Need help on basic 1.5km point to point link.

[pete27]

Hi,

I would like to set up a link between by house and office (point to point) but am having difficulty figuring out what I need to make this work. Sorry, but I'm rather new at all of this. Hopefully someone can help me out. Here is my situation.

Environment – Middle of a small city (25k pop).
Range – 1.5 km (0.9 miles)
Terrain – flat (less than 2m (6ft) change in elevation from site to site)
Not line of site. Trees and a few 2-3 story buildings (college campus) are between the two sites.
Desired throughput – ideally 10Mbps, but even 2Mbps would be acceptable.

Both sites are two story buildings and antennas can be mounted about 7m (20ft) high. The electronics can be mounted indoors at both sites, but outdoor mounting might be easier to install. The outdoor climate is extreme (-25F to 100F). Depending on what size antenna I need, they could be either mounted inside in a window or outdoors. Antenna cable runs can be kept to less than 2m (6ft).

Because this is a non-line of site situation, I am assuming 900Mhz is the way to go. Do you agree? If so should I be looking at the XR9 or the SR9? Based on the specs the XR9 seems to be the better board. However previous posts seem to indicate some disagreement about this.

Also what type of antenna should I use? Ideally I would like to use something smaller like a patch antenna at the office site (I don't own the building) but if necessary I could probably convince my landlord to let me install a larger yagi or parabolic. At my house I can use anything.

BTW, I did attempt to use the Radio Mobile program and generated a radio link profile. All I can say is that it verified that the ground is as flat a I suspected. Other than that I don't really know what most of the other numbers mean. If this is helpful, here are the coordinates:

Site 1

44d03'13 N
91d38'09 W

Site 2

44d02'36 N
91d38'48 W

Hopefully all of this is possible. Thanks for your help.

Pete

[UBNT-Mike.Ford]

Hello Pete,

Its hard to judge if this link will work.

In terms of Hardware I would choose XR9 with some grid type antennas for a point to point link.

The one problem i see with the link, is that bieng in an urban enviroment you can run into tremendous amounts of 900Mhz interference that will bring the link to its knees.

The things here is that I cannot guarantee that it will work. It needs to be tested for your specific application.

Thank you,

[WHT]

900 MHz is too iffy in an urban environment. You're problems in going to be the two story buildings in the way, so 5.8 Gig with a smaller Fresnel zone might be an idea...but even then, you'll need at least 15 meter masts at both ends.

BTW, Nanostation5 radios with their internal antennas would give you a 33 dB fade margin with a 12 Mbps internet speed test check.

Re-run RM with 15m masts at both ends and you'll see your clearance is 11 meters, which would clear the 8 meter buildings by 3 meters (your necessary Fresnel zone). Those are just rough numbers to get an idea.

[pete27]

Hi all,

Thanks for the quick response. If I am understanding this correctly, it sounds like the problem isn't so much a matter of whether I would be able to transmit a 900mhz signal between these two points, its that even if I could I will probably pick up so much junk along the way that the signal would be worthless. Is that correct?

Therefore a better option would be to place 15 meter masts at both ends to create a line of sight and use 5.8 gig radios. Unfortunately this may not be an option for two reasons. The first is I doubt I can convince my office landlord to let me install one. The second is that it would probably drive the cost above what is feasible. However before I make that assumption, can anyone give me a ballpark cost of a 15m mast?

There might be a third option. Next door to my office building is a six story apartment building. On the fifth floor of this building I have a relative living in one of the apartments and his windows face in the direction of my house.

I would have to send a signal from my office window through about 10m of concrete apartment building to his windows located about 50m away. Then I could rely the signal to my house. It sounds like a 5.8 Gig radio would be best to send to my house. What would be best to send a signal from my office to the apartment?

Regarding the Nanostation5 radios, these look quite interesting. This might work well in the apartment. However at my house this would have to be installed outside on the mast and I'm a bit concerned about whether it would survive a Minnesota winter. I see they are only rated to -20C (0F) and temps here can go well below that. Would a Powerstation 5 be a better choice in this case?

Thanks again,

Pete