Antenna Comparison Review (Lots of antennas inside)

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xdavidx
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Re: Antenna Comparison Review (Lots of antennas inside)

Post by xdavidx » Thu May 30, 2019 9:02 pm

swwifty wrote:
Thu May 30, 2019 6:55 pm
I separated the antennas based on the wavelength they are operating at. Since B12 is the longest wave length in LTE around 700mhz I tried to separate them at least one wave length which is about 17 inches.
Where did you measure the 17 inches from/to? I was thinking of doing the same thing, but with the shape of these antennas, I didn't know where that would be. The center of each case? The edge? If so, which edge?

xdavidx
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Re: Antenna Comparison Review (Lots of antennas inside)

Post by xdavidx » Thu May 30, 2019 9:41 pm

swwifty wrote:
Thu May 30, 2019 7:01 pm
That is really interesting. It is important to keep in mind though that the tower you connect to is not necessarily the one with the strongest signal. Handoff between towers is not simply controlled by the client. The tower itself can hand off a UE to a different base station if needed, due to a variety of factors. This could explain why when you were aiming one way you saw weaker signals and such.

That being said. If you don't have clear LOS, then more than likely you have a lot of multipath going on, which can cause all kinds of strange behavior in signal strengths and reliability.

I regularly see signal strengths in RSSI bounce from -65 to -80 on B12 and on band 2 from -80 to -90. The leaves coming out after this past winter made a huge difference in signal strength, and performance. I was getting over 100mbps down in winter, and now can only muster about 75.
If a tower hands off to another one, will the client show the true tower in the stats?

I may not have been clear about weaker signals. What I meant is that if I pointed the antennas at a known tower, my RSRP, SINR, etc. were worse than if I pointed 180 degrees away from the tower. And it did this with 2 towers that are close to 180 degrees from each other at my house. It was weird that it would do the exact same thing for each of them, but maybe it was a perfect storm where one bounces off something in the direction of the other one and back to me and the other bounces off something else in the opposite direction and also back to me. They are playing monkey-in-the-middle with me! I'll have a much better LOS when the antennas are 30 feet higher.

Here is how things looked for my testing today vs how they will look with the antennas on the roof (30 feet higher, or maybe even 40 feet higher, although I'm showing 32 feet higher in these images):

ESE tower with my top antenna about 8 feet high:
tower_sw_8ft_antenna.jpg

ESE tower with my top antenna about 40 feet high:
tower_sw_40ft_antenna.jpg

NW tower with my top antenna about 8 feet high:
tower_ene_8ft_antenna.jpg

NW tower with my top antenna about 40 feet high:
tower_ene_40ft_antenna.jpg


I didn't realize I had that obstruction for the NW tower in my testing today. I knew my house might have been partly in the way and some trees, but I didn't realize the hill across the street was being clipped. That makes me feel good, because it means I can gain quite a bit once I clear it.

The towers have been entered as 100 feet tall. I don't know their exact heights.

The leaves make a big difference for my T-Mobile cell phone reception too. I have to use a booster system provided by T-Mobile in order to get a reasonable signal on my circa 2012 phone (HSPA+, no LTE). The LTE phones in the household aren't as strong without the booster, but at least they can function. I have that booster unit inside a window on the 2nd floor and the other unit that it creates a cellular bubble with on the main level toward the other end of the house. First off, I originally had the window unit a few inches from the window and it wasn't working very well. I found that if I leaned the top of it against the glass, it made a big difference. Secondly, as you said, when the leaves come out, the signal strength goes down. And if the leaves/grass/whatever is wet, that really affects it too. It doesn't have to be raining. It is worse until things dry out.

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max
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Re: Antenna Comparison Review (Lots of antennas inside)

Post by max » Fri May 31, 2019 1:11 am

I'm professional in antennas. I wanna to comment situation in receive a better signal from the rear (back) of the antennas.
This possible if you not receive direct signal, if you not have line of sight to base station.

swwifty
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Location: NE GA Mountains

Re: Antenna Comparison Review (Lots of antennas inside)

Post by swwifty » Fri May 31, 2019 8:46 am

xdavidx wrote:
Thu May 30, 2019 9:02 pm
Where did you measure the 17 inches from/to? I was thinking of doing the same thing, but with the shape of these antennas, I didn't know where that would be. The center of each case? The edge? If so, which edge?
don't over think it too much, just from the edge. Over 17 inches is okay too, I just wouldn't have them closer at any one point then 17 inches.

swwifty
Posts: 487
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Location: NE GA Mountains

Re: Antenna Comparison Review (Lots of antennas inside)

Post by swwifty » Fri May 31, 2019 9:23 am

xdavidx wrote:
Thu May 30, 2019 9:41 pm
If a tower hands off to another one, will the client show the true tower in the stats?

I may not have been clear about weaker signals. What I meant is that if I pointed the antennas at a known tower, my RSRP, SINR, etc. were worse than if I pointed 180 degrees away from the tower. And it did this with 2 towers that are close to 180 degrees from each other at my house. It was weird that it would do the exact same thing for each of them, but maybe it was a perfect storm where one bounces off something in the direction of the other one and back to me and the other bounces off something else in the opposite direction and also back to me. They are playing monkey-in-the-middle with me! I'll have a much better LOS when the antennas are 30 feet higher.

Here is how things looked for my testing today vs how they will look with the antennas on the roof (30 feet higher, or maybe even 40 feet higher, although I'm showing 32 feet higher in these images):


I didn't realize I had that obstruction for the ENE tower in my testing today. I knew my house might have been partly in the way and some trees, but I didn't realize the hill across the street was being clipped. That makes me feel good, because it means I can gain quite a bit once I clear it.

The towers have been entered as 100 feet tall. I don't know their exact heights.

The leaves make a big difference for my T-Mobile cell phone reception too. I have to use a booster system provided by T-Mobile in order to get a reasonable signal on my circa 2012 phone (HSPA+, no LTE). The LTE phones in the household aren't as strong without the booster, but at least they can function. I have that booster unit inside a window on the 2nd floor and the other unit that it creates a cellular bubble with on the main level toward the other end of the house. First off, I originally had the window unit a few inches from the window and it wasn't working very well. I found that if I leaned the top of it against the glass, it made a big difference. Secondly, as you said, when the leaves come out, the signal strength goes down. And if the leaves/grass/whatever is wet, that really affects it too. It doesn't have to be raining. It is worse until things dry out.
If your mobile device (in this case your LTE Modem) hands off to another tower you will see that switch. I'd recommend using the 'at!lteinfo' command to see all the cells that are in range. Keep in mind that even though we use the term "towers" each physical tower has many different "cells" on it that are typically sectorized. Keep a close on the PCI numbers in the at!lteinfo command. Typically cells that are on the same tower have PCI numbers that are very close to each other. If the numbers are far apart in range, typically you are seeing a signal from a cell that is mounted on a different physical tower, or perhaps a different sector that is pointing away from you. Self-interference is the one of biggest challenges in LTE.

I suspect that you might have the tower numbers reversed. If you see the signal increase when you move the antenna 180 degrees that is a sign that the signal is in fact coming from a different direction. The signals don't scatter as much as you'd suspect. Read about multipath, and you'll see what I mean. When they scatter they tend to degrade or cancel each other out in phase and make the signal really weak. Remember the dBM scale is logarithmic. If you see a +3dBm increase in signal thats a signal twice as strong! 10dbm is 10x stronger!

I've heard of boosters causing issues with other LTE devices. I have a feeling that your booster might be taking the signal your modem is connecting too and amplifying it, then sending it back out. I'd highly recommend trying these tests at your house with the booster off to rule that out as causing any issues. Those boosters can cause some serious havoc on RF signals.

If you are having issues with signal through glass it more than likely has some coating, or its possible the bug screen on the outside is a metal mesh and killing the RF signal. I've experienced and learned this the hard way before.

xdavidx
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Re: Antenna Comparison Review (Lots of antennas inside)

Post by xdavidx » Fri May 31, 2019 8:12 pm

max wrote:
Fri May 31, 2019 1:11 am
I'm professional in antennas. I wanna to comment situation in receive a better signal from the rear (back) of the antennas.
This possible if you not receive direct signal, if you not have line of sight to base station.
Thanks max. That does appear to be what is happening here.

xdavidx
Posts: 267
Joined: Tue May 28, 2019 4:04 pm

Re: Antenna Comparison Review (Lots of antennas inside)

Post by xdavidx » Fri May 31, 2019 9:30 pm

swwifty wrote:
Fri May 31, 2019 9:23 am
If your mobile device (in this case your LTE Modem) hands off to another tower you will see that switch. I'd recommend using the 'at!lteinfo' command to see all the cells that are in range.

Yep, I'm using it to keep an eye on them already. There are generally 3-5 other towers chatting away at lower signal strengths at any moment in time here, at ground level and even at the 2nd story level.
swwifty wrote:
Fri May 31, 2019 9:23 am
Keep in mind that even though we use the term "towers" each physical tower has many different "cells" on it that are typically sectorized. Keep a close on the PCI numbers in the at!lteinfo command. Typically cells that are on the same tower have PCI numbers that are very close to each other. If the numbers are far apart in range, typically you are seeing a signal from a cell that is mounted on a different physical tower, or perhaps a different sector that is pointing away from you. Self-interference is the one of biggest challenges in LTE.

Correct, correct, correct and correct. :P

I just wish they'd show the base 10 Cell ID (also close in value for a given tower, typically) instead of the Physical Cell ID for each of those other cells, because the last 3 of Cell ID is what I have committed to memory and it is what shows in the status results. Would have been nice if it was consistent or showed both on each screen.
swwifty wrote:
Fri May 31, 2019 9:23 am
I suspect that you might have the tower numbers reversed. If you see the signal increase when you move the antenna 180 degrees that is a sign that the signal is in fact coming from a different direction. The signals don't scatter as much as you'd suspect. Read about multipath, and you'll see what I mean. When they scatter they tend to degrade or cancel each other out in phase and make the signal really weak.

You may not have read above that I've been to each of these towers, so I know which one is which. There isn't any confusion there. I suspect that my environment is closer to what you reported you saw at the state park vs what you see at your base location. I just have a lot of towers bouncing things around.
swwifty wrote:
Fri May 31, 2019 9:23 am
Remember the dBM scale is logarithmic. If you see a +3dBm increase in signal thats a signal twice as strong! 10dbm is 10x stronger!

Correct. More on that further down.
swwifty wrote:
Fri May 31, 2019 9:23 am
I've heard of boosters causing issues with other LTE devices. I have a feeling that your booster might be taking the signal your modem is connecting too and amplifying it, then sending it back out. I'd highly recommend trying these tests at your house with the booster off to rule that out as causing any issues. Those boosters can cause some serious havoc on RF signals.

Definitely a good thing to consider, but not the case in this situation. This booster isn't like all the analog systems on the market. This one is digital and only boosts what it needs to for the phones connected to it from a single provider (in this case, T-Mobile), and only boosts to the degree needed based on the relative location of the two units (they talk to each other over a 5 GHz system, but not 802.11, for some reason).

Where it might come into play is if the AT&T frequency matches one of the few T-Mobile frequencies that the booster supports and if my antennas are close enough to the booster unit that creates the cellular bubble. This would cause similar interference to another tower sharing frequencies, except this "tower" is very close. The bands in common between AT&T, T-Mobile and the booster are bands 2 and 4.

I've done some testing with the booster off and on and haven't noticed a difference in stats, but it is always in the back of my mind that it is theoretically possible, so I'll continue to do A/B testing with the booster on/off. What I haven't done yet is to test it with one of the T-Mobile LTE phones downloading something. That will be a good test. No T-Mobile LTE phones were at home during my initial deck testing and my HSPA+ phone wasn't actively doing much.

I'm getting an LTE phone in another month or so. If I have to chose between reasonable T-Mobile signals in the house without the booster or great signals with the booster, I'll choose the former in exchange for better internet with the LTE modem and external antennas. Right now, with my HSPA+ phone, I can barely use it in the house without the booster on.

The other variable is that the bubble created generally ends at the unit by the window. If I mount the antennas on the opposite side of the window unit from the booster coverage unit, it should be outside the bubble and not be impacted much, *if* it can be impacted at all.
swwifty wrote:
Fri May 31, 2019 9:23 am
If you are having issues with signal through glass it more than likely has some coating, or its possible the bug screen on the outside is a metal mesh and killing the RF signal. I've experienced and learned this the hard way before.

No bug screen. What is interesting is if I slide the other half of the window open that does have a bug screen and lean the unit against the bug screen, it gets a better signal (as does my cell phone, directly). The glass attenuates the signal more than the bug screen. I just found it interesting that having the unit touch the glass makes a big difference in signal strength and end results.


Now, I have done some other testing today. I took the flat panel antennas and my rig to one of the towers and tested a couple blocks away from the tower with a clear line of sight. The antennas do have a better signal with them facing toward the tower than away. They were good either way, but still better with the antennas facing forward. RSRP values were about 10 times stronger forward than reverse for the higher frequency bands (1900 and 2300) and about 4 times stronger for lower frequencies (700). That all makes sense and does confirm that the antennas aren't pointing the wrong way inside the cases.

That also means that I'm getting better signals on my deck by pointing away due to the signals bouncing back from the opposite directions. Although highly variable, it seems pretty wild to get a high test score of 75 Mbps download from a directional antenna picking up the signal from the opposite direction of the tower! :lol:

swwifty
Posts: 487
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Location: NE GA Mountains

Re: Antenna Comparison Review (Lots of antennas inside)

Post by swwifty » Sat Jun 01, 2019 1:53 pm

Very interesting information. Please be sure to keep us up to date with your further tests! They are a great asset to this forum.

You must be getting some constructive multipath in the opposite direction of the tower, and some destructive multipath in the direction the tower is facing. Quite interesting, I've seen antennas very sensitive to any direction changes like that, but never a significant difference when facing backwards!

xdavidx
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Joined: Tue May 28, 2019 4:04 pm

Re: Antenna Comparison Review (Lots of antennas inside)

Post by xdavidx » Sun Jun 02, 2019 7:31 pm

swwifty wrote:
Sat Jun 01, 2019 1:53 pm
Very interesting information. Please be sure to keep us up to date with your further tests! They are a great asset to this forum.
Thanks. If not for your in depth review of all those antennas, I probably would have ended up with some of the 9/11 dBi yagis. And although those probably would have worked, I'm glad I have the higher gain panels. So thanks a lot for all your diligent work.

I'll be posting more as I go. I'll create a separate thread.
swwifty wrote:
Sat Jun 01, 2019 1:53 pm
You must be getting some constructive multipath in the opposite direction of the tower, and some destructive multipath in the direction the tower is facing. Quite interesting, I've seen antennas very sensitive to any direction changes like that, but never a significant difference when facing backwards!
Although I'll provide more details in another thread, I saw the same behavior today on my roof. I did a bunch of testing at the peak with one tower and then decided to try with the antennas about 12 feet lower by moving down to my chimney. I was hoping to provide a less optimal path for the one I was picking up at the peak so that I could get the weird 180 degree boomarang tower again, although with a more direct line of sight.

That seemed to work, as I did pick up the boomerang tower again. However, I picked it up in the opposite direction again. In fact, I got my fastest test result of the day (70 mbps), while pointing in the opposite direction, on that tower!

Thanks again for your insights.

xdavidx
Posts: 267
Joined: Tue May 28, 2019 4:04 pm

Re: Antenna Comparison Review (Lots of antennas inside)

Post by xdavidx » Sun Jun 02, 2019 7:53 pm

I had some typos in a post above regarding the directions of the towers. In case anyone is following along and is confused, I fixed them in the original post, but I can't fix them in the part quoted by swwifty. In his reply, it quotes, "I didn't realize I had that obstruction for the ENE tower in my testing today." That should read, "I didn't realize I had that obstruction for the NW tower in my testing today."

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