Some one explain this please

[U812]

When I first started running subs in my pool if I got much below 4 ft. Good bye signal. I always figured it was the chemicals in the pool. But Dave Welch told me he never had this problem in his pool.

I've lived here 5 years now. don't know if the water was renewed before we moved in or not but recently it was.

It's loaded with chemicals as a pool will be but now that the water is new I can dive down to the deep end, sit on the bottom or hover and I never lose signal.

Could it be that the water was so old that the build up over the years of chemicals made the water hard on reception?

I was running my Seawolf tonight and I took out the neutral trim it was working so well. For the first time I could hover and cruise around at 6 ft or more with perfect control.

Steve

BTW Dave I was using that micro FM GWS RX.

[pmackenzie]

Radio waves are very poor at penetrating water.
To comunicate with real submarines at sea they use very low frequencies, 3 to 3000 hz.
http://hypertextbook.com/facts/2001/LisaWu.shtml
Any chance you have switched to a lower frequency? ( ie from 75 mhz to 27mhz)
Pat Mackenzie

[U812]

That's the frequency I'm on. 75 mhz. Always has been. The only variable is the new water in the pool. Thanks though.

Steve

[Aeroengineer1]

Steve,

This is a very hypothetical idea, but perhaps your pool has accumulated salt from the air over the years (this due to your relative location to the ocean) and that reduced your signal to the point that you has problems at depth. I am not sure how much salt it would take to reduce the signal, but an idea. This is the one thing that the chemicals would not break down, and would not drastically change the pool pH to the point that is could not be brought to within tolerances with the pool chemicals.

Adam

[U812]

Adam,

I think your on to something here. I would have to guess the water was about 8 years old. Maybe more. Although I live in the valley we are subject to a heavy marine layer that comes in. Sometimes the fog is so thick you can't see the other side of the backyard. Great for late night lasers though.

Marine layer is just that. And has a salt content. That time 8 years of exposure may have produced this effect.

It was so nice to hover at the bottom of the pool and have full control. You can't dive that deep in the lake because after 3 ft. You can't see it.

Thanks for the input Adam.

Steve

[Kmot]

Pools normally have a suction drain at the very bottom as well as the skimmer at the top. So I would be "very" surprised to realize that pool water could be "old" let alone 8 years old if you have a functioning pump system.

This is very strange! Perhaps it is the "new" chemicals allowing better reception? The waters new Shock Treatment perhaps?

[Aeroengineer1]

Kmot,

One thing to remember, the water in the pool is just recirculated. Pools get cleaned of micro organisms through the chlorine/filtration process, and the other chemicals help maintain the pH. Salt, though, would not be filtered out. When the salt gets into the pool it would ionize, ie it would disperse itself very evenly,and there is not method of filtering it out.

Steve,

Why not see if there is some sort of a salinity test and go to a neighbor's pool, that is if you really want to exclude this as a thoery. Just a thought. Test the pool to see if you loose reception, and if you do test the water.

Adam

[EngineerW]

One thing you may try is to allow the chlorine level in your pool to drop. Chlorine will out gas naturaly from the pool water to the point where the level will be very low. The down side of course is algae growth. When I was testing my ohio class boat in my pool I allowed the chlorine level to drop and kept the Ph as neutral as possible. I could control the boat all the way to the bottom. The algae went nuts and my lovely wife made me fix the water.

In a perfect world, fresh water (distilled) will allow radio waves to propagate as well as they would in air. The problem you are fighting in your pool is that most of the radio energy is being reflected off the surface of the pool. There are two causes of the reflection. The first is the conductivity of the water. The more disolved minerals in the water (chlorine) the more the signal is reflected to the point where all the energy is reflected and none gets through to the sub. The second cause is the imedance mismatch between air and water. The impedance mismatch causes a discontinuity causing energy to be reflected at the air-water boundry.

In both cases the higher in frequency you go the more pronounced this problem becomes which is why submerged subs use ULF frequencies to communicate with the outside world.

So, if you can use 27Mhz use it, if you can live with a green pool do it and you should be able to dive and control that really cool SSN-21 all the way to the bottom. BTW, that SSN-21 of yours is the coolest!

Steve, I may know the science and math on this stuff but with two small kids and a REALLY demanding job I just dont have the time to build things these days. For that I envey you.

Cheers,

EW

[U812]

Thanks guys for all the input here. I'm using both 27 and 75 mhz.

EW. thanks for the input and the kind words. I can only hope that you get a chance to build a sub soon. The late night hours are good for that. Wife asleep and kids to bed.;)

Steve

[TMSmalley]

I have run subs in a fair number of pools ever the years. All seem to have differing characteristics as far as the ability to allow radio wave propagation. A few have let me go right down to the drain grate. The pool at the townhouse I live lets me to right to 6 feet no prob but they are always cleaning and working on it.

Hotel pools always seemed the worst. Most, at about 3 1/2- 4 feet or so, seem to block the signals and the failsafe blows the tank. I always assumed it was the chemistry of the water and the care that was taken in its maintenance ph etc. It would be a fun thing to test.

Dave- how about dumping a few begs of rock salt into your pool and see if that makes any difference?! :D

Dav

[Kmot]

One thing to remember, the water in the pool is just recirculated.
Yeah, didn't think about that.

That's cuz I'm always dropping my subs in the toilet. Always a new batch of water. :p

[U812]

Dave- how about dumping a few begs of rock salt into your pool and see if that makes any difference?! :D

Dav

HA! That's a good one Tim. but really those are good ideas. As I said before my pool was drained last week and re filled. Treated and put back in operation. I too can dive that deep now. It must have been the age of the pool water as far as I can tell now.

Going to do some more tests this week with my fleet and see if they all respond the same way.

Steve

[Subdave]

Hi Tim,
Actually it is Don Oslers pool. I will pass on your suggestion about the rock salt. :eek: But I would not hold my breath :D
So Steve, how did the propulsor work??? BD.

[U812]

Good but I have a bad battery pack so it was a short run. I'm making up a new pack now to test tonight. Worked very well. Thanks Dave.

Steve