Aligning yagi antennas

[salamander99]

This might be an impossible task, but I have a situation where I need to align two yagi antennas - one at the top of a ridge and one at the bottom. The frequency is 900mhz using LoRA. I can get between 119db and 127db signal strength and there is challenging terrain between the two antennas. Is there an app I can use to help align the two signals?

 

[mmckenna]

Google earth works well. If you use the Ruler function you can draw a line between the two antenna locations on the map. It'll give you a heading from the first point to the second point. Draw the line in the opposite direction and it'll give you that heading.

If you have a smartphone that has a built in compass, it'll give you the heading.

Usually these antennas have several tens of degrees of beamwidth, so getting it spot on may not be required, but it'll help.

 

[salamander99]

I did try that, I think. I took an ios compass reading at 224 SW at the top, then 45 NE at the bottom. I aligned the antennas to that orientation, but I believe there might be terrain in between the two points that is blocking or slightly blocking the signal. I was hoping to use a scanner of some sort to help isolate exactly where the beams are.

 

[merlin]

I think 900 Mhz is most of your problem. You don't give the separation distance but 1/4 watt would be a challenge at 1 Km
433 Mhz would do better where terrain issues are involved.
LoRa was never intended for such applications

 

[mmckenna]

I'd agree with @merlin sounds like topographical shielding.

I've got a 900MHz data link running from a water tank to a pump station, and it's about a mile through dense forest. 1 watt, high gain Yagi's and 900MHz has worked well, rock solid link. But having any dirt between that would probably kill it. -119 and -127 are pretty low signals.

 

[prcguy]

See post #2 here: Bearing calculator for directional antenna

With this app you can point to another known location on a map and get precise bearings then use the phone camera with the app to optically align the Yagi. However, in non line of site cases best signal can be when one or more antennas are off pointed.

 

[salamander99]

The distance between the two antennas is roughly 1400 linear feet and 600 feet elevation, mostly over a steep elevation drop, through trees and rock out croppings. I am transmitting sensor data from a water pump station at the bottom of the mountain up to a solar cart on the top of the mountain. Even with the low signals, I get fairly reliable data transmission (at LoRA limitations).

Thanks for the tips everyone

 

[salamander99]

See post #2 here: Bearing calculator for directional antenna

With this app you can point to another known location on a map and get precise bearings then use the phone camera with the app to optically align the Yagi. However, in non line of site cases best signal can be when one or more antennas are off pointed.

Your last sentence - what do you mean by off-pointed?

 

[prcguy]

Your last sentence - what do you mean by off-pointed?

Instead of each Yagi pointed at each other it could end up one or both point off to the side somewhere picking up a reflection better than direct.

 

[Ubbe]

I was hoping to use a scanner of some sort to help isolate exactly where the beams are.

You are probably using spread spectrum and a low bitrate and forward error correction to make a signal between -119dBm to -127dBm to work, so no scanner or radio can measure spread spectrum signal strengths, they don't even have that kind of sensitivity if the values are real and not just some uncalibrated ones from the LoRA module.

What antennas are used? Try shifting between vertical and horisontal polarisation as one can work better than the other.

/Ubbe

 

[FKimble]

Also if one ant is at elevation and the other at a much lower elevation, then not only do the yagis need to be point closely toward each other, then must also have some tilt, otherwise the low ant is hitting the side of a hill and the high mounted ant is pointing way over the lower one. As close as they are the tilt will be way off of level! How much elevation difference is there?

Frank

 

[salamander99]

You are probably using spread spectrum and a low bitrate and forward error correction to make a signal between -119dBm to -127dBm to work, so no scanner or radio can measure spread spectrum signal strengths, they don't even have that kind of sensitivity if the values are real and not just some uncalibrated ones from the LoRA module.

What antennas are used? Try shifting between vertical and horisontal polarisation as one can work better than the other.

/Ubbe

I am using this yagi antenna from amazon. I have also tried this omni antenna

Instead of each Yagi pointed at each other it could end up one or both point off to the side somewhere picking up a reflection better than direct.

Yes, that is the orientation I found worked the best. I had a suspicion it was a reflection.

Also if one ant is at elevation and the other at a much lower elevation, then not only do the yagis need to be point closely toward each other, then must also have some tilt, otherwise the low ant is hitting the side of a hill and the high mounted ant is pointing way over the lower one. As close as they are the tilt will be way off of level! How much elevation difference is there?

Frank

The yagis I'm using have an adjustment angle of about 30 degrees. I used the adjustment as much as possible, to avoid aiming them into the dirt, but it's hard to tell with no line of sight. I've used Unifi's design tool, which gives me the ability to calculate optimum azimuth and tilt using their UISP equipment (not yagi).



Because I'm not installing the yagis on tall antennas, this is more accurate to what I'm dealing with for direct line of sight:

 

[Ubbe]

I am using this yagi antenna from amazon. I have also tried this omni antenna

It's a dualband antenna and not much gain nor directivity at 900Mhz. The gain figure are for the 2GHz band that are easier to achieve.
"Frequency range (MHz): 698-960 / 1710-2700 MHz"

I would suggest trying a proper single band 900MHz antenna, that will be bigger than the one you have. There are several at Amazon and guys here at RR have tried most of them and it is a couple that actually works and others that are a joke, the antennas not the guys.

/Ubbe

 

[salamander99]

It's a dualband antenna and not much gain nor directivity at 900Mhz. The gain figure are for the 2GHz band that are easier to achieve.
"Frequency range (MHz): 698-960 / 1710-2700 MHz"

I would suggest trying a proper single band 900MHz antenna, that will be bigger than the one you have. There are several at Amazon and guys here at RR have tried most of them and it is a couple that actually works and others that are a joke, the antennas not the guys.

/Ubbe

Thanks, that would be great if I could get specific model recommendations. Amazon links appreciated

 

[mmckenna]

Thanks, that would be great if I could get specific model recommendations. Amazon links appreciated

I've got a 900MHz data link at work, like I said above. About a mile between a water tank and a pump station. Dense coastal redwood forest.

The link is running the antenna on each end. Aiming was done using Google Earth.

PC9013N : Laird 13 Element Yagi Antenna for 902-928 MHz includes a 19 in pigtail terminated with an N-Female Connector

PC9013N is a 13 element Yagi Antenna operating within 902-928 MHz frequency range. This Yagi antenna has a maximum power input of 200 W and includes a 19 in pigtail terminated with an N Female connector. U-bolts; maximum mast diameter is 2 1/8 and are supplied for mounting. It is an excellent...

www.arcantenna.com

System is now rock solid.
Not sure if it'll necessarily fix your issues, you may need to raise one or both of your antenna up higher to get over the stuff blocking your link.

​

 

[Ubbe]

Thanks, that would be great if I could get specific model recommendations. Amazon links appreciated

Problem is the search function here at RR. I cannot make it search for antenna+yagi+amazon and the result to show just the posts that have those exact three words and not just one of them.

It was a $50 yagi that worked well and there where even up to $200 ones that where useless.

/Ubbe

 

[AM909]

Problem is the search function here at RR. I cannot make it search for antenna+yagi+amazon and the result to show just the posts that have those exact three words and not just one of them.

How about Googling "antenna" AND "yagi" AND "amazon" site:forums.radioreference.com

https://www.google.com/search?q="antenna"+AND+"yagi"+AND+"amazon"+site%3Aforums.radioreference.com