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    openLRS and 2.4 Ghz and Submarines

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    david f
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    openLRS and 2.4 Ghz and Submarines

    Post  david f on Sat Nov 20, 2010 1:12 pm

    Hi Richard, I hope you don't mind if I've dragged another shoebox full of stuff over from the Facebook premises.
    Please feel free to delete it but I think this is important since it could be the death of our hobby!

    Once again my thanks to everyone for their valuable (if slightly dusty!) contributions:

    David ForrestAssociation Of Model Submariners
    ‎2.4Ghz and submarines?
    I've just bought myself another Futaba FF9 transmitter not least because I am concerned about the future of 40 Mhz (which we need for submarines) and because the Flyboys are offloading them on Ebay (Going to 2.4ghz etc.)
    The one I got came with a 2.4Ghz Spektrum module. The question is can i use this for anything... useful (Polite answers only please!) If I bought a receiver could it be used for aircraft AND surfce boats or just one or the other??See More
    September 30 at 11:37am ·LikeUnlike · Comment



    Richard J Huggett As far as I know David, 2.Ghz is legal for all boats and aircraft(and cars as well.) My Chinook helicopter came with a 40Mhz radio when I bought it, but the new upgraded versions come with 2.4Ghz radios.

    The plus benefit is that you can buy ...an rx and use it in a surface boat, buy another rx and use it a plane, a car or a helicopter with the same tx.

    I've had three GiantCod 2.4Ghz outfits and never had a problem with any of them.
    http://www.giantcod.co.uk/giantcod-24ghz-6channel-mode2-digital-transmitter-plane-versio-p-403852.html for the six channel version.
    http://www.giantcod.co.uk/giantcod-24ghz-6channel-mode2-digital-transmitter-plane-versio-p-403852.html for the four channel version.See More
    September 30 at 11:46am · LikeUnlike.David Forrest That's very interesting stuff. Thanks.
    September 30 at 12:40pm · LikeUnlike.David Forrest I didn't realise that 2.4Ghz is legal for surface and aircraft use. That is a big benefit but a shame it doesn't get through a few mm of water.
    September 30 at 2:11pm · LikeUnlike.Richard J Huggett I had a long chat to Andy L about using 2.4Ghz in a surface running sub, but the end conclusion was that it wouldn't really work, not even if the rx was mounted high up in the sail there would still be the problem of sealing the connections through the deck. Andy also seems to think the signal wouldn't penetrate the wtc very well either, because the majority of it would be below water. As you say David, it's a great shame, with the really low prices on 2.Ghz equipment nowadays.
    September 30 at 2:59pm · LikeUnlike.William Macleod i tried it in a sub with the extention rx module in the sail and as the water level came up to the Rx the radio went into failsafe.
    September 30 at 7:13pm · LikeUnlike.Richard J Huggett I guess that sort of answers the question David...one good thing though, with all the flyer boys selling up their 40Mhz equipment, there should be some good deals for us.
    October 1 at 9:02am · LikeUnlike.William Macleod the problem is that the flyers are on 35Mhz which is for aircraft only.
    October 1 at 9:30am · LikeUnlike.David Forrest Yes, but if you buy sets such as the Futaba FF9 which has plug in modules in the back, you can change them to 40Mhz easily.
    October 1 at 9:36am · LikeUnlike.David John Jacques ‎2.4 can be used on any model boat, plane or car
    October 1 at 1:01pm · LikeUnlike.David Forrest Thanks, Dave. So it is a really handy system - shame we can't use it!
    October 2 at 8:41am · LikeUnlike.Paul Cook I have been "stocking up" on futaba 8-9 channel Rx's & my xtal frequency as i feel we are going to lose the 40mhz equipment soon.
    I have the futaba 14mz with 40 mhz module as a FF8 as a back up.
    October 7 at 5:14pm · LikeUnlike.Richard J Huggett I've just bought a Corona rx from HobbyKing on 40Mhz and I'm just about to order a couple more...just in case Paul's prediction comes true.
    October 7 at 5:54pm · LikeUnlike.David Forrest Paul has an interesting view which is presumably based on Ripmax and Futaba thinking. The main problem wil be that the manufacturers stop offering 40Mhz quite soon. I imagine that the Govt. will keep the "frequency slot" unsold for a fe...w years more.
    Once the frequency slot is sold we will be quietly illegal. I've always wanted to be a real pirate!See More
    October 8 at 9:42am · LikeUnlike.Paul Cook Hello all, as you know i work at HobbyStores, owned by Ripmax(main UK Futaba importer), we also deal with Hitec, Jeti, Sanwa, Spektrum as a model shop, my fear with us all as submariners ALL of the new radios coming out other than the odd 2... channel sets on 27mhz are on 2.4ghz, there nothing from the above companies on 35mhz of 40 mhz, the use of 2.4ghz has allowed these companies to save money essentially as they only have to make one set of gear rather than say a set on 35 and 40 as in the past, as the 2.4ghz is legal for everything from cars, trains, boats, planes helis, tv cameras etcetc, but as we know its totally useless to us.

    Now all the model submariners in the worlld could write to futaba etc to "protest" etc, how many model submariners are there? i can tell you that there are about 40,000 registered BMFA (british model flying assciation) members in the UK alone, let alone the AMA (american equivalent) who are all now most probably using 2.4ghz, heck i now use it to fly models on. So my advice to you all is if you see 4 + channel upwards 40mhz gear in a shop offer the shop to buy for a cheaper price than thyre asking, they will probably be glad to see it to you! Yes you read correctly USE YOUR LOCAL SHOP - otherwise that will be the next to go!!See More
    October 8 at 10:16am · UnlikeLike · 1 personLoading....Paul Cook On the brighter side, alot of the "toy" market (NIKKO) etc still use the 40mhz on their models, so i dont see the 40mhz band being "sold" off just yet.
    October 8 at 10:27am · UnlikeLike · 1 personLoading....Richard J Huggett That makes interesting reading Paul, I can imagine the uproar amongst model submariners if the 40Mhz/27Mhz bands were to go. We'd up like the old CB radio users(of which I was one for years)..anarchy would reign supreme in the streets!

    I app...reciate your point about using your local shop, I'd love to be able to...if I had one. All I have is a model railway shop and Modelzone, neither of which is any good to me at all. I have to buy online, and just recently I've started buying online from Hong Kong...my new Corona rx cost me just over a tenner, and that was including postage to my door. By the time I'd have driven into Eastbourne, Brighton or Worthing, paid some huge fee to park my car and had to walk a mile from parking space to shop, then driven back home again, my £10 rx would have cost me twice as much.

    Maybe I should move to Norwich...See More
    October 8 at 10:56am · UnlikeLike · 1 personLoading....Paul Cook Hiya Richard, obviuosly you can only use your local shop if you had one, but then surely Eastbourne would have had one at some point? Model Zone, we have just had one open up in Norwich, the word "competition" was used to me by a friend, we... dont sell airfix etc we are all RC so competition, NO!

    I suppose your nearest best shop is SMC in worthing, i like Westbourne in Bournemouth though, been there a couple of times.See More
    October 8 at 11:17am · UnlikeLike · 1 personLoading....Richard J Huggett We used to have a decent model shop in Eastbourne named "Bob's Models", run by a chap named Bob Kinnell. He was a r/c modeller himself, and the shop was brilliant, but after a few years of trading he was running at a loss, so down the pan i...t went, more's the pity.

    Modelzone don't do but very little in the way of 'proper' r/c stuff, plenty of RTF boats/planes/cars etc, but mention the word 'submarines' and there's just blank looks amongst the staff. The model railway shop is good for things such as brass tube/rod/light metal stocks and paint, but that's about it really. Oh, and styrene sheet.

    SMC in Worthing is a good model shop, but due to the distance and car parking fees, I buy online from them now. They excel in that, I normally get 48 hour delivery from them, and I've never had a complaint yet with them or their service. I bought my Chinook from them, ordered it online in the morning and it was delivered at 1900hrs that evening by courier(ok, the driver lives close to me, but that is still extraordinary service in anybody's book)

    I'm not sure if EM Models in Tunbridge Wells are still going, they used to be a good shop, as was Maritime Models in Greenwich...Bernie and I used to spend many a happy hour in there.

    Maybe we should all make Hobby Stores the AMS's nominated store!See More
    October 8 at 12:45pm · LikeUnlike.David Forrest Well it would seem that model submarines are going to go increasingly "niche" if newcomers to the hobby can't even buy r/c equipment.
    BTW was the Bob mentioned above the inventor of Bob's model board speed controller. (Heavy loss, fire assis...ted speed control? Only joking they were good in an age where "carbon footprint" meant that you'd been to the coal cellar!)See More
    October 8 at 2:52pm · LikeUnlike.Paul Cook There is of course the possibility that 40mhz gear may still be produced, but looking at what i see, its looking doubtfull, yesterday we had a whole new consigment of RTR brushless racing boats come in, all on 2.4ghz.
    October 9 at 9:53am · LikeUnlike.Richard J Huggett David: No, Bob Kinnell wasn't the man you were thinking of, I don't know that Bob was, I can't find out anything about him.

    Paul: I take it then that 2.4Ghz is much cheaper to produce than 40Mhz is?
    October 9 at 10:06am · LikeUnlike.David Forrest The more I think about it, the more depressing I find it for the long term future of our hobby.
    Newcomers to model subs will either have to buy elderly second hand equipment or an expensive, specialist "submarine transmitter" made by a sma...ll specialist company at a high price.
    27 Mhz is no answer because it is usually only for a couple of channels.See More
    October 9 at 10:18am · LikeUnlike.Richard J Huggett You still see the good old Futaba M series on 27Mhz for sale, they were good old radios, might be worth snapping one up if you see one on ebay or somewhere similar.

    Or buy a shed load of Corona rx's...I've just ordered two more from HK.
    October 9 at 10:21am · LikeUnlike.Paul Cook Whats even more depressing guys is this, most newcomers to this hobby wont be able to build their own model submarine, the amount of people we get in the shop "what i got to build it"?? Cant i just use it, "can you use a screwdriver sir" du...h, NO! Can you build it for me, i will pay you! they say! This is on a Tamiya car kit! let alone anything else!

    I am 40 next year, i doubt there is anyone younger than me in my flying club that has build a model form a kit or plans, these so called "artf's types" that have the nerve to call themselves modellers!See More
    October 9 at 10:29am · LikeUnlike.Richard J Huggett The ARTF type of model does have a lot going for it(take the Thunder Tiger sub as an instance)it does get people started in the hobby, but as you say Paul, once Mr Joe Public has bought his TT sub, does he have the skills needed to maintain... it? Or repair it? It's doubtful...

    Some of the modern, up to date pre-fabbed kits are reasonably easy to assemble, but then there's the ballasting and trimming to do, the radio to set up properly, etc...I wonder how Mr Joe Public would fare with the building of an early Darnell kit from the ground up?

    Is there no way that 2.4Ghz can be modified for our use with the addition of an signal amplifier to boost the tx power? Or would that make illegal to use?

    It looks as though the future of model submarines is going to be limited to a pond filled with Thunder Tiger subs...or am I just depressing myself?See More
    October 9 at 10:40am · LikeUnlike.Paul Cook Having built (assembled) at TT Neptune, its not actually that easy if you dont follow the instructions closely.

    We in the UK are limited to power output of our 2.4ghz sets.
    October 9 at 10:56am · LikeUnlike.David Forrest Well actually Paul's comment makes me less depressed. There will always be a (very few admittedlly) enthusiastic sub builders for whom assembling or modifying a transmitter for 40Mhz will be no problem compared with building a submarine. I... suppose most of the AMS membership fit in to this category.
    Sheerline are going to have a problem though. I wonder if Chris has thought about this one?See More
    October 9 at 11:14am · LikeUnlike.Richard J Huggett Now you're depressing me!
    October 9 at 11:17am · LikeUnlike.David Forrest Sorry! Depressed is probably the wrong word anyway. Concern for the future hobbyist is it.
    Where is Nigel when you need him? He is very good at thinking of solutions!
    October 9 at 11:41am · LikeUnlike.Paul Cook I will ask chris when i see him, as you know he only live about 30 mins from me. He may even be on here?
    October 9 at 11:46am · LikeUnlike.Richard J Huggett I can't really see the 40Mhz band going out of use, but maybe the problem will lay in the lack of equipment being readily available..ok, so there will be a large hole in the hobby for some enterprising person to set up a business specialisi...ng in building and repairing 40Mhz radios, much like the old Kingshill Navigator of bygone years.

    Incidentally, I used to live next door to the chap who built these under licence, they were marvellous radios, you simply told him exactly what you needed and he would build it for you. Twin sticks, dual use sticks, multi function switches...he was a genius when it came to radios. He worked out of his garden shed, which was a local attraction for modellers, sometimes you couldn't move in our area for modellers. But, he parted company with his wife and moved away, and shortly afterwards I did the same, so I lost contact with him.

    Maybe someone like Andy Lawrence would take up the challenge of keeping the 40Mhz radio alive and well?See More
    October 9 at 12:01pm · LikeUnlike.Steve Juden I can see a market for an adaptor to convert 2.4GHZ radios to 40MHZ.
    October 12 at 6:50pm · LikeUnlike.Paul Cook Yes it called buy a 40mhz module now?


    Last edited by david f on Tue May 31, 2016 12:07 pm; edited 5 times in total (Reason for editing : Including 433Mhz option which is starting to look promising. Helps with "Search.")
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    david f
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    Re: openLRS and 2.4 Ghz and Submarines

    Post  david f on Sat Nov 20, 2010 1:19 pm

    Richard, I forgot to say that you've done well to have already updated the advice on the website.

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    Re: openLRS and 2.4 Ghz and Submarines

    Post  Tom(ADMIN) on Sat Nov 20, 2010 2:54 pm

    Excellent David, thank you...you are doing really well here! Saves me a lot of work...
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    david f
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    Re: openLRS and 2.4 Ghz and Submarines

    Post  david f on Fri Nov 26, 2010 4:12 pm

    I have recently been in touch with Chris of Sheerline who shares our concerns.
    His only suggestion, at the moment, is to buy up and modify secondhand 6 channel transmitters and modify them for 40Mhz.
    He is looking into the matter and suggests that Futaba sets are potential candidates for conversion.

    Speaking with Nigel. He wonders if it would not be possible for 35Mhz to be freed up and used for both surface and air??

    That would need a bit of representation but there is no doubt about it that the move to 2.4GHz is a threat to new entrants to model submarines.

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    Re: openLRS and 2.4 Ghz and Submarines

    Post  Tom(ADMIN) on Fri Nov 26, 2010 4:42 pm

    I believe that some 35Mhz radios can be run successfully on 40Mhz by just removing the 35Mhz crystals and replacing them with a set of 40Mhz ones, although they do have be from the same manufacturer...ie, use a set of Futaba 40Mhz crystals in a Futaba 35Mhz radio.

    I don't possess a 35Mhz radio, so I can't try this for myself, but if anyone has got one, it may well be worth a try and see what happens. It does seem a simple way out though, maybe too simple...but it has to be worth a try.

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    Re: openLRS and 2.4 Ghz and Submarines

    Post  Guest on Wed Dec 15, 2010 9:45 pm

    You may get a signal of some sort, but the range would be dreadful.

    Some receivers can work successfully with both 35 and 40mhz crystals e.g. Jeti Rex 4. But don't try it with a transmitter if you value your model.

    My thoughts are, that although 35 and 40mhz will likely be abandoned by the major manufacturers, smaller Chinese outfits will step into the breach and fill the void.

    My experiences with some of the cheaper brands of R/C equipment have been very positive up until now.

    It's also worth pointing out how cheap R/C equipment is now. The main thing that prevented me from getting a submarine back in the days when I was a schoolboy (1980's), was the high cost of a 3-4 channel radio set. I think a lot of people forget just how expensive that kit was.
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    Re: openLRS and 2.4 Ghz and Submarines

    Post  david f on Thu Dec 16, 2010 7:11 am

    Richard,
    I was trying to carry some big boxes of stuff into our new place and somebody has parked a great big American car on our driveway!

    Why who is it in there? It's Andy!

    Where have you been!

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    Re: openLRS and 2.4 Ghz and Submarines

    Post  Tom(ADMIN) on Thu Dec 16, 2010 8:17 am

    People dump stuff anywhere nowadays David...no thought for anybody!
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    Re: openLRS and 2.4 Ghz and Submarines

    Post  nigele(ADMIN)2 on Thu Dec 16, 2010 3:11 pm

    That a very special car that,it should be parked somwhere very secure.

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    Re: openLRS and 2.4 Ghz and Submarines

    Post  Tom(ADMIN) on Thu Dec 16, 2010 3:18 pm


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    Re: openLRS and 2.4 Ghz and Submarines

    Post  Guest on Thu Dec 16, 2010 4:46 pm

    I think Nigel must have dumped his Winnebago outside your drum, David. I only go in for European motors myself.
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    johnrobinson
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    2.4GHZ and submarines

    Post  johnrobinson on Fri Oct 21, 2011 11:03 pm

    HI Guys
    I have just changed a Zap 9 Futaba TX and RX from 35MHZ to work on 40MHZ there has been a few people who are worried about being able to get 40MHZ radio sets but i didn't find it very hard to convert zap 9 to work on 40MHZ. May be its one of the ways that you could go to be able to use your old 35MHZ radios to work on 40MHZ. Reason why i did it was my old Zap 9 plug in TX module and RX had been scrapped and 2.4 GHZ plug in module fitted and RX unit. so old 35MHZ plug in module and RX had been sitting around doing nothing in a box. So it seems the ideal thing to do with it was convert it to 40MHZ as I'm going to use it in a smaller submarine, plus there must be alot of 40MHZ radio sets that don't work any more that have faults and could be repaired. Other point i would like to make one of the bands that we can use on model boats is 458MHZ licence free, as i have a radio set that i built on that frequency, yes i no it is not suitable for submarines under water frequency is to high to get through water. I'm going to use 40MHZ TX unit to design Ariel that will be in the water not on the bank side Ariel in the air as a RF signal most of it will be lost trying to get through the surface of the water, you can not just put your normal Ariel on your TX transmitter in to the water as it will be to long in lenght to work, at its best Ariel becomes alot smaller in length to work under water.
    John
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    david f
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    Re: openLRS and 2.4 Ghz and Submarines

    Post  david f on Sat Oct 22, 2011 1:11 pm

    Wow, John you have dusted off a really old thread with some rather odd contributors who have now departed this forum!

    But the problem of 40 Mhz has not gone away.

    My view is that it is always going to be difficult to "legally" convert 35Mhz transmitters to 40Mhz. Receivers - no problem.

    But converting transmitters to work with your underwater radio system - now you are talking.

    In my view, you really need to demonstrate that system at a pond somewhere. Then you could really get the ball rolling!

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    2.4 GHZ AND SUBMARINES

    Post  johnrobinson on Sat Oct 22, 2011 6:48 pm

    HI David
    Yes i do no what you are saying about converting 35 to 40MHZ and not being legal on the transmitter side, but if this was transmitting under water the legal side of it would not be there as you are not transmitting in to air, i don't think it would apply but i might be wrong, problem is i have not got a small sub to try transmitter Ariel in the water to do a real test but i suppose what i can do is say put transmitter Ariel in the water one side of the pond and put a receiver with Ariel in the water the other side of the pond i could do a reasonable test of range. Receiver Ariel would be cut to a shorter length because it is under water and receiver front end re-tuned for working on shorter Ariel under water, transmitting Ariel would stand on a float pointing vertically down wards, thin coax going up to transmitter. I have worked out how to use different bands useing Ariels under water but have not done 40MHZ but can not see there being a problem, because you are not transmitting into air. The legal power is 100MW erp i would think you would be able to use RF power amp to put more power into antenna into water as you would not be transmitting in to air
    John

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    Re: openLRS and 2.4 Ghz and Submarines

    Post  Tom(ADMIN) on Sat Oct 22, 2011 6:54 pm

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    Re: openLRS and 2.4 Ghz and Submarines

    Post  david f on Sun Oct 23, 2011 2:31 pm

    I see your problem. You need a "submarine simulator".

    I'm tempted to say get any "target" and use that. But a better simulator would be a target with a submerged tube underneath the target ( a bit like a cylindrical keel)into which you cram the receiver with a crumpled bit of aerial(what we normally do!) and as much electrical interference in the tube that you can get.(An unsuppressed motor perhaps.)

    It would not take too long to knock up (much quicker than Richard's hull. Sorry Richard!) and you could motor round the pond and test everything out.

    Maybe someone has a hull that they could give you. (I'm afraid I don't have a surface boat - I only build things that sink!)

    BTW one slight worry. I have no great fears of interference from a submerged aerial but what happens if you accidentally hoist it out of the water while it is still on? Will it shut down the nations radio networks etc. etc !?

    And make sure that your transmitter remains a "black box" i.e don't tell any of us what you have got in there.
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    Re: openLRS and 2.4 Ghz and Submarines

    Post  Hermann on Sun Oct 23, 2011 3:58 pm

    Hello everyone,

    I am really afraid that the days of the 40MHz band for model radio control are already counted as 2.4GHz become more and more common also for ship modellers (as I experienced again today when I was at the pond). And how useful 2.4GHz are for submarine applications you can see in that short video dealing with a video camera transmission out of a Tupperware box:

    http://www.myvideo.de/watch/8261454/Kamerauebertragung_auf_2_4GHz_unter_Wasser

    The conditions will not be much better with reasonably increased transmitter power within the regulations...

    I think John's approach of transmitting RF directly beneath the water surface (replacing the transmitter "aerial" by a matched "aquarial") deserves an interesting discussion. I don't know if this may be legal or not (I would hope so). At least it would depend upon the residual RF signal emerging from the water surface into the air and if you succeeded to match your transmitting antenna("aquarial") well to the transmitter PA output with sufficient suppression of harmonics and spurious frequencies.
    Of course the design of such an underwater antenna needs some research and appropriate measurement equipment (preferably a network analyser and a spectrum analyser).
    From the technical point of view this is not a basic problem, the key question remains: Would it be legal or not? Who can answer?

    Best regards
    Hermann


    Last edited by Hermann on Sun Oct 23, 2011 4:00 pm; edited 1 time in total (Reason for editing : correction of a typing mistake)

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    Re: openLRS and 2.4 Ghz and Submarines

    Post  Tom(ADMIN) on Sun Oct 23, 2011 4:41 pm

    I guess for someone like John, a licenced amateur radio user, it would be legal, but as for the rest of us mere mortals I'm not sure about the legality of it?

    No doubt John will enlighten us (I hope...)


    And this may be a silly question, but I have to ask...we all tell people that 2.4gHz radio is no good for submarines, but has anybody actually ever tested it?
    I've used a 2.4gHz set in a Robbe Sea Jet jetski, with the rx tucked away right at the bottom of the hull and alongside the motor (a Graupner Speed 600 BB Turbo), the aerial folded around inside the hull, and below a huge rooster tail of spray. The boat would go out of sight without any interference or any signs of a fail safe kicking in.

    I also used a 2.4gHz set in a model canal boat, the rx was flat on the hull bottom, below the water line, and with a load of timber above it.

    Was I just lucky, I wonder?


    Rich
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    Hermann
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    Re: openLRS and 2.4 Ghz and Submarines

    Post  Hermann on Sun Oct 23, 2011 11:10 pm

    Hello Richard,

    in this short video (see link in my last posting) you can see that in this brief experiment the camera signal transmission through water on 2.4GHz reached only about 30cm deep.

    Radio frequency waves at 2.4GHz suffer a realtive high attenuation in water due to the conductivity and also due to the alternating polarisation of the water dipole elements. A H2O element behaves as a dipole and will follow the alternating field polarisation - this requires energy and results in losses (like friction). That's just the effect you take benefit from when cooking your meal in a microwave oven (that also operates on 2.4GHz).

    A signal of 2.4GHz will shurely penetrate the water surface but will be attenuated rather quickly with increasing depth, much quicker than waves on lower frequencies.
    I am sure John will confirm this.

    Best regards
    Hermann
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    2.4GHZ AND SUBMARINES

    Post  johnrobinson on Mon Oct 24, 2011 8:00 pm

    HI Hermann
    Yes Hermann has just about summed it all up, you could not use a worse frequency to transmit through water apart from 10GHZ. Because i am a radio ham i used to do a lot of fast scan TV which is real time video i have built a 160 watts amplifier for 1.2 GHZ and even that would not get far through water, have got a TV transmitter on 2.4 GHZ knocking out 35 watts which is a lot of power on that band and that would not get far through water. Most losses happern from going from air through surface of the water, signal reflects off the surface of the water and this gets worse as the angle of the radio waves hit the water the losses are huge, so like i said transmitting Ariel needs to be in the water and like Hermann said the lower the frequency the less the losses are, but useing low frequency has to be a compromise if frequency is to low band width is not wide enough to send fast data. 40MHZ is ideal because it is legal for us to use i my self can not see us losing it. What i won't to do in the future is use a low frequency radio link that we will all be able to use and the Ariel system will be in the water and not have to worry about interferance to other bands, i have just finished doing electronics for low frequency for video link under water full colour picture but won't have the problems with trying to get through water like high frequencys do
    All the best John
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    nigele(ADMIN)2
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    40 MHZ A FEW POINTS.

    Post  nigele(ADMIN)2 on Mon Oct 24, 2011 8:54 pm

    Hi guys,

    This is all way beyond my electronic abilities and understanding, but I have had a ring round some of my old contacts in the trade to try to find out what the situation is in regard to 40mhz,this is what I have found out.

    40MHZ will be available to us there are NO PLANS TO WITHDRAW IT.

    2.4 MHZ will not work underwater,Paul Cook did some tests at his local lake and found that the best he could obtain was three feet out,and 6 inches down, not a lot of good to us.

    A 2.4 MHZ modular TX will operate using a 40MHZ module ( Futaba/Robbe).

    One leading maufacturer will be continuing to supply 40 MHZ TX'S AND RX'S for the forseeable future.

    France uses 41 MHZ for land and air, Paul Cook kindly checked out the part numbers for the French 41 MHZ module against the UK 40MHZ module and they are the same.

    The problem as I see it is getting a better signal to the boat and eliminating interferance, this I think is where a submerged arial would come into its own AND I FOR ONE WANT ONE.

    Just to point out one of the good points of everyone except us changing to 2.4, I have been to several shows this year and I have been able to sail all day long without having to share the chanel at all...wow, what a bonus!




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    Hermann
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    Re: openLRS and 2.4 Ghz and Submarines

    Post  Hermann on Tue Oct 25, 2011 9:44 pm

    Hi John, hi Nigele,

    hopefully our experience and theoretical considerations will convince all those guys who still believe 2.4GHz will do the job for submarines. Recently in a German modeller forum there had been one lad who reported about an experiment he had done together with a friend who is a sports diver. They had put a 2.4GHz receiver and a servo inside of a Tupperware box and while giving steering commands from shore his friend went down in a pond. He claimed to have had contact down to about 12m (approx. 36 ft!). On 13m contact was lost. He confessed not beeing an expert but he said that this has been true. Some other modellers including me wouldn't and couldn't believe it. I asked him whether there had been perhaps a telephone cable for communication (that might had served as a waveguide), another one asked how they had measured the depth. That was the key question for explanation: The guy said that there had been a long vertical iron tube with depth marks on! So their observations could be explained by the metal tube serving as waveguide for signal propagation with less attenuation!
    Recently after work I had made a rough experiment in the EMC laboratory of our company to get some feeling about the attenuation of 2.4GHz waves in normal water. I put a scratchbuit dipole antenna on the bottom of a large plastic storage box connected to a measurement receiver (type ESIB of Rohde&Schwarz)via a coax cable, fillde water in so that the dipole was just covered by water and then I arranged a transmitting antenna (double ridge guide horn antenna of ARA) above the box just in direction to the dipole with appropriate polarisation. The antenna was connected to a signal generator (of Gigatronics). With the receiver tuned to the signal on 2.4GHz I filled up the box with water centimeter per centimetre and found that the receiver signal became smaller by approx. 1 dB per cm (That's only a rough value, by the next opportunity I will repeat the experiment more accurate). But with 1 dB per cm you would roughly find that the field strength will shrink to one tenth at 20cm depth, 1/100 in 40cm and 1/1000 in 60cm! Any more questions left?

    Nigele, I hope 40MHz will be still available also here in Germany as a legal frequency for model radio control although there is a strong migration to 2.4GHz of many modellers. I can't predict how the regulation authority will act when they discover that most obvious modellers have changed - I'm only afraid they don't think of us few submarine modellers...
    Industries do react and have reduced or even ceased production of their 40MHz equipment. That's not a problem for myself (I have even built transmitters and receivers by myself in former times and could do so again if neccessary) but for others. And when there is no 40MHz equipment left on the market - why still keeping 40MHz for model control at all?
    But you are right - the more surface ship modellers change to 2.4GHz the more we take benefit from it - having no problems with occupied frequencies. So let's look on the bright side of life...

    Best regards
    Hermann

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    david f
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    Re: openLRS and 2.4 Ghz and Submarines

    Post  david f on Thu Oct 27, 2011 8:31 am

    Yes indeed!

    What is the implication of the French equipment at 41Mhz, Nigel?
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    johnrobinson
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    2.4GHZ AND SUBMARINE WILL NOT WORK UNDER WATER

    Post  johnrobinson on Thu Oct 27, 2011 9:35 pm

    HI Hermann
    Don't no about having leaks in submarines all i ended up with was leaks in the bathroom needed a trip to the local hard ware shop to buy new fittings, but have sorted bathroom out now now to more interesting stuff. I see you did a test in your lab when you did your test i take it you used tap water, point i am coming to if you where in a pond the range would be even less like the losses you said 1DB at per CM is a lot and if you looked at a standard 2.4GHZ transmitter knocking out 20DBM of RF you will not get very far under water, you said that some lad had done a test to see how far they could get under water with 2.4 GHZ and he had said 12M my thoughts was there is no way you can get that far under water on 2.4GHZ, like you said Hermann there had to be something acting as a wave guide for it to travel down to that depth, one thing that would be interesting to do in the test that you did would be to put TX Ariel in the water as well and see if losses change in water but dipole would have to be smaller because it is under water. You are Lucky that you have this test gear that you can use Hermann at work i used to be able to use test gear like that where i worked but am no longer there, have got a fair bit of test gear at home but not like that. Thanks for trying test
    John
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    Re: openLRS and 2.4 Ghz and Submarines

    Post  david f on Sun Aug 10, 2014 12:06 pm

    I just wondered how people are getting on, now that 2.4Ghz has "swept the market."

    My observations are:

    - I don't have any problems now operating on 40Mhz at my local club now that everyone has moved on to   2.4 Ghz. (Norwich sub weekend was a bit of a special case but it worked out quite well.)

    - I have been able to buy a "lifetime supply" on eBay of transmitters, receivers and crystals. (I can also modify 35Mhz  equipment if I need to.)

    - But this approach is not really very suitable for someone just entering the r/c submarine hobby.

    - Some discussion on Subcommittee of US legal use of 433Mhz equipment. But how well does it propagate in water (it can't be any better) and is equipment available?

    - No sign of any niche commercial providers of 40Mhz equipment setting up.

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    Re: openLRS and 2.4 Ghz and Submarines

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