Long Range Wifi

[Scott L.]

Possible project needing designing.
Looking for the design of an antenna aiming device that can be controlled remotely (hardwired) from ground level, and need to be able to be controlled within a ~ 120 degrees left/right, and +- 15 degree elevation with 1 degree control steps or less in each direction. The weight of the dish is ~10 pounds. The entire assembly needs to be weather proof able to stay locked in position during heavy wind, rain, sleet, and snow. And as light as possible. It will be mounted atop a 21’ galvanized steel pipe 1-1/4” ID. The dish requires a ~2” mounting pipe to bolt to.
The cost needs to be as low as possible. Possibly two units required.
One dish mounted 80+ feet in the air atop a 60’ communications tower, the other 60 feet mounted in a tree.
The power source for the control needs to able to be carried either to base of tree/tower, or small enough to be carried up ladder with control panel.
This is for a long range wifi link, that needs to be fine tuned, but the actual dishes are too high above a safe standing/tie in point to tune other than lowering dish, setting elevation and re raising dish.

[sanddrag]

Take a look at the offerings from Ubiquity.

[gblake]

I'll say the obvious.

It sounds like you need a commercial pan/tilt unit (PTU), with an appropriate weather resistance rating.

There are reasons why vendors can stay in business mass producing those, instead of being put out of business by home-brew devices.

[GeeTwo]

Unless it does really need to be wifi, I recommend looking at the xBee line of products. They offer a wide variety of ranges and bandwidths to carry a wireless serial connection between two endpoints.

[Foster]

Originally Posted by sanddrag

Take a look at the offerings from Ubiquity.

They make some off the shelf devices that hams are using locally to try to set up a network. You listed some tight tolerances, remember that trees are designed to move and twist in the wind. In my area there is always a 5-10 knot breeze blowing

[Scott L.]

Originally Posted by sanddrag

Take a look at the offerings from Ubiquity.

I actually am using 2 AC pbe-500 Ubiquity dishes. They are great.

Some tree movement is ok, the dish returns to the same position when the wind dies down. The link is ~ 1.1km

[gblake]

If you are trying to link a pair of dish antennae, why do you need to be able to swing one of them through such a wide range (~120 Deg Az & +/- 15 Deg Elev)?

Also, my gut tells me that putting a weather-proof PTU, and a (small) dish antenna, and cabling, atop a 21' pipe atop a 60' tower, isn't going to end well. My gut is often wrong, but that seems like a bunch of mass at then end of a floppy lever arm.

It might not crash and burn, but don't you think it has a good chance of swaying/oscillating enough to foul up your data link?

[Scott L.]

Originally Posted by gblake

If you are trying to link a pair of dish antennae, why do you need to be able to swing one of them through such a wide range (~120 Deg Az & +/- 15 Deg Elev)?

Also, my gut tells me that putting a weather-proof PTU, and a (small) dish antenna, and cabling, atop a 21' pipe atop a 60' tower, isn't going to end well. My gut is often wrong, but that seems like a bunch of mass at then end of a floppy lever arm.

It might not crash and burn, but don't you think it has a good chance of swaying/oscillating enough to foul up your data link?

rethinking the specs, a pan of 45 degrees, and elevation of +-5 degrees would be more than enough for fine tuning. The elevation control is most important, because the entire mast pipe can be rotated. The 60' tower is guyed and stands atop 2+ cubic yards of concrete and with me at 60' has only slight sway. and the 21' foot pipe extends maybe 18' above that.

the dish mounted in the tree extends maybe 14' unsupported, and a tree was chosen as the cheapest option,$120, as opposed to installing another 60' tower at a cost of ~$1800

[gblake]

Originally Posted by Scott L.

rethinking the specs, a pan of 45 degrees, and elevation of +-5 degrees would be more than enough for fine tuning. The elevation control is most important, because the entire mast pipe can be rotated. The 60' tower is guyed and stands atop 2+ cubic yards of concrete and with me at 60' has only slight sway. and the 21' foot pipe extends maybe 18' above that.

the dish mounted in the tree extends maybe 14' unsupported, and a tree was chosen as the cheapest option,$120, as opposed to installing another 60' tower at a cost of ~$1800

I'm worried most about the final 18' of pipe plus PTU and other payload, in the winds (different from ground level) at 80'.

Separate thought:
Can you align the router dish while at the top of the tower, then tweak the mounting fixture a known amount (use a shim?) (the tweak should be small) to get the dish close enough to the right elevation when it's later on the pipe, and has only moved a known distance higher than the spot whet you aligned it?.

Blake
PS: over several years, expect the tree to grow taller. The trees around my house have grown more into my satellite TV line-of-sight over the last 15 years.

[Al Skierkiewicz]

Scott,
The tree with a dish is not a solution. Trees grow...
I would move to a yagi at the tree location. It has a bit wider aperture and doesn't need to stay pointed in exactly the right direction.
In reading your original specs, you have one dish mounted 80' feet up on a 60' tower? There is also some panel antennas that have pretty decent gain and a great front to back ratio. We are using those to link to the university next door (they rent space here). Approx path is a few hundred meters. They are powered over ethernet. I have to ask why you are mounting one at 80 feet. Do you have some obstacles?

[Scott L.]

Originally Posted by Al Skierkiewicz

Scott,
The tree with a dish is not a solution. Trees grow...
I would move to a yagi at the tree location. It has a bit wider aperture and doesn't need to stay pointed in exactly the right direction.
In reading your original specs, you have one dish mounted 80' feet up on a 60' tower? There is also some panel antennas that have pretty decent gain and a great front to back ratio. We are using those to link to the university next door (they rent space here). Approx path is a few hundred meters. They are powered over ethernet. I have to ask why you are mounting one at 80 feet. Do you have some obstacles?

Yes, my obstacles are trees. The theoretical throughput is ~400mbps. When tuned the best can at the moment, I usually get 90-160mbps, which I'm fine with, but I have trees entering the fresnel zone, and link drops to unusable in rain with the leaves on the trees.

[DonRotolo]

Yagis at both ends will give you plenty of link margin if it is only trees. I fear you are really hitting up against the speed of light.

WiFi has some very tight send-and-respond timing, particularly at high throughput. 1.1 km is a significant fraction of the ultimate limit for 802.11 distance, specifically because of the time it takes for the signal to travel - at the speed of light.

Oh, and your dish-on-a-pole-on-a-tower will come down in the first or second ice storm - you get those in PA, right? Don't ask how I know.

Oh, and what Al said about trees. (But, perversely, although a tree WILL grow, your antenna won't get any higher off the ground as it does).

I encourage you to learn about WiFi link timing and do the math for 1.1 km. You will be surprised at how tenuous that link is, but not for signal strength. Try 802.16 instead, built exactly for what you want to do.

[Scott L.]

Originally Posted by DonRotolo

Yagis at both ends will give you plenty of link margin if it is only trees. I fear you are really hitting up against the speed of light.

WiFi has some very tight send-and-respond timing, particularly at high throughput. 1.1 km is a significant fraction of the ultimate limit for 802.11 distance, specifically because of the time it takes for the signal to travel - at the speed of light.

Oh, and your dish-on-a-pole-on-a-tower will come down in the first or second ice storm - you get those in PA, right? Don't ask how I know.

Oh, and what Al said about trees. (But, perversely, although a tree WILL grow, your antenna won't get any higher off the ground as it does).

I encourage you to learn about WiFi link timing and do the math for 1.1 km. You will be surprised at how tenuous that link is, but not for signal strength. Try 802.16 instead, built exactly for what you want to do.

https://dl.ubnt.com/datasheets/Power...Beam5ac_DS.pdf

The dishes are the PBE-5AC-500. 5.8GHZ Carrier using 80MHz channel.
Light travels 300,000km/s, so a 1.1km distance would take 3.67uS one way
Tower is a rohn 25G series.
21'pipe is 1-1/4" ID with 1.66"OD

[gblake]

Originally Posted by Scott L.

https://dl.ubnt.com/datasheets/Power...Beam5ac_DS.pdf

The dishes are the PBE-5AC-500. 5.8GHZ Carrier using 80MHz channel.
Light travels 300,000km/s, so a 1.1km distance would take 3.67uS one way
Tower is a rohn 25G series.
21'pipe is 1-1/4" ID with 1.66"OD

If you do have any doubts about your expected throughput, and if you already have the equipment, take it to the two sides of an easily accessible 1.1km wide unobstructed "valley", and then see how much throughput you can get. That will put an upper bound on what you can try to achieve shooting through the trees.

In the same vein, attach some weight lifting weights to the pole to represent your equipment, plus ice & snow, then mount the pole on something sturdy (at ground level), then pull hard on its top with a rope to mimic a strong wind. See what happens (be out of the way if anything breaks loose).

For the weight and wind loadng test, if you can attach the pole to something at ground level using the same brackets you want to use to lock it in place up in the air, even better. See how they hold up when you abuse them.