Electronic spider repellers - such differing opinions

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
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"James Harris" wrote in message

Had a daughter who was terrified of spiders. Got one of those things for her bedroom and although I never saw any evidence what so ever that it did anything, peace was restored, so I suppose it worked.
Andrew
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On Thursday, 5 June 2014 12:32:19 UTC+1, James Harris wrote:

Well there are around 650 specaies of spider in the UK alone. I doubt they all react the same, as they don;t lok act or live in simialr places or ways.

It could be even placebos 'work'

Just like any other appliences.

Oh yes but they all have 8 legs.

I've heard that with the mice & rat electronic repelant that they get used to them after a few weeks so they do work but the critters get used to the sounds like humans would if they have titntitus.

And doe sit matter where you plug in in.....upstairs, downstairs, dolton abbey, near a door or window ?

Location of house, type of house, south, north facing, time of year, (I heard october is the worst for spider infestation as they come in during long persiods of damp weather), lighting, heating, humidity, in the room.
all intersting questions, it might be worth asking on an Arachnology group I'd rely more on them than a store or manufacturer pushing a product or a reviewer.
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James Harris wrote:

I've got an electronic elephant repeller. Works wonderfully.
(All depends on point of view, dunnit!)
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Scott

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Scott M wrote:

So you're not troubled by electronic elephants? That must be a relief.
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i've got a mate in africa who would like to buy it off you :)
i'd be really weary of these 'electronic' repellers, they started with rat repellers decades ago, and now thye seem able to repel every kind of 'pest' foxes, cats, squirrels, dogs, teenagers and now spiders,
i posted this years ago here, but maybe i can milk it again :)
A friend had seen a rat in his garden, worried it was going to chew through the bricks to get into his house, then chew on his throat whilst he slept (or some similar bollox made up to make them look bad) he went and bought one of those 'ultrasonic rat repellers'
he put it in the garden and was convinced it worked as he didn't see anymore rats,
i doubted how it could work as rats communicate in the ultrasonic range, so it's not exactly a sound they woudlnt have heard before (unless the makers have it saying 'go away mr rat, your not welcome here' in ultrasonic or something)
At the time i kept fancy rats, so i brought one round to his house and put him down on the lawn infront of the 'rat repeller' My pet rat wandered around a little to get his bearings, then casually walked over to the repeller unit and gave it a good sniffing and investigation, then lost interest and started rooting around for bugs in the grass to eat.
My friend took the unit back to the shop the next day to complain, and was tol that 'pet rats have different hearing to wild rats' and the stupid twonk believed him, so it was re-installed in the middle of his lawn magically working to keep only wild rats away, but let any nice friendly pet rats play infront of it as if it didnt work :)
BTW, spiders apparently hate conkers, so a possible much cheaper way to keep spiders away from those shit scared of the things,
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Gazz wrote:

We once got a whole bunch of them to put earths on to make them legal in Australia, so I got some mice and cockroaches and put them in an enclosure with the repeller and none of them acted any differently on or off.
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On Thursday, 5 June 2014 14:27:15 UTC+1, Scott M wrote:

That's an expensive option.
My father always kept a nutmeg in his pocket to keep the elephants away. When we kids pointed out that there were no elephants in South Wales he claimed that was proof of the nutmeg's efficacy.
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I have never heard so much rubbish in my life. You want to encourage spiders, they are good for the house and generally keep flies down.
I can remember building a circuit many years ago which claimed no only to deter spiders, but cats and squirrels as well, now I never tried it on Squirrels, but my neighbours cat picked it up and took it outside, so maybe he thought it was a mouse. No it did nothing to spiders that I could see. It was ultrasonic pulsed I do not understand the electromagnetic ones, I just hope they do not transmit crud so radios don't work though. Brian
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On Thu, 5 Jun 2014 16:19:46 +0100, Gazz wrote:

Not at all surprised. Before we realised that deporting mice 100 m down the paddock wasn't far enough or the cat adopted us we had a couple of mice/rat ultrasonic dubries. Doubt they had much effect, the mice still came in in the autumn. The could hear it though, mouse in cage, switch on device, mouse visibly jumps but doesn't seem otherwise bothered nor when the device was switched off. Repeat a few times and each jump becomes smaller and smaller.
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On 06/06/2014 00:40, Dave Liquorice wrote:

I once tried a ultrasonic cat repel device. Same result, first time cat was frightened, but not enough to run away. Within the week it took no notice of it. It was still working because the pulse on ramp up/off ramp down was just in the human audible range.
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That's the placebo effect.
I did once decide that there might be some value in the high voltage dust reducers, because you do get a significant dust build up on the old glass TV screens, but when I tried one, it didn’t do a damned thing.

Yep, the placebo effect.

Nope.

Corse they do, but you don’t see anyone reporting a consistent result with a particular type of spider either.

Nope, it makes no difference how long you wait, none of them work.

Nope.

There are lots of fools around, that’s why snake oil salesmen are so effective and why there are fools that are still into homeopathy and changing what they eat when they are diagnosed with cancer and start sticking needles into themselves etc. And why even more stupid people pay huge amount of money for ground rhino horn etc.
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On 06/06/2014 07:58, Rod Speed wrote:

Is it broken? I have one and you have to clean the dust off the collector plates every week.

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Well seeing as the 'high voltage dust reducers' use an electrostatic type charge to attract the dust, it works in a similar way to turning a CRT tv off,
only the static created by the tv is a lot more powerfull than the dust reducer and has a larger area.
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Nope, it collects dust fine, but doesn’t have any effect on my hay fever etc.

Sure, but I got no result in the weeks I did that except wasting my time like that.
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On 05/06/2014 12:32, James Harris wrote:

Spiders tend to move indoors during the autumn. I have found an old remedy that is to distribute conkers (horse chestnuts) about the area of the house you want to clear. An old country remedy but it works for me.
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Bert Coules wrote:

Reffffeeerrrreeeeeeee!!!! That was below the belt that was, picking on my grammaticals like that for a cheap joke! I dunno! As a penance, go and write some more non-canon Holmes ;-)
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Scott M wrote:

I'd be happy to, but you'd need to convince the BBC to buy them, which at the moment they're extremely reluctant to do. Apologies for the not-very-good joke at your expense.
Bert
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We have an *imitation* wasps nest!
Experience so far is that it works as the otherwise regular loft visitors have gone elsewhere.

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On Fri, 06 Jun 2014 10:40:38 +0100, Tim Lamb wrote:

So do we!
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