Cantenna Testing

I was member of Melbourne Wireless for some time while I lived in Abbotsford (node CIA).

During this time I tested the beam pattern of a Harris Coffee Tin used as a circular waveguide. The polar plot below summarises the results. Essentially, the device under test, a harris coffee can of internal diameter 98mm, with a tuned 1/4 (28mm of copper instead of 31mm) wave stub was placed on a post and rotated in an anechoic chamber. From about 8m away, a series of measurements of received signal power were taken by a spectrum analyser. A signal generator was used to launch a constant 10dBm at 2.462 GHz (choice of frequency is a long story, I’ve now forgotten) through a source at the device under test. The directivity or gain of this cantenna is found to be between 6 and 7dBi. I did intend at that time to make modifications and perform further testing to determine the improvement gained by adding an extra length of can to make it 5/4 guide wavelengths long; a choke; a spreader. It’s been some years since I’ve had access to the equipment and the chamber though, in fact I think with the movement of Telstra’s research laboratory team into the CBD, it is likely the facility no longer exists.

Network Architecture

I also did some thinking at that time about feasible ways to construct a network architecture to provide some degree of mesh routing for the wireless community of Melbourne. There are slides to document the design thoughts (also in PPT format.)

Test Result Overview

Gain approximately 6.5dB in a quite symmetric lobe.

At 2.462 GHz
At 2.462 GHz

 

Detailed Test Results

Recorded by: Roger Venning
Date: ########
Frequency: 2.462GHz
Device under test: Cantenna no. 1
Equipment: Signal generator: 10dBm output power. <src?>.  Measurements with Spectrum analyser.
Seems that you would expect to receive -44dBm from an isotropic radiator with this setup.
Azimuth Magnitude – dBm (Azimuth) Magnitude (mW) Normalised gain (azimuth) Elevation Magnitude – dBm (Elevation) Magnitude (mW) Normalised gain (elevation) mean (mW) Average normalised gain
0 -37.15 1.90E-04 7.1 0 -37.8 1.70E-04 6.4 1.80E-04 6.8
5 -37.22 1.90E-04 7 5 -37.71 1.70E-04 6.5 1.80E-04 6.8
10 -37.45 1.80E-04 6.8 10 -37.8 1.70E-04 6.4 1.70E-04 6.6
15 -37.83 1.60E-04 6.4 15 -38.01 1.60E-04 6.2 1.60E-04 6.3
20 -38.31 1.50E-04 5.9 20 -38.38 1.50E-04 5.9 1.50E-04 5.9
25 -38.92 1.30E-04 5.3 25 -38.9 1.30E-04 5.3 1.30E-04 5.3
30 -39.6 1.10E-04 4.6 30 -39.53 1.10E-04 4.7 1.10E-04 4.7
35 -40.34 9.20E-05 3.9 35 -40.34 9.20E-05 3.9 9.20E-05 3.9 3dB
40 -41.27 7.50E-05 3 40 -41.3 7.40E-05 2.9 7.40E-05 3
45 -42.31 5.90E-05 1.9 45 -42.36 5.80E-05 1.9 5.80E-05 1.9
50 -43.29 4.70E-05 1 50 -43.45 4.50E-05 0.8 4.60E-05 0.9
55 -44.44 3.60E-05 -0.2 55 -44.42 3.60E-05 -0.2 3.60E-05 -0.2
60 -45.82 2.60E-05 -1.6 60 -45.29 3.00E-05 -1 2.80E-05 -1.3
65 -47.37 1.80E-05 -3.1 65 -46 2.50E-05 -1.8 2.20E-05 -2.4
70 -48.65 1.40E-05 -4.4 70 -46.61 2.20E-05 -2.4 1.80E-05 -3.3
75 -49.84 1.00E-05 -5.6 75 -47.65 1.70E-05 -3.4 1.40E-05 -4.4
80 -51.13 7.70E-06 -6.9 80 -49.17 1.20E-05 -4.9 9.90E-06 -5.8
85 -52.62 5.50E-06 -8.4 85 -50.17 9.60E-06 -5.9 7.50E-06 -7
90 -53.99 4.00E-06 -9.7 90 -50.24 9.50E-06 -6 6.70E-06 -7.5
95 -55.28 3.00E-06 -11 95 -50.74 8.40E-06 -6.5 5.70E-06 -8.2
100 -56.4 2.30E-06 -12.2 100 -52.86 5.20E-06 -8.6 3.70E-06 -10
105 -57.5 1.80E-06 -13.3 105 -55.45 2.90E-06 -11.2 2.30E-06 -12.1
110 -58.61 1.40E-06 -14.4 110 -55.09 3.10E-06 -10.8 2.20E-06 -12.3
115 -59.19 1.20E-06 -14.9 115 -54.34 3.70E-06 -10.1 2.40E-06 -11.9
120 -59.52 1.10E-06 -15.3 120 -55.59 2.80E-06 -11.3 1.90E-06 -12.9
125 -59.66 1.10E-06 -15.4 125 -57.6 1.70E-06 -13.4 1.40E-06 -14.3
130 -59.54 1.10E-06 -15.3 130 -56.72 2.10E-06 -12.5 1.60E-06 -13.7
135 -59.59 1.10E-06 -15.3 135 -54.76 3.30E-06 -10.5 2.20E-06 -12.3
140 -60.12 9.70E-07 -15.9 140 -54.2 3.80E-06 -10 2.40E-06 -12
145 -61.1 7.80E-07 -16.9 145 -55.68 2.70E-06 -11.4 1.70E-06 -13.4
150 -62.31 5.90E-07 -18.1 150 -59.96 1.00E-06 -15.7 8.00E-07 -16.7
155 -63.3 4.70E-07 -19.1 155 -64.9 3.20E-07 -20.7 4.00E-07 -19.8
160 -62.13 6.10E-07 -17.9 160 -67 2.00E-07 -22.8 4.10E-07 -19.7
165 -59.57 1.10E-06 -15.3 165 -61 7.90E-07 -16.8 9.50E-07 -16
170 -57.36 1.80E-06 -13.1 170 -58.34 1.50E-06 -14.1 1.70E-06 -13.6
175 -56.12 2.40E-06 -11.9 175 -57.05 2.00E-06 -12.8 2.20E-06 -12.3
180 -55.8 2.60E-06 -11.6 180 -57.16 1.90E-06 -12.9 2.30E-06 -12.2
185 -56.14 2.40E-06 -11.9 185 -59.29 1.20E-06 -15 1.80E-06 -13.2
190 -56.95 2.00E-06 -12.7 190 -62.36 5.80E-07 -18.1 1.30E-06 -14.6
195 -58.25 1.50E-06 -14 195 -60.24 9.50E-07 -16 1.20E-06 -14.9
200 -60.25 9.40E-07 -16 200 -55.6 2.80E-06 -11.4 1.80E-06 -13.1
205 -62.6 5.50E-07 -18.4 205 -52.79 5.30E-06 -8.5 2.90E-06 -11.1
210 -64.04 3.90E-07 -19.8 210 -51.45 7.20E-06 -7.2 3.80E-06 -10
215 -63.42 4.50E-07 -19.2 215 -51.29 7.40E-06 -7 3.90E-06 -9.8
220 -61.7 6.80E-07 -17.5 220 -51.86 6.50E-06 -7.6 3.60E-06 -10.2
225 -60.49 8.90E-07 -16.2 225 -52.69 5.40E-06 -8.4 3.10E-06 -10.8
230 -59.7 1.10E-06 -15.5 230 -53.5 4.50E-06 -9.3 2.80E-06 -11.3
235 -58.9 1.30E-06 -14.7 235 -53.5 4.50E-06 -9.3 2.90E-06 -11.2
240 -58.6 1.40E-06 -14.4 240 -53.59 4.40E-06 -9.3 2.90E-06 -11.2
245 -58.8 1.30E-06 -14.6 245 -55.35 2.90E-06 -11.1 2.10E-06 -12.5
250 -58.58 1.40E-06 -14.3 250 -57.05 2.00E-06 -12.8 1.70E-06 -13.5
255 -57.6 1.70E-06 -13.4 255 -54.53 3.50E-06 -10.3 2.60E-06 -11.6
260 -56.33 2.30E-06 -12.1 260 -52.44 5.70E-06 -8.2 4.00E-06 -9.7
265 -55.61 2.70E-06 -11.4 265 -51.86 6.50E-06 -7.6 4.60E-06 -9.1
270 -55.15 3.10E-06 -10.9 270 -51.93 6.40E-06 -7.7 4.70E-06 -9
275 -53.73 4.20E-06 -9.5 275 -51.77 6.70E-06 -7.5 5.40E-06 -8.4
280 -51.84 6.50E-06 -7.6 280 -51.29 7.40E-06 -7 7.00E-06 -7.3
285 -50.15 9.70E-06 -5.9 285 -50.67 8.60E-06 -6.4 9.10E-06 -6.2
290 -48.68 1.40E-05 -4.4 290 -50.03 9.90E-06 -5.8 1.20E-05 -5.1
295 -47.3 1.90E-05 -3.1 295 -48.82 1.30E-05 -4.6 1.60E-05 -3.8
300 -46.12 2.40E-05 -1.9 300 -47.37 1.80E-05 -3.1 2.10E-05 -2.5
305 -45.2 3.00E-05 -1 305 -45.98 2.50E-05 -1.7 2.80E-05 -1.3
310 -44.18 3.80E-05 0.1 310 -44.89 3.20E-05 -0.6 3.50E-05 -0.3
315 -42.98 5.00E-05 1.3 315 -43.93 4.00E-05 0.3 4.50E-05 0.8
320 -41.73 6.70E-05 2.5 320 -42.98 5.00E-05 1.3 5.90E-05 1.9
325 -40.64 8.60E-05 3.6 325 -41.99 6.30E-05 2.3 7.50E-05 3
330 -39.77 1.10E-04 4.5 330 -41.08 7.80E-05 3.2 9.20E-05 3.9 3dB
335 -39 1.30E-04 5.2 335 -40.17 9.60E-05 4.1 1.10E-04 4.7
340 -38.36 1.50E-04 5.9 340 -39.39 1.20E-04 4.9 1.30E-04 5.4
345 -37.85 1.60E-04 6.4 345 -38.79 1.30E-04 5.5 1.50E-04 5.9
350 -37.48 1.80E-04 6.8 350 -38.31 1.50E-04 5.9 1.60E-04 6.4
355 -37.22 1.90E-04 7 355 -38.01 1.60E-04 6.2 1.70E-04 6.6
3.80E-05

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