Jan 272014
 

How not to do it:  The images below with the airconditioner in front of the RocketDish and the RocketDish in the middle of the roof, rather than at the edge, are how not to setup your RocketDish!  The RocketDish MUST be at the edge of the roof so that there is clear air under it for 10FT to 20FT.

Solution:

  1. Replace the 30dBi RocketDishes with the 34 dBi RocketDishes (3FT in diameter).  This will do two things: Get us 4 more dB, and make the beam narrower.
  2. Fresnel zone:  7 mile links need at least 50’ of clear air in the middle of the link.  We need to check the height of the towers at each end and if there are any buildings sticking up into the Fresnel zone?
  3. Enable DFS Channels on that link? If not, replace the radios with US RocketM5‘s and enable DFS and use 5500-5700…
  4. But, You could switch it to 5840 RIGHT NOW and get more power. You have it on 5240 which is in the low band and restricted to 100mw.  If you move it to 5840 (available on US), you can get 1,000mw…
  5. We changed the encryption to from WEP to WPA2-AES because WEP hogs the CPU:  We got an IMMEDIATE gain of 60Mbps (went from 180 to 240 immediately)

FOOTNOTES

1.   MCS is modulation and coding scheme.  The target receive signal level to achieve a  MCS 15 data rate of 144 Mbps is:   -64 to -69 dBm.   This level should also provide a 20 dBm SNR in very noisy areas.

2.   This link passes through a city of about 400,000 people – but the path of the signal is not very densely populated:  However, there is a federal border patrol facility where at least 100  agents are stationed, right in the path, and we speculate that they are using much or most of the 5GHz spectrum.

3.  Ubiquiti gear on each side of the link:  RocketM5 with RocketDish 30dB parabolic antenna

4.  F-64 dbm signal strength is the most optimum in any link.

5.  When the RocketDish was setup in middle of the roof, with an airconditioner too close to is and thus partially blocking the signal:  We were troubleshooting of low data-rate issue with this link:

Analysis of the link: 

The Tx/Rx are only 180/180… Should be 250-300 each. Signal -62 is not a strong enough signal for MCS 15 [see footnote 1]. So, this link needs the larger 34 dBi RocketDishes, rather than the 30dBi RocketDishes which we are using.   7 miles isn’t that far, unless the link passes through a congested area, as this one does (see footnote 2).   In a rural or suburban area, we get 240mbps-270mbps over 10 miles with the 34dBi rocket dishes.   LMK:

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