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Author Topic: RFI from Electronic clock  (Read 2098 times)
AI8O
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« on: November 27, 2010, 05:58:01 PM »

I just removed from my shack a "Micronta Electronic Flourescent Display Alarm Clock"
 Radio Shack Catalog Number 67-753B.

The RFI was making 2m reception impossible anywhere within 30-35 feet of the clock.

The Clock was generating RFI from 500 KHz to over 200MHz.
The RFI was especially bad from about 125 MHZ to 174 MHz.

The RFI consisted mostly of a loud buzzing peaking about 149 MHz.

Applying Chokes to the power cord did not significantly reduce the RFI, apparently the RFI was being generated inside the clock and propagating directly through the plastic case of the clock.

Dan
AI8O

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W2MV
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Posts: 207




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« Reply #1 on: December 02, 2010, 08:31:38 AM »

When you said you applied chokes to the power cord, what type were they?
If you only applied toroids and still had RFI, it could have been differential-mode RFI in which case a "brute-force" filter might help since it attenuates both common and differential mode signals.
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WX7G
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« Reply #2 on: December 02, 2010, 09:16:15 AM »

Solution: Get rid of the device.
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W2MV
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Posts: 207




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« Reply #3 on: December 02, 2010, 12:17:41 PM »

That would work too, if you don't absolutely need that particular model.
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ZENKI
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Posts: 960




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« Reply #4 on: December 04, 2010, 01:46:00 AM »

All governments around the world are too blame for not enforcing EMC regulations. Simply put we giving the Chinese fraudster factories a licence to print money in our economies with all the fake EMC ticks and approval notices. I wonder when our politicians are going to wake upto this scam?

Resident manufacturers in our own countries would go to jail or face huge fines, yet Chinese importers can get away with this abuse of the law.

It is sad that our political system is so corrupt that  we set high standards for our own citizens and companies and turn a blind eye to all this imported equipment.

Its now getting to a point where just about every piece of equipment that I buy has a switch mode supply that is a  HF jammer and this is from
big  name companies like Nokia, Linksys. Panasonic Sony and just about everyone else.

I generally take this stuff straight back to the shop. Before I leave the shop I tell them plainly that if this stuff interferes I will bring it back and get them to  sign that I stated this.

EMC laws are now just being ignored by all manufacturers and thats  just a sad reflection on the state of our governments. But its okay that the Chinese are making profits and stealing our jobs because our factories are going over there where they dont have to worry about making fraudulent statements about EMC compliance. Nobody gives a damn over here or there.

My neighbor just installed an inverter with a Solar system, the inverter has EMC marking all over it. This inverter is made in China and its so bad I can hear it 2  blocks away when its turned on from 500khz to 30 mhz. When I look at it on a spectrum analyzer it has birdie spikes and hash noise every 10khz. Its a proper HF jammer! I am fighting and trying to get this thing  turned off. The manufacturer claims that it meets EMC standards. A proper European made inverter on the same system that I documented caused no interference. Like I said  the Chinese companies and their importers who bribe the Politicians are screwing HAM radio with this QRM. They could not do it with with BPL now they doing it by stealth through  allowing the EMC laws to be ignored. Just look at the Plasma TV's well Solar installations are 100 times worst than BPL!!



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KI4SDY
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« Reply #5 on: December 15, 2010, 05:40:26 AM »

I would have sold the clock at a yard sale.  No more RFI! Grin
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W2MV
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Posts: 207




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« Reply #6 on: December 20, 2010, 12:03:57 PM »

Good!. I hope your neighbor didn't buy it and starts transmitting RFI again.

I have to concur with Zenki. The deluge of RFI-producing switch-mode power supplies is everywhere and I think is now hams' biggest interference issue. Hams now have to be concerned about a consumer appliance that they (or worse, their neighbors) might purchase and cause grief.
Even when the devices have the "FCC" logo on them (and many do not), that does not seem to mean very much as far as the power supply's ability to jam HF from far away.
After Googling the subject a bit, apparently the RFI problems associated with switching p/s's are well-known to private industry and the government, yet nobody seems to be taking action to fix the problem.
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