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## Re: [Amps] Ten-Tec Titan 10 Meter Input SWR

 To: donroden@hiwaay.net, amps@contesting.com Re: [Amps] Ten-Tec Titan 10 Meter Input SWR Gerald Williamson via Amps TexasRF@aol.com Sun, 11 Jun 2017 17:12:42 -0400
 ```Don, all you say is correct and good. BUT (seems there always is a but), as a practical matter, the input R+j of an amplifier varies with drive level and usual test equipment will not provide useful data. If you drive it with a transmitter there is no way to extract R+j data at that power level. Without good R+j data the smith chart is unusable for this problem. 73, Gerald K5GW In a message dated 6/11/2017 1:13:19 P.M. Central Daylight Time, donroden@hiwaay.net writes: "True SWR" doesn't change, but *WHERE* it is measured will vary widely. exception : perfect Z load for perfect Z line where Zload=Zcoax You are measuring VOLTAGE inside the coaxial line and the voltage varies along the length of the line like a sine wave. Some distances from the wrong Z load = peak voltage Some distances from the wrong Z load = minimum voltage Some distances make for a close-to-perfect input match. 1/4 wave away from the above perfect match is a point that your transmitter probably won't like. In other words, changing the coaxial length *COULD* improve your situation, but it could also make it worse. The Smith Chart is your friend, or just make five jumpers of 1,2,4,8,16 feet with a handful of couplers and start substituting jumpers between the meter and the load. One combination will *MATCH* or make a length that the transmitter likes. Others will make it worse. This is why it's important to measure the Z *AT* the load and not through an arbitrary length of coax. Don W4DNR >> ## On a related note, why is it, when I increase the length of 50 >> ohm coax from my drake amps to the xcvr, that the >> input swr rises ?? Its flat with 4 ft or less.... but rises >> when say 5-8 ft is used. Thats on all bands. > > on the outside of the coax braid. The true SWR does not change. _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinfo/amps ```
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