Roberts wrote
Rod Speed wrote
F Murtz wrote
Stephen wrote

There seems to have been an increase in the local cat population.
At first I tried to adopt a live and let live attitude but now
cats are sitting on my car, scratching at the fence panels, and
going to the toilet. Things have got so bad that I have dug up a
couple of flowerbeds and replaced them with gravel.

I have a toddler and I know dog mess contains germs that can cause
blindness, I don't know whether the same is true of what the cats
leave behind, but regardless, I don't really want him playing with
it! I have searched the internet and it claims some smells act as a
deterrent: citronella is one suggestion. How volatile is that?
Would it evaporate too quickly?

Many of he powders available from B&Q and garden centres seem to
contain pepper. The problem with these seems to be that the smell
washes away after the rain and has to be topped up. Is there a catering supplier I could get very large (kg)
quantities of pepper from cheaply?

Ammonia seems to be another suggestion and Jeyes fluid. Again Idon't know how volatile these are and the
ingredients in Jeyes sound almost as unfriendly as the cat litter!

There was a product that used to be highly recommended which was a
PIR activated water spray. I don't imagine it was intelligent
enough to aim and target the intruder, so I presume it just
operated a wide fan spray? Is that right?

I think these are £40-£50 and I would need more than one, which
makes things expensive. I could make one. I have seen 12v dc
solenoid valves but do such things as 12v PIR exist? The ones I
have seen are 240v for lights. I'd prefer not to mix and match
voltages and SELV would be better for obvious reasons.

The RSPB web site seems to favour ultrasonic deterrents but these
cost as much. Has anyone made their own? Does anyone know the ideal
frequency? I remember using 40kHz piezo transducers once upon a
time but I wonder whether they would be loud enough or the right
pitch. Again PIR controlled but I think either of these could be
made DIY for a fraction of the retail price.

What do you think?

Been racking my brain for a method involving an angle grinder.

You throw it at the cat, stupid.

No thats not the way, You get one of the cages and trap the cat.
Then put it in a vice (wearing gloves of course) Cut off one of the
cat's legs with the beloved angle grinder and let it go.It will then
tell all of the other cats don't go there look what happened to me.

Thats not gunna work. You have to get one of the cages that
has a miniture cattle crush at the end of it, to make it a lot
easier to hold the cat while you apply the angle grinder.
http://en.wikipedia.org/wiki/Cattle_crush