Homebuilt ROVs Forum

Hi all,

I am new to ROVs and RC controllers and have a question I'm hoping you can help with. If you didnt have a DSC unit, and relied on the TX to 'talk' wirelessly with the RX on board the ROV, would a tether (made of cat 5 cable for example) trasnmit the signal to the ROV? I have a design for an ROV that uses this principle, but I want to use mine in saltwater and am worried the concept may not work in saltwater. Any thoughts?
Many thanks

mg

I'm building much the same thing at the moment (very possibly from the same plans). It should work fine because the signal travels through the cable irrespective of the water surrounding it.
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Hi guys, just a thought from other information I have read. I am no expert but at least I can pass on what I have read about this.

Using an RC system to transmit a signal on a conductor i.e. CAT5 in principle one would think it would work well. But there may be an inherent issue that comes to mind. Radio antennas are "tuned" lengthening your antenna via directly connecting to it may in all likelihood lose its transmit and receive ability. Especially over the length of the tether. You might be able to do this if the signal could be amplified at the transmitter. It might also be possible to achieve this if you used coaxial cable and relocated the antenna. There are a lot of folks that are well versed in this area in RC and Robotics’ forums and probably on here also. Did you buy the design plans or is this a concept you have yourself? Like I said I am no expert just passing on some things I have read.

Cheers, Anthony

bikerbones1968 wrote:Hi guys, just a thought from other information I have read. I am no expert but at least I can pass on what I have read about this.

Using an RC system to transmit a signal on a conductor i.e. CAT5 in principle one would think it would work well. But there may be an inherent issue that comes to mind. Radio antennas are "tuned" lengthening your antenna via directly connecting to it may in all likelihood lose its transmit and receive ability. Especially over the length of the tether. You might be able to do this if the signal could be amplified at the transmitter. It might also be possible to achieve this if you used coaxial cable and relocated the antenna. There are a lot of folks that are well versed in this area in RC and Robotics’ forums and probably on here also. Did you buy the design plans or is this a concept you have yourself? Like I said I am no expert just passing on some things I have read.

Cheers, Anthony

Thanks Anthony, something to consider for sure. The plans are from http://rovrobotsubmariner.com/ and only cost a few dollars. The author assures me it won't be a problem, I just wanted some other opinions before I buy all the RC gear, otherwise I will go the path of simple switches down a tether.

Cheers

mg

This is quite ironic, I purchased the same design plans a while back when I first decide to build an ROV, downloadable PDF file. It was only while researching deeper into RC controller options did I find mention about lost signal issues due to the nature of antennas and how they work. Might be ok on a short tether in a swiming pool but I have my doubts over a 150' to 200' cable lenght it would work.

I have the same plans, although I've used them more for inspiration than making a direct copy.

I know little to nothing about rc, but my feeling is the signal from the transmitter should be clear enough over that length. Cat5 has a maximum length of 100m as ethernet cabling, and I suspect it's much the same in this case. I'll be hopefully taking mine for its first test-dive this coming fortnight using 50-75m cat5 tether so I'll be able to confirm either way.

For the record I'm using 2.4Ghz instead of the 40 that Ian recommends because no-one makes it any more.

I basically used the plans I purchased for the same reason. Since then I have decide to do everything from scratch and build as I go.

Please keep me posted to how it goes with your test. I am still gathering parts and pieces for my build so nothing yet is carved in stone for the final design.

Anthony

Over in this thread:

viewtopic.php?f=15&t=370&p=1270&hilit=router#p1270

biglakeexile said he had this setup (with the RC controller antenna extended) working at a 70 foot depth.

Also, Seadragon did some tests a while back with a wireless router (2.4 Ghz, the same frequency as your controller, if I read correctly). He did the test on land, but I think he said it worked though something like 1000' of wire.

Welcome to the forum, and good luck on your ROV m_g!

Just read the other posts. I will have to get some more details before I journey down that path. 1000' over wire almost sounds too good to be true.

Ok great, thanks! Haven't seen any specific mention of why this wouldn't work in saltwater, so am keen to give it a try. Thanks for all your help, will post my results.
Cheers