After I completed the ROV I took it to a pool and everything worked fine. The tether was just in a open roll then and I had 90 up and 70 down speed with 80m tether. Now I put it on a cheap spool with a slipring and the bandwidth dropped to sub 2Mbps. I have been trying to figure this out for days now and it is driving me mad. Bypassing the slipring I get 10Mbps, resistance is where it should be around 10Ohms. When I connect directly with a short UTP I have no problems. First I thought it was the pigtail of the connector which is around 20cm un-twisted but it worked fine in the pool.
So my question is, if I get the Fathom-X will I increase the bandwidth of the single pair (now I use 2 pairs). If anybody knowledgeable could point me in any direction I would be grateful. Attaching a pic of the setup for reference. Maybe I should point out that I did upgrade the pix and the Pi software to the recent version, not that I think it matters.