LTE MIMO antenna choice and positioning

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minthral
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LTE MIMO antenna choice and positioning

Post by minthral »

Hi all,

I'm trying to figure out the best way to position MIMO antennas and figured I would start a post here because I can't really find anything consolidated via google search. Please feel free to chime as this info is from my research and I may have something wrong. I'm technical (work in IT), but new to LTE/routers.

Do you need external antennas? Yes because the placement of a router often isn't the best location to pickup LTE signal and it small antennas have little gains.

Which antenna should I get? There are narrow band antennas that cover certain frequency ranges and wideband antennas that cover large frequency ranges. In my experiments, I found that carrier aggregation or 'Advanced LTE' plays a big part in speeds. I get Verizon bands 4 (~1900 Mhz), 5 (~800 Mhz), and 13 (~700 Mhz) from a single tower, so to cover all those I need wideband antennas. When all of the bands are used, my iphone gets speeds 3+ times greater than locking into a specific band or an older iphone 5s cellphone without this feature. I think most people will be in a similar situation whether they know it or not, which means many should get wideband antennas that cover all frequencies and an LTE modem that supports this feature. Most of the higher end modems support it (cat 6+), but the older ones do (for example, the Cat 4 modem in the new MOFI4500 SIM7). The downsize of wideband antennas is they wont give as much gain as well as narrow band antennas for the same price and they pick up everything, including possibly signals that you don't want.

Next question is which wideband antenna should I get? This one depends on where your tower is located, geographical layout, and how much money you want to spend. There is a trend that directional antennas with large grids give the most gain. The lower frequencies are more reliable, travel further, allow lower speeds, and antennas provide lower gain; likewise the higher frequencies are less reliable, travel less distance, are easier to boost, and allow faster speeds. I bought two of the Bolton Technical parabolic grid antennas (sold by various brands, but made by same company simplewifi) because my tower is 8-10 miles away and during winter with no tree leaves, I can actually see it from house (on slight hill in comparison to tower). From my research, these are literally the best wideband directional antennas out there:

https://boltontechnical.com/bolton-tech ... l-antenna/

Price is $250 per, which translates to ~$700 with LMR400 cables and surge protectors. The realistic gains are ~20 db at ~2000 Mhz and ~10 db at 700 Mhz. If trying to boost the lower ranges, many long periodic Yagi antennas can offer similar gains. For comparison a large dedicated 2000 Mhz antenna allows 23 db gains. +1 db is doubling the sound so its big difference, but this doesn't mean you're going to see faster speeds. The key is to get signal better than -100 db in order for it to work reliably.

I would highly recommend ZDA communications if you're looking for antennas. They got like 1000's to choice from and sell direct from South Carolina...including cables, surge protectors. They are very friendly and helpful if you call them.

Cell towers use MIMO technology which essentially means there are different antennas that attempt to communicate with receiving devices. It's a standard for LTE cellphones to have 2 antennas, with new 5G phones now having 4.

In order to get the most reliable LTE connection, you need to have 2+ antennas on your router. Realistically speaking, there are a few high end modems that allow 4 antennas for LTE and Cradlepoint routers can do it, however most LTE modems only allow 2 antennas. Most will be using 2 antennas today for that reason, but in the future 4 will be come common with 5G.

Now that its established that you need 2 high gain wideband antennas, where to put them? Most antennas are designed to be installed on a 2 inch thick pole (or 'mast') using u-clamps. This can be metal conduit for electrical wire or PVC for plumbing, both sold at 10 foot lengths (though PVC is flexible and wont work well). The ideal location for antennas is somewhere away from obstructions that could block or bounce signals, facing the direction of the cell phone tower. That typically means as high as possible, which means a pole on a house roof. It isn't simple to install a tall pole and run wires gracefully it on a roof (asphalt shingles, metal, or ceramic tiles). A more practical solution is to use a chimney or house wall to brace the pole to vertical surface with clamps. House plumbing vents are short PVC pipes that could be used, but they may not be on the right location. Need to keep in mind that there will be a storm occasionally with 100+ MPH gusts, you best secure everything tightly.

I have 2 antennas, so does that mean I need 2 poles installed? Since it's difficult to get a mast installed (correctly), many will only have 1 pole, but you can place 2 antennas on it. The first antenna goes on top and the second goes about 2 feet below the edge of the first antenna. This is what most people do and it works fine, however technically its better to have the antennas spaced horizontally because when signals bounce on hills, they are more likely to scatter side to side. An idea is a "T" pole, however you need to have 5+ feet between them horizontally so it may be more realistic to have a separate pole. The spacing of antennas has to do with reducing interference, where you don't want one antenna receiving or sending the same wavelength. The actual size of wavelength depends on the frequency, but apparently it's about 17 inches for 700 Mhz and shorter for higher frequencies, so 2 feet should be adequate. More space wont help as the goal is position them correctly for best signal and spacing is to prevent inference.

Why are people installing antennas at 45 degree angles? The short answer is 'polarization.' In summary, cell towers shoot waves horizontally, however when the signals bounce around, they turn at difference angles by the time they make it to the receiver. A receiving antenna only picks up signals at one orientation. For example, if its horizontal, it picks up only horizontal signals. If its vertical, it only picks up vertical signals (which often don't exist, so an antenna 90 degrees from its designed orientation wont work). If you place the antenna at 45 degrees, it picks up a little of both and that is a more realistic angle that radio waves will come in on after bouncing around. Since you have 2 antennas, you install each at opposite 45 degrees to form an X pattern, allowing them together to capture the most signals. However if you are in ideal location and close to the signal (ex, in an apartment and down the street is an 5G node out the window), you will get worse signals putting the antenna at 45 degrees as all the signals are coming in horizontally.

Now that they're installed, how do I ensure directional antennas are pointed correctly? This is all about trial and error. You point them in the general direction you think the cell tower is and then test the signal strength using a tool (surecall has a hand held for $200) or details found in router, then also run a speed test. Slowly turn the antenna and test again to find what gives the best performance.

Once the antennas are positioned correctly, everything else will deal with your router settings and drama with service provider as they don't want people to be using their service with routers. Verizon does have a 'connected home' plan that is only 40 GB and cost nearly $150 per month. In order to do that, you must have a Verizon certified router which means a Cradlepoint router for $500-800. The other option is to try GoldenOrb router (many out there and can be had for $50-150) with a modem (can be had for $50-300) and an unlimited data plan from a reseller (PagePlus for Verizon has a $55 per month plan). The last option is kind of a gamble as I personally got blocked right after trying to activate and others report it works fine for months then gets blocked.

Any feedback appreciated.
Dr-BroadBand
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Re: LTE MIMO antenna choice and positioning

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