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Aiming the Yagi Directional Antenna for Optimum Internet Access

It has been raining again here north of Newton,TX  and it seems we will never tie up all the details associated with finishing up this job.  When it rains on a job site that means mud and plenty of it.  It limits my world to the inside of the Old Girl and the small area around my parking area that is elevated and graveled.  Venturing outside the area means rubber boots — and MUD!

My cell signal has been pretty dismal lately and I do not know if that is due to the recent thunderstorms and the associated high winds blowing my yagi directional internet  cell tower antenna off kilter or if the tower I was tuned into changed something with its’ settings.   I suspect even though I cannot verify it that sometimes the cell providers will change the broadcast and receive settings on the towers themselves and even a minute change can have a devastating effect on my transmit and receive capabilities from inside my RV.

If you are new to MyOldRV you may not know that I usually end up in some pretty remote job site locations in my 1993 National Dolphin 32D Pusher. Because of the remote boondocking locations that are the general norm with me, I must use a bi-directional cell phone amplifier in conjunction with a Merlin At&T aircard to get phone and internet signals.  I recently did a series a blog articles entitled the Ultimate RV Internet Access Project which explains how I went about selecting the Wilson amplifier, the correct antennas and cables to capture a signal from a cell tower over 20 miles away.

If you have to pull in a very remote cell tower signal, a directional yagi antenna is just about your best bet.  If you research the yagi antennas you will hear about how difficult they are to aim.  Of course they are more difficult to aim than an omnidirectional antenna like the Wilson Trucker Antenna but you don’t have to be a rocket scientist by any means!

First off, I do not fool with the yagi antenna if the Wilson Trucker antenna is close enough to the tower to work well.  What is the point?  As you can see in the above picture, the yagi directional antenna and the Wilson Trucker antenna are mounted on the same steel mast.  Dual antenna cables run into my recreational vehicle and all I have do do is unplug one from the Wilson 801245 SOHO amplifier and screw the other one in.   I use the signal strength utility in my Merlin/AT&T aircard software to check my signal strength.  First I check the signal strength with no amplifier in use and then I go to each additional equipment implementation in logical steps.  Just as a point of reference I have found a signal strength of greater than -100dBM to be unusable.  -80 to -90dBM is serviceable and if you get below -70dBm in my remote boondocking locations you have a good, solid wireless signal.

So today was a good day to really fine tune the yagi antenna and I decided to document how I go about it.   The first thing I need is a general idea of where the closest AT&T cell phone tower is located.  I use Antennasearch.com to fish around for the closest tower.   Their information tells you the location of the towers and who the provider is.  If I am really stretching the distance

The indexed base of the yagi antenna mount

The indexed base of the yagi antenna mount

out, I will drive to the location with my GPS and mark it.  Then I return to my RV boondocikng site and use the direction finder on the GPS to point the yagi antenna.  That gets me in the ballpark and then the fun begins.  The process is much more logical and intuitive than it is scientific so anyone can do it.  I use a flagpole base for the bottom of my yagi and Wilson Trucker antenna mount.  As you can see in the picture, I have used a Sharpie to make marks around the bottom of the flagpole base.   There are 12 of them and they are just spaced out pretty evenly.  I didn’t do it by radians or degrees, there is no need to.  You just need a reference point that corresponds to a hash mark on the antenna pole itself.   I just rotate the pole around to where I think it is pointing toward the cell phone tower, note the index mark, and then I go back inside the the Fish Bus to continue the process.

Next, get your computer up and running and if you are in the ball park as far as your aimed antenna,

Using my laptop to aim the yagi directional antenna

Using my laptop to aim the yagi directional antenna

you are going to be able to get an internet connection. I use the aircard tool to check my signal strength and then I open one browser window and go to Speedtest.net to check things out. Speedtest is going to check the latency, upload and download speeds for the current settings.   Now, if I am in a hurry, I will just do a hit or miss run at it and quit once I get satisfactory results.  When I have an hour or so to fool with it like I do today I will go through each and every index setting on the antenna and check the results as far as signal strength and speedtest results.

Sometimes, I am surprised by the results. At this location north of Newton,TX I am NOT tuned in to what I think is the closest tower to the northeast of my location.  As a matter of fact, the yagi directional antenna is pointed toward the southwest to some tower which I believe is across the Sabine River in Louisiana.   Heck, that is just fine by me!  I’ll take me some o’ that Cajun cell phone signal no problem!

The chicken scratch that equates to a good internet connection

The chicken scratch that equates to a good internet connection

Let me give you some tips about fine tuning the aiming process on the yagi directional antenna. Trust me, this was learned through trial and error! Once I have an internet connection, I test that index position and write down the results on a scratchpad. Then I move to the next index position and repeat the process and write it down. And again and again and again till I arrive back at my starting point. Sometimes I will lose the signal. When that happens, I consult my notes and return to the last location with a signal and re-connect. Then I skip the index mark with no signal and procede to the next one. Sometimes I am lucky enough to maintain the signal all the way through the process and sometimes a viable signal is only present through a small arc. Once I make it through the entire 360 degree arc, I go back and ultra fine tune the yagi. I take the strongest signal reading and move one index mark to each side and test;  I test one index mark to the left, the strongest index reading and one index mark to the right. I then choose the strongest of the three and lock it down. If you look at my scratch pad, you will see where I recorded multiple dBm readings for each index mark. It has been my experience that a consistent dBm reading is more indicative of a good signal than the lowest dBm reading. For example, if one of the index marks shows a series of dBm readings like 63,69,77,65,81 and another index reading shows 73,70,72,75, I will choose the latter if the speedtest results are also decent. It makes for a better, more reliable connection.

You know, this is really wonderful technology we are dealing with. I am from the generation before there were cell phones and personal computers which makes me a fairly old fart. To sit here on this overcast day in 2009 deep in Southeast Texas and even be able to post this to my blog makes me shake my head in wonderment. Gotta love it!

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