|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.