A question regarding electronic noise while recording near a communi

["uskroeger" uskroeger]

Hello,
I've uploaded a sample of a California Thrasher
(CalThrasher+Electronic...mp3) singing early in the morning on a still
day, but within 100 yards of a mountaintop communication array.
Microwave, cell phone, something like that.
I discovered that when listening to the recording on my computer that
there was a background electronic echo that wasn't noticable at the
time of recording.  Might there be a simple way to shield the
equipment so as not to pick up this noise?  The site is fairly remote
and has species that are not easy to find in other areas.
I use a Marantz PMD-671, Telinga Twin Science with dish.

Also, is there a trick to keep narcissistic insects from hovering
right in front of the dish and filling everything with their buzzzzzz?

Thank you.

Barney Kroeger
Nevada City, California