[LHA-misc] RFI/EMI with Home Automation devices

[Clay J. <cl...@nw...>]

Being an Amateur Radio Operator ('Ham'), I think I'm probably a bit more 'in
tune' (intended pun, there) with potential RF interference (aka RFI, or EMI)
than most; and, my radio shack (also server room, telecom switch room and
home office) is definitely a 'high RF' environment.  But, I still got 'bit',
and since it involved Home Automation, I thought I share my experiences so
someone else doesn't have to learn quite as much as I did...

I've got a Siemens "Gigaset" phone system, which consists of a base unit and
4 remotes which are cordless.  The system uses Spread Spectrum Technology
(meaning it's transmit/receive frequencies CHANGE) in the 2.4 Ghz range.
The base unit is hung on the wall behind my monitor (until I get around to
moving my ISDN TA, which feeds the phone lines into the GigaSet - at which
point the base unit will move to a phone panel in the garage).

At a hamfest a few weeks ago, I got a great deal on 4 X10 'XCams', along
with the receiver and other goodies.  I started setting up the XCams this
weekend and discovered that if the camera was more than 2' from the
receiver, I got LOUSY reception, or none at all.  After sratching my head
for a while, I unplugged the Gigaset (thereby interrupting all of our phone
service execpt our backup 'POTS' - my wife sometimes hates my gadgets), and
presto, the XCams started working just fine.  Turns out the Gigaset and the
XCams share the same frequency allocation - and the Siemens people want to
'own' the whole band (interestingly enough, there was NEVER any interference
TO the Gigaset phones FROM the Cameras, just the other way 'round.

So, I plugged the Gigaset back in and opened up the X10 receiver.  I
discovered that it had an F type connector (ala cable TV) on the back, for
channel 3/4 out.  I clipped the lead from the oscillator to the connector,
and connected the (input) antenna lead to the F connector.  Then, I took a
piece of coax cable (RG6, for the purists out there), stipped the inner
conductor, and wrapped it around the antenna of a camera about 50' from the
receiver.  Presto - hard wired video!

Tonite, I'm gonna open up one of the cameras and see if I can figure out how
to more permanently mount a cable - also, there's a thinner 75 ohm cable out
there that I'm gonna try as well.   I figure that since only one camera is
powered at a time, a regular cable TV splitter will probably work OK for
feeding signals from multiple cameras into one receiver.

I'll keep the list posted on my results - and, as soon as I get a web server
up, I'll put pictures of the whole mess up as well.

Thought this might be interesting for other folks who are starting to dabble
in wireless stuff around the home - turns out that the same frequencies are
being used (or proposed) for all SORTS of 'consumer' gadgets.   And, of
course, the manufacturers are taking a 'caveat emptor' approach the the
whole problem....

Clay Jackson
N7QNM