Hello all,

I am hoping someone here can offer some advice for a wireless link i am trying to accomplish. I have used quite of bit of Mikrotik hardware and have played with the wireless stuff (2 - 5 ghz) up to 1 km LOS. But what i am trying to accomplish it a bit out of my field of experience.

I am attempting to setup a wireless link from a DSL terminal point on the side of a hill to another location 4.7km away with no high speed internet available. The problem i am struggling with is this is a NLOS link. From what i have been reading 900mhz would be the way to go for this application, but i am struggling with picking radios and antennas. I am also starting to question if this will be possible at all. I appreciate any advice anyone can offer.

I have attached an elevation profile from Google Earth. And the high points between my two locations are hillside/rock.

Thanks

If your endpoints are at vy begining and end of your profile (e.g. the small 700m ASL hump at left side and the end of the picture at the righ pix side) - may be - with 20dBi or more yagis on 900MHz (XR9s) and 5MHz/10MHz channels ... and the highest obstruction is rock or sparse vegetation ... again, may be you can take advantage of something called knife effect. A 20dBi loop yagi can have 2.2m long boom.

On both sides the antennas will be tilted upwards a few degree. The signals hiting the obstacle at 1.75Km should bend down. But this is just the theory. I don´t know how to calculate the attenuation when this effect came up because the signals bent downwards - and - spread horizontally (I mean, if it was a 10º beamwidht after the obstruction it could means 30 ... 50º beamwidht, spreading the power).

And you have 2 obstructions ...

I took a risk when I built my NLOS links a couple of years ago: I plotted the terrain profile, simply brought the cards, a pair of 17dBi yagis and set up ROS for the narrower BW, default speeds, cross the fingers and went to the field. If I need to do the same today ... I use an AirView900E spectrum analyzer from ubnt and a 900MHz weak signal source from DownEast microwaves. With this setup (Us 50 spectrum analyzer and the weak signal source have 10dBm, a single frequency unit costs Us60) I can predict the signal attenuation and redo calculations to figure the chances.

Regards;

Oops, i apolgize i didnt clarify that. You are correct my two locations are at the very beginning and very end of that profile. This is shooting up a mountain valley so the 2 obstructions are hillside/mountainside (the valley has a slight "S" shape to it). I am going to research some Yagi antennas and i was already planning to use XR9's. Would a grid antenna make sense for this type of link over a yagi?

I am going to research some Yagi antennas and i was already planning to use XR9's. Would a grid antenna make sense for this type of link over a yagi?

Depends on ... a 20dBi loop yagi can have 220 inches long (5,5m)!!! A long yagi goes the same way ... 45 or more directors. An helical antena, to reach the same gain will have more or less the same lenght (at least more than 2.5m boom).

So to have gain ... or looooong yagis or 2/4 stacked. So to reach 20dBi will be necessary 4 x 14dBi yagis, or 2 x 17dBi.

I still thinking about improve my 900MHz beams as well. I use 17dBi yagis but they're cell phone ones, too much broad in frequency covereage to be true (870 ... 930MHz).

Those 2.4GHz grid refletors, where manufacturer claims 25dBi on 2.4 will have after feeder changes something like 16dBi on 900MHz.

Now: a 1.5 meter diameter TVRO dish on 915MHz, with the correct feeder will reach 21dBi.

I don't know where you are and if 900MHz antennas are easy to get there. But 17dBis ones are common here ... a pair ... a 2 way 900MHz splitter, stack them at the correct distance and there will be ~20dBi gain.

Regards;

hey drno.... any update on your link??

seems like no update till date on that link...

anyways I have a very interesting situation... got to get a 5 kms NLOS link in the city operational at 5 Ghz....

inputs in this regard will be very useful.

thanks,
-sid

Hi,
it depends if you can use some lower frequencies like 100-500MHZ.
In US they have new bands (TV Whitespace) available for connecting rural areas.

http://www.carlsonwireless.com/solution ... dband.html
or
http://www.ktswireless.com/products-and ... radio-awr/

I hope it helps.

If you can use legaly low frequencies 400MHZ-1000MHZ you can get mini pci cards from here:

https://www.xagyl.com/store_ca/home.php?cat=327
https://www.xagyl.com/download/XC420M_Datasheet.pdf

they will work with mikrotik because they are based an Atheros AR5414A chipset.

has anyone used Xagyl with Routerboard??

i think for 5.8 GHz link a Sextant should be quiet sufficient for 600 mtrs nLOS through medium forestation... am i right??