Home mounting of WiFi antenna - advice sought for a too-short antenna mast

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On Tue, 11 Sep 2012 18:28:01 +0000 (UTC), "J.G."

No. Parachute cord is too thin and too bouncy. Tie some to a tree and put your weight on it. Notice how it stretches. The local ACE Hardware stores have 100ft lengths of shoddy 11mm rope in assorted garish colors for $10 to $17. However, for stabilizing the ladder, yellow polypropylene utility rope (wire pull rope) is good enough.

I've seen the results a few such sideways slips. Usually, it's from improper placement of the ladder legs. If one ladder leg goes into a gopher hole, the ladder (and you) will go sideways.
I've also had it happen to me, when I put a ladder leg onto a knot hole on my redwood deck, which popped out and sent the ladder sideways. Fortunately, it wasn't very high and I broke my fall by ripping out the rain gutter (and shredding my hands).

As I mentioned, the two clamps are slightly twisted. It's not enough to make any difference, but it just looks odd.
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If you have real estate, I would try to mount the sat dish on a pole in the ground. Yeah I know, you mountain folk have trees to contend with.
BTW, there are people in Castro Valley that use satellite internet. The east bay has it's share of hillbillies, but most of the trees are long gone due to being used in construction, clear cutting for ranching, etc.
Over at Mono Lake, they put up a gazebo at an historical mill site. I've seen the historical marker many times, but the gazebo was new (or newish). Anyway, it turns out the wood for Bodie came from around Mono Lake, which explains a lot of the clear cutting.
When you head further east into either the East Sierras or Nevada, wood was a real premium. Ah, but there was no shortage of stone. ;-)
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Do the math. The CONUS geosync birds vary in elevation from 41 to 47 degrees elevation at longitude 122. In order to clear a 150ft tree, one would need more than 150ft of land clear of trees to the south. On the local postage stamp size lots, that's unlikely. (One acre is 208 x 208ft). However, if the slope is downward to the south, that effectively shrinks the trees a bit, which will help.
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On Sun, 26 Aug 2012 13:43:39 -0700, miso wrote:

I've done that before, using an old satellite dish stem as the mount point. Poles are ugly though. And the guy wires tend to flip the kids as they run through them, forgetting about them until the last second.
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On 9/11/2012 11:29 AM, J.G. wrote:

The setups I've seen don't use guy wires. I've seen a real wooden telephone pole used and also galvanized pipe.
Guy wires are usually bad news. They do dramatically reduce the cost of installation hardware. But they are hard to see.
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Agreed. Even a Rohn 25 is self supporting to 20 ft. Same with a 10ft steel pipe. I start using guy wires at 20ft and up.

Before a falling tree in Feb 2012 trashed all the antennas on my roof, I had a 10ft pipe with a mess of antennas on top, that was supported by three guy wires. Because it was a tilt over base, the guy wires were mandatory. I was constantly tripping over or walking into the guy wires. I'm going to replace it with a tripod base, which doesn't require guy wires.
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On Sat, 25 Aug 2012 08:20:22 -0700, Jeff Liebermann wrote:

I noticed this has two sets of mounting holes, so that you can reverse the short arm of the J.
I thought about drilling a second set of holes in the long end, but, I worried about the cantilever being too far out in that case for the heavy rocketdish (which is heavier than a dish tv antenna).
By adding about 10 inches of EMT tubing to the long end of the J, I'm hoping not to change the geometry all that much. Of course, I have to bolt (lag screws) it into something really solid!
In hind sight, it might have been easier to erect an ugly but straight pipe in the ground!
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On Sun, 26 Aug 2012 08:36:24 +0000 (UTC), "J.G."

Why not just get the correct mount for the eaves? There's only so much fabrication before it's cheaper, easier, and better to get the right mounting hardware. <http://www.eavemounts.com <https://www.google.com/search?q=satellite+dish+eave+mount&tbm=isch or see my original posting.
If you're not a believer, calculate the wind load on the dish at your maximum expected wind gusts. Clamp the mount into a bench vice, attach a load cell, and pull on the mount at the calculated tension. On big installs, I actually do this.
<http://dl.ubnt.com/datasheets/rocketdish/rd_ds_web.pdf The Rocket dish is about 1 meter in diameter.
Handy spreadsheet: <http://www.ok1dfc.com/eme/10mprojekt/Wind%20load.xls Use the 2nd tab for a solid dish. 60 mph = 97 km/hr From the graph for a 1 meter dish, that's 750 newtons or 169 lbs.
Can your modified mount survive a 169 lb pull at the middle of the dish? I don't think so. Note that the wind load varies with the square of the wind speed, so getting max wind speed is fairly important.
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wrote:

About 1 millisecond after I hit send, I found that I had goofed. I hate it when that happens. The wind load should be:
From the graph for a 1 meter dish, that's 187 newtons or 42 lbs.
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On Sun, 26 Aug 2012 09:27:37 -0700, Jeff Liebermann wrote:

As Jeff well knows, the winds in the Santa Cruz mountains are terrific, so, I'm sure this temporary rig of my spare Ubiquiti Nanobridge M2 will fail his calculated wind-load tests!

What I'm doing right now is following Jeff's advice by surveying the noise level swiveling 180 degrees (the house is in the way for the other half) ... so the mount isn't permanent.
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On Sun, 26 Aug 2012 09:12:35 -0700, Jeff Liebermann wrote:

I might have to remove the mount anyway because I just now, belatedly, realized WHY it's tilted. See picture below:

For some strange reason, it didn't dawn on me (until now) that the fact the pipe was circular did NOT indicate that the location of the holes didn't matter.
Notice I'm slightly off in my holes, hence, the dish is actually mounted crooked. Up 'till now, I thought the J arm was bent - but it's my mind that was warped.
Funny how the FIRST time you do stuff, the 'obvious' suddenly becomes obvious!
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Yep. The DBS satellites are 3 degrees apart across the ecliptic. If that was the only criteria, the dish pointing accuracy would need to be less than +/- 1.5 degrees. However, there are multiple birds in each satellite slot, which means too narrow a beamwidth can become a problem if a bird drifts too close to the edge of the slot. I found that out the hard way when I tried to use a 3 meter dish for DBS reception. With the worm gear adjustment on the dish azimuth, I could individually pick out which of the 5(?) birds were in the 101 slot. Too narrow a beamwidth is NOT a problem with most DBS dishes. The feed horn and dish parabolic contours are designed to give about a 2.1 degree -3dB beamwidth, which is what's needed to cover the entire 3 degree slot. However, for that to work, the dish has to be aligned to something like +/-0.5 degrees. It can be done, but it takes LOTS of practice and patience[1].

Well, I bought one for my Droid X for only one stupid reason. I wanted an easy way to determine if I had a chance to shoot through a hole in the forest canopy. I think you've seen my 101 hole: <http://802.11junk.com/jeffl/pics/DBS/slides/101a.html With the Droid app, I can take a photo of the tree canopy from a prospective antenna location and mark where the satellites should be. I then send the JPG to the tree trimmer and mark where to trim the branches. That's not a problem you'll have in the flats, but in the forest, the app is quite useful. <https://play.google.com/store/apps/details?id=com.agi.android.augmentedreality I've never bothered to run my own setup. I'll post a photo when I have time.
[1] I fixed one install where the dish was on the roof, near the edge of about a 4ft overhang. I'm on the roof doing the adjustments and getting good signal. As soon as I climb off the roof, the picture and signal fall apart. I climb back on the roof, and it's back to normal. What was happening was the roof was bending very slightly from my weight. I moved the dish back from the edge to the middle of a load bearing wall, and everything stayed put.
Another nightmare was a dish on a pole set in concrete. The owner said that they had to realign the dish every few months. The problem was obvious. The hillside was a slow moving avalanche. It eventually collapsed into a ravine a few years later.
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As you probably know, you can spot slides with trees. Trees just don't grow at angles. We may not have forests to deal with, but lots of sliding land around the bay.
It is tough to get better than 3 degrees out of a cell phone or GPS flux gate. It seems to me you would have to trim a lot more trees than needed to get your window.
I'm curious what the next step above a Lensatic Cammenga (+/-2.25 degrees) I see some boating flux gates spec 0.5RMS. Now that means if you want +/- 3 sigma, you are at +/- 1.5 degrees.
There is some irony that the best compass you can buy is probably a big dish and a geosynchronous satellite.
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I live on a hillside. Plenty of trees simulating a slow motion mud slide. I have one oak that I've been watching for about 30 years. I think it's time to take it down before it creates a big problem.

I can get very accurate during the bi-annual "solar outage" <http://en.wikipedia.org/wiki/Solar_outage> in late Feb and late Sept. I can't use it to aim the dish, but I can use it to see where I should clear the tree branches.

Dunno. I don't use a compass. I get the dish vertical with a bubble level. I preset the elevation and the skew (for dual LNB's). I then just spin the dish around the best guess azimuth. Works every time.

I think a GPS receiver is just as accurate for speed and direction. I've ridden on a straight road and noticed that the GPS indicated direction was absolutely stable and never changed.
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On 9/12/2012 10:47 PM, Jeff Liebermann wrote:

GPS direction is basically computed from waypoints as you move. [The FCC has a web page to get the bearing between two waypoints. The GPS does a similar computation.] But getting a bearing at a fixed location means you aren't moving. ;-)
The higher end GPSs have fluxgate compasses because if you aren't moving fast enough, the GPS can't compute the bearing. I gather even without SA there are time dependent errors in the GPS signal. Hiking up a steep hill usually slows you down, so the differential waypoint technique starts to get very inaccurate. The GPS will switch from the virtual compass to the fluxgate compass based on the speed estimate.
It you take a GPS and "park it", but log the trail based on raw readings, you can see the location wander. Some GPSs filter this wandering since people are confused if they are still and the GPS indicates they are moving.
There is a lot of "enhancements" in GPS tracking that can fool you into thinking the GPS is better than it really is. For instance, if the GPS has mapping, it will snap onto a road even if the actual position is off a bit. Once in a while this scheme can snap onto the wrong road.
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On Sat, 25 Aug 2012 00:12:38 -0700, miso wrote:

Satellite sucks with 700ms latencies & severe bandwidth limits; but it does provide the Santa Cruz mountains with 10 Mbps to 20 Mbps if you go with Viasat Exede Ka band (forget HughesNet, which is Ku band). Plus you can't buy and set up your own equipment.
This antenna and radio I'm mounting is for 2.4 Ghz WiFi, which has to handle a lot more noise - but otherwise it works fine at the 10Mbps to 20Mbps range up here in the Santa Cruz Mountains.
The alternative is 5Ghz equipment, depending on the WISP (e.g., Etheric) but the drawback is you can't own and set up your own equipment.
Most of us up here in the mountains set up our own equipment. We're not as smart as you guys but luckily the WISPs are all pretty good about it (Surfnet, Hilltop, Ridgewireless, etc.). So we learn just enough to get it working & for the kids not to kill us when it goes down. :)
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On 8/26/2012 1:19 AM, J.G. wrote:

If you recall the old war driving days, i.e. when wifi was actually work to find, there were tools to log "hits" geographically. I had fired the software up about a year ago for yucks. Amazing the number of WISPs out there. I used a dual band dongle. I found maybe one 5.8GHz WAP.
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On Friday, August 24, 2012 2:53:38 AM UTC-4, J.G. wrote:

Use a yagi. I mounted mine on an old dish mount. Made it out of pvc and used a 90deg fitting to put it on the dish mount. Lots of element calculators on the net will give you the specs. You need to know the frequency. Works great and vety little wind load.
http://www.jamesgangnc.com/yagi.jpg
I was getting 0 to 1 bar on our hot spot and now get 3 to 4. 4 is the max.
I used some leftover small copper tubing for the elements. I used a holesaw to make a hole under the driven element to attach the rg6.
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