Using Ladder Line
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| Jul 27th 2011, 19:43 | |
WA0CBWTotal Topics: 0 Total Posts: 0 |
I have become a big fan of using ladder line to feed my double Zep antenna. The disadvantage is getting the ladder line into the shack and across the plumbing and duct work in the basement to the tuner. There have been articles in several ARRL publications about using two pieces of coax to transition from the ladder line outside to the tuner inside. This works great and I have had no problems but I do have a question. In one of the articles it described tying the coax braid together and both ends and connecting each end to the station ground. Another article shows only the tuner end coax braid connected together and grounded at the tuner end. My question is how should it be done and why? |
| Jul 28th 2011, 02:50 | |
N0NBTotal Topics: 0 Total Posts: 0 |
It seems to me that common mode current theory would argue for grounding only one end of the coax runs. The next question is, which end. It seems to me that assuming the ground lead to the shack runs along the same route as the coaxes, that the coaxes should be bonded to the ground system at the far end nearest to the ground system. Otherwise, if they are bonded at the tuner to the ground lead at the shack end the result is a long and parallel path for noise currents and an interesting impedance on the shields. |
| Jul 29th 2011, 22:16 | |
0006092697H80Total Topics: 0 Total Posts: 0 |
You definitely need to connect the shields together at each end, otherwise you are doing a completely different arrangement. The shields can be grounded at either, both or neither end in order to make the transition properly, but it is a good idea to ground at least one end if it is near your station ground. If you calculate the voltages on the line (based on the SWR and power level) and they are appropriate to usual coax lightning arrestors, and near your station ground, it is also a great spot do introduce lightning protection. |
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