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.


-- 
borunner

borunner wrote:
> 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.
> 
> 


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?

This may not help much, but when you cut your cable for final length from 
CM15A to antenna, make sure it is an EVEN multiple of 38", which is a full 
wavelength at 310mHz. I would'nt put a connector on the antenna end since 
any connector (even BNC) has loss. FWIW, I got my best range by just 
stripping away about 19 inches (1/2 wave) of shield from the coax and fixing 
the crude 1/2 wave antenna as high in the attic as I could get.

"Frank Olson" <use-the-email-links@yoursecuritysource.com> wrote in message 
news:DX2dl.49719$Nv1.39856@newsfe03.iad...
> borunner wrote:
>> 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.
>>
>>
>
>
> 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? 

On Jan 19, 12:03=A0pm, "D&SW" <d...@verizon.net> wrote:
> This may not help much, but when you cut your cable for final length from
> CM15A to antenna, make sure it is an EVEN multiple of 38", which is a ful=
l
> wavelength at 310mHz. I would'nt put a connector on the antenna end since
> any connector (even BNC) has loss. FWIW, I got my best range by just
> stripping away about 19 inches (1/2 wave) of shield from the coax and fix=
ing
> the crude 1/2 wave antenna as high in the attic as I could get.
>
> "Frank Olson" <use-the-email-li...@yoursecuritysource.com> wrote in messa=
ge
>
> news:DX2dl.49719$Nv1.39856@newsfe03.iad...
>
> > borunner wrote:
> >> I recently modified my CM15A with a BNC connector and built an eggbeat=
er
> >> antenna after scouring various web sites and convincing myself that th=
is
> >> 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. =A0After 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. =A0I am thinking I=
 may
> >> have too long a cable from the antenna to the CM15A, currently it's
> >> about 18 ft. =A0Anyone 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 th=
e
> >> cable run really wants to be about 10 feet. =A0The next step after tha=
t 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? =A0Any feedback is appreciated.
>
> > Can you tell us what your system's comprised of? =A0Number and type of
> > modules? =A0Have you installed a coupler/repeater?? =A0Are you having p=
roblems
> > with other devices?

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.
http://www.ocarc.ca/coax.htm
I 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

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...


-- 
borunner

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


-- 
borunner

borunner wrote:
> Now I'm thinking I'll have to get an inline amplifier.
> 
> 
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...