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Vertical Antenna "Noisy"

Oct 13th 2013, 14:30

VE3QN

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
My Cushcraft R5 vertical which has been up for 15 years has just recently begun to exhibit a noise floor of S8 - S9. This is apparent with all other elements (e.g., tuner, lightning arrestor, etc) removed. The noise is not evident on either of my two other antennas nor did I hear it when I monitored 20m from my mobile. The noise is apparent on all three of my HF rigs. It is not coming from my home or my shack as I tried running my FT-857D on battery and pulled the main breaker - no change. Is there an explanation for this? There are only passive elements in the antenna and no DC is supplied to it. The antenna and transmission line appear to be physically intact.
Thanks in advance.
Bryan VE3QN
Oct 13th 2013, 23:51

W1VT

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0

It is likely that you are seeing fretting corrosion, which may cause very poor electrical contact of aluminum that seems bonded together properly. A corrosion inhibitor is often recommended when joining aluminum tubing to prevent this. While aluminum is a good conductor, aluminum oxide is not.

Zack Lau W1VT
ARRL Senior Lab Engineer
Oct 14th 2013, 13:43

VE3QN

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
Thanks so much, Zack. It's about time to change the antenna anyway. Not the best time of year for that up here, however.

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