[Ham-Mac] ethernet hash

Wed Feb 3 11:20:13 EST 2010

The problem with this is the noise goes away when the power adapter is  
unpluggged, but the Mac & PC are still plugged together. It's the dish  
receiver/ethernet adapter. Relocating it may not solve the problem  
either since the noise seems to be conducted over the ethernet cable.  
It would be amazing if a piece of equipment which needs a quiet  
environment is causing lots of its own noise. It doesn't take much  
signal to desense a receiver, even if the primary is tens or hundreds  
of harmonics away. I would ask the internet provider if they could  
swap out the receiver - it may be defective.

There is a good reason most of us are not troubled by this sort of  
noise - Macs tend to have very low noise characteristics. Many of the  
PC folks have figured this out as well. Unfortunately the networking  
box providers are slowly learning the lesson, so we tend to hear quite  
a few birdies from their boxes. But broadband noise of this sort tends  
to be rare and caused by boxes with major problems.

Jack B, W6FB

On Feb 3, 2010, at 8:07 AM, John Merrill wrote:

> To me it sounds like a combination of the internet hooked to the
> PC/Mac. Which to me says the PC/Mac's(NIC) are generating the noise
> when hooked to the internet. I'll bet when you place the satellite
> dish on the other end of the house the noise does not go away as long
> as the PC/Macs are close by the radio. IMHO.
>
> John N1JM
>
> On Wed, Feb 3, 2010 at 8:42 AM, EZ Rhino <EZRhino at fastmovers.biz>  
> wrote:
>> HI David,
>>
>> Actually, I've done about all of those.  My rig is connected to the  
>> computer via MicroHam USB II interface, which has optical  
>> isolation, so I really doubt it gets into the radio that way, and I  
>> did unplug its USB cable with no reduction in noise.  I've also  
>> tried putting ferrite on the power injector cable.  If I unplug the  
>> PSU the noise goes away, and so does my internet :-).  Remember, I  
>> did try eliminating the computer altogether by plugging in the cat5  
>> to an airport extreme router with no change.  I can have one end of  
>> a cat5 in my iMac with the other end open with no noise....as soon  
>> as the other end goes into something the noise returns.  So at this  
>> point I think I'm hosed, and will need to relocate the dish away  
>> from my shack.
>>
>> What really gets me with all this:  Why doesn't every ham with  
>> ethernet/internet and a radio have this problem?  I wonder how many  
>> have this and don't know it.
>>
>> Chris
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> On Feb 3, 2010, at 2:23 , David Ferrington, M0XDF wrote:
>>
>> Chris, you need to do some tests, I know you said if you unplug the  
>> CAT5 from your Mac it goes away, but that doesn't tell us what is  
>> causing it, just how it's being transmitted.
>>
>> So, Is your rig connected to the Mac, what's it like when it isn't?  
>> Maybe it's only transmitted via the USB interface to your rig.
>>
>> What happens when you disconnect the PSU but leave it plugged in  
>> and on - do you still get the spike, it might be the PSU.
>>
>> There must be some electronics in the dish, hence the need for the  
>> PoE (and there has to be something converting the downlink to IP)  
>> and testing that may not be easy, but it you can disconnect the  
>> CAT5 from the dish, do you still get the RFi with and/or without  
>> the CAT5 going into the Mac.
>>
>> Once you have this determined, you could try some ferrite in  
>> various places.
>>
>> Assuming regardless of what you do, you only get the interference  
>> when the CAT5 is in the Mac, put some 'beads' on the CAT5 where it  
>> enters the Mac (you might be hard pushed to use rings with CAT5, it  
>> could break the wires).
>> I'm not hopeful of this doing much with CAT5e, but it's at least  
>> worth a try, especially if the screen is carrying the RF, then that  
>> suggests your screen is not earthed.
>>
>> Also try ferrite on the cable between your Mac and the rig.
>>
>> Since you're using CAT5e and assuming the grounding on the shield  
>> is good, we must assume something is injecting the RF into the  
>> cable and its being transferred into the Mac. Whether it's then  
>> going down the USB cable to your rig or being radiated via the Mac,  
>> we don't know yet.
>>
>> Have you spoken with your dish provider, possibly, you have a  
>> faulty dish or electronics, or as Mark said, a faulty PSU, and it  
>> may be a known problem.
>>
>> Lastly, this kind of access is rare in the UK, so I'm going on how  
>> I'd track it down and not from any experience.
>>
>> 73 de M0XDF
>> --
>> I don't mind that you think slowly but I do mind that you are  
>> publishing
>> faster than you think.
>> -Wolfgang Pauli, physicist, Nobel laureate (1900-1958)
>>
>> On 3 Feb 2010, at 01:17, EZ Rhino wrote:
>>
>>> It is Cat5e, shielded.
>>>
>>> Chris
>>>
>>
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- Jack Brindle, W6FB
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