
Alarm Sensors
All questions about the Intruder Sensors: Entry, Motion, and Glassbreak.
14 Messages
Saturday, August 18th, 2018 8:11 PM
How to Add antenna to an Entry Sensor
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1 year ago
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dean_33
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5 years ago
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jtip10
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5 years ago
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parkswr
1 Message
4 years ago
If it doesn't though, is there any reason anybody can come up with that it would be a bad idea to route the antenna extension over the top of the door and outside the building so the signal isn't blocked. It could readily be attached to the top of the door at the jamb making it hard to see if you don't know it's there.
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yaroshevich
14 Messages
4 years ago
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jaweiss
1 Message
3 years ago
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sevensiamesecats
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2.2K Messages
3 years ago
Plus, the "effective length" of the antenna has to be "right" for the frequency it is being used for.
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Jim
39 Messages
1 year ago
The various articles on using a full wave long wire are unfortunately very incorrect. Nobody in the RF business uses a full wave antenna, they are notoriously hard to impedance match to the transmitter, and you do not in any case drive them from one end.
You can disassemble the sensor and attach a wire to the internal antenna, and have it exit a hole in the plastic casing that you drill. The sensors all use 433.92 MHz transmitters, so you want a quarter wave long monopole type antenna which is a total wire length of 6.800 inches. Be sure to include any of the internal wire antenna in the total length calculation.
For a more compact antenna you can use a loaded coil antenna (about 3.5 inches long) or a helical coil antenna (about 2 inches long), if you know exactly how to design them, however they will not have quite as much gain.
(edited)
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Jim
39 Messages
1 year ago
As an alternative to the single quarter wave monopole antenna, you can use a helical coil antenna designed for 433 MHz. This is actually available in stock at Mouser Electronics:
https://www.mouser.com/ProductDetail/Linx-Technologies/ANT-433-HETH?qs=K5ta8V%252BWhtZ6g8XdsIJRaw%3D%3D
(edited)
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