Tech Talk
Divider

       
Divider


VSWR AND TRANSMISSION LOSS

VSWR Return Loss (dB) Reflected Power (%) Transm. Loss (dB)           VSWR Return Loss (dB) Reflected Power (%) Transm. Loss (dB)
1 oo 0 0 1.38 15.9 2.55 0.112
1.01 46.1 0.005 0.0002 1.39 15.7 2.67 0.118
1.02 40.1 0.01 0.0005 1.4 15.55 2.78 0.122
1.03 36.6 0.022 0.0011 1.41 15.38 2.9 0.126
1.04 34.1 0.04 0.0018 1.42 15.2 3.03 0.132
1.05 32.3 0.06 0.0028 1.43 15.03 3.14 0.137
1.06 30.7 0.082 0.0039 1.44 14.88 3.28 0.142
1.07 29.4 0.116 0.0051 1.45 14.7 3.38 0.147
1.08 28.3 0.144 0.0066 1.46 14.6 3.5 0.152
1.09 27.3 0.184 0.0083 1.47 14.45 3.62 0.157
1.1 26.4 0.228 0.01 1.48 14.3 3.74 0.164
1.11 25.6 0.276 0.0118 1.49 14.16 3.87 0.172
1.12 24.9 0.324 0.0139 1.5 14 4 0.18
1.13 24.3 0.375 0.016 1.55 13.3 4.8 0.21
1.14 23.7 0.426 0.0185 1.6 12.6 5.5 0.24
1.15 23.1 0.488 0.0205 1.65 12.2 6.2 0.27
1.16 22.6 0.55 0.0235 1.7 11.7 6.8 0.31
1.17 22.1 0.615 0.026 1.75 11.3 7.4 0.34
1.18 21.6 0.682 0.0285 1.8 10.9 8.2 0.37
1.19 21.2 0.75 0.0318 1.85 10.5 8.9 0.4

VSWR Return Loss (dB) Reflected Power (%) Transm. Loss (dB)           VSWR Return Loss (dB) Reflected Power (%) Transm. Loss (dB)

1.2 20.8 0.816 0.0353 1.9 10.2 9.6 0.44
1.21 20.4 0.9 0.0391 1.95 9.8 10.2 0.47
1.22 20.1 0.98 0.0426 2 9.5 11 0.5
1.23 19.7 1.08 0.0455 2.1 9 12.4 0.57
1.24 19.4 1.15 0.049 2.2 8.6 13.8 0.65
1.25 19.1 1.23 0.053 2.3 8.2 15.3 0.73
1.26 18.8 1.34 0.056 2.4 7.7 16.6 0.8
1.27 18.5 1.43 0.06 2.5 7.3 18 0.88
1.28 18.2 1.52 0.064 2.6 7 19.5 0.95
1.29 17.9 1.62 0.068 2.7 6.7 20.8 1.03
1.3 17.68 1.71 0.073 2.8 6.5 22.3 1.1
1.31 17.4 1.81 0.078 2.9 6.2 23.7 1.17
1.32 17.2 1.91 0.083 3 6 24.9 1.25
1.33 17 2.02 0.087 3.5 5.1 31 1.61
1.34 16.8 2.13 0.092 4 4.4 36 1.93
1.35 16.53 2.23 0.096 4.5 3.9 40.6 2.27
1.36 16.3 2.33 0.101 5 3.5 44.4 2.56
1.37 16.1 2.44 0.106 6 2.9 50.8 3.08

ABOUT VSWR AND TRANSMISSION LOSS


When setting up an antenna, you may think that VSWR match is more critical than it really is.  See the chart above to find out how much power is actually lost due to slight mismatches and how much power is reflected back into the amplifier where it is lost by heat.  It is arguable that a VSWR of 1.38 and better is more than adequate for transmission powers of up to 500 watts.  This means that at the most you will be getting 2.5% of 500 watts reflected, which is 12.5 watts.  12.5 watts is really not that much in relation to a high-power amplifier, and 12.5 watts lost from power sent over the air will mean nothing to additional distance coverage.  Use caution however, since some transmitters do not like this much reflected power and instability results, causing spurious signals and other problems.  See your transmitter documentation for more information on antenna matching.

Note however that most people strive for better than 1.38 simply due to the fact that they cannot stand the thought of losing even a small percentage of power due to heat rather than transmission.  On very low power transmissions like micro-power broadcasting, the additional 2.5% of energy not wasted may bring someone who was in the fringe area into a more acceptable clean transmission range.




Divider

     
Divider


>>>> send your questions to <<<<

info@technolab-inc.com

© Unauthorized duplication of any styles, images or fotos prohibited by TECHNO LAB INC.