Topic: 2.4Ghz and water (Read 4745 times)

essex2visuvesi · « **on:** January 22, 2013, 03:29:35 pm »

A daft question I know but.... here goes

I understand that 2.4ghz does not penetrate water well, so is of no use for submarines per se, but my question is this.... how far does 2.4GHz penetrate before being lost..... Is it more or less than a foot?

sailorboy61 · « **Reply #1 on:** January 22, 2013, 03:47:28 pm »

My guess is thats going to be a huge variable depending on distance, angles density etc... trial and error.

essex2visuvesi · « **Reply #2 on:** January 22, 2013, 04:10:37 pm »

ok thats what I thought.

My plan was this.....
I have a model GA stingray thats quite small, and a dead mini 4ch foamy RC plane with an all in 1 receiver/servos/esc etc. This got me thinking about putting the electronics into the little stingray. I thought it would be fun to give it limited dive abilities but am unsure if the 2.4Ghz would be suitable.
While writing this I had an idea.... I will put the radio gear in a margarine tub and sink it, seeing how deep I can get it before the signal is lost. As long as I can get around 30cms It'll be worth doing.
Will report back

sailorboy61 · « **Reply #3 on:** January 22, 2013, 04:13:07 pm »

30cm next to the TX may be fine, but 30cm 6M away would probably loose the lot??

essex2visuvesi · « **Reply #4 on:** January 22, 2013, 04:17:37 pm »

Guess its back to the drawing board then.... maybe ill just make it a surface runner

Bob K · « **Reply #5 on:** January 22, 2013, 04:48:03 pm »

I have a 2.4GHz Planet Rx in my 1.3m WW1 cruiser. Originally I had the Rx horizontally on top of the battery compartment lid, fairly close to the waterline. Going over half way across the lake I lost control. Then I mounted the Rx vertically inside the superstructure with the aerial as high as possible and it has not lost signal at distance since then. It appears the Rx aerial needs to be as high above the waterline as possible to maintain a good signal.

The current ship I am building has almost no freeboard at all so I am fitting a 40Mhz system under watertight compartment hatches.

essex2visuvesi · « **Reply #6 on:** January 22, 2013, 06:21:56 pm »

http://www.parkzone.com/Products/Default.aspx?ProdID=SPMAR6410

this is the thing I'm on about.

upscope · « **Reply #7 on:** January 22, 2013, 08:02:38 pm »

Way back in 2006 when 2.4ghz was negotiated by the BMFA (British Model Flying Association) for use model flying use in the UK, I as a model submariner was curious to see "IF" it would work in a submarine, I knew in theory that it would not, but I wanted to see it for real!!Working in a model shop gave me the opportunity to get hold some test gear, the gear was Futaba 6EXA on 2.4ghz.

So I got a waterproof box with 2.4ghz rx, a servo and a battery in, a few inches under the surface with tx nearby it worked as the green light on the rx could be seen along with servo working, a few inches deeper still had control, but as the tx was moved further away, the signal was lost completely. There was the answer, it does work underwater, but only at few feet range, and shallow.
Paul Cook

Norseman · « **Reply #8 on:** January 22, 2013, 08:17:41 pm »

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3355409/

From about 5.2, 5.6 _ the only serious thing I unearthed re 2.4 underwater.

Dave

dreadnought72 · « **Reply #9 on:** January 22, 2013, 10:44:57 pm »

2.4GHz is on the S-band part of the microwave spectrum. It's used for space communications, weather and surface radar, and microwave ovens. The last is the big clue as to why we can't use it on model subs: a microwave oven works by vibrating water molecules - the frequency is one which is in harmonic resonance with the molecular size of H₂O. Turn on the radio, and the molecules vibrate.

For our purposes, the energy in the 2.4GHz signal (which we want to get to the boat) is lost in the first few cms of water: it's spent on wobblin' it.

Andy

Norseman · « **Reply #10 on:** January 22, 2013, 10:52:22 pm »

Quote from: dreadnought72 on January 22, 2013, 10:44:57 pm

wobblin' it.

No way is 2.4 gonna pass through me then .... might warm me up at the lake though

Dave

upscope · « **Reply #11 on:** January 23, 2013, 08:07:02 am »

Quote

2.4GHz is on the S-band part of the microwave spectrum. It's used for space communications, weather and surface radar, and microwave ovens. The last is the big clue as to why we can't use it on model subs: a microwave oven works by vibrating water molecules - the frequency is one which is in harmonic resonance with the molecular size of H₂O. Turn on the radio, and the molecules vibrate.

The above posted by Dreadnought, was the theory that I knew, but seeing work or not in this case was the absolute definitive proof!

Separated quote for you

Tug-Kenny RIP · « **Reply #12 on:** January 23, 2013, 12:12:18 pm »

Would a glass of water next to the TX warm up ??

ken

Subculture · « **Reply #13 on:** January 23, 2013, 01:17:58 pm »

Take a blooming long time with the power of our sets!

Tug-Kenny RIP · « **Reply #14 on:** January 23, 2013, 07:47:07 pm »

ken

NFMike · « **Reply #15 on:** January 23, 2013, 08:05:32 pm »

It may well be apocryphal but many years ago I heard that flight deck crews on carriers would warm themselves by standing in front of an aircraft with it's radar on.
Basically being microwaved

I have no actual evidence of this happening, but I think this was before domestic microwaves brought the principles (and possible health concerns) into the public eye.

Tug-Kenny RIP · « **Reply #16 on:** January 23, 2013, 08:09:38 pm »

From the inside... out

Ken

Norseman · « **Reply #17 on:** January 23, 2013, 08:13:42 pm »

They say that Ken but I don't believe it. I say outside inwards.
Someone will now launch an Exocet at me but I can't see inside out working

Dave

Southern Sailor · « **Reply #18 on:** January 23, 2013, 09:00:52 pm »

What on earth happened to the reproductive capabilites of those guys who stood in front of the radar?? The mind boggles at such behaviour - ah well, they were probably air force! Happy sailing. Brian

JayDee · « **Reply #19 on:** January 23, 2013, 10:34:45 pm »

Hello,
I was a Radar Operator, we used to tilt the beam down to warm our hands in the very cold German winters !!.
Never stood in front of it while it was on.
Often wondered if it had anything to do with only having Boy babies, 3 of them, but no Girls.
Anybody else have the same happen ???.
John,

malcolmfrary · « **Reply #20 on:** January 24, 2013, 08:18:41 pm »

The figures in Norseman's link look like straight penetration, with no real consideration of reflection. Surface reflection would probably reduce the power available for water penetration enormously, probably by enough to lose signal immediately on the aerial going below the surface level.

wibplus · « **Reply #21 on:** January 27, 2013, 06:34:57 pm »

I use a Spektrum DX7 TX which will also fly my helicopters. The system in air use is fully connected within "line of sight". However, when I installed the same system in my Bugsier tug, I had the RX just below decks and the result was a dodgy connection which had to be rectified by moving the RX into the superstructure to obtain reliable connection. It seems that even random dipping under the surface of water will disturb the connection.

News:

Author Topic: 2.4Ghz and water (Read 4745 times)