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[john to perdo]

Hi:Has anyone found an easy way to soup up
a CM19a USB transceiver for better range?
(like extend the antenna to the length of
other 315MHz devices, or add a ground plane
under the unit). These are both
possibilities, but I thought I would ask if
anyone has tried this before I dug into it.
As it stands it almost makes it to the
location I desire. I don't need much of an
improvement.
Thanks, John

[r. evans]

Hi John;
I currently have a spare  CM19A in stock
that I can afford to "Play" with (the case
was damaged in a clumsy, big footed helper
incident)and have been wondering the same
question myself, Maybe I can answer this
question for both of us. How long would you
recommend extending the antenna?

[john to perdo]

Hi: Sorry for the delayed response, I would
start at about a total length of about 12 or
13 inches. I think that is pretty close to
one quarter wave length at 315 MHz. One
could also put a metal cookie sheet under
the CM19a, that also might help. You might
have to ground the cookie sheet to something
(like a cable shield) on the inside of the
unit to get full advantage of the cookie
sheet. I would start with a longer antenna
and then start messing with the cookie sheet.
THanks, John

[socal]

What is the CM19A used for exactly?  I have
one and really do not know what it used for.

[anonymous]

It is an X-10 RF(315MHz) to USB interface.
It is used to transmit signals (via rf) to
or from your computer to things like the
Ninja pan and tilt camera mount. It is a bi-
directional unit and can also receive
signals from the various X-10 hand held
units and rf motion sensors etc and send
them into your computer. It only is useful
IF you have software on your computer that
interfaces with X10 devices. I use it to
couple my Home Seer (www.homwseer.com)
software package to my Ninja camera mounts.
Home Seer tells the camera mounts which
direction to turn. Hope this helps.
John

[Brian H]

FCC site says it is 312Mhz. So the antenna
maybe slightly shorter than for a 315Mhz. I
have seen web pages on other uses for that
module. Will post data if I find it.

[john to perdo]

Thanks, Yep, Actually I got the 12 or 13
inches mentioned previously by measuring an
antenna on an X10 AC device. I just did a
rough calculation to see if the 12 to 13
inches approximated a quarter wave antenna
at 315 MHz and it seemed OK. I didn't check
part 15 of the fcc regs but you are correct,
if part 15 says the band is 312 HHz. then
that is what we should be using. Apparently
people commonly round it off and call it 315.
Thanks again, John  

[Brian H]

I used the FCC registration number. Most of
all the X10 stuff is 310Mhz. The CM19A was
listed as 312Mhz.  

[tbird2340]

So did you try this and did it work? I would
like to increase the range on mine as well..

[john to perdo]

Yep, I extended the total antenna length to
13 inches and it seems to have made the
difference. It now works every time (so
far). I think it was on the hairy edge of
working before, and this seems to have made
the difference. It now works consistently.

For what its worth, I set the CM19a on a
wooden shelf and hung the 13 inch antenna
straight down off the shelf and I ran the
USB cable to the CM19a in along the shelf
perpendicular to  the antenna. There is no
other metal near the CM19a. Hope this helps.
John

[tbird2340]

So how did you extend the antenna? What did
you use?

Thanks!

[john to perdo]

I just used one conductor from a piece of
telephone wire, the yellow one to be exact.
It is just a piece of a number 24 or 26
solid wire. Nothing special.
John

[tbird2340]

And did you just solder / splice it into the
wire already there or did you totally remove
the one and add this one?

[john to perdo]

I used the existing wire. I just nipped off
about 1/4 inch of insulation from the
antenna and twisted the phone wire to it
(after nipping off 1/4 of insulation from
the phone wire). It isn't really necessary
to solder a connection like this (unless you
really want to). John

[tbird2340]

And that helped improve the range? Does it
have to be an exact length?