[RFI] KG2V's new RFI rule of thumb...

[Dale]

Gentlemen,

To a great extent, I also agree with Charlie's "rule".  However, the REAL problem exists in two areas: regulatory bodies (such as the FCC and the EU Commission, among others) and manufacturers.  

In the USA, we have no requirements for the majority of consumer electronic devices to meet radiated emissions of any sort below 26 MHz.  The allowable levels above 26 MHz are such that these gadgets won't necessarily interfere with each other or most other consumer systems (whether or not TVs and FM stereo systems are connected to antennas or CATV feeds).  Licensed spectrum users (hams, and others) did not get a lot of respect with the allowable levels, but some reduction of emissions beats no reduction.  

You then have the manufacturers screaming about cost.  Well, the FCC caved in on susceptibility issues for Part 15 devices, but the EU stayed firm and insisted on a minimal level of RF withstanding for electronic devices that carry the CE mark.  When you see a device having a cord or cable with a molded-on ferrite device, yes, you certainly know it is there because the product is a "screamer".  The issue is then: how bad of a screamer?  You probably won't know until you try it.

Some folks, like Jim Brown, K9YC, and Ed Hare, W1RFI, have been posting comments and suggestions on this reflector for years about how to reduce (or eliminate) these unwanted emissions.  Yes, it takes work, some money (not a lot, necessarily), and just plain effort to overcome the problems.  In a lot of instances, adding some extra ferrites (as beads or toroids) might be enough to cure a particular problem.  In other cases, you are better off to dump the offender and try something else.  The problem arises, of course, when that something else belongs to a neighbor and not you.  

One sorry situation has emerged over the past several years regarding "name brand" equipment: cheap ripoff copies or accessory items that do not meet any emissions specs.  I am sure that we have all heard about various instances of battery packs and/or battery chargers that have caught fire.  Some of them were found to be fake copies of OEM equipment, sold real cheap and made you-know-where.  Those same vermin are also real good at eliminating components in power supplies that are supposed to suppress emissions.  So, one thing to consider when buying equipment or accessories, look carefully to see if all regulatory and safety agency markings are in place (FCC, UL, etc.).  Sadly, those markings get faked, too, but you have to start somewhere.  If an item proves to be a screamer, contact the (supposed) legit manufacturer and burn their ears.  See what reaction you get.  Legit makers should want to placate irate customers, others won't care.  Buy accordingly.

One last comment: to the best of my knowledge, European and FCC emission requirements were "harmonized" many years ago.  That's a "nice" way of saying that EU and FCC emission requirements are very similar or, in some instances, identical.  It's the Europeans who had the guts to tell the manufacturers that their junk must withstand external RFI.  It is possible that the extra ferrite is there so that the subject switch is not affected by RF fields of up to 3V/m in its vicinity.  That's one reason I look for a CE Mark on computer products.  The big names tend to make one box that can sell in many markets.  They have proven to me that adding some RFI insurance is not expensive - the "cry babies" would like you to think it is.  Yeah, I'm not being polite, but then RFI is not a polite subject in many venues.

73, Dale
WA9ENA



-----Original Message-----
>From: Jeff Stevens <jeff at mossycup.com>
>Sent: Aug 24, 2013 1:29 PM
>To: rfi at contesting.com
>Subject: Re: [RFI] KG2V's new RFI rule of thumb...
>
>This really strikes me as a rule of thumb with a large kernel of truth
>to it.  Having to choke external leads simply suggests that the
>product could have been engineered better from the start.
>
>One of the most comical manufacturer supplied external choke
>experiences I've had involved one iteration of the Linksys WRT54
>access point/switch that I purchased 5+ years ago.  This particular
>product is very well known to contribute to VHF RFI -- as many poorly
>designed Ethernet devices do.   If I recall the instructions there
>were a dozen or so steps in the manual to get the unit up and running.
> The last step read something like this (paraphrasing):
>
>"European users must install the supplied snap-on choke to the power
>cable as close as practical to the WRT54."
>
>I think there was a black and white diagram showing how to snap the
>TDK branded choke onto the power supply lead.  This implies two thing.
> First, the manufacturer didn't give a hoot about RFI when they
>designed the product.  Second, Europe must have more strict RF
>emissions requirements than North America.
>
>Just a somewhat comical manual.
>
>-Jeff
>W7WWA
>
>On Sat, Aug 24, 2013 at 1:05 PM, Charlie Gallo <Charlie at thegallos.com> wrote:
>> I've come up with a new rule of thumb:
>>
>> If the manufacturer puts a ferrite on the leads of a device, it isn't enough, and the item is an RFI bomb
>>
>> --
>> 73 de KG2V - Charles Gallo
>> Quality Custom Machine-shop work for the radio amateur (sm)
>>
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