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The Effect Of Insertion Loss On Transmitted Power (dB to % loss)
Original Information Provided by Neil McKie WA6KLA
HTML'd by Mike Morris WA6ILQ
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Note that insertion loss is cumulative - on the transmit side it starts at the transmitter output connector and includes everything in the path on the way to the base of the antenna.
Insertion loss also affects the receiver - it starts at the base of the antenna and includes everything in the path to the receiver connector. With a transmitter, if you want a higher signal level you just use a bigger amplifier. On the other hand, with a receiver, you can't amplify it back. Once the signal is lost any amplification brings up the noise level as well as any remaining signal. So making that extra effort to lower the loss in the antenna system really is worth it.

Loss dB % Loss
0.1 2.28
0.2 4.50
0.3 6.67
0.4 8.80
0.5 10.9
0.6 12.9
0.7 14.9
0.8 16.8
0.9 18.8
1.0 20.6
1.1 22.4
1.2 24.1
1.3 25.9
1.4 27.6
1.5 29.2
1.6 30.8
Loss dB % Loss
1.7 32.4
1.8 33.9
1.9 35.4
2.0 36.9
2.1 38.3
2.2 39.7
2.3 41.1
2.4 42.5
2.5 43.8
2.6 45.0
2.7 46.3
2.8 47.5
2.9 48.7
3.0 49.9
3.1 51.0
3.2 52.1
Loss dB % Loss
3.3 53.2
3.4 54.3
3.5 55.3
4.0 60.2
5.0 68.4
6.0 74.9
7.0 80.0
8.0 84.2
9.0 87.4
10.0 90.0
11.0 92.1
12.0 93.7
13.0 95.0
14.0 96.0
15.0 96.8
20.0 99.0


That's right - even 1db of total insertion loss is 1/5 of your power, 1.3db is 1/4 of it, and 1.75db is 1/3 of it!
Just 3 db is half of your power. And in a duplex environment (i.e. single antenna) the same 3db will cost you half of your receive signal.

So watch those nickel-plated connectors and adapters at anything above 100 MHz.

Original web page created and HTML copyright © Michael R. Morris WA6ILQ 2002
Last modified September 2006

This web page, this web site, the information presented in and on its pages and in these modifications and conversions is © Copyrighted 1995 and (date of last update) by Kevin Custer W3KKC and multiple originating authors.   All Rights Reserved, including that of paper and web publication elsewhere.