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CM15A antenna mod

I recently modified my CM15A with a BNC connector and built an eggbeater antenna after scouring various web sites and convincing myself that this would get me the range I need for my X-10 motion detectors, which was barely 20ft and of course my current motion detectors are about 25 ft away through one external wall. After rechecking my soldering work and all my connections it's not really working very well even being in the same room I'm now only seeing about 10 ft of range. I am thinking I may have too long a cable from the antenna to the CM15A, currently it's about 18 ft. Anyone have suggestions on how my RF reception can be improved? Next step will be to cut my cable to the minimum I need, I'm looking to put the antenna in the attic space above the computer so the cable run really wants to be about 10 feet. The next step after that is to get an inline signal booster (Ten Tec) but I'm thinking I should be able to get this to work since I am not looking at a huge range improvement? Any feedback is appreciated.

Reply to
borunner
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Can you tell us what your system's comprised of? Number and type of modules? Have you installed a coupler/repeater?? Are you having problems with other devices?

Reply to
Frank Olson

Reply to
D&SW

ge

Connectors aren't your problem - BNCs are not a problem until above UHF. 310mhz is below that so BNCs or even PL259s are OK. I'd focus on the coax to address loss. Try to keep the feedline as short as possible. Here is a site which will help you determine how much loss your particular coax.

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would think you'd want 50-ohm coax so be sure you're not using cable-TV or other 75 ohm line. Investing in some low-loss cable would help for sure. I'd go with a halfwave dipole for good omnidirectional performance and make sure it matches the polarization of your receiver, IE if the receiver's antenna is vertical, then so should be the TX antenna to avoid any polarization penalty. If a halfwave dipole isn't cutting it, then build a gain antenna like a 5/8 wave. It won't be too large at 300MHZ.

I'd also think about improving the RX antenna. With X10 I've improved my reception just by using clipping a lead on the antenna to provide some more length.

Let us know your results! Thanks, Corey J. Anderson

Reply to
ElectricLab

right now my system is pretty basic. CM15A with a couple of switches. I've added the motion detector and chime, but the lack of range on the motion detector is what got me started on the antenna mod to get better range. Going to adjust the cable length next...

Reply to
borunner

Now I'm thinking I'll have to get an inline amplifier.

Reply to
borunner

You might have an easier solution.. Why not get get a Xm10 receiver (I don't have the part number at hand) for about $20, and plug it in near the motion sensor?

No antenna mod, etc, just different scripts on the cm15a...

Reply to
J Miller

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