I was wondering (besides cable power loss), is there a reason I can’t power the FathomX from the teather cable? I know there may be a little noise from running power thru here but it would be a lot more convenient if I didn’t have to source another battery just for the receiver end.
Another question. The BluRov2 comes with a ubec for the fathomX. Why would we need a BEC when the board itself comes with a regulator and spec’ed for 7-28V ? Couldn’t we just go directly off the LiPo battery?
Oh I posted too quickly. Sorry looks like the ubec is only for the raspberry pi and the Fathoms are actually going to directly to the battery. Nevermind!
To answer your first question: yes, you should be able to send power down the un-used wires in the tether. The Fathom-X uses only one twisted pair (out of 4) so that leaves 3 twisted pairs for whatever you want to do. If you use DC power (and a good power supply) noise shouldn’t be much of an issue. What will be an issue is that the wires are very small gauge and won’t carry much power. You will probably have to go with a fairly high voltage in order to get any power at all down to the ROV.
How are you powering the rest of your ROV? Do you have a battery onboard at all? The Fathom-X has a pretty wide voltage input range so you can connect it to most batteries.
If you want to power it through the tether, that is possible, as Paul mentioned. It can draw up to about 700 mA peak but is usually much lower than that.