[Ham-Mac] ethernet hash

[EZ Rhino]

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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