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MR74 Mesh with Patch antennas - 1600ft?

Conversationalist

MR74 Mesh with Patch antennas - 1600ft?

Hello gurus - I have a location sitting on 5 acres that is completely open minus the main office building.  This location was setup months ago with a full Meraki deployment.  All is well however the management at this location has brought in some construction trailers at dropped them in the back section of the property.  The distance from the back of the main building and the closest trailer is 1600 ft with clear LOS.  I have a couple of MR74's and some spare patch antennas from another project that I would like to use but am unsure if I can achieve a mesh at this distance - specific to Meraki I have only ever run mesh at around 200ft.  This location is in the middle of nowhere with no neighboring wifi so I would assume a relatively low noise floor but was hoping someone could let me know if they think this is possible?  Thanks

4 REPLIES 4
Kind of a big deal

Re: MR74 Mesh with Patch antennas - 1600ft?

I think that is probably pushing the boundaries.  However, if you have the kit, I'd temporarily set it up and see if the performance is acceptable.

Head in the Cloud

Re: MR74 Mesh with Patch antennas - 1600ft?

Dining some quick calculations, you should get a connection, but it’s not going to be the fastest. Here’s my thoughts... (working purely on the 5GHz spectrum, I would expect 2.4GHz to perform better).

 

  1. Free space path loss over 1600ft will be about 100dB
  2. The patch antennas will give you 6.5dBi gain at each end (I actually think the data sheet has the antenna gain round the wrong way, possibly 8dBi for 5GHz, but let’s go with what it states)
  3. As you stated, assume a low noise floor, 90dBm, as there is little else around

On this basis I’d then look through the MR74 data sheet for a combination of TX power and RX sensitivity, plus the antenna gain, gives you the 100dB you require. Theoretically you should be able to achieve VHT40 MCS6 with 100dB loss (19dBm TX plus 13dBi antenna gain, and a receive sensitivity of -68dBm). Noice floor shouldn’t be an issue.

 

Now this is all just a quick theory calculation, and as @PhilipDAth stated, the only real way to check it is to set it up and see how it goes. But the theory says it should be okay (it may work even better if you can get your hands on some sector antennas).

 

Although it’s not a massive distance it’s also worth giving quick consideration to the Fresnel zone. This will be about 9ft radius over your distance. So to achieve the best possible outcome you really need the antennas mounted 9ft above the tallest obstruction in the line of sight, or if it’s completely clear then at least 9ft above ground level.

 

Hope this helps.

Getting noticed

Re: MR74 Mesh with Patch antennas - 1600ft?

Cisco has some Excelsheets for range calculation. It is based on Cisco APs and antennas but it might give you an estimate:

 

See this thread on the Cisco Community forums

https://community.cisco.com/t5/wireless/calculating-coverage-area-using-directional-antennae/m-p/274...

 

Conversationalist

Re: MR74 Mesh with Patch antennas - 1600ft?

This is likely the most informative reply I have received on any forum in a very long time.  Thanks a ton!

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