Home mounting of WiFi antenna - advice sought for a too-short antenna mast - Page 4

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

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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. ;-)



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

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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.



--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: Home mounting of WiFi antenna - advice sought for a too-short antenna mast
On Sun, 26 Aug 2012 13:43:39 -0700, miso wrote:

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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.

Re: Home mounting of WiFi antenna - advice sought for a too-short antenna mast
On 9/11/2012 11:29 AM, J.G. wrote:
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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.


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

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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.

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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.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: Home mounting of WiFi antenna - advice sought for a too-short antenna mast
On Sat, 25 Aug 2012 08:20:22 -0700, Jeff Liebermann wrote:

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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!

Re: Home mounting of WiFi antenna - advice sought for a too-short antenna mast
On Sun, 26 Aug 2012 08:36:24 +0000 (UTC), "J.G."

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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.







--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

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

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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.




--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: Home mounting of WiFi antenna - advice sought for a too-short antenna mast
On Sun, 26 Aug 2012 09:27:37 -0700, Jeff Liebermann wrote:

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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.


Re: Home mounting of WiFi antenna - advice sought for a too-short antenna mast
On Sun, 26 Aug 2012 09:12:35 -0700, Jeff Liebermann wrote:

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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!


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

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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].

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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.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

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


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

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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.

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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.

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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.

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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.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Re: Home mounting of WiFi antenna - advice sought for a too-short antenna mast
On 9/12/2012 10:47 PM, Jeff Liebermann wrote:
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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.


Re: Home mounting of WiFi antenna - advice sought for a too-short antenna mast
On Sat, 25 Aug 2012 00:12:38 -0700, miso wrote:

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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. :)

Re: Home mounting of WiFi antenna - advice sought for a too-short antenna mast
On 8/26/2012 1:19 AM, J.G. wrote:
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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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