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Passive antennas increase power and range



No disassembly or soldering necessary



Inexpensive

Easy to install

I’ve been experimenting with my Z-Wave Plus system to increase the range of my battery powered door/window sensors. I use them to monitor my rat/mouse traps and needed more distance. See my other instructable https://www.instructables.com/id/Wireless-Mouse-Tr...

If you don't want to read all the tech info below, try taping a straight 8" copper or piano wire to a sensor as close to the internal antenna (see the black pen marks in picture 1 & 2) as possible and see if it increases the range. Also tape an 8" wire to your Z-Wave hub near the internal antenna, for the Smartthings V3 hub tape it to the front on the right side as you are looking at the face of the hub, directly in line with the power connector. All passive antennas should be vertical. To test, trigger the sensor 10 times before and after adding the antennas then check history to see how many events are recorded.

Placing the wire close to the internal antenna is critical. Both my sensors were taken apart to find where the internal antennas are located, they are opposite the battery. The antenna in picture 1 looks like a small spring under the black mark. The antenna in picture 2 is almost a complete rectangle, marked by the black lines. Put the passive antenna directly over any of the black marks. By moving the passive antenna in the first picture over the internal antenna the sensor went from recording 0/10 to 10/10 successful open close events recorded in history from the same location.

My SmartThings Antenna Instructable, most info is repeated in the last step of this instructable.

https://www.instructables.com/id/SmartThings-Anten...

Testing Procedure

Passive antennas (thin copper wires) were attached to the sensors and tested for signal strength with a Hackrf One SDR (Software Defined Radio). Lengths of ¼, ⅝ and 1 wavelength were compared with no antenna. The ⅝ wavelength antenna performed the best.

Below are the results in dB. dB is a log scale so a 3dB increase in power is 2x the power. For example if you go from -50dB to -47dB the power has increased by 3dB or doubled.

Power Levels were measured at 916MHz US Z-Wave PLus frequency. For each measurement separated by a comma in the data below, the door sensor was triggered ~10 times and the peak of the 10 triggers was recorded.

916MHz Peak Power Test Results

5/8 wavelength passive antenna (Best Performance!)

-55.6db, -55.4db, -55.6db, -55.6db, -56.3db

1 wavelength (Longer is NOT better!)

-59.9dB, -59.4db, -59db

1/4 wavelength (Most internet info recommends 1/4 wavelength passive antennas, 5/8 is MUCH better!)

-64.7dB, -66.4db, -62.8db

No passive antenna (stock)

-71db, -68.5db, -69.1db, -67.4db

Note

Z-Wave and Z-Wave Plus use the same frequency. Z-Wave Plus is the newer version with longer range and better battery life so get Z-Wave Plus if you can.

These are the two sensors I'm using.

Monoprice Z-Wave Plus Door/Window Sensor, NO LOGO (This one had the best measured power gain with the 5/8 antenna) Update: The sensor was taken apart to locate the internal antenna, place the passive antenna on top of any of the black marks in photo 2.

https://www.monoprice.com/product?c_id=122&cp_id=1...

Monoprice Z-Wave Plus Door and Window Sensor, No Logo (Had a much lower power gain) Update: The sensor was taken apart to find where the internal antenna was located and showed a huge improvement in the amount of recorded test events (0/10 recorded events old location, 10/10 new location) by moving the antenna over the black dot in the 1st picture.)

https://www.monoprice.com/product?p_id=24259