •  EN50561-1 has been adopted but some

amateurs are considering legal challenge to the way the standard was set up

•  Notches provide some protection for amateur bands but not to our SWL’s

•  Some evidence that intermods are filling in the notches as we predicted

•  As 50561-2 PLA and 50561-3 VHF are being drafted more parties are worried about the levels set in the EN50561-1

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Advancing amateur radio since 1913

SMPSUs

•  Two types of mains USB charger –  Genuine Apple iPhone charger (blue trace) –  Generic USB charger model TC038 (red trace)

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iPhone charger (QP)

Generic USB charger (QP)

EN 55022 limit (QP)

3030

Advancing amateur radio since 1913

How can you help us? •  COMPLAIN if you see these problems •  Use the Forum EMC Matters to tell us

– http://forums.thersgb.org/index.php?forums/emcmatters/

– Collect data / ask for help / share your knowledge •  Volunteer to help with investigations •  Our aims are

– To help people identify the source of interference – To collect data to influence standards evolution, lobby

suppliers and press regulators for enforcement

11/10/2014 21

Advancing amateur radio since 1913

Plasma TV •  Problems may increase as the plasma ages •  Cooperation of the set owner is key as suppliers

will only deal with them •  One of our committee has had good success with

manufacturers getting problems resolved particularly with Panasonic and Samsung

•  Contact Ken Underwood G3SDW directly or via the EMC Matters forum

•  Problem will go away as sets go out of production

11/10/2014 22

Advancing amateur radio since 1913

How can interferers be found ?

•  Use leaflet EMC04 to help diagnosis •  Location of source – portable receiver use a poor

antenna to get closer to source •  Record Frequencies - problems observed •  Use different Modes to characterise interference •  Try at different times and in different weather •  We are building examples of characteristics to

look for

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Advancing amateur radio since 1913

Tools to use •  Portable / mobile receiver / am radio •  Transceiver or Comms Receiver •  Narrowband SDR (<200kHz) eg funcube dongle •  Spectrum Analyser or Wideband SDR (>1MHz) •  Choice of Antenna

– Normal antennas tell if a problem – Loops sensitive and portable – Small active dipoles allow polarisation check – Current loops when safe to use

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Advancing amateur radio since 1913

KX3 with HDSDR

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Advancing amateur radio since 1913

Funcube dongle Pro+ SDR Sharp

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Advancing amateur radio since 1913

Softrock ensemble SDRSHARP

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Advancing amateur radio since 1913

Winradio SDR 30MHz spectrum

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