Tether Connectors / Twisted Pairs

Hello team,

For tether connections I am currently using Bluetrail 8 pin bulkheads & connectors on my BR2, tethers, and deck leads. I have found them to be a bit too delicate and I have broken a few pins in the field and in the shop. Since we are only using 1 twisted pair (in our 4 twisted pair tether) with the Fathom X gear I was thinking of moving down to the bluetrail 4 pins because they look much more durable.

My questions are:

  1. Is it even possible to utilize the other 3 pairs (ie with additional sensors, fathom X boards, cameras etc) in the tether or will there be too much crosstalk? Is it possible to increase bandwith this way at all? - If only 1 pair is utilizable, should I just use a bluetrail 2 pin?
  2. Do any of you have any other tether connector recommendations?
  3. The single pair tether uses the same 26AWG as the 4 pair tether, why can’t the single pair tether go to 300m?
  4. Would it be stupid to ‘parallel’ the twisted pairs. Would this increase bandwith/increase redundancy or would that be a terrible idea?

Thank you all very much,

Hi @johannv,

You can use the other pairs for other communication protocols (e.g. RS-485), or potentially for things like supplemental power to top up the battery, but it generally wont’ work well to use multiple Fathom-X boards on separate tether pairs (although you can use multiple Fathom-X boards on a single pair, or double up on wires to reduce resistance).

Sub-conn micro-circular are probably the main other option at the moment, and is what’s currently recommended in our connector standard, but I believe they’re a decent amount more expensive. We’re also working on an option, but good things take time.

Not certain, but presumably it’s something to do with their being enough capacitive cross-talk with the other pairs that it ends up helping the signal get through to the other end. We’ve done testing and it maintains the connection further with 4 pairs than 1, and we’ve rated the tethers accordingly.

As far as I’m aware that should work to reduce the resistance. I’m unsure whether it would necessarily improve the signal integrity, but it might do. Feel free to try it out, run a network test (or few) with each configuration, and see what works best :slight_smile:

Hi Eliot,

Thanks for the quick reply and info.

If I use multiple Fathom-X’s on the same single pair does that increase bandwidth in any way? What would be the advantage of a setup like that?


It depends on what’s in your system, and how it’s being limited.

I believe the HomePlug AV protocol uses separate frequency channels for different connections, so if you have a long tether that limits the data rate below what a Fathom-X is capable of communicating at then adding another one for some of the devices in the vehicle could potentially allow them to in total have a bit more bandwidth available, as compared to an Ethernet Switch which just adds additional connections to the input of a single Fathom-X.

Perhaps a more uniquely useful approach would be for reducing the wires required for multi-part vehicles, because each part can contain a Fathom-X board and they can all be using the same pair of wires for shared communication (and potentially power). That could potentially make sense for vehicles with unique enclosure requirements, or for tether-connected vehicle swarms.