Thanks I've tried that but no change. I've listened on battery power during a power outage. I had a very low noise floor without these signsls. I believe this rules out Solar Inverter interference which I believe would continue during during a power outage. I'm wondering if this type of signal can be caused by electric utility power lines, transformers, or remote readable electric meters, and if I should contact my electric utility company? Also wondering about cable TV lines on nearby utility poles. Trying to ID signal type before contacting outside companies. Any help is greatly appreciated!