Many mains powered equipment do not comply EMC standards. They
may emit interference on HF frequencies and cause man-made noise. The
emission measurement up to 30MHz is done by measuring the conducted
emission. Although the standardized EMC compliance setup is specified
in detail you can get pretty accurate results with a simple home made
setup.
Standardized conducted
emission setup
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Simple "home lab" setup
to find good and bad devices
|
- Feed the mains power to Device Under Test (DUT)
- Filter out any interference coming from mains network
- Sample the conducted emission to an analyzer or receiver
Home made LISN schematics for
amateur radio
Home made LISN. The enclosure is quite tight and you may consider to use a bigger box.
Downloads
- Schematics (PDF)
- Layout (PDF)
- BOM (Excel)
- PCB Gerber files
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As you can see the RF sampling point is only connected to the
neutral wire. That will represent very well the conducted emission. But you
can check the emission also in the line wire by swapping the input and/or
output polarity of the LISN. That's why there is a -10dB attenuator and a
transient limiter to protect your receiver or analyzer.
Home made LISN. The enclosure is quite tight and you may consider to use a bigger box.
Mains input IEC connector
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RF output and optional
GRP terminal
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Shuko socket output for DUT
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LISN revision A. Note that
also thru hole parts are mounted on surface.
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LISN revision B layout
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Here is USB charger emission measurement with a RX. S9 is approx
the European CISPR Class B AVG limit with this LISN. See USB charger comparison here.
You don't need a spectrum analyzer.
You don't need a spectrum analyzer.
A
HF receiver with a reasonably calibrated S-meter is sufficient. Turn VFO to seek
noise on each band. It can be wide band noise or only at some frequencies
and see the S-meter reading. The ranking here is for this LISN with 10dB
attenuator.
Thermostat emission measurement with tinySA Ultra spectrum
analyzer.
CISPR Class B AVG limit is 46dBuV. Note the 10dB attenuator in LISN by setting this offset to analyzer. See a thermostat interference case here
CISPR Class B AVG limit is 46dBuV. Note the 10dB attenuator in LISN by setting this offset to analyzer. See a thermostat interference case here
Downloads
- Schematics (PDF)
- Layout (PDF)
- BOM (Excel)
- PCB Gerber files
SAFETY WARNINGS
- Use only a mains socket with a protective ground (PE) connection, otherwise the ground will have half of the mains voltage via the filter capacitors,
- Be extremely careful during building and using the LISN to avoid electric shock.
- When you are using a transceiver as a EMC receiver, disconnect microphone, keyer etc to prevent accidental RF power to the LISN.
Update
2023-04-01 OH7SV- Use only a mains socket with a protective ground (PE) connection, otherwise the ground will have half of the mains voltage via the filter capacitors,
- Be extremely careful during building and using the LISN to avoid electric shock.
- When you are using a transceiver as a EMC receiver, disconnect microphone, keyer etc to prevent accidental RF power to the LISN.
Back to OH7SV ham projects