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Author Topic: Non-mod, passive reflector/radiator/yagi range extension - any special advice?  (Read 16555 times)

LW

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Hello everyone,

I read with great interest eleswhere in this forum the following ideas for increasing the range of the CM15a:


...I simply taped a 9.5 inch piece of 14 gauge bare wire on to the side of the existing small antenna on the CM15A.
I did not cut or remove the original antenna (In fact I did nothing to it), because I did want to hurt my warranty in the event I actually want to return it. Anyway this simple mod actually works, and I can now get the DS10's to trigger events in the Active home software...

...my simple modification allows the CM15A to pick up all 8 DS10's from all over my home now, 100 feet or more through two walls even...

In a follow-up post, Puck called this solution a passive reflector, or Yagi. Relatedly in the same discussion:


...I have also read in another post that simply putting a 9.5 inch 14 gauge wire taped directly to the side of the DS10 will also greatly increase its distance...

Puck identified this as a passive radiator.

We get possession of our house tomorrow, and I'm eager to set up my stuff so that the CM15a picks up everything reliably, without doing anything to void my 5-year warrantee, and without having to spend a lot of time finding the best spot in the house for CM15a receptivity. So I'm going to try these passive reflectors and radiators. Those who mod the CM15a antenna report being able to communicate with it from down the street; I don't need such a range, I just want it to work around the home. But the excerpts that I quoted above raise a number of questions for me, and I would be grateful for any answers. When it comes to electronics, I am such a newbie.

  • 1.) Should I enclose the 14 guage wire in anything, or cover it with electrical tape?

  • 2.) Does the orientation of the wire make a difference? e.g., should the wire be parallel to the CM15a antenna? or should it be perpendicular? or should I coil the wire around the CM15a antenna for maximum multi-directional reception?

  • 3.) How close does the 14 gauge wire need to be to the CM15a to do its job well?

  • 4.) Would I do well to mount these RF reflectors/radiators around the house? ("Honey, what's that?" "It's another RF reflector - blame a man named Yagi."  :P )

  • 5.) Could one long (5'-10') string of 14 gauge wire in the attic do the job of many separate RF reflectors and radiators scattered around the home (wherever the CM15a and my modules are)?

  • 6.) We have an amplified TV antenna. Is it likely to interfere with these RF reflectors/radiators?

Thanks in advance again. Have a good one, everybody.


[TTA Edit: Added description to LINKs (actually used original QUOTEs), increased QUOTE FONT size, formatted TABLE.]
« Last Edit: March 23, 2007, 05:24:27 PM by TakeTheActive »
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dave w

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OK I can help here, but don't mean to steal any thunder.

  • 1.) Nope, you can leave it "natural". and don't get real hung up on the 14ga wire size. 14ga solid is easy to come by, but a coat hanger will work as well.

  • 2.) Yes, to act as a passive radiator, it should be parallel and close to the CM15A antenna. Taping in directly to the CM15A antenna will work well.

  • 3.) (see #2).

  • 4.) Assuming you are talking about putting passive radiators on motion detectors or "Pam Pad" remotes the passive radiator should be mounted on left side of the unit.

  • 5.) Nope, won't work, maybe my mental wandering below will better explain.

  • 6.) No, very unlikely.

Now to really confuse you. I don't know where the 9.5" wire came from. The transmitting frequency for Palm Pads, Active-Eyes, Stick-A-Switches, etc. is 310MHz.

A quarter wavelength antenna is 9", and a half wavelength antenna for 310 MHz is 18".
I use half wave passive radiators on several motion detectors and a palm pad. It's simple. A 18 inch coat hanger is hot glued at the 9" center point, to the left side of the "xxxxEYE"  motion detector (the antenna loop inside the PP's and xxxxEYE motion detectors are mounted internally near the left side of the unit housing). 

This works good for increasing the range. On other units I use an 18" 26 ga insulated wire, hot glued to the left side of the detector, but I don't center it. One end of the wire is attached at the bottom of the motion detector, forming a flexible antenna, extending about 16" above the mounted motion detector. This also works good.

Will 9" work better? I haven't tried it, but tend to think not.

9" is a quarter wave and quarter wave antennas usually need a good ground plane, which isn't possible here. I think the original 9.5" came from the fact that roughly 9.5" of antenna was rolled up in a little ball inside the CM15A with the rest of the wire shoved in the hollow antenna tube which is what you see on the side of the CM15A.Since wire (and coat hangers) is fairly cheap you could try both 9" and 18" lengths to see if there is an observable difference.

My real point is; don't get all hung up on "14ga" or "9.5". These things X10 transmitters are pretty sloppy, so try 9" and 18" of some wire you have laying around the new house.

This should be fun...lets us know how you make out ;)


[TTA Edit: Added description to LINK, formatted TABLE.]
« Last Edit: March 23, 2007, 05:31:47 PM by TakeTheActive »
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HA Dave

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I did a fast and dirty mod on my CM15A out of shear frustration. There are much better mod's there than mine!

I had mounted the CM15A in a central area of the house and extended the USB to get the unit as high up as I could, and away from the PC. You know... all the normal stuff. But I was at a point where it was void the warranty or throw the thing away. I don't think most user's have that same problem.

I posted my mod not as a recommendation, but as when all else failed.... here is what I did.

The passave reflector/antenna glued to the side of the XXeye sounds interesting! And I may try that one someday... so far... I haven't needed to.
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LW

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Hi,

Many thanks for your replies.

Dave_X10_L, that seems to me a perfectly good mod. "Fast and dirty" is sometimes the best solution, and I may give this a try if I really have to mod. What confuses me about your post, though, is that you describe using Cat5 cable, which to me signifies 4 sets of two wires (blue + blue/white, brown + brown/white, orange+orange/white, and green+green/white), but in your photos I did not see these. The last picture seems to me to suggest that a cable with a single wire was soldered on...? Maybe there is more than one kind of Cat5 cable.

Dave W, what you wrote is helpful to me, but it also raises in my mind two more questions. I don't mean to be a bother, but here goes:

1. Is there any reason not to fold the new wire RF reflector/radiators when attaching it to the CM15a or other wireless modules, so that it spans the height of the device to which it is being attached (external or internal antenna)?
2. Is there any benefit to adding two or three of these RF reflector/radiators to a device?

Have a good night, everyone.
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HA Dave

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Dave_X10_L, that seems to me a perfectly good mod. "Fast and dirty" is sometimes the best solution, and I may give this a try if I really have to mod. What confuses me about your post, though, is that you describe using Cat5 cable, which to me signifies 4 sets of two wires (blue + blue/white, brown + brown/white, orange+orange/white, and green+green/white), but in your photos I did not see these. The last picture seems to me to suggest that a cable with a single wire was soldered on...? Maybe there is more than one kind of Cat5 cable.


I used a single strand of wire. Where I got that wire was from a left over peice of CAT5. I just pulled out one (the orange one if I remember correctly), stripped off it's insulation an taped it to the antenna tube. Then I soldered a exposed area of the old antenna wire, to the single strand of wire (just like it looks like in the picture). I had orginally planned on using 14 guage wire. But, I had no scrap 14 guage wire, only 12 guage. And I had a scrape hunk of CAT5................
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Puck

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2. Is there any benefit to adding two or three of these RF reflector/radiators to a device?

Short answer, no.

Because the the X10 motion sensors & remotes don't have a real dipole antenna, the principles of a Yagi antenna's reflector and directors don't theoretically apply. Some have found that the 1/2-Wavelength wire close to the module does help increase the range; I'm thinking the signal is really being coupled and re-radiated by this as opposed to being reflected.

A real reflector (still 1/2-Wavelength long) would be in parallel with the transmitter's antenna, 1/4-Wavelength away (~ 9 inches) and in the opposite direction of where the receiver is located.

If you wanted to add more, you would add just the one reflector (as above) and add multiple directors on the opposite side (towards the receiver). The directors would be a little shorter (~ 0.4-Wavelength [~7 inches long]) and ~ 0.34-Wavelength spacing [~6 inches]. This would look very ugly throughout the house.  :P

You would be better off with mod'ing the CM15A's antenna to better receive the weaker signals. If you don't feel comfortable with opening the unit and making an external antenna, I recommend the mod submitted by jdacal : Re: Project To Increase Range Of CM15A

I picked up a $2 rabbit ears antenna at the dollar store and removed one of the telescope antennas from it. I used this mod of my 2nd CM15A (used for monitoring) and it works very well.
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