| Those virturally undetectable wires will need to be located. If you don't locate your detector between sets of wires, or accidentially locate it directly in front of the thin wires, you will reduce performance.
On a side note, most detectors these days are so damn sensitive, you won't notice.
For those on long, straight, flat hwys that are obsessed with maximum performance, and metal wires, films, tints or additives will decrease sensitivity.
I read up on this back when photo radar came to Ontario, Canada. Thankfully, it's gone now. | 
