Keeping directional WiFi antennae pointing at access point

[Anonymous]

There are many excellent WiFi antennae today, such as the RepeatIt, which are highly directional. Fine in a marina but useless at anchor. The gain far exceeds the practical range under conditions when you are swinging +/- 20 degrees. I also have a 26dB yagi, where the problem is even worse.

How about a direction-stabilised platform of some kind? How could one easily put something like this together using parts available to the hobbyist and amateur? Maybe modify an old tiller pilot? Any ideas?

 

[jerryat]

Good Gracious Lemain my friend, is having a WiFi connection really that important when you're cruising!! /forums/images/graemlins/wink.gif We went off sailing precisely to get away from the vast majority of that sort of thing.

True, we used to go to an internet cafe about once a fortnight if one was reasonably available, but if not, what the hell, we did without.

Everyone to their own thing of course, so to try and help ( /forums/images/graemlins/smile.gif) setting up a tiller pilot to a circular wooden disc upon which you mount your aerial should solve the 'problem'. Set it to 'Fine course correction' and it would be very accurate I would suggest.

It'll certainly need some 'tuning' in order that the disc turned to the correct degree (perhaps an arm fixed to the disc allowing the same lever length as required for a tiller?) but it's feasible I think.

No doubt someone will be along in a minute with something much simpler, but that's my 2p worth!

All the best, Jerry

 

[ShipsWoofy]

[ QUOTE ]
Good Gracious Lemain my friend, is having a WiFi connection really that important when you're cruising!! We went off sailing precisely to get away from the vast majority of that sort of thing.

[/ QUOTE ]

/forums/images/graemlins/shocked.gif

Please issue a list of acceptable pastimes that we can follow on our own boats so we can conform to your ideal.

Thank you
Love from the rest of the sailing world.

 

[jerryat]

Eh? /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/confused.gif

Sense of humour disappeared this morning?

 

[davidbains]

I think at anchor you're better off with a mobile signal.
3 Mobile are offering a good deal at the moment.
I think WiFi may be why some yachts never leave their marinas.
However when I'm at sea I make do with Navtex and VHF and RTTY,
and Ham if I'm really at a loose end. There's also plenty of jobs in the
never ending refit!
Of course a motor home or apartment doesn't swing about.

 

[Loginname]

He didn't read your post, assumed you were talking on behalf of the sailing fraternity, and didn't realise that you were talking about yourself and (presumably) SHMBO.

....so he took it upon himself to respond on behalf of the sailing fraternity which, of course, is what he was accusing you of! Funny old world.

 

[sailinglegend420]

Having the same problem with our Repeatit because we are often over 1 Km away from the wi-fi base. Tried tying up to a mouring buoy behind us in the Morbihan, but when the tide changed we had over 5 knots pulling the buoy around our stern which tore off the davit. Will try a stern anchor next time. There are few places we haven't been able get a good wi-fi service with a bit of patience.

We find internet access great not only for the weather, but also for keeping in touch with family or other cruising friends via Skype. At only about 2p per minute to call any landline it is a lot better than a local sim card which we had last year.

 

[William_H]

The design you want is fairly simple as compared to that for an autopilot. But still tricky to make yourself. (mainly the mechancal bits.

You need atable for the antenna whic can be motor driven in azimuth.
On this you also need to mount a compass. The compass needs to have a tiny mirror attached to the card rim this reflects a light to 2 Light dependant resistors in such a way that light on one LDR will drive the mpotor one way and light on the other will reverse the motor. The outpu of the 2 LDRs if equal will stop the motor drive.
You point the table with antenna to get the best signal then adjust the bezel containing the LDRs and light source to line up with the mirror on the compass then engage the motor drive.
Providing the motor can exceed the rate of any ship swing it won't get out of range of the mirror LDRs so the table should be maintained at the selected compass heading.

Well that is my design idea anyway. I am not sure about the tiller pilot in that it gives an amount of movement in proportion to the error then waits for the heading to be corrected. It would certainly be difficult to get it to cope with large ship swings. ( I may be wrong)

olewill

 

[CaptainBob]

Lemain, this RepeatIt thing you mention - is it one of these:

http://www.faculty-x.net/su2410-usb.htm

?

The details on that page don't mention "directional", but I guess it must be to get the kind of range they're talking about within the allowed power.

I've bought a "Three" dongle and get mixed results. Sometimes it drags along slower than a 28.8 dialup modem, and others it's faster broadband than I have at home! At £5 a month I can't complain though.

Your project... could you use a couple of optical switches cunningly placed looking through some kind of homemade compass - get the switches to trigger a motor to turn the antenna until something blocks the light to the optical switches... if you get my drift... but then, a fixed bearing isn't much good really if you're actually relatively close to the hotspot, and moving about a bit as well as rotating.

 

[Anonymous]

Thanks guys,....

Like nearly 80% of the cruisers in this part of the Med, good internet is essential for us. Most of us have not finished working; some, like us, are far too young to retire and we rely on internet. If we couldn't get it, we'd have to go back to a desk ashore /forums/images/graemlins/frown.gif Thankfully, we manage either via WiFi or 3G/GPRS, although the latter is not excellent here in the Mar Menor and elsewhere - it all depends where you are. UK mobile services are mostly prohibitively expensive for us to use - strictly for those whose companies are paying the bill, I think.

Firstly, I don't think that stabilising the entire boat is usually a good idea. Sometimes it could be ideal, of course, and suit the conditions, but on the whole I don't think that it is a 'general' strategy. I think we need some kind of stabilised platform. Ideally 360 degrees or +/- 180, but that is expensive and difficult. In practice, we seldom swing or horse by more than 120 degrees or +/- 60 degrees over a given couple of hours. I would be happy to reset the system every couple of hours if I could get a stabilised platform during that time.

Tiller pilots come with their own inbuilt compass. One could either mount the tiller pilot on the platform or off the platform and physically remove the fluxgate from the TP and mount that on the platform. It all comes down to mechanics and linkages. If the TP is mounted on the platform then the mounting would have to be a pivot at the centre, allowing the lubber-line of the platform to be the same as the TP's.

Imagine a socket that can be (?temporarily) secured to the deck, cabin roof, etc., into which a small platform rests via a spigot. Imagine the TP secured to the deck by means of its usual pivot, so that as the arm moves, the table rotates, via a lever or linkage (probably wood). The fluxgate has been removed from the TP and mounted in a waterproof box attached to the table, connected via a carefully-screened cable. You might need to do something about the limit switches or add new ones as the TP is very powerful. In use, you set the table so that it is at its mid-range of usable travel when the ship's head is in, where the average wind/tide is holding it. Next you mount the antenna onto the table so that it is facing the access point. Now you energise the TP, which rotates the table to keep the fluxgate at the preset heading.

That would work but are there better or easier ways? Is there a neater way to implement this design?

 

[Anonymous]

Yes, that's the one and it is very directional. You can forget about mounting it on the bracket supplied unless you are in a marina. Yes, your ideas are perfectly sound - the real problem is implementing it without a decent workshop with loads of gash bits to hand. A fixed bearing is fine as over short distances there is ample gain right around the antenna. We would expect to see around 3dB around the full 360 degrees, and a main lobe at the front, with two smaller side-lobes either side of the main lobe. In practice the side-lobes can make a highly-directional antenna usable. I have had good results with my 26dB yagi at times even when we are horsing badly.

 

[jerryat]

Hi Lemain,

Sorry. In my post I hadn't realised you were still working, so now understand your requirements.

>>>>.... Imagine a socket that can be (?temporarily) secured to the deck, cabin roof, etc., into which a small platform rests via a spigot. Imagine the TP secured to the deck by means of its usual pivot, so that as the arm moves, the table rotates, via a lever or linkage (probably wood). The fluxgate has been removed from the TP and mounted in a waterproof box attached to the table, connected via a carefully-screened cable. You might need to do something about the limit switches or add new ones as the TP is very powerful. In use, you set the table so that it is at its mid-range of usable travel when the ship's head is in, where the average wind/tide is holding it. Next you mount the antenna onto the table so that it is facing the access point. Now you energise the TP, which rotates the table to keep the fluxgate at the preset heading. ............ <<

This is exactly what I had in mind in my first post! Not sure it'll work, but can't really see why not, after all, the 'beam angle/spread' of the aerial must be at least 5-10 degrees isn't it? So the TP wouldn't have to be absolutely perfect every time.

Do let us know what you end up with!! /forums/images/graemlins/smile.gif

 

[Anonymous]

Jerry, no offence taken /forums/images/graemlins/smile.gif The TP's fluxgate repeatability should be better than 1 degree and it is only repeatability that we need - and then only over a short time. What is vital is the centre of the fluxgate to be exactly in the middle of the antenna, so they both rotate about the same axis. The lager axis of movement, i.e. the length of the anchor rode, is irrelevant when the access point is very distant...imagine standing on the deck with an HBC - the distant point does not change bearing appreciably. There are other ways - e.g. getting the signal to peak - but I don't think I'd ever get such a scheme working without a decent workshop and lab. It's hard enough getting the bits together for something simple like this when you don't have a workshop at home to make up the bits first.

 

[rrees]

other option is to use a wifi repeater.
We are looking to use one of these.
This will also have a booster connected so want be using a directional antenna.

 

[Anonymous]

How would a repeater help? If you have a directional antenna pointing to the access point then you have to keep it pointed in the right direction. As the boat swings at anchor or on a mooring, the signal keeps dropping out. That causes horrible problems with timeouts and downloads failing. Some software hangs when the internet goes down for a few minutes, which is even worse.

We sometimes use a repeater in a marina where we don't need a directional antenna. I have a 15dB omni on a repeater which is good for many marina systems and that allows us to use a couple of laptops on board using only the internal WiFi cards, which is handy.

 

[rrees]

I see.
My main help in the past has been a booster / amp
They are illegal in many parts but I could provide you a link to one

 

[Anonymous]

Boosters are a bit anti-social as they can wipe out everyone else's signals though it isn't just burners that do this - a high gain omni antenna has exactly the same effect. Legally, you are supposed to reduce the output power when using a high gain antenna. A high gain antenna is a wiser choice and might allow you to run at lower power on occasions, making it easier for others to access the system. Both you and everyone else win.

I suspect that the RepeatIt is way over the limit if you adjust the power output right up.

 

[whipper_snapper]

Since you will always have a computer on and connected, I would be tempted to write a little program to do it.

A standalone fluxgate sends nmea or seatalk that can be read over a serial interface. These are relatively cheap and anyone buying a new autopilot from Raymarine will have found that it is cheaper to buy a complete kit, with compass, even if they already have one. So there may be a few going very cheap at the moment.

A stepper motor will cost a few pounds and a controller a few more pounds from a mob like this. http://www.active-robots.com/products/phidgets/phidget-motor.shtml

A program that looks at the heading and tweaks the motor would be easy enough to do. It has the advantage that you can, for instance, use your program to stop the whole thing making multiple turns and wrapping the wire around itself, and you can fiddle with the update frequency and sensitivity all within your software.

Looks like a fun project - for some values of fun.

 

[Robin2]

In order to have the Tiller Pilot fluxgate compass affected by the direction of the antenna, what about mounting the TP "backwards". That is, with the control end attached to the base on which the antenna sits and the ram fixed to the boat.

Of course if you don't already have a TP this is an expensive solution, and a home grown PC program may be a better and cheaper solution.

 

[rogerthebodger]

I have used a number of windscreen wiper motors which include a worm gearbox as an actuator in various applications (direction controlled by polarity of 12VDC input.

This could be driven by a simple relay circuit driven by a parallel printer port of a PC or laptop. The NMEA compass message from a flux gate compass could be used to get the heading and with some simple software used to compare with the known direction of the signal to drive the printer port.

May consider this for my satellite TV dish