motco Posted May 6, 2007 Share Posted May 6, 2007 The potential causes of false alarms with Doppler microwaves are many, especially if they are ambiguous, or single channel non-direction sensing types. As has been said already, water in pipes - 4" soil pipes and surface water downpipes are especially bad, fluorescent lights (on, of course), swinging objects, vibration of mountings, local RF interference from taxi firms, and again as has been said, penetration thorough non-metallic walls, and reflection. Each individual unit might have subtly differing detection patterns and the absolute range of any side lobes is directly related to the size of the target, unless the device is FM like the old Frowds units. For example, a 30 metre range device will see a man at 30m, a cat at much less, and a bus, lorry, or worst of all, a train at huge distances. If the environment is already known to be hostile to PIR - and it obviously is or you wouldn't be using a dual detector - then you are left with an almost unsupported microwave and anyone old enough to have used microwaves in the days of Solfan and their peers will know how dodgy they were/are. You should be aware that every metal object in the area is just like a highly polished relective surface to a microwave and will cause rearward detection into all points of the compass. Finally, cross-talk between microwave units is always a possibility when they are in a common environment. Link to comment Share on other sites More sharing options...
magpye Posted May 6, 2007 Share Posted May 6, 2007 any one old enough to have used microwaves in the days of Solfan and their peers will know how dodgy they were/are. Good lord, there is someone else around with a long memory, Solfan, happy days, especially when some idiot pointed them at or near a roller shutter. Want some paperwork, I've got some? Someone told me I was ignorant and apathetic, I don't know what that means, nor do I care. Link to comment Share on other sites More sharing options...
Guest anguscanplay Posted May 6, 2007 Share Posted May 6, 2007 Good lord, there is someone else around with a long memory, Solfan, happy days, especially when some idiot pointed them at or near a roller shutter. Want some paperwork, I've got some? me i prefer munford and white ultrasonics - two visits a year to turn them up and down again depending on the season - ah good old days Link to comment Share on other sites More sharing options...
magpye Posted May 6, 2007 Share Posted May 6, 2007 me i prefer munford and white ultrasonics - two visits a year to turn them up and down again depending on the season - ah good old days Don't forget the old Westool USDs, they made such a high pitched sound that I could hear. I could walk down a High Street past open shop doors and know they were inside !! Someone told me I was ignorant and apathetic, I don't know what that means, nor do I care. Link to comment Share on other sites More sharing options...
Guest anguscanplay Posted May 6, 2007 Share Posted May 6, 2007 Good lord, there is someone else around with a long memory, Solfan, happy days, especially when some idiot pointed them at or near a roller shutter. Want some paperwork, I've got some? me i prefer munford and white ultrasonics - two visits a year to turn them up and down again depending on the season - ah good old days Don't forget the old Westool USDs, they made such a high pitched sound that I could hear. I could walk down a High Street past open shop doors and know they were inside !! stop it were starting to sound like arfur Link to comment Share on other sites More sharing options...
magpye Posted May 6, 2007 Share Posted May 6, 2007 stop it were starting to sound like arfur Can't think of anyone better to emulate! Someone told me I was ignorant and apathetic, I don't know what that means, nor do I care. Link to comment Share on other sites More sharing options...
Guest anguscanplay Posted May 6, 2007 Share Posted May 6, 2007 stop it were starting to sound like arfur Can't think of anyone better to emulate! you forgot the ironic yellow man thingy - its up there next to the BIU selection lol Link to comment Share on other sites More sharing options...
Truss and France Posted May 6, 2007 Share Posted May 6, 2007 Eli If you can still get hold of them try one of these a Pulnix PA7012, its a quad PIR and it is the 'dogs bxxxxxxs' I have never liked or personally used a dual tech. Kev Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.