============================================================ X10 Transmitter radiation patterns revision-0 copyright Bill Fernandez 5-FEB-2004, all rights reserved ============================================================ INTRODUCTION I have various RF transmitters from X10.com, and I have sometimes wondered: o How strong is each transmitter? o Which one is the the strongest? o How should I orient (aim) them to get maximum signal strength? o Does the position of my hand on the transmitter make a difference? Having recently purchased a good field strength meter I decided to make some informal tests to answer these questions. EQUIPMENT The field strength meter I used is an "HF-Detektor II Profi" (professional radio frequency field strength meter) from Aaronia AG in Germany (website www.electrosmog.com). It measures RF field strengh over a range of 3MHz to 3GHz with an accuracy of 1dBm under optimum conditions. The X10 RF transmitters I tested were: o KR19A "keychain" remote o KR22A "credit card" remote o CR14A Ninja "Pan 'n Tilt" remote o SH624 Security system handheld remote o KR10A Security system keychain remote o SS13A "Stick-a-switch" remote wall switch PROCEDURE The field strength meter measures the aggregate field strength of all frequencies over the range of 3MHz to 3GHz, and there was so much RF "pollution" in my test environment that I could not make accurate signal strength measurements of each transmitter alone. So I decided just to get quick and dirty answers to the questions of best orientation and field strength relative to each other. So bear in mind that these are very rough, crude tests, not precisely controlled measurements. To test for "best orientation" of each transmitter, I held the field strength meter in my left hand, with it's telescopic antenna fully extended and oriented vertically. I held each transmitter in my right hand, about a foot to the right of the recieving antenna, and at a height that placed it even with the middle of the antenna. Then I held down various buttons, and rotated the transmitter to various orientations relative to the recieving antenna and experimented with different hand positions. I watched the meter's output looking for field strengh variations, and tried to find the orientation that gave the maximum reading. To test the relative power of each transmitter, I laid the antenna of the field strength meter on the floor in front of me with its antenna running "up and down" (toward and away from me, on the floor). Then drew an imaginary line from the middle of the antenna to the right, and placed each transmitter on the floor, and on the line, at the distance needed for the meter to register a given signal strength. ORIENTATION TEST RESULTS (1) There was one common trait shared by all the transmitters, and I'll describe it like this: The faceplate of each transmitter is flat. Now imagine the faceplate extending into an infinite plane. Now orient transmitter so that the line formed by the receiving antenna lies in the plane of the faceplate. This will give you maximum signal transfer from the transmitter to the receiving antenna. In other words to get the maximum signal strength I would: (A) Hold the field strength meter in my left hand with it's antenna running vertically. (B) Hold the transmitter under test in my right hand about a foot away. (C) Orient the transmitter vertically so that an imaginary vertical line through the faceplate (running from top to bottom) is parallel to the receiving antennal, and an imaginary horizontal line through the faceplante (running left to right) intersects the antenna. (This would be easier to convey with pictures.) If from this initial orientation you rotate the transmitter around either the vertical or horizontal imaginary line, the signal strength shown on the meter rapidly and markedly decreases. On the other hand, if you onlyrotate the transmitter about a third imaginary line, running from front to back (like an arrow through the heart of the transmitter...), then there is far less change in signal strength. Now, given the above, let's keep the antenna in the plane of the faceplate, but rotate each transmitter around an imaginary line runnning from front to back (like an arrow through the heart of the transmitter...) and see if the signal is transmitted more strongly to the left, right or top of the faceplate. KR19A "keychain" remote The strongest direction of transmission is to the LEFT, followed by out the TOP, followed by to the RIGHT. KR22A "credit card" remote The strongest direction of transmission is to the LEFT, followed by RIGHT, followed by TOP. Further, pressing a button on the top row produces a far weaker signal than pressing a button on the bottom row. CR14A Ninja "Pan 'n Tilt" remote This transmitter is far stronger than the previous 2. The strongest direction of transmission is to the LEFT, followed equally by the TOP and RIGHT. Pressing a button on the top row vs bottom row makes a small difference in signal strength. SH624 Security system handheld remote The strongest direction of transmission is to the RIGHT, followed equally by the TOP and LEFT. KR10A Security system keychain remote The strongest direction of transmission is to the LEFT and RIGHT equally, followed by the TOP. SS13A "Stick-a-switch" remote wall switch RELATIVE SIGNAL STRENGTH TESTS This test is to determine how strong each transmitter is relative to the others. I used the same, fresh set of Duracell, AA alkaline batteries in the KR10A, SH624, and CR14A. The other remotes use button cells, and I didn't have fresh spares to test with. In order of increasing signal strength: 8" -- KR22A "credit card" remote 14" -- KR10A Security system keychain remote 16" -- KR19A "keychain" remote 19" -- SH624 Security system handheld remote 23" -- SS13A "Stick-a-switch" remote wall switch 36" -- CR14A Ninja "Pan 'n Tilt" remote