I'm looking at using a 1/4 wave whip antenna for a transmitter. If possible I'd like to cover the antenna in very thin (0.02 mm) aluminised kapton for reasons unrelated to the radio system; to be clear the Kapton will not be directly touching the antenna, it will be about 3 cm away. I have a feeling that although this material is very thin there is a significant possibility that I will end up with a very different radiation pattern than a typical 1/4 wave omnidirectional antenna if I surround the antenna in Kapton. I'm just not sure how to go about investigating this? I'd like to be able to predict the effect (either reduction in received signal - putting some extra factor in my link budget - or change in radiation pattern) but I have no idea where to start with this.
What is the governing principal in this scenario?