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yaroshevich

14 Messages

Saturday, August 18th, 2018 8:11 PM

How to Add antenna to an Entry Sensor

Link to adding an antenna to an SS3 entry sensor to increase its range.

https://www.dropbox.com/s/bg1loj7rieq04e2/Entry%20Sensor%20Antenna.pdf?dl=0

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3 years ago

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dean_33

33 Messages

6 years ago

Thank you very much Yaroshevich, The photos in your article provide exactly the information that I need.

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jtip10

1 Message

6 years ago

Could one similarly extend the range of a motion detector?

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yaroshevich

14 Messages

Yes, the motion sensor is on the same frequency as the entry sensor, so the articles' recommended antenna lengths are similar. The big difference however, the motion sensor has a printed circuit trace antenna, so you can't just cut it. Instead, solder your new antenna to the trace end which is on the side next to the corner mounting hole.

To do this, you must first scrape the green solder mask down till you see copper. Last, trim the total length (including the trace length) for 27.22" (or 13.61" for a half-wave, or 6.8" for a quarter-wave antenna).

Here is the link to a one-page PDF showing where to connect the antenna:
https://www.dropbox.com/s/lusjnxvp057typc/Motion%20Sensor%20Antenna.pdf?dl=0

6 years ago

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parkswr

1 Message

6 years ago

Hmm, this has me thinking.  I have a metal sided outbuilding where I can't get signals to pass through to the base station.  This might get a signal through.

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

6 years ago

Just so the antenna is not next to metal. Perhaps a rod antenna on top could be used. You could also use a quarter-wave antenna which is one-fourth the length.

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jaweiss

1 Message

5 years ago

Hi, why do you need to cut off the original antenna on the circuit board?  Couldn't you just solder directly onto the existing antenna?

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Jim

44 Messages

@jaweiss​ Yes you can solder onto the OPEN CIRCUIT END of the internal antenna, not the drive end but the open circuit end, but be sure to include the length of the internal wire used in your total wire length calculation.

3 years ago

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sevensiamesecats

2.2K Messages

5 years ago

Radio frequency is a strange beast, unlike lower frequencies which go from one place to another without much caring what the "geometry" of the path is.  However, radio frequencies "bounce" if they hit a bend or "roughness" in the path.  If the joint is in the "right place", the bounce can cancel out some of the signal.

Plus, the "effective length" of the antenna has to be "right" for the frequency it is being used for.

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Jim

44 Messages

3 years 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

44 Messages

3 years 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

Another alternative is a "loaded coil" type whip antenna, which shortens the length of the monopole.  Here is a design for one tuned to 433 MHz, that ends up being about 3.5 inches long.  Be sure to include any length of the internal antenna up to the solder point in the lengths:
I would actually modify this design to use a bare wire that is very stiff, so that the antenna can stick out from the case and not require any external support.  But you would have to redesign the number of turns in the coil and the coil diameter depending on what gauge of wire you use.  Since the antenna won't slide through a hole, unlike the simple quarter wave monopole, you will need to cut a slot in the plastic casing to allow the antenna wire to reach its correct position when the case is assembled.

(edited)

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