I have a Sporty's SP-200 Nav-Com handheld using AA batteries witha Av-Comm 400 series headset and I am getting static noise from the engine as it increases with an increase in throttle. I have only taxied around @ 12-1500 rpm and had to turn it off it was so annoying. I aslo do not have an electrical system on the plane. Which is the culprit, the headset or the radio ? And what can be done to eliminate the noise.