Re: [Hampshire] Ethernet connection Unscreened

2009/11/27 Roger Munford <rogermunford@???>:
> I am working on a project that, at the last moment added an ethernet
> connection, between two water proofed housings about 1 meter apart.
> Within the boxes normal Cat 5 is used but through the housings and
> connecting the two is a rather chunky specialist submarine cable which
> has no shielding and no twisting of pairs. This setup scarcely works but
> it does work a bit. The housings have already been manufactured and the
> connection is a spare unused one which the designers thoughtfully added
> but not with ethernet in mind. Should this sort of degradation be
> expected? Any advice/comments would be gratefully received.
>
> Roger
>

Is the cable carrying anything else apart from Ethernet?
Is the cable going to be left underwater?

Twisted pair cable is done that way to filter out common mode interference.
I.e. The cables can pick up interference, but as they are twisted,
both cables pick up similar interference, so a sensor at the end that
only measures the difference between the signals will filter out all
the common mode noise.

Now, interference is minimal under water because radio waves are
massively attenuated underwater.
So, the only interference you will get is from whatever else the
submarine cable is carrying.
If it is only 1 meter apart, you should be able to get 10Megs, and
maybe even 100Megs.

When you say "scarely works" what do you mean?

If you are able to fix the ethernet to use half duplex, it should
improve the performance as less interference will result.

There will not be a case of "I definitely will not work". It will be a
matter of judgement and approximations.

Kind Regards

James