Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Submarines => Topic started by: NickKK on September 01, 2011, 09:51:55 pm
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Any one use this on a sub yet ? how's it working range and depth wise ?
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Hi Nick
I'm afraid it won't work at all under water. The recommended frequency's are 40 meg or 27 meg
The Tech guys could probably elaborate better.
Ken
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Yes it's completely useless for subs below a few mm of water.
We have talked and written about it quite a lot on other forums etc.
Basically cling on to your existing 40Mhz equipment and buy more while you still can.
It is a bit of a problem for the model sub hobby :((
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Cheers guys ... Good to know that before I start :-))
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Its the reason why actual subs use very low frequencies for communications when submerged. High frequencies dont penetrate the water very well.
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Over to you sub john! O0
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Reply #5
HI DAVY 1 Attenuation of radio waves in fresh water as lakes has salt at approximately 300mg/litre and a conductivity of 0.0546 mhos per metre, this can be used as a bass line to work out losses through water of radio waves the attenuation of radio waves becomes worse as frequency goes up, as some body else said thats why real full size subs use LF its all to do with losses through water and its even worse for a full size sub as its in salt water. You couldn't get anything worse to transmit through as water goes plus it does change according to how hot the water is. As I said some where on a thread biggest problem we have is TX Ariel is not in the water losses through this are stagering most of your signal skips off the surface of the water like you skim a pebble across the surface same thing happens to the radio waves
john
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I've got a U47 too mate, with an F14 transmitter and 40 meg. I thought it was a rare boat but since being on here everybody seems to either have one or has had one in th past. 8)
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Reply #5
HI DAVY 1 Attenuation of radio waves in fresh water as lakes has salt at approximately 300mg/litre and a conductivity of 0.0546 mhos per metre, this can be used as a bass line to work out losses through water of radio waves the attenuation of radio waves becomes worse as frequency goes up, as some body else said thats why real full size subs use LF its all to do with losses through water and its even worse for a full size sub as its in salt water. You couldn't get anything worse to transmit through as water goes plus it does change according to how hot the water is. As I said some where on a thread biggest problem we have is TX Ariel is not in the water losses through this are stagering most of your signal skips off the surface of the water like you skim a pebble across the surface same thing happens to the radio waves
john
Fantastic, it wont work under water then, a simple no would have done. {:-{
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Fantastic, it wont work under water then, a simple no would have done. {:-{
LOL!
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Personally I always think it's nice to know why something doesn't work, rather than just being told it doesn't without any explanation.
I think something that would be of great benefit to the future of model submarines is a combined receiver and transmitter system that you could place on the side of the pond/pool.
This device should be able to interpret the signals from a common brand of 2.4ghz radio (perhaps Spektrum or Futaba), convert it into something lower frequency and transmit it underwater in a lower frequency or perhaps sonically. A special RX would be required to accept the signals, and these would need to be small enough to compete with current 40mhz units, and allow their use in smaller models.
If such a system was commercially available, I don't think anyone would mourn the loss of availability of 27 or 40mhz sets, which aren't ideally suited to this hobby anyway.
I wonder what the law is regarding underwater transmission of radio signals, is it the same as in air I wonder?
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Reply #10
HI Subculture, I agree it is nice to have a explanation why things don't work than just a plain NO, but I'm sorry to say it does not seem to work like that.
A lot of laws regarding transmitting RF into air i would imaging wouldn't be relevant in water but i could be wrong because i am a radio amateur i can use bands that other people can not use
which is very usefull.
Subculture can you tell me what submarine shows that i would be able to go and sail the sub at i know that we are coming to the end of the year so it will have to be next year.
All the best John G7SCL
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For a huge boat like your Gato, the small ponds present at most model shows these days will be a dead loss.
However submarine days like the events at Barrow, Norwich and Brockwell Lido would suit well.
The first two are on this month and Brockwell Lido event is in November . Details of all three are on this forum and elsewhere.
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It is nice to see a full explanation of the why's and why not's ... cheers .. So using 40mhz,,, Any one ran an antenna along the outside of the hull? Then all you would need is to remove the steel antenna from the remote and dangle a strip of wire in to the water ? I think that would be as close to an underwater system as we are going to get .. Unless some one comes up with a ultra low rf system
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read this about johns sub, uses low rf frequency:
http://www.modelboatmayhem.co.uk/forum/index.php?topic=32161.msg322211;topicseen#msg322211