[CALV-MESH] Test Results

[Karl Long]

Last Saturday, 6/3, I went to Dunkirk Park. I set up two nodes (WRT54GS and GL) with batteries and tripods. Both nodes were set to minimum power 1dBm (1.3 milliwatts). I put one node on top of my car and walked away from it with my other node.

Signal strength is what is shown when you do a WiFi scan. I am not sure,
 but I believe it is dBm. Minimum receive is about -92 dBm.  

Percent 
connectivity is shown in "mesh status." Except where noted, all test 
cases showed 100%.  

I measured the distance using a stride that has consistently given me 
about two feet per stride.  All measurements given are based on this 
measurement.  When in doubt, I walked it off again.

Part One - both nodes have stock antennae (two each)s. 

Separation       Signal       Percent               Notes
Distance (ft)    Strength    Connectivity

14                     - 44
46                     - 44
68                     - 61                                         2
120                   - 69                                         
200                   - 71
300                   - 69                                         1, 3
510                   - 82            94 %
650                   - 80            90 %                     1

Discussion 

As expected, signal strength fell with distance, except in the two cases marked "Note 1." In both of these cases the line of sight (in particular, the first Fresnel zone) was significantly better than the previous location.

I was surprise to see that two nodes with minimum power and stock antennae still had 90 % connectivity at 650'.

I would like to have tested longer distances to see how far I could go with this configuration, and with high power (19 dBM = 79 mW).  Extrapolation suggests that high power, stock antennae would be usable to at least a mile.

Part Two - Stock antenna at the car, a custom antenna at the other end, both node at minimum power.  All tests conducted at 650'. Antenna dB compared to stock antennae estimated from these test results.

Antenna                             Signal Strength    dB              Notes

Stock antennae (two)         - 80                     0                 reference
10 element collinear          - 73                     1 - 7           2
Small Horn (can)                 - 73                    5 - 7
Large Horn (can)                 - 66                  14                 3

Part Three - Both nodes have custom antennae and low power at 650'.

Antenna                             Antenna           Signal Strength             Notes

Small Horn                         Large Horn       -61                                2
Collinear                            Large Horn       -65                                3

Discussion

Note 2 - Results in part two suggest that the collinear and small horn are both about 7dBref, while Part tree suggests that the small horn is 4dB better than the collinear. I found the collinear, while omnidirectional horizontally, was hard to peak vertically.

Note 3 - It is hard to tell because of the line of sight issues, but the Large Horn antenna at 650' seems to compare to somewhere between 100' and 250' with stock antennae only.  I would like to do those measurements again with better line of sight.