|Large plate capacitor|
Over the past few weeks I have been very busy with work and not really anytime for radio or anything else really. I was on the radio for a very short time last week and the weather outside was very humid and HOT! The antenna I have is the MFJ 1788 loop and I have always been able to get a decent SWR on most bands the antenna was designed for. But for some reason I was not able to get an SWR under 2.1:1 on some bands the best I could do was 3.1:1. It turns out that the Humidity can affect the MFJ 1788 antenna and my guess is since the antenna has a large moving plate capacitor the humid air affects the air gap between the plates? The other day the weather was back to cooler non humid conditions and I tried the antenna again and the great SWR was back again. The antenna had not moved and nothing had changed other than the weather.