[TowerTalk] M2 20M5 SWR measurements

[Tony Brock-Fisher]

Jorge-

Assuming your 8.35 foot jumper is lossless, it should not affect the SWR on the line. The addition of transmission line changes the complex impedance, but not the SWR. A perfect SWR meter would not show any difference with the addition of a length of lossless transmission line. A vector impedance meter of course would see a difference. For example, as transmission line is added, a Smith chart would show the different points along the line as a circle, having different real and complex impedances, but having a consistent SWR.

So what you are seeing is changes in the reported SWR with the two meters you have due to impedance changes. This can be for one of two (or more) reasons:

1. There is RF on the outside of the coax. Try adding several beads on the coax and see if this makes things calm down, and gets identical readings with and without the jumper. Many SWR meters can be affected by RF on the outside of the line.

2. The meters are sensitive to the load impedance, and are not 'perfect' or 'ideal' SWR meters. Perhaps try a Bird meter.

All of this is not really saying anything about the antenna itself. But you have to satisfy yourself that you are accurately measuring SWR before you can worry about what is happening at the antenna.

73,

-Tony, K1KP