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DCF77 reception interference due to pulse power supply operation

TechEkspert 4419 46

TL;DR

  • A DCF77 watch reception problem turned out to be local interference from an SMPS power supply replacing a faulty unit.
  • A longwave receiver pinpointed the noise source, and the interference varied with inverter operation and the current drawn from the supply.
  • The noisy unit was an EA 10850D1 MW Power supply, while the quieter replacement was a GSM36B12 MW MEAN WELL supply.
  • The first PSU showed distorted input current with repeated spikes and no active PFC, while the second drew a more sine-like current.
  • SMPS supplies can produce strong RF interference and disrupt weak radio signals, even though they offer high efficiency and compact size.
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  • #31 21342746
    CosteC
    Level 39  
    Posts: 5325
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    TechEkspert wrote:
    I put additional filters on a few LED fixtures because they were interfering a lot with RTL-DVBT dongle listening
    .
    Out of curiosity, what filters?
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  • #33 21342792
    kris8888
    Level 41  
    Posts: 6958
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    But such a filter probably only eliminates interference that could go into the mains. What goes into the ether directly from such a power supply will go anyway. The only good thing is that the mains power supply as an extensive" transmitting antenna" will radiate less junk.
  • #34 21342810
    Anonymous
    Level 1  
  • #35 21342883
    buszyl33
    Conditionally unlocked  
    Posts: 745
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    Rate: 179
    gulson wrote:
    The manufacturer of such power supplies should be punished!
    This is unthinkable.
    How is a non-technical person supposed to function in this world, how is he supposed to know why a watch goes out of sync and what else.

    Administrator! Absolutely right. Maybe report it to the CBA while it still exists?
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  • #36 21342897
    terminus
    Level 21  
    Posts: 416
    Help: 29
    Rate: 169
    My DIY DCF has a signal indicator in the form of an LED on the signal line, if it flashes rhythmically around 1 Hz - it is ok. Irregular or continuous light - disturbed signal.
    DCF reception is completely prevented by a switched-on CRT TV standing in the other room, about 2 m from the antenna.
    On the other hand, a switched-on Lenovo laptop with HP monitor (CCFL) completely prevents PR1 225 kHz reception at my place (but does not interfere with DCF).
  • #37 21343180
    CosteC
    Level 39  
    Posts: 5325
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    Rate: 1645
    ledo99 wrote:
    @CosteC this is not possible - the device has to pass approval as a whole - as for the rest - cheap was not...
    .
    Let's look at the instructions first. Then to the standards perhaps?

    And seriously, devices in practice are divided into commercial and industrial. For commercial they must comply as supplied ("as a whole"). Industrial not necessarily as far as I know - you can sell an inverter without a filter as long as it is documented and the appropriate filter is available, documented. It also makes sense because there are different standards: EU, Chinese, US and so on.

    Why?
    E.g. we have 3 inverters side by side in a machine and one filter to prevent interference leakage outside the machine. Cheaper, smaller, better but requires an informed user.

    Back to the topic: What is the model of the heat pump? What does the manual say? What does the invoice say?
  • #38 21343863
    TechEkspert
    Editor  
    Posts: 7181
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    kris8888 wrote:
    But such a filter probably only eliminates interference that could go into the mains. What goes into the ether directly from such a power supply will go anyway. The only good thing is that the mains as an extensive" transmitting antenna" will radiate less junk.
    .

    The filter reduced the shortwave interference heavily, here I used a filter from a broken ATX power supply: Reducing interference from an LED plafond power supply. .
  • #39 21344096
    CosteC
    Level 39  
    Posts: 5325
    Help: 400
    Rate: 1645
    TechEkspert wrote:
    kris8888 wrote:
    But such a filter probably only eliminates interference that could go into the mains. What goes into the ether directly from such a power supply will go anyway. The only good thing is that the mains as an extensive" transmitting antenna" will radiate less junk.
    .

    The filter reduced the shortwave interference heavily, here I used a filter from a broken ATX power supply: Reducing interference from an LED plafond power supply.
    .
    Nice article, nicely done FFT. Not many people know how to set up the FFT correctly on an oscilloscope :) .
    Interesting, this platoon has good PF - little distortion. But it sows. Well, but how is it not sowing when the filters are poor....
    Informative. Thank you.
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  • #42 21344332
    Anonymous
    Level 1  
  • #43 21345015
    elukam
    Level 18  
    Posts: 404
    Help: 8
    Rate: 181
    What we have in civilised countries to combat such banditry are standards and the legal obligation to comply with them. It is the failure to comply with CE marking conditions that causes similar problems.
    Our popular auction site is rife with Chinese production that does not comply with any standards. All these items are the same as those on the popular Chinese auction site, the only difference being that there they are available 2-5x cheaper.
    The penalties for placing a substandard device on the market (illegally CE-labelled) are very high, only that somehow nobody seems to care. 8 years of practical impunity in this area have taught people that they can get away with anything. Now, on the other hand, there is a war situation and, on top of that, the economy is going downhill. Sometimes, however, the state gradually starts to remind itself of its capabilities and then....
  • #44 21345150
    CosteC
    Level 39  
    Posts: 5325
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    ledo99 wrote:
    I do not have access to service documentation
    .
    Google my friend in this case.
    ledo99 wrote:
    now I'm wondering about an inverter fed three phase and doing one phase 30A
    .
    Efficiency will not drop significantly?
    ledo99 wrote:
    then I would probably also address the interference problem.
    .
    I would check the PE continuity "already". Although the chances are small the consequences are unpleasant. And this is probably the simplest problem.
  • #45 21345732
    Anonymous
    Level 1  
  • #46 21353406
    dktr
    Level 26  
    Posts: 937
    Help: 45
    Rate: 729
    I'm starting to hear Christmas tree lights and all the decorations on the bands from 10 metres down from about 3pm, it's slowly going from a background of 3s to 9s, just 3 weeks ago it was quiet at this time.
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Topic summary

✨ The discussion revolves around interference issues affecting DCF77 signal reception, primarily caused by a switching power supply (SMPS) model EA 10850D1 MW Power. Users shared experiences of various devices, including chargers and power supplies, that generate significant electromagnetic interference (EMI), disrupting radio and TV signals. Suggestions included using EMI filters, relocating devices, and selecting higher-quality power supplies to mitigate interference. The conversation highlighted the importance of proper shielding and filtering in electronic devices to prevent signal degradation, especially during the holiday season when additional electrical devices are in use.
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FAQ

TL;DR: If a DCF77 clock stops syncing, a 230 V plug-in SMPS may be the cause; one expert found “the source of the strong interference was the SMPS power supply” and fixed reception by swapping adapters. This FAQ helps clock, radio, router, and LED users identify noisy supplies, compare models, and choose filters or placement that restore stable reception. [#21339333]

Why it matters: Local RF noise from chargers, LED drivers, and cheap adapters can break time sync, TV, Wi‑Fi, and longwave reception even when the original radio signal is fine.

Feature EA 10850D1 MW Power GSM36B12 Mean Well
Observed DCF77 impact Strong interference blocked sync Much lower interference
Interference character Whirr, load-dependent, inverter-modulated Shorter-range hum
Mains input waveform Repeated double current spikes No extra spikes superimposed
Idle behavior Cyclic current spikes Current resembles a sine wave
Output noise Higher ripple/noise Lower ripple/noise

Key insight: Replacing a noisy power supply usually works faster than adding complexity. If replacement is impossible, a properly enclosed 230 V EMI filter can reduce conducted noise, but it will not fully cure direct radiation from a badly designed adapter.

Quick Facts

  • A longwave receiver quickly exposed the DCF77 problem source: a replacement SMPS near the ONT, switch, and router, not weak signal from Germany. [#21339333]
  • Moving a noisy scooter charger about 3 m away from an active TV antenna restored reception, which shows distance alone can cut coupling sharply. [#21339795]
  • A DIY DCF setup used a 1 Hz LED signal indicator, while a CRT TV only 2 m from the antenna fully blocked reception. [#21342897]
  • Reported interferers covered several bands and use cases: 225 kHz longwave, 443 MHz garage remotes, TV antenna amplifiers, Wi‑Fi video links, and UKF/FM radios. [#21341525]
  • High-power equipment can also be involved: one heat-pump case discussed a 9 kW monoblock and the difficulty of filtering currents around 30 A. [#21344182]

How can I find which switching power supply is interfering with DCF77 clock reception using a longwave receiver?

Use a longwave receiver as a sniffer and compare devices one by one. 1. Tune near the DCF77 longwave area and walk the receiver around each adapter. 2. Unplug or swap one supply at a time. 3. Keep the unit that produces the weakest buzz or hum. This method identified a replacement SMPS feeding internet gear as the actual source, while the DCF77 transmitter itself was not the problem. [#21339333]

Why would an EA 10850D1 MW Power supply disrupt DCF77 reception while a GSM36B12 Mean Well supply causes much less radio interference?

The EA 10850D1 showed stronger switching artifacts on both the mains current and the DC output. Its interference changed with load, sounded like a whirr, and its input waveform had repeated double spikes plus cyclic spikes at idle. The GSM36B12 still lacked active PFC, but it produced a shorter-range hum, no added spike train on the input waveform, and cleaner output noise. [#21339333]

What is active PFC in a switching power supply, and how does it relate to input current waveform distortion?

“Active PFC” is a power-factor-correction circuit that shapes mains input current to follow the AC voltage more closely, reducing distortion and improving power factor. In the thread, both compared adapters lacked active PFC, but the noisier one drew a more distorted current with extra spikes. The cleaner adapter also had no active PFC, which shows PFC is not the only factor controlling RF noise. [#21339333]

What is an EMI filter, and how can it help reduce radio interference from plug-in power supplies or LED luminaires?

“EMI filter” is a mains-side suppression network that blocks high-frequency noise from traveling between a device and the 230 V line, usually using chokes and capacitors. In practice, forum users bought standalone modules, inlet-integrated filters, or reused ATX filter boards. One added filter heavily reduced shortwave interference from an LED luminaire, especially by stopping the house wiring from acting like a long antenna. [#21343863]

Mean Well vs MW Power power supplies — which is usually the better choice for low RF interference and cleaner output noise?

In this thread, the Mean Well unit was clearly the better choice. The GSM36B12 Mean Well adapter produced less RF interference, had a more benign input-current shape, and showed lower output noise than the EA 10850D1 MW Power supply. One commenter summarized the practical lesson bluntly: “MW Power is not Mean Well,” after seeing the measurement results and brand confusion in shops. [#21339502]

What do repeated current spikes on the mains input waveform of a non-PFC SMPS indicate about its operation and interference behavior?

They indicate pulsed energy draw tied to the switching stage, not smooth sine-like current consumption. In the measured EA 10850D1, repeated double spikes rode on the mains current waveform and remained visible even at idle as cyclic spikes. That matched the audible whirr on the longwave receiver and the stronger DC output noise, so the spike pattern was a practical warning sign for higher interference. [#21339333]

How should I test a power supply for output ripple and RF noise under load before using it with radios, routers, or sensitive devices?

Test it under a steady load and again at idle. Measure output ripple on the DC side, listen for RF noise with a nearby radio, and compare more than one adapter before installation. One experienced commenter stressed that even reputable supplies can generate surprising “garbage” at the output, and that routers, switches, Bluetooth audio adapters, video intercoms, and radio receivers do not all tolerate that noise equally well. [#21340445]

Which filters can be added externally on the 230 V side to suppress interference when I cannot replace a noisy power supply?

Use a ready-made 230 V EMI mains filter, either as a boxed standalone module, an IEC inlet with integrated filter, or a small board mounted inside the enclosure. The thread explicitly rejected an external active-PFC add-on for single plug-in supplies and recommended filtering instead. The critical condition is safe construction: mains voltage is live, so the filter must be enclosed, insulated, and installed correctly. [#21339793]

How do two-wire Class II power supplies with a C7 'figure-eight' connector compare with grounded supplies in terms of EMI and shielding?

Two-wire Class II supplies can be more difficult to quiet, but they are not automatically bad. The thread noted that many C7 “figure-eight” adapters have no PE connection, and one comment argued that missing PE can worsen interference because the design cannot use Y capacitors to PE in the same way. Another comment added that good topology and shielding still let some ungrounded laptop and DIN-rail SMPS stay acceptably quiet. [#21340342]

What real-world devices most often cause radio and TV reception problems, such as LED bulbs, Christmas lights, scooter chargers, heat pumps, or laptop adapters?

The most frequent offenders in this thread were cheap SMPS adapters, LED lamps, Christmas lights, scooter and battery chargers, CRT TVs, laptops with monitors, heat pumps, shavers, and work-lamp inverters. Reported failures included blocked DCF77 sync, lost TV reception, degraded Wi‑Fi video, interference on 225 kHz longwave, UKF/FM noise, and broken 443 MHz garage remotes. Seasonal holiday lighting was singled out as a major rise in band noise after about 3 pm. [#21353406]

How can I tell whether interference is traveling through the mains wiring or being radiated directly into the air from the power supply?

Check whether a mains filter or physical separation changes the problem. If adding a filter greatly reduces interference, the house wiring was carrying and re-radiating much of the noise. If moving the device several meters away works better than filtering, direct radiation is dominant. The thread showed both cases: a charger needed about 3 m of separation from a TV antenna, while an added mains filter strongly reduced shortwave noise from LED lighting. [#21339795]

What is DCF77, and why are radio-controlled clocks so vulnerable to local interference from chargers and SMPS adapters?

“DCF77” is a longwave time-signal service that radio-controlled clocks decode, using a weak received signal that is easy to mask with nearby electrical noise. These clocks are vulnerable because a charger or adapter only centimeters or meters away can generate stronger local interference than the wanted time signal. In the thread, one noisy SMPS alone was enough to stop sync, while a CRT TV in another room could also block DCF reception completely. [#21342897]

How well do popular HiLink PCB-mount AC-DC modules perform in RF interference and ripple measurements compared with external plug-in adapters?

This thread does not provide measured HiLink results, so it cannot rank them against plug-in adapters. A commenter specifically asked how the popular HiLink soldered modules would perform, but nobody posted ripple plots, RF recordings, or side-by-side measurements. The safe takeaway is narrower: the thread only measured two external supplies, and those results showed large differences even between superficially similar adapters. [#21339502]

What practical alternatives are there when DCF77 reception is poor, such as using a DCF77 Emulator app or building a local mini transmitter synchronized from NTP?

You can emulate DCF77 locally with a phone app or build a local transmitter. One poster recommended a Google Play app called “DCF77 Emulator,” which drives the phone speaker coil; the key limitation is that real DCF77 must be absent, or frames overlap and decoding fails. Another poster said the watch must almost touch the phone, and suggested a mini transmitter synchronized from NTP as the more practical fixed solution. [#21341525]

Where can I place a DCF77 clock or antenna for the best reception when nearby equipment like CRT TVs, routers, monitors, or chargers is generating interference?

Place the clock or antenna as far as possible from noisy electronics and test positions before fixing it permanently. Keep it away from CRT TVs, chargers, routers, laptops, monitors, and LED drivers; in one report, a CRT TV only about 2 m away completely prevented DCF reception. Because many clocks lack continuous signal-quality indication, using a DIY 1 Hz LED indicator or a longwave receiver makes placement much easier. [#21342897]
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