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Defenders Mega-sonic Cat Repeller

(Created Feb 2012)

It's sad that I have even bothered to have gone to the trouble of creating this web page. All I will say is we have had problems with local cats fouling our lawn, and had tried a variety of remedies with varied degrees of success and expense. As a last resort, I purchased this inexpensive cat repeller in 2010, after learning a friend had had success with a similar but much more expensive product. I also purchased the mains adaptor as I didn't wish to spend a fortune on 9 volt alkaline batteries, or worry about them going flat.

I recently had to purchase another unit to stop cats fouling another part of my property. These are photos of the newer unit, though to be honest, the packaging and product looks very much identical to the one I purchased two years ago.

The Mega-sonic cat repeller was also previously known as the 'Big Cheese' Cat Repeller. Like other similar products, it works by detecting any change in heat signature within its vision of detection, and then emitting an ultrasound which apparently irritates or annoys cats (very young children and teenagers can also hear it apparently). Suffice to say, this product may not work with all cats, especially deaf ones !

It is sold in the UK through Amazon, B&Q and other retailers, from as little as £15 for the repeller and £10 for the mains adaptor.

The PIR (heat) sensor, loudspeaker, LED and 'test' button are on the front. A stake can be attached to the unit for fixing into soft ground, or it can be hung on a wall (though the 1 inch screw they supply is far too short). Just like any other type of PIR sensor, it works by detecting significant 'changes' in infra red heat signature within is detection range, which is likely to be caused by movement. When the unit is triggered, the red LED lights up for about 25 seconds in which time it is also emitting the ultrasound.

One important point worth noting, is if there is no further change in the infra red signature, the repeller will not be set off again.

For example, if a cat wonders into the detection range and triggers the repeller. If the cat stays put and puts up with the noise, the repeller will switch off after 25 seconds. Only if the cat decides to 'move' again, is it likely to trigger the repeller and cause it to sound for another 25 seconds.

The test button on the earlier repeller had a tendency to stay jammed-in when depressed. As a consequence, the unit would not stop emitting an audible sound from its speakers. Pulling the green button out and refitting it was necessary. It's too early to tell, but the button on my newer unit doesn't seem as tight-fitting in its round hole, so hopefully is less likely to 'jam' when depressed.

The red LED can be quite difficult to see if you are testing the unit from a distance. One useful tip is to place a portable radio (set on MW) next to the repeller and tune the frequency until you can hear the throbbing noise on the radio coming the repeller when it is triggered.

The master on/off switch and socket for external mains adaptor can be seen here.

On my earlier unit, when I did briefly fit some Duracell batteries to it, I found the connectors were very loose fit onto the battery terminals. I tried re-adjusting the clip on connectors with a pair of pliers but it didn't help. In any case, I use mains power.

The new mains adaptor is different to the one I purchased in two years ago. The earlier model was a 'transformer' type mains adaptor. This newer one which I think was introduced from October 2011 from the date stamp of the supplied instructions, is a 'switched mode' power supply – similar to what is supplied with mobile phones and other gadgets nowadays. Personally, I'm not convinced this new type of mains adaptor will be as reliable as the old style transformer type mains adaptor. Only time will tell.

It is supplied with a 5m extension lead. If you need extra leads or splitters, you should be able to find them on eBay by searching for '2.1 5.5 extension'

Shows the old mains adaptor on left, new model on the right.

Rated at 9 volts DC output at 500mA. The Repeller doesn't use anything near 500mA so could easily be used to power more than one repeller if you buy the appropriate splitters and extension cables. I think I measured 60mA with the speaker sounding in test mode.

The barrel connectors are 5.5mm outer diameter, and 2.1mm inner diameter. Note that the centre pin is Negative polarity – the opposite of most gadgets which use the same 9 volts and barrel connector where the centre pin is usually positive polarity.

Location, location, location and persistance

I position my cat repellers to guard our bare lawns only.

One thing I have discovered is to ensure that walls and other nearby objects do not fall within the vision of detection, otherwise, it will desensitise the repeller when the weather is hot. The closer the object is to the repeller, the more it may be desensitised. What happens is the repeller may fail to distinguish a nearby brick wall which has been baked by the sun, to a cat wondering across the lawn further away.

If you have had persistent problems with cats fouling your lawn, you also need to properly clean up the area. This may involve hosing down the area after removing the new cat mess. I personally mix a bit of Jeyes fluid in an old watering can full of water, and use that 'clean' up an area after removing the cat mess. If you fail to clean up the area properly, the cats will just keep on returning.

Cats are also very smart. They may find blind spots in the repeller's field of detection. You may need to move the repeller or install more than one unit.

I'm happy with the results from the repeller installed two years ago. The repeller hasn't completely eliminated the problem, but it is a significant improvement when compared to the years before I had the repeller. I'm hoping the second repeller which has just been installed will be just as effective.

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