[hpsdr] Ozy with Gb Ethernet

[Donald Kay]

jeff millar wrote:
> Donald Kay wrote:
> 
>> ***** High Performance Software Defined Radio Discussion List *****
>>
>> Hi Fred,
>> It was very bad here. The original setup had a couple of
>> 65 ft runs of cat 5e, one to the front of my house and
>> one to the rear where the shack is. The network equipment
>> was all linksys so maybe that had something to do with it.
>> Also, although I have some 100BT here it was mostly older
>> 10BT stuff. I have seen speculation on the web that these
>> are harmonics of the frame rate but I don't know that for
>> sure.
>>
>> The interfering signal shows up every 30 khz but every other
>> one is quite strong. I saw it from about 80 meters through
>> all the HF bands.
>>
>> Moving to a wireless network solved the problem.
> 
> 
> I think the problem came from the Ethernet cable carrying some switching 
> power supply noise on the _outside_ of the cable.  If the interference 
> came from frame rate, it should have created moving spurs because frame 
> rate comes from a variety of random processes.
> 
> A 30 kHz switching supply would produce even and odd harmonics with 
> different amplitudes.
> 
> Look for an old piece of equipment, because 30 KHz is a low frequency 
> for modern switchers.
> 
> jeff, wa1hco
> 
10baseT has a continuous echo packet exchange that is used as a connectivity
indicator (the link dead detector). I don't know whether it runs at 30 khz
or not but I can tell you that the interfering signal has a steady tone to
it when no one is using the net. As soon as someone loads a web page you can
clearly hear changes in the tone.

You may be right, I'm certainly no expert at this kind of thing. I probably
could have tamed it with a little ferrite but I didn't pursue it since
I already had a parallel wireless net which I could switch to.

-don (KI6FOM)


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