[RFI] Is it true this is "immune" to generating RFI?

[qrv at kd4e.com]

They seem to be somewhat careless in their use of terms so that
it quickly becomes unclear when they refer to incoming vs outgoing
RFI/interference ...

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whitewolf499 says: Apr 25, 2013. 11:03 AMReply
Good Afternoon From UK, Linda. I have a query, although I am no 
technical wizard, but is there no danger of this device generating Radio 
frequency interference, given that the cables over which the power 
travels may act as an antenna. This has happened many times here in UK, 
Europe and North and South America. I am not saying this WILL happen, 
only quoting the experience of what is called Power Line Transmission 
devices, which uses power cables to pass data between distant points in 
the same building. You are to be praised for your efforts posting, and 
this is a genuine concerned enquiry. Thanks for youre time, Best 
Regards, Gary
skinny*k says: Apr 25, 2013. 7:34 PMReply
whitewolf, I believe that the problems with Power Line Transmission 
devices that you are referring to have to do with sending (analog or 
digital) signals over building mains wiring—AC powerlines—as with X10 
and other devices or protocols.
MW0GKX says: Apr 25, 2013. 5:30 PMReply
It is sending low voltage, low amperage voltage over a data line. It is 
NOT the same as data over power line, PLT, as the cable is made for data.

I use a similar set up in my shack with no RF problems at all.
6
eLab (author) says: Apr 25, 2013. 1:39 PMReply
Thank you! Well, that is a common concern about PoE adapters but 
Ethernet communication is "kind of immune" to this type of 
electromagnetic radiation, besides the power lines being used in these 
cases are very low power. Therefore using some wires for power and some 
wires for data in the same cable, should not affect the transmission of 
data packets or the speed itself.
maestro_au says: Apr 25, 2013. 1:53 PMReply
I'd add two more reasons - twisted pairs used in ethernet cable (and 
phone lines) are paired & twisted in an effort to minimise 
radiation/induction with an AC / RF signal on the wire.

PoE is DC and tends towards embedded devices with a steady current draw, 
therefore limited scope for radiation even from a straight wire conductor.
8
darman12 says: Apr 25, 2013. 10:46 PMReply
That is a good point. Also note that the use of STP (shielded twisted 
pair) network cables rather than UTP (unshielded twisted pair) network 
cables will reduce the likelihood of interference.


> Maybe I missed it because I only took time to skim, but I didn't see
> where it said anything about not *generating* RFI. I saw one comment
> that said something about ethernet not being particularly prone to
> *receiving* RFI. My experience has been that PoE systems have all the
> usual ethernet egress of RF across the HF-VHF spectrum *plus* many of
> them have even worse issues caused by the switching power supply.
>
> I have a PoE system that powers an access point located atop one of my
> towers. Its original power supply completely trashed 160 meters. I cured
> that by going to a DC injector and using a linear bench supply to
> provide power. Clearing up all the ethernet carriers while there is ~200
> feet of CAT6 running up into the midst of my antenna farm is not so easy.
>
> 73,
> Paul N1BUG
>
>
>
> On 04/25/2013 08:45 PM, Jim Brown wrote:
>> On 4/25/2013 3:25 PM, qrv at kd4e.com wrote:
>>> http://www.instructables.com/id/Power-Over-Ethernet-PoE-Adapter/
>>>
>>
>> I've run into PeE systems that were VERY VERY VERY noisy on HF. I didn't
>> bother to stick around to fix them, but I suspect they might have been a
>> candidate for the bucket treatment.
>>
>> 73, Jim k9YC
>
>


-- 

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