Ethernet signal degradation

[capnahab]

I have FTTH and reliable download speed of 900MBps wired to a mikrotik router. This goes to a mikrotik  Wireless AP 

This claims 574MBps . Sat right next to it I am getting 125MBps. I know there are many reasons for this including antenna optimisation, software set up in the AP etc. I am interested in the ethernet cable initially which is CAT6. It has to run outside the building then back in the cellar and then to the AP. I think it is about 50-60 metres.  I don't think there are any joins. 

Is there likely to be much degradation in this length of cable ?. Can I test it ?.

[licquorice]

There will be no measurable degradation whatsoever.

[countrypaul]

The Ethernet cable will work at either 100Mb/s or 1000Mb/s (10Mb/s unlikely now), assuming your router doe not support anything higher, it won't use any intermediate speeds. If you are therefore getting over 100Mb/s on WiF you can assume it is working at 1000Mb/s.

If the signal is poor due to problems with the cable there may be retransmits etc. The simplest way to test it would be to put a PC in place of your AP and run it for a little while. Running a speed test should give you an idea of available performance over your ethernet cable.

Depending on what OS you have, you may be able to look at the Ethernet statistics.