Electronic spider repellers seem to come in two forms:
- ultrasonic which presumably emit some air pressure waves which are either at a fixed or variable frequency
- electromagnetic which presumably superimpose a signal on the mains wiring
Right so far?
The surprising thing is that reviews of them seem to vary enormously. For a given unit (which may combine both of the above functions) on Amazon UK some people say it is wonderful while others say it doesn't work at all!
Anyone any ideas as to why the reviews differ so much? For example: Do none of them work and any benefits are just coincidence or people's imagination? Are some units faulty but with no way to tell whether they are working or not? Do spiders differ? Do some people just not wait long enough? Does plugging in a second electromagnetic unit diminish the effect of a single one?
Any other causes of such widely differing opinions?
James