[RFI] Internet Modem / Router Cable Length and RFI

[Roger (K8RI)]

I'll repeat, I have 2 130'runs of CAT-5 from the 8 port switch  to the 
two computers in the shop and about 30' in the other direction, for a 
total of roughly 160 ft linear run, (directly under the 160 half sloper 
and partially under the center fed, half wave, 40 meter sloper. plus the 
runs to the servers and the two smart TVs which I had forgotten.  That's 
maybe another 30 amd 70 feet. Not sure, and I run the legal limit  for 
most bands 160 through 440 except 2-meters with no detectable ingress or 
egress except for an HT setting directly on the case within inches of 
the USB and eSATA connectors and that barely breaks the squelch.  Move 
the HT a couple inches and no problem.

It would be interesting to know the make and models of the power 
supplies that cause problems.  Are they "good" power supplies, or the 
typical cheap ones found in discount store computers? Actually I'd not 
be surprised to see supplies under $100 listed although I'm sure there 
are probably good ones under that and poor ones over that $100 mark.

The higher priced modular supplies tend to be well built.  I've never 
run into a bad one, but I'm far from having tried them all. It'd be 
interesting to stick the spectrum analyzer on them.

The biggest problem here is slow wireless as there are so many local 
networks competing for space.

73

Roger (K8RI)



On 6/2/2015 12:06 AM, KD7JYK DM09 wrote:
> : I love EMT for shielding.  BUT -- to provide shielding, the EMT, like
> : any cable shield, must be bonded to the shielding enclosure (or ground
> : plane) of the equipment at both ends. Simply grounding the EMT is
> : insufficient.
>
> Makes sense.  I could also use metal flexible conduit from one end to the
> other and have a continuous piece of metal for the conduit, some even have a
> separate bonding wire within them.  Planned to mount the DSL modem/router in
> a metal box anyway and use a linear supply.  Conduit connected to the
> enclosure at one end and clamped to the back of the computer at the other is
> reasonable.
>
> "engineers working in computer networking advise many practices that we use
> for analog systems should not be used for unshielded CAT5/6/7 cables. We
> should not, for example, bundle them, because it creates small
> discontinuities in the balance of the pairs, and of the coupling between
> pairs."
>
> Wouldn't the balance between the pairs be relative to the pairs, which
> wouldn't change, even when bundled, unless it was a bundle of multiple CAT5
> cables?  In my case it would be a single cable from point A to point B in a
> straight line with about 4' rise at one end and a 6' drop at the other,
> enough to get from the router on one floor to a computer on another.
>
> "Putting these cables in EMT could have the same effect. The result is
> increased error rates, thus slower data rates."
>
> I guess we'll see what happens when the time comes.  It may turn out
> everything is adequately quiet, although I wouldn't completely rely on it.
> 40' of wire on a broadband hash generator is asking for trouble.
>
> Kurt
>
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