Nat, et. al.:
Last year I gave a talk on this topic and created some graphs that are not
in the ARRL material but are derived from the formulas in that material. The
graphs show additional loss in dB as a function of SWR and show the power
loss between the transmitter and the antenna for 1500 watts and 100 watts
output. The losses are shown for SWR of 1:1, 2:1 and 3:1.
The graphs are available in PDF format for download at the following URL:
ftp://ftp.skypoint.com/pub/members/t/tao/papers/SWR_Graphs.pdf
Comments are always welcome.
Tod, KØTO
-----Original Message-----
From: owner-towertalk@contesting.com
[mailto:owner-towertalk@contesting.com]On Behalf Of Nat Heatwole
Sent: Friday, May 25, 2001 6:03 PM
To: towertalk@contesting.com
Subject: Re: [TowerTalk] dB Loss Equivilents for SWR Values
Whoa. Thanks for all of the fast responses. The most popular suggestion
appeared to be looking in the ARRL Handbook. I checked out the handbook and
with some consideration I figured out the following formula to get
equivalent coax db loses from an SWR value:
((SWR - 1) / (SWR + 1)) ^ 2 * 100% = % Lost
10log(100/(100 - % Lost)) = Loss In dB
So if your SWR's 3.0/1:
((3 - 1) / (3 + 1)) ^ 2 * 100% = 25% Lost
10log(100/(100 - 25)) = 1.25db Loss
Thanks for all the information!
73, Nat, WZ3AR
<heatwole@clark.net>
Damascus, Maryland
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