Are there other 2.4ghz antennae suitable for use marine use besides the 8db unit from hyperlink?
I'd like to find one with a better vertical beam angle. Having only 15 degrees and then dealing with the rocking motion would end up making the target area pretty small.
It'd have to be capable of being mounted in a ratcheting mount, to allow getting under low bridges. The arch is about 9' above the waterline.
Thanks,
-Bill Kearney
If you want something with a wider vertical pattern why not just get a
5dbi rubber duckie? I doubt that such a small antenna will need to be folded down for any bridge you'd really want to go under. ;-)Mini-Box sells some $10 5.5dBi antennas that terminate in N-Male connectors. The intension is that you screw them directly onto the N-female on the outside of their weatherproof cast aluminum box. It also looks like a nice way to mount an acess point outside. I'm sorely tempted to pick up one of their boxes and antennas.
-wolfgang
On Wed, 21 Jun 2006 13:58:21 -0400, "Bill Kearney" wrote in :
See the Marine section of the Wi-Fi Wiki below.
Which, informative as it may be otherwise, contains nothing of use in answering my questions.
Disclaimer: I've never done a marine wi-fi installation so much of the following is speculation and guesswork. I did work for Intech designing marine VHF, SSB, ADF radios, so I know a bit about vessel installations.
Ever consider making a gimbal mount that maintains a vertical orientation? Kinda like the gimbal rail mounts for keeping drinks from sloshing. The truly sloppy way would be to just hang the 8dBi omni antenna upside down from the flexible coax cable and let gravity keep it vertical. A weight might be required at the antenna tip. However, I suspect you might find this aesthetically disgusting and want something a bit more elegant.
If you can find something with a ball and socket arrangement, the antenna base can be screwed into the top of the ball, and a counterweight screwed into the bottom of the ball. As the vessel rolls with the waves, the antenna remains roughly vertical.
Instead of an omni antenna, I suggest something directional. For example, the common build it thyself biquad antenna has a vertical and horizontal beamwidth of about 60 degrees with about 9-10dBi gain.
One of my biquads was crammed into a 6" electrical box, which should be sufficiently waterproof for marine use. I'm a fan of pressurized boxes but I didn't do it for this package. Basic biquad construction:
On Wed, 21 Jun 2006 22:12:04 -0400, "Bill Kearney" wrote in :
I disagree.
Yes, but I'm still faced with the challenge of getting it mounted.
I've got enough room inside the radar arch to put the router up there so my RF cable lengths could remain quite short.
I'd consider using an N-female bulkhead socket if I could find an 8db (or greater) antenna that would plug into it. That way I could have the short
5db unit plugged in 'most of the time' and only use an 8db stick when needed. But I can't seem to find an 8db antenna with an N-male connector, they all seem to have either a pigtail or an N-female on them.Actually a plain bulkhead mount won't work as it can't adjust it's angle. So I'd have to get some sort of adapter that'd let me use the antenna on a regular ratcheting marine mount.
Although a bit of digging turns up some from Pacific Wireless. Anyone tried them?
I'd prefer something that looked good. This is a brand new 37' boat, I'm not about to go bodging up some hack on it. I've got some dandy homemade (metal mesh) parabolic screens setup on the home WiFi router and the wife will have NONE of that on the new boat.
-Bill Kearney
I don't need connectivity THAT bad . If it's rocking that much, beyond what a 5db antenna might readily handle with a 15 to 30 degree vertical beam, then I'm not likely to be getting much work done anyway.
But it does mean that using a flush bulkhead mount N-female will not be a good idea. I wouldn't be able to change the angle enough to fine tune it's alignment.
I'd like to find a way to use a ratcheting mount and also have the ability to swap antennae. Most of what I'm seeing out there expects to use a pigtail running through the socket or a pole mount. I've not yet found a pole mount suitable. I'm open to suggestions on sources for one. The problems being finding something that's going to be resistant enough to the harshness of a marine setup (full sun exposure all day, salt water, etc). Beyond just being resistant to the elements it's preferable to have materials that won't cause discoloration of the surfaces under them should they corrode or otherwise lose their finish. It's a white gelcoat on the arch, stuff dripping makes things look ugly. Up on the roof of a building you might not care, on a white boat you do.
That way I could open up the possible antenna choices to those using an N-female on the bottom and run a small N-male to RP-TNC pigtail on the WiFI device inside the arch (or nearby).
Yeah, I'd really like to keep it a clean-looking setup. For both aesthetic and resale value reasons.
For in-marina use, or when docked at a fixed pier that'd be workable. For our home port, where I know the location fo the base station, it'd be great. But when we're travelling I won't know where the base station is located and I'm not sure I'd want to get into hunting for it. I'd rather just switch to a higher gain omni and let it do the work. But then we're back to the vertical beam issues. The further we are from the base, the wider the vertical spread so (hopefully) it'd work.
Impressive stuff, thanks for the links!
I'm now looking to find a suitable way to mount an N-female equipped antenna onto a powerboat radar arch. Anyone know of suitable mounts? Or a way to 'cleanly' attach a pole antenna to a marine-style ratcheting base? The ratcheting base is important not just for low-clearance situations but also for changing the tilt.
-Bill Kearney
On Thu, 22 Jun 2006 03:12:43 GMT, Jeff Liebermann wrote in :
I have done a fair amount of marine Wi-Fi, and can also draw on the experiences of other boaters I know.
It's probably not going to work very well without a really heavy weight, low friction bearings (not just a simple ball and socket, and difficult in an external marine environment), and serious damping -- otherwise it will tend to get out of phase with the boat, and actually be worse than a fixed mount.
The problem I've seen with high-gain directional antennas, other than mounting and aiming, is that they tend to be sensitive to boat movement, even just small movements in a slip, resulting in wireless connections that go in and out annoyingly. (I'm guessing there's considerable multipath in many marinas.) I generally get the best results with higher-gain omnis, mounted as high as possible.
I know of someone experimenting with a Hawking HWU8DD , mounted with suction cups to a hatch, so he can set it up and remove it easily. He says getting it aimed and keeping it aimed is sometimes a hassle, and it's not good for a boat swinging at anchor, but is otherwise pretty happy with it.
I've been surprised at how many Wi-Fi signals I see in many marinas. Not only to many marinas provide Wi-Fi, often free, some boats are offering free Wi-Fi to other boats in the marina.
The alternative to marine Wi-Fi is cellular data -- I sometimes get better results that way, especially in remote anchorages. As in the case of Wi-Fi, a good external antenna can help, although I've gotten quite good results with my cell phone up on deck, with a laptop down below connected to the cell phone via Bluetooth.
"Bill Kearney" hath wroth:
Connectivity is currently the holy grail. The search for connectivity has some similar characteristics.
Well, that means you can use a higher gain antenna. However, I was more concerned about the pointing accuracy than the rocking motion. If the marina access point is sufficiently close, almost any antenna will work.
True. However, a short piece of LMR-400 coax between the antenna and the N feedthrough bulkhead connector might be sufficiently flexible to orient the antenna. What I'm concerned with is the omni radiationg power in all manner of direction except the direction you want. That's why I suggested a directional antenna.
The typical marine antenna mount has a nifty lever for lowering the antenna. However, adjusting it for vertical requires a wrench. There is no fine adjustment as the meshing "teeth" are rather coase.
Add UV embrittlement and not having accumulated salt jam the mechanism. I could probably design a custom mount for the intended purpose out of stainless. Unfortunately, I don't know of any existing commerical product that will tilt, swivel, rotate, aim, and remain vertical. I was thinking of modifying a motorized outdoor video camera mounting and adding circuitry that would maintain a fixed direction once set as stabilized by a solid state gyro. Something like this camera: |
Then, there's the manual version. See: |
It's worth the effort aiming the antenna. A few marina maps I've seen show the exact location of the access points. You can probably get the location by just asking.
Hunting is not that horrible. Most client radios have a signal strength indication. They're not particularly responsive, so it won't exactly be easy to adjust. If you were to use a 24dBi barbeque grill dish antenna, with a 7 degree beamwidth, aiming will be almost impossible. However, a 60 degree wide 9dBi biquad is very easy to aim.
The omni vertical beamwidth issue is a killer. It's so bad that it even happens on vehicles. One mobile wi-fi user tells me that he had to install a bubble level from a 4wd shop to make sure the antenna is fairly level. Worse, some access points are overhead on light poles and rooftops, which are impossible to "aim" the vehicle (short of using a bumper jack).
Omni's also have a bigger problem. They pickup garbage from other wi-fi users from all directions. In a marina, you're probably also going to have reflection problems from masts and rigging. A directional antenna will not eliminate these problems, but certainly will reduce them dramatically.
N to N bulkhead feedthough connector with a pair of drilled metal plates (washers) on both sides for strengh. |
On Thu, 22 Jun 2006 10:23:55 -0700, Jeff Liebermann wrote in :
I suggest a high-grade tripod head.
How is it that a duck has such a wider pattern for an apparent identical gain over a stick?
Looking at Hyperlink, my current antenna supplier for the stillborn wifi communication project, the 8.5dBi stick I have is a very narrow pattern compared to a similar duck.
Needless to say, and as discussed in this thread, wider is better. I already know that I have only enough knowledge to be dangerous but my understanding (such as it is) has it that dBi is a measure of gain in reception. Thus, one 8.5dBi gain is the same as the other.
If that's so, why would anyone want a heavier, more expensive, taller (of some issue on some boats) stick antenna over a duck?
Thanks.
L8R
Skip
Morgan 461 #2 SV Flying Pig KI4MPC
"Believe me, my young friend, there is *nothing*-absolutely nothing-half so much worth doing as simply messing, messing-about-in-boats; messing about in boats-or *with* boats. In or out of 'em, it doesn't matter. Nothing seems really to matter, that's the charm of it. Whether you get away, or whether you don't; whether you arrive at your destination or whether you reach somewhere else, or whether you never get anywhere at all, you're always busy, and you never do anything in particular; and when you've done it there's always something else to do, and you can do it if you like, but you'd much better not."
On 22 Jun 2006 11:31:37 -0700, "Skip - Working on the boat" wrote in :
The higher the gain the narrower the pattern, and vice versa. That's how the gain is achieved.
The duck has lower gain -- a standard rubber duck is about 2 dBi.
The gain won't be the same for different patterns.
Hmmm...
Well, technically, the duck is 9, and despite the "9" in the PN, the stick is 8.5, but who's counting?
Well, I certainly found that to be true in the inverse - the higher I got in the sticks, the skinnier the pattern.
What's confusing to me is that the same dBi duck is so much fatter than the stick...
L8R
I forgot about the tree mounted antenna I built a few years ago. Intead of the dish antenna being on top of the ball, it was suspended from the bottom. I added a few pounds of fishing weights to help keep it vertical. There was no counterweight. The socket surface was covered with PTFE sheet that I form fitted (i.e. beat on it with a mallet) to the shape of the socket.
It does a fair job keeping the antenna in position as the 150ft tree sways in the wind. I won't claim it's perfect, but I don't recall it ever getting stuck. It's probably unsuitable for the current project, but might be useful for someone that wants to build an omni antenna mount that remains vertical. I'll see if I can find photos.
The typical 9dbi gain biquad has a -3dB 60 degree beamwidth. An antenna with more gain will have a corresponding narrower beamwidth. I just don't see the vessel rocking around +/- 30 degrees in a slip. It might swing around at anchor, which will be a problem. I guess for a vessel that is only anchored at the bow, an omni antenna would be better than a directional. However, with both a bow and stern anchor, there's isn't going to be much swaying, and a directional antenna should work.
On 22 Jun 2006 14:03:00 -0700, "Skip - Working on the boat" wrote in :
That isn't a standard "rubber duck" antenna.
On Thu, 22 Jun 2006 21:18:09 GMT, Jeff Liebermann wrote in :
Anchoring bow and stern is a bad idea, because the boat can't then respond to wind and current, and can interfere with other boats swinging on single anchors, with unpleasant or even harmful results. When two anchors are used, both should be at the same end of the boat.
Yep, if you tie down the stern and wave action picks up the boat can't ride up and over. The waves then swamp the boat. More than a few fishermen have had their boat sink because of this, especially if it's got any sort of transom door. You'd only want to use anchors at each end in a VERY calm and well protected situation. Even then you're still at risk from the usual jackass sending out a huge wake...
Well, let me rephrase that then.
Who would want a stick when a "non-standard" rubber duck (or whatever other label Hyperlink or any other manufacturer may choose to apply) has a much fatter pattern, lighter weight and considerably lesser cost?
L8R
Skip
Morgan 461 #2 SV Flying Pig KI4MPC
"Twenty years from now you will be more disappointed by the things you didn't do than by the ones you did do. So throw off the bowlines. Sail away from the safe harbor. Catch the trade winds in your sails. Explore. Dream. Discover." - Mark Twain
Hmmm, what're your thoughts on the panel type antenna for the base? Which ones, at what db, are worth considering?
True, but there are several problems with directional antennae in this situation. The obvious one being the effort to get them aimed. But there's also the hassle of dealing with getting a mount that's adjustable 'enough' that'll also withstand being up on a radar arch in a boat that goes over
35mph. Using a NEMA box or other enclosure is problematic given the amount of drag it'd incur. That and there's a finite amount of room up on the arch anyway. I can fit another stalk up there, but not much more without it looking crappy.Indeed, good point.
I wouldn't need 'total' adjustability, being able to rotate about 180 degrees and tilt in 5-10 degree increments would probably be sufficient for most situations. Mainly, swing the antenna around and tilt to better aim 'toward shore' when anchored in unfamiliar areas.
Hah, it'd certainly be no small challenge getting the admiral to buy off on THAT idea. Glomex makes one that's only single axis but if you mounted it on it's side you could probably rig up a way to use it to at least get rotation. Couple it with some sort of servo control on the PC and it'd be able to hunt on it's own, heh.
Those do not usually have enough clamping strength to handle being up on a radar arch. I've used the RAM mounts before, and they're great, but they don't seem like the sort of that that'd work in this particular situation.
So whose sells such a beast, designed for marine use? No, I'm not making one myself.
Yes, this is true. I actual fired up a drawing program and made some diagrams plotting the beam widths over the expected distances. The typical
15 degree beam width only allows a 20' aiming window at the distance I'd be using at our home port. Thus this whole tangent on considering swappable antennae. A pair of them; say a 5 and an 8db would probably cover most situations. I'd leave the 5db unit on their most of the time and only swap out if I encountered really poor coverage. The trick is in finding a way to get one of them mounted that's reasonably easy to adjust. I'm not finding a lot of options on how to get an antenna that's expected to be on a pipe-mount attached to a ratcheting marine mount. I'd want to be careful about starting to add extensions to the typical base as that also increases the likely stresses on it.Another good point. If I can find a way to rig up a solution that allows easy swapping then at least I can switch to a directional when it becomes an obvious problem.
Yeah, but that has zero adjustability.
I'm looking for ideas on getting an adjustable mount that'll handle the typical N-type stick antennae. I suppose a plate of some sort, or a z-shaped angle bracket would work. Spin a nut on the marine 1" thread mount to hold it down and then put the antenna through the other side of the bracket. Any ideas on a source of something like this? I'd want one designed to survive a marine environment (as in, not rust out, drip and discolor the gelcoat).
-Bill Kearney
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