Antenna: Inside or Outside the WTC? - Hi, I'm a newbie!

[tang]

Building my first sub and started wondering about proper antenna location. Is it beneficial to radio range to run the antenna throughout the flooded hull, as opposed to running it within the WTC?

FYI, I'm building a Dumas Akula. It's already apparant why cylindrical, serviceble WTCs are so desirable!

[craigf]

A good question! I was

A good question! I was wondering about this too. I'm also building my first sub, and there is some detailed instructions for running the antenna outside of the WTC and spreading it out inside the hull. I think the concept of importance is that the antenna should be stretched out to maximize its effect, what with radio reception being reduced under water. This is best done by extending the ant outside the WTC rather than having it bunched up inside it. Anyway, that's my interpretation...

[tang]

I agree. Coming from the

[color=#000000]I agree. Coming from the r/c car world, I instinctively want to run the antenna through a hollow plastic tube (aka]

[stevel14]

Hi,

In general, you want to

Hi,

In general, you want to have the antenna streched out as much as possible with no loops or overlaps for the best reception/performance. This is similar to the antenna on a car, where the further it is extended, the better the reception on the car's radio. Keeping the antenna in the WTC (unless you have a BIG one) does now allow you to stretch it out all the way.

That said, I have tried both methods in my SMW U.S.S. Blueback and found little difference in performance over the distances that I operate the boat over. Radio performance will degrade the further the receiver is from the transmitter, but since most RC sets have a range of 2-3 miles, we would have to be operating the model way past visual range for the performance to usually suffer too badly.

If you do keep the antenna in the WTC, do not cut the antenna. The antenna length is related to the frequency of the radio, and cutting the antenna will do more than just reduce the set's range. Your best bet would be to wrap the antenna around a wooden or plastic dowel, making sure that you do not cross the antenna over itself.

If you extend the antenna outside of the WTC, a spot of silicon sealant should keep the antenna opening watertight, but not make it impossible to remove the antenna if needed in the future. I also use some silicon to seal the end of the antenna to keep water from touching the wire inside.

Steve Laubmeier
#2442

[tang]

Thanks Steve! I (we) appreciate

Thanks Steve! I (we) appreciate your experiences with this. I'm going to use the antenna tube outside the WTC, just need to find one long enough to carry the entire wire. Two tubes could be used "in series" if the joint is watertight, hrm....

[Guest]

Put your antenna wire in

Put your antenna wire in flexible silicone or vinyl tubing. It comes in any length, and can be secured to a rigid tube coming out of the WTC.

[JWLaRue]

With one exception, I'm also

With one exception, I'm also one of those that has always left the antenna inside the WTC, though I do make an effort to spread it out. I've had no problems with range (distance or depth).

The exception is with my SSY Skipjack that uses a D&E WTC-3.5. In this case, I use the supplied external antenna, but leave it coiled up.

-Jeff

[tang]

Thanks!

Thanks!

[liftmys10]

I was also wondering about

I was also wondering about this. In the instruction manual for the Albacore, it says to drill a small hole in teh wtc and have the antenna wire out of teh wtc so it can stretch. But wouldnt the water mess up the wire? I dont know so i left it bunched up in the wtc. Range isnt that good. 6ft deep, i lost radio connection. I wonder if it can go deeper if the wire was out of the wtc.

[bradv]

For the Dumas Akula, the

For the Dumas Akula, the instructions specify to run the antenna around the inside perimeter of the top of the WTC. I've had no problems with this, achieving undisrupted ranges of ~40m (then ran out of lake).

However, I did decide to extend the antenna out of the WTC, not so much for range but for salt water running. I occasionally run in a lake which is a mixture of salt and fresh, which means I can only submerge the antenna ~3" before I lose reception. To combat this, I did exactly what Art has mentioned. I drilled a small hole in the top of the WTC and ran a piece of silicon tuning out of this with the antenna inside, then sealed the top with silicon. This is ~3" long, and passes through a conical guide and then hole up to the top of the sail on the upper hull. This then lets me submerge in the salt/fresh mix until my 2" long periscopes etc. are ~ 1" under water. This at least lets the whole sub be submerged and still work, though running in this mix I rarely dip the whole scope length under as at distance reception becomes bodgy.

As submarine radio reception depth is very heavily influenced by the water type in which you're running (eg. *very* roughly, sea water ~1", chlorine pool ~6', lake water ~10') extending the antenna out of the WTC by a small amount isn't going to make much of an impact for normal running in pools or lakes. As the Dumas Akula is a dynamic diver, the top of the WTC tends to sit just under the water, which is why extending the antenna out is really only helpful in providing a noticable (though still small) increase for salt running.

Note however to make sure the wire at the end of the antenna doesn't touch the water so as not to short out your receiver!

[tmsmalley]

A tube isn't absolutley essential.

A tube isn't absolutley essential. Run the antenna wire along the outside of the cylinder and seal the end of the wire to keep water from coming in. To do that, fold it over on the end and use a piece of heat shrink tubing over the end - a little silicone over the end and you are fine. The idea is that you don't water to sneak into the WTC by working its way along between the insulation and the conductor of the antenna.

Art Meyer - who knows a "little" about electronics (former GE jet engine engineer), has always said you will get better range if you keep the antenna as straight as possible without letting the loops cross each other and seal the end so it doesn't gound to the water.

[craigf]

seal the end so it

seal the end so it doesn't gound to the water

I was thinking of using a connector on my antenna wire. I will have a few wires going out of the WTC, and bottom line with my connector is the antenna connection would be wet (though water won't be able to seep into the WTC via the antenna wire). Are you saying this won't work very well, and is highly undesirable? Thanks.

[chips]

One proven reliable method is

One proven reliable method is that used on D&E Miniatures WTC's. There is a threaded brass rod that penetrates the end cap of the WTC. The brass rod is threaded through a hole drilled in the end cap. The outside antenna wire is soldered to a brass washer, and a brass nut secures the washer (and wire) to the rod, the connection is then covered in RTV. The receiver antenna is cut shot and another brass washer is soldered to it, this is connected to the inside protion of the threaded rod with another nut. The same sort of connection is used for the battery leads on the D&E WTC 3.5.

[craigf]

Ah, thanks, that gives me

Ah, thanks, that gives me some more ideas I hadn't thought about. So with the D&E method, the antenna connector and the antenna "copper" (at the join) in effect gets wet? I had not thought this would be a problem, but the comment about "grounding to the water" (?) got me wondering.

I was going to use a tiny SMA antenna connector (plated brass), the ones I have are waterproof...O-ring etc. should keep water out if the SMA was screwed through the WTC...I think.

[JWLaRue]

>>> in effect gets wet?

>>> in effect gets wet?

No....if water touches the antenna it will short/ground it out.

The threaded rod, nut and exposed antenna wire on the D&E WTC is thoroughly covered with RTV to waterproof it.

-Jeff