garage remote jamming
Dave Houston
http://www.washingtonpost.com/wp-dyn/content/article/2007/02/25/AR2007022501417.html
http://www.washingtonpost.com/wp-dyn/content/article/2007/02/26/AR2007022600636.html
http://davehouston.net
http://tech.groups.yahoo.com/group/roZetta/
roZetta-...@yahoogroups.com
Neil Cherry
> Here's another case of military signals jamming garage door openers.
>
> http://www.washingtonpost.com/wp-dyn/content/article/2007/02/25/AR2007022501417.html
> http://www.washingtonpost.com/wp-dyn/content/article/2007/02/26/AR2007022600636.html
Actually isn't this a case of consumer products using a military
frequency and the consumer paying the price for it?
--
Linux Home Automation Neil Cherry nch...@linuxha.com
http://www.linuxha.com/ Main site
http://linuxha.blogspot.com/ My HA Blog
Author of: Linux Smart Homes For Dummies
Robert Green
news:slrneu9sh...@cookie.uucp...
> On Tue, 27 Feb 2007 13:52:51 GMT, Dave Houston wrote:
> > Here's another case of military signals jamming garage door openers.
> >
> >
http://www.washingtonpost.com/wp-dyn/content/article/2007/02/25/AR2007022501
417.html
> >
http://www.washingtonpost.com/wp-dyn/content/article/2007/02/26/AR2007022600
636.html
>
> Actually isn't this a case of consumer products using a military
> frequency and the consumer paying the price for it?
I think anything that says "must accept harmful interference" is susceptible
to getting "stepped on" in some way. That's getting more and more likely as
the spectrum gets auctioned off and re-allocated.
I'll bet a lot more than just garage door openers are taking hits. The
WashPost would hardly be interested if three people's RF HA interfaces or
some wireless alarms went amuck so it wouldn't make the news. I've had
times when none of my X-10 RF or RS wireless thermometers would respond and
then, just as mysteriously, the problems vanish. I live near a bunch of
military radio towers so that may make my experiences atypical.
--
Bobby G.
Brian W. Antoine
>On Tue, 27 Feb 2007 13:52:51 GMT, Dave Houston wrote:
>> Here's another case of military signals jamming garage door openers.
>>
>> http://www.washingtonpost.com/wp-dyn/content/article/2007/02/25/AR2007022501417.html
>> http://www.washingtonpost.com/wp-dyn/content/article/2007/02/26/AR2007022600636.html
>
>Actually isn't this a case of consumer products using a military
>frequency and the consumer paying the price for it?
Exactly, and now look at how 2.4Ghz is allocated. All of our favorite
wi-fi toys are in the same position, we can not cause interference and
we are required to shut-up and suffer any interference caused us.
Dave Houston
>On Tue, 27 Feb 2007 13:52:51 GMT, Dave Houston wrote:
>> Here's another case of military signals jamming garage door openers.
>>
>> http://www.washingtonpost.com/wp-dyn/content/article/2007/02/25/AR2007022501417.html
>> http://www.washingtonpost.com/wp-dyn/content/article/2007/02/26/AR2007022600636.html
>
>Actually isn't this a case of consumer products using a military
>frequency and the consumer paying the price for it?
I wasn't making a value judgement but merely putting this on the CHA record
to raise awareness of the situation. The topic has arisen a few times here
and elsewhere. The first incident I recall was around Homestead AFB a few
years ago.
I believe most of the frequency bands where low-power, unlicensed use is
allowed by the FCC are subject to the same thing. Most carry an FCC required
disclaimer that they are not allowed to interfere with licensed use and must
accept interference from licensed use.
With more and more HA applications using RF in some manner, it will likely
be an ongoing issue, especially for all-RF systems like RadioRA, Z-Wave,
ZigBee, etc. It's one more reason why I think a reliable PLC system (e.g.
HomePlugCC) will eventually be the preferred retrofit solution.
And, those who import X-10 gear from the USA to save money should be aware
that the French military uses the same RF frequencies that N. American X-10
gear uses.
Dave Houston
>I wasn't making a value judgement but merely putting this on the CHA record
>to raise awareness of the situation. The topic has arisen a few times here
>and elsewhere. The first incident I recall was around Homestead AFB a few
>years ago.
Correction: It was around Eglin AFB.
http://www.msnbc.msn.com/id/6663032/
Here's a detailed explanation of this particular system.
http://www.gao.gov/new.items/d06172r.pdf
Bill Kearney
> be an ongoing issue
Oh please, that's just completely unsubstantiated FUD.
> It's one more reason why I think a reliable PLC system
Which have proven themselves to be horrendously unreliable in residential
settings. No thanks.
> And, those who import X-10 gear from the USA to save money should be aware
> that the French military uses the same RF frequencies that N. American
X-10
> gear uses.
Unless you're worried about being able to turn the lights off as their army
retreats it shouldn't be much of a concern...
Robert Green
news:dZudnUaUzvLjDXjY...@speakeasy.net...
> > With more and more HA applications using RF in some manner, it will
likely
> > be an ongoing issue
>
> Oh please, that's just completely unsubstantiated FUD.
I wouldn't say that. This is at least the third instance I've heard or read
about where significant numbers of people have had to retool to accommodate
new RF interference from military ops. If there are three we know about
that usually means that there are plenty more that we don't hear about. If
you were to experience any problems and called the Post to say your Lutron
RA system was hosed, it would very likely *never* be considered newsworthy
because so few others would likely be calling in. Same for an X-10 or
Z-wave system. Not enough users for anyone to care if the Marines were
jamming them. Garage openers and automobile key fobs? Lots of users to
complain.
> > It's one more reason why I think a reliable PLC system
>
> Which have proven themselves to be horrendously unreliable in residential
> settings. No thanks.
If it's absolutely, positively got to work without any possibility of
interference, go hard wired. Neither PLC nor RF is immune to interference.
> > And, those who import X-10 gear from the USA to save money should be
aware
> > that the French military uses the same RF frequencies that N. American
> X-10
> > gear uses.
>
> Unless you're worried about being able to turn the lights off as their
army
> retreats it shouldn't be much of a concern...
Hey, if it weren't for General Lafayette, we might not have gained our
independence from Merry Olde England. Some Frenchies have spunk. Look at
Napoleon. (-:
--
Bobby G.
Dave Houston
>"Bill Kearney" <wkearney-99@hot-mail-com> wrote in message
>news:dZudnUaUzvLjDXjY...@speakeasy.net...
>> > With more and more HA applications using RF in some manner, it will
>> > likely be an ongoing issue
>>
>> Oh please, that's just completely unsubstantiated FUD.
>
>I wouldn't say that. This is at least the third instance I've heard or read
>about where significant numbers of people have had to retool to accommodate
>new RF interference from military ops. If there are three we know about
>that usually means that there are plenty more that we don't hear about. If
>you were to experience any problems and called the Post to say your Lutron
>RA system was hosed, it would very likely *never* be considered newsworthy
>because so few others would likely be calling in. Same for an X-10 or
>Z-wave system. Not enough users for anyone to care if the Marines were
>jamming them. Garage openers and automobile key fobs? Lots of users to
>complain.
As military, police, fire, etc. need additional frequencies, the bands used
by unlicensed low-power consumer applications are a logical place to look.
As we've seen in this case, they can't even be bothered to ask the FCC what
technologies they will likely be stepping on and how many people they might
inconvenience. I doubt this will be the only instance.
>> > It's one more reason why I think a reliable PLC system
>>
>> Which have proven themselves to be horrendously unreliable in residential
>> settings. No thanks.
>
>If it's absolutely, positively got to work without any possibility of
>interference, go hard wired. Neither PLC nor RF is immune to interference.
I did say "retrofit". I agree that hard wired is best but it's not always
easy to retrofit. I would keep an eye on HPCC (HomePlug Command & Control).
Yitran Communications was chosen to supply the chips and they showed a
system at the most recent CES show. It is supposed to be reliable and low
cost.
http://www.itrancomm.com/comnd.htm
One footnote to the KKR-Texas Pacific buyout of TXU is that they are
planning a system wide Access BPL system using the same HomePlug based
technology from Current that has been operating in the Cincinnati area for a
few years now (with no apparent problems despite ARRL propaganda).
Access and in-house BPL prove PLC can be reliable. It remains to be see if
HPCC can be both reliable and low cost but the next couple of years should
answer that.
Bill Kearney
>
> I wouldn't say that. This is at least the third instance I've heard or
read
> about where significant numbers of people have had to retool to
accommodate
> new RF interference from military ops.
Three of the SAME THING. Garage door openers using a set of frequencies the
vendors KNEW were usable by the military and likely subject to interference.
If anything the people stuck with these openers should be bitching to the
vendor of their garage door opener, not the military. But no, it's just
more fashionable to bash the military.
> If you were to experience any problems and called the Post to say your
Lutron
> RA system was hosed, it would very likely *never* be considered newsworthy
> because so few others would likely be calling in.
Find a situation where an actual RadioRA setup has suffered from outside
interference. Lutron's gone out of their way to make that an extremely
unlikely situation.
> If it's absolutely, positively got to work without any possibility of
> interference, go hard wired. Neither PLC nor RF is immune to
interference.
Which would be rather impossible for a garage door opener IN your car.
Sure, the usual wall-mounted controls are certainly not going to suffer the
interference.
> Hey, if it weren't for General Lafayette, we might not have gained our
> independence from Merry Olde England. Some Frenchies have spunk. Look at
> Napoleon. (-:
Waterloo, 'nuff said.
Bill Kearney
> HPCC can be both reliable and low cost but the next couple of years should
> answer that.
Hasn't that been said before, like once every ten years? Echelon comes to
mind...
PLC just seems to be the kiss of death for nearly every tech product that's
attempted to piggyback onto residential AC wiring. It stands to reason new
ones will tank too.
Robert Green
news:45e5d3ff....@nntp.fuse.net...
It's puzzling to me why there aren't bands for low power RF control purposes
that don't allow any high power transmitters.
> >> > It's one more reason why I think a reliable PLC system
> >>
> >> Which have proven themselves to be horrendously unreliable in
residential
> >> settings. No thanks.
> >
> >If it's absolutely, positively got to work without any possibility of
> >interference, go hard wired. Neither PLC nor RF is immune to
interference.
>
> I did say "retrofit". I agree that hard wired is best but it's not always
> easy to retrofit. I would keep an eye on HPCC (HomePlug Command &
Control).
> Yitran Communications was chosen to supply the chips and they showed a
> system at the most recent CES show. It is supposed to be reliable and low
> cost.
Agreed re: retrofit.
--
Bobby G.
Robert Green
> > > Oh please, that's just completely unsubstantiated FUD.
> >
> > I wouldn't say that. This is at least the third instance I've heard or
> read
> > about where significant numbers of people have had to retool to
> accommodate
> > new RF interference from military ops.
>
> Three of the SAME THING. Garage door openers using a set of frequencies
the
> vendors KNEW were usable by the military and likely subject to
interference.
Unfortunately the reports also include remote car door openers and alarms.
That would really impact some people quite badly like those with wheelchair
vans, like my Dad. I'm waiting for something to jam up the kneeling van's
remote controls.
> If anything the people stuck with these openers should be bitching to the
> vendor of their garage door opener, not the military. But no, it's just
> more fashionable to bash the military.
I'd bash the FCC or whoever didn't allocate enough spectrum correctly to
serve low powered needs like WiFi, cordless, cameras, etc. The truth is,
everyone is warned. All those devices usually say: "Must accept harmful
interference."
> > If you were to experience any problems and called the Post to say your
> Lutron
> > RA system was hosed, it would very likely *never* be considered
newsworthy
> > because so few others would likely be calling in.
>
> Find a situation where an actual RadioRA setup has suffered from outside
> interference. Lutron's gone out of their way to make that an extremely
> unlikely situation.
It would be interesting to know how true that is. We don't have unfettered
access to Lutron's tech support department. Nor do we know how many RA
installations there are per square mile compared to garage door and car
openers so it's hard to say whether Lutron is better or just far less likely
to have an RA house near an airbase. I tend to believe it's the smaller
user base that's masking any problems. It could be that as RA is indoor
it's better shielded and more resistant to interference than outside
openers.
My admitted very limited understanding of RF is that no matter what error
checking and redundancy you do, a low power system can always be drowned out
by a more powerful transmitter. If I am not mistaken, it's called jamming
and what we are seeing may easily be military tests to neutralize cellphone
and RF-triggered IEDs. They won't work when you jam them. My hunch is that
neither will Radio RA if the right frequency interference is close enough
and strong enough.
Now if I *cared* enough about Lutron RA, I'd go to their site and look for
information about how they've solved this problem. Or I'd email their tech
support because it's certainly a valid, straight up sort of question for
them:
Could Lutron Radio RA suffer from the same problems being reported across
the country for radio operated garage and car door openers?
If not, why not? Did they choose a more isolated frequency? Do they use an
encoding method that somehow allows a weaker signal to "pass thru" a
stronger one? What makes them immune from the same problem a rolling code
garage or car door opener suffers when "jammed?"
It's crate swamping time, so I'll leave that investigation to others. I
don't foresee myself switching to Lutron any time in the future, so it's
kind of moot 4 me.
> > If it's absolutely, positively got to work without any possibility of
> > interference, go hard wired. Neither PLC nor RF is immune to
> interference.
>
> Which would be rather impossible for a garage door opener IN your car.
> Sure, the usual wall-mounted controls are certainly not going to suffer
the
> interference.
(-: Eventually it will be lasers because RF is too easily jammed and
listened in on. Your car will have a pan/tilt aiming device and your garage
a receiver "target" that needs to see a specially encrypted and
authenticated message before it opens. The area of "house" to "car"
information technology is in its infancy but it's taking on many fascinating
twists like GPSs, IPods, remote video, cellphones and more.
> > Hey, if it weren't for General Lafayette, we might not have gained our
> > independence from Merry Olde England. Some Frenchies have spunk. Look
at
> > Napoleon. (-:
>
> Waterloo, 'nuff said.
Everybody's entitled to a bad war here and there. Ask GW.
--
Bobby G.
>
Robert Green
The home powerline is far dirtier, electrically, than it has ever been. But
the same can be said for the RF spectrum. There are more and more
transmissions emanating around the world every day. Both control mechanisms
have been, and will be, subject to interference and signal propagation
issues. That's just life. There are lots of new protocols bouncing about
that may or may not survive. It's too early to tell.
I think our discussions have previously boiled down to a fairly
straightforward cost v. reliability graph, with people who value flawless
performance over price on one end, and me on the other end. I love the fact
that I can put switch points wherever I want them for $1 to $100, depending
on how complicated I want them to be. I value the portability, the
universality and the patent-free nature of X-10.
More importantly, our usage profiles and the unique demands we make on our
systems further separate us, Bill. I like the idea that if I implement a
dog feeder for four dogs, that I still have plenty of addresses left I can
use. I also have controllers that are a snap to address. I like the speed
with which I can set up remote operations. I'm hoping that the powerlines
aren't going to get any worse in terms of signal suckers and interference.
I truly believe that Jeff Volp may have very well bought another 20 years of
use from X-10. If that's true, it works out to about $25 a year to preserve
my existing investment. Less if I had built them myself (but even *I* like
reliability!).
I think your perspective on PLC has not adjusted for the fact that someone
used his noggin and built a demonstrably better mousetrap. The XTBs change
the landscape. I agree that PLC was often as bad as you've noted, but that
was before the XTB.
I'm not sure where you live, but I think it's close enough to a rat's nest
of military transmitters on Nebraska Ave. that you may not be totally immune
if there's a city wide attempt to lock down all remote IED's by jamming.
--
Bobby G.
Robert Green
<stuff snipped>
> As military, police, fire, etc. need additional frequencies, the bands
used
> by unlicensed low-power consumer applications are a logical place to look.
> As we've seen in this case, they can't even be bothered to ask the FCC
what
> technologies they will likely be stepping on and how many people they
might
> inconvenience. I doubt this will be the only instance.
I went to the Lutron site and about all I could find in the FAQ about
vulnerability to jamming from higher powered transmitters is this:
*****************************************************************
http://www.lutron.com/radiora/ra_faq.asp#Q16
"Q16: Will other equipment in my home or neighboring homes interfere with my
RadioRA system?
RadioRA operates at a frequency different from most remote controls,
cellular/portable phones, and other wireless devices. The RadioRA
communication protocol ensures that any device operating at the same
frequency will not affect the lighting on your system. Also, your system
will not affect other RadioRA systems. During startup, your system searches
for other systems in the area and creates a unique system code to prevent
cross-system interaction."
***************************************************************
I think a careful read of that says that while a new military transmitter on
the RA frequency won't turn your lights on inadvertently, there's no
assurance that the user will still be able to control the lighting either!
"Will not effect your lighting" is legally not quite the same as "will not
effect your ability to control your lighting." While a new super USMC
transmitter obviously won't turn on your lights when it's "on air" because
of the complex ID protocol RadioRA uses, it doesn't mean the RA messages
from RA controllers to RA switches themselves won't be blocked entirely by
the interference.
I'd say Lutron's tech staff are the only ones who can conclusively rule on
the question. I imagine that in the light of news stories describing how
other home radio-controlled devices are being affected by new military
transmitters it would be important for them to describe exactly *how* they
are immune and what steps they would take for the consumer if it turned out
they weren't. It would be nice to know what, if anything, is operating at
the same frequency, or could be in the future, as well.
In reading through their site, I see nothing that leads me to believe
they've developed a radio product that can operate in the presence of a
stronger signal operating at the same frequency. If these recent "garage
door killing" transmission tests ARE designed to neutralize remotely
detonated bombs, it would seem RA is a security risk if it allows remote
operation during a jamming transmission. (-: Watch out for the men in the
black helos, Bill. They might be coming to confiscate your gear!
Maybe someone else can ask Lutron directly since I've about exhausted my
interest in this subject unless someone can prove *ANY* home-based RF
solution can operate in the presence of a much stronger transmitter
operating on the same frequency. I know of military frequency hopping
systems that are resistant to jamming, but they're very pricey. I'm still
of the mind that you can shout all you want in the middle of a hurricane,
but no matter how loud you shout, no one will hear you. If it absolutely,
positively has to work, first time, every time, then go hardwired!
Here's are the numbers I culled from the site.
RadioRA toll-free hotline at 1.877.610.7410
Customer Service 1.888.LUTRON1 8AM-8PM EST
Technical Assistance 1.800.523.9466 24 hours a day, 7 days a week
--
Bobby G.
Dave Houston
>I went to the Lutron site and about all I could find in the FAQ about
>vulnerability to jamming from higher powered transmitters is this:
>
>*****************************************************************
>http://www.lutron.com/radiora/ra_faq.asp#Q16
>
>"Q16: Will other equipment in my home or neighboring homes interfere with my
>RadioRA system?
>
>RadioRA operates at a frequency different from most remote controls,
>cellular/portable phones, and other wireless devices. The RadioRA
>communication protocol ensures that any device operating at the same
>frequency will not affect the lighting on your system. Also, your system
>will not affect other RadioRA systems. During startup, your system searches
>for other systems in the area and creates a unique system code to prevent
>cross-system interaction."
>
>***************************************************************
>
>I think a careful read of that says that while a new military transmitter on
>the RA frequency won't turn your lights on inadvertently, there's no
>assurance that the user will still be able to control the lighting either!
That's a nice mixture of technobabble and deliberate disinformation.
IIRC, RadioRA uses 418MHz ASK which is the same frequency and modulation
used by _most_ RF remotes (X-10's 310MHz being the exception).
Assigning a unique "housecode" may prevent accidental interoperability
between neighbors but it will not prevent (any more than Z-Wave using
encryption) capture & playback or jamming. Insteon and UPB require
enrollment of each device which does prevent casual neighborly interference.
But, methinks you are arguing with a RadioRA dealer who already knows all
the above. ;)
Bill Kearney
> I think your perspective on PLC has not adjusted...
You assume too much. PLC in a residential setting will continue to be a
market failure. Not because of anything inferior in the PLC gear, but
because of all the screwy things that can be found in nearly all residential
settings likely to be a candidate for automation. At least with the
airwaves there's regulations on frequency allocation and use.
> I'm not sure where you live, but I think it's close enough to a rat's nest
> of military transmitters on Nebraska Ave. that you may not be totally
immune
> if there's a city wide attempt to lock down all remote IED's by jamming.
No interference whatsoever with our gear out here off Bradley Blvd. But
then neither does a friend's place just east of Tenleytown. So much for
that FUD.
Bill Kearney
> I think a careful read of that says....
More like 'in a desperate attempt to find a way to spin FUD...' Give it a
rest.
> Maybe someone else can ask Lutron directly since I've about exhausted my
> interest in this subject unless someone can prove *ANY* home-based RF
> solution can operate in the presence of a much stronger transmitter
> operating on the same frequency.
I've no idea why you're attempting to stretch the argument to such a
ridiculous extreme.
Bill Kearney
> That would really impact some people quite badly like those with
wheelchair
> vans, like my Dad. I'm waiting for something to jam up the kneeling van's
> remote controls.
What next, spin trying to say it'll harm children? Yeesh, that's just
pathetic.
> or just far less likely
> to have an RA house near an airbase.
Heh, if you can afford this gear, you don't live near an airbase...
Robert Green
>
> > I think your perspective on PLC has not adjusted...
>
> You assume too much. PLC in a residential setting will continue to be a
> market failure. Not because of anything inferior in the PLC gear, but
> because of all the screwy things that can be found in nearly all
residential
> settings likely to be a candidate for automation. At least with the
> airwaves there's regulations on frequency allocation and use.
Arf Arf! The FCC is too busy regulating Janet Jackson's boobs to care about
who runs illegal transmitters. My PLC system is fine now that I have it
"turbocharged" with the XTB. I think it's the sign of the good basic design
of X-10 that a problem like signal suckers and interference can be solved
without wholesale equipment replacement.
> > I'm not sure where you live, but I think it's close enough to a rat's
nest
> > of military transmitters on Nebraska Ave. that you may not be totally
> immune
> > if there's a city wide attempt to lock down all remote IED's by jamming.
>
> No interference whatsoever with our gear out here off Bradley Blvd. But
> then neither does a friend's place just east of Tenleytown. So much for
> that FUD.
Neither places are near any military transmitters that I know of, although
Tenleytown is close to the WTOP towers across from Sears. Two sample points
does NOT make a compelling argument that ALL RadioRA installations are
immune. Perhaps if you lived near Quantico, VA where this last batch of
remote door openers were affected, you'd have a different tale to tell.
You didn't respond to this query before, so I'll ask again. How many
LutronRA users do you estimate there are there per 1K US residents compared
to the number of people per thousand who own car door or garage door remote
openers? The problem is appearing with door openers simply because there
are so many of them in operation, IMHO, compared to RadioRA sites.
--
Bobby G.
Robert Green
>
> > I think a careful read of that says....
>
> More like 'in a desperate attempt to find a way to spin FUD...' Give it a
> rest.
If you were to make *technical* arguments more compelling than "neaner
neaner" I might believe that RadioRA is far superior to the RF systems that
have been knocked out by military transmissions. "It works for me" really
only tells us about your location, your installation and your operational
parameters.
The question here is very simple: "Does RadioRA provide protection from the
kind of interference that has been shutting down RF car and garage
controllers across the country?" So far the answer to that is "nobody seems
to know for sure."
> > Maybe someone else can ask Lutron directly since I've about exhausted my
> > interest in this subject unless someone can prove *ANY* home-based RF
> > solution can operate in the presence of a much stronger transmitter
> > operating on the same frequency.
>
> I've no idea why you're attempting to stretch the argument to such a
> ridiculous extreme.
Ridiculous extreme? Military transmitters have been interfering with home
and car RF controllers across the country. The problem's quite real for
hundreds, if not thousands, of people. Because this is a discussion group,
and the claim has been made that RadioRA isn't prone to the shutdowns that
have plagued people in Colorado and Virginia (you *are* making that claim,
aren't you?) it really requires some further investigation. I've provided
Lutron's tech support numbers so that anyone considering Lutron's RadioRA
can ask for themselves, at the source, whether RA is resistant to the
problems facing other home control RF users. That's not extreme. It's just
being thorough.
Since you don't live in an area known to be affected, your implication that
RA is resistant to jamming really isn't substantiated simply by your
experience. Want to convince me? Find an RA user near Elgin AFB or
Quantico that's unaffected. Or post some sort of technical explanation as
to why RA is immune to jamming that shuts down other RF controllers and I
surely will "give it a rest." Right now, my admittedly limited
understanding of radio transmissions tells me that a stronger transmitter
will completely drown out a weaker one on the same frequency.
I can think of one way of making a transmitter/receiver somewhat "jam
proof" - it's a modification of earlier military technology - and that's to
use two completely separate transceivers on very different bands in the same
unit. If one of the bands is jammed, the radio falls back to a far
different frequency. I've seen nothing in the RA literature to lead me to
believe they've got such a system, but it's possible. Details like that
would tend to shut down debate and "give it a rest" a lot faster than
yelling FUD in a crowded radio spectrum that's only getting more crowded.
Will RA fall victim to the same sort of environmental changes in its
transmission medium that hobbled X-10 in theirs? Only time will tell what
happens in this increasingly wireless world.
--
Bobby G.
Robert Green
So in reality, X-10 is the one that actually "uses a frequency different
from most remote controls, cellular/portable phones, and other wireless
devices" not RadioRA. How ironic!
> Assigning a unique "housecode" may prevent accidental interoperability
> between neighbors but it will not prevent (any more than Z-Wave using
> encryption) capture & playback or jamming. Insteon and UPB require
> enrollment of each device which does prevent casual neighborly
interference.
If RadioRA is jam-proof, I'd sure like to know how they did it.
> But, methinks you are arguing with a RadioRA dealer who already knows all
> the above. ;)
Really? I don't remember him revealing that he was any more than a
satisfied customer. Did I miss a post?
--
Bobby G.
Dave Houston
>So in reality, X-10 is the one that actually "uses a frequency different
>from most remote controls, cellular/portable phones, and other wireless
>devices" not RadioRA. How ironic!
Except that X-10 also uses 418MHz for its Powermids.
>Really? I don't remember him revealing that he was any more than a
>satisfied customer. Did I miss a post?
It's his level of satisfaction and a mention that he left some test gear at
a client that make me suspicious. ;)
Marc_F_Hult
<ROBERT_G...@YAH00.COM> wrote in message
<9N2dncCwPcN4VHrY...@rcn.net>:
>I can think of one way of making a transmitter/receiver somewhat "jam
>proof" - it's a modification of earlier military technology - and that's
>to use two completely separate transceivers on very different bands in the
>same unit.
[ ...] ]
>Will RA fall victim to the same sort of environmental changes in its
>transmission medium that hobbled X-10 in theirs? Only time will tell what
>happens in this increasingly wireless world.
Sounds like a new angle for the aluminum siding pitchmen: Protect your
loved ones from the black-helicopter conspiracy with your very own 50,000
cu ft faraday cage.
----
How did your wheel chair turntable project turn out? Any pictures?
... Marc
Marc_F_Hult
www.ECOntrol.org
Jeff Volp
> Right now, my admittedly limited
> understanding of radio transmissions tells me that a stronger transmitter
> will completely drown out a weaker one on the same frequency.
There is a technique that uses spread-spectrum and correlation between a
received signal and a pseudo-random pattern. It is possible to recover a
weak signal even in the presence of jamming with this method. Bandwidth is
limited, and it takes time to search until a pattern match is found. But it
amazing how that signal pops out of the noise when correlation is achieved.
GPS receivers use this technique to recover the weak satellite signals.
Jeff
Bill Kearney
> would tend to shut down debate and "give it a rest" a lot faster than
> yelling FUD in a crowded radio spectrum that's only getting more crowded.
>
> Will RA fall victim to the same sort of environmental changes in its
> transmission medium that hobbled X-10 in theirs? Only time will tell what
> happens in this increasingly wireless world.
And meanwhile it's nothing but unsubstantiated FUD claiming it's "possible".
Shit, ANYTHING is possible. You want proof it can't be interferred with,
well, show me one that has suffered from interference. Otherwise you're
just spewing "chicken little" style nonsense. Meanwhile PLC continues to be
fraught with perils, often not within it's realm of control, that will
further hamper it's uptake into the residential market.
In the context of this thread I'm merely less than sympathetic to the
"problem" of the garage door openers being interferred with because the
vendors have known about this for YEARS.
Bill Kearney
> >satisfied customer. Did I miss a post?
>
> It's his level of satisfaction and a mention that he left some test gear
at
> a client that make me suspicious. ;)
What makes you anything, Dave, is an unfathomable mystery. I've no
connection to any of this gear besides being an informed customer. Granted,
quite a bit more informed than the average customer.
Marc_F_Hult
<ROBERT_G...@YAH00.COM> wrote in message
<9N2dncCwPcN4VHrY...@rcn.net>:
>Right now, my admittedly limited
>understanding of radio transmissions tells me that a stronger transmitter
>will completely drown out a weaker one on the same frequency.
We trust that BobbyG understands that the limits of what his understanding
happen to be does not constrain or alter the actual physics of the matter.
This summary of spread spectrum may be helpful:
http://www.sss-mag.com/ss.html
Also, I recall reading in an industry rag an explanation of Lutron's choice
of 418mhz that stated that Lutron could and would change RF strategies if
needed. The statement surprised me.
... Marc
Marc_F_Hult
www.ECOntrol.org
Robert Green
> "Robert Green" <ROBERT_G...@YAH00.COM> wrote:
>
> >So in reality, X-10 is the one that actually "uses a frequency different
> >from most remote controls, cellular/portable phones, and other wireless
> >devices" not RadioRA. How ironic!
>
> Except that X-10 also uses 418MHz for its Powermids.
>
> >Really? I don't remember him revealing that he was any more than a
> >satisfied customer. Did I miss a post?
I don't need no stinkin' Powermids to run X10 RF! I've had enough problems
with them recently (too much RF on the 418MHz band, I wonder?) that I am
going to retire them for a $100 system that Smarthome sells. The are at
least 10, if not 20 years old, so I got my money's worth. I'm monitoring
for some feedback at their site since some IR gear appears to get completely
flummoxed by interference from plasma TV's. I'll try to remember to post
the URL when I make up my next order.
I've been having to turn then Powermids on and off remotely via X-10 RF so
that only the pair I am currently using is powered up, but that's a bit of a
bear. IR is certainly something that can be handled via wire pretty easily.
I'll bet someone here could even figure out a mod to make the Powermids work
via wire only, but it's probably not even worth the effort since I can sell
them intact on Ebay.
> It's his level of satisfaction and a mention that he left some test gear
at
> a client that make me suspicious. ;)
I just assumed that meant he had test gear (of some sort, not necessarily RA
related), a client and an occasionally faulty memory, like a lot of us. I
have test gear, and I often leave it at friends and clients alike, but I'm
very obviously NOT a Radio RA dealer. I don't think Bill's a dealer,
either, just a very satisfied customer who had been traumatized by X-10 and
PLC demons and is very relieved to be free of them.
I've got to go search out ways to declack some TM751 or RR501's. For
coverage reasons, I need two units in the basement. In monitoring the dogs
at night, I can clearly see they awaken and get antsy every time they hear a
relay clack. I don't need a single extra reason in the *world* to make one
of the Devil's Four awaken in the middle of the night. I haven't had an
uninterrupted night of sleep since last year. Maybe a declacked transceiver
will help. I recall seeing a mod that used solid state relays . . .
--
Bobby G.
Dave Houston
>I don't need no stinkin' Powermids to run X10 RF! I've had enough problems
>with them recently (too much RF on the 418MHz band, I wonder?) that I am
>going to retire them for a $100 system that Smarthome sells. The are at
>least 10, if not 20 years old, so I got my money's worth. I'm monitoring
>for some feedback at their site since some IR gear appears to get completely
>flummoxed by interference from plasma TV's. I'll try to remember to post
>the URL when I make up my next order.
What Smarthome system? It probably uses 418MHz - almost all of the IR
extenders do.
Dave Houston
>IIRC, RadioRA uses 418MHz ASK which is the same frequency and modulation
>used by _most_ RF remotes (X-10's 310MHz being the exception).
To confirm that they use 418MHz, here's a FAQ from a dealer...
http://www.mrelectric.com/radiora/ra_faq.htm
Dave Houston
But, by definition "spread-spectrum" is not "on the same frequency".
Jeff Volp
> "Jeff Volp" <Jeff...@msn.com> wrote:
>
>>"Robert Green" <ROBERT_G...@YAH00.COM> wrote in message
>>news:9N2dncCwPcN4VHrY...@rcn.net...
>>
>>> Right now, my admittedly limited
>>> understanding of radio transmissions tells me that a stronger
>>> transmitter
>>> will completely drown out a weaker one on the same frequency.
>>
>>There is a technique that uses spread-spectrum and correlation between a
>>received signal and a pseudo-random pattern. It is possible to recover a
>>weak signal even in the presence of jamming with this method. Bandwidth
>>is
>>limited, and it takes time to search until a pattern match is found. But
>>it
>>amazing how that signal pops out of the noise when correlation is
>>achieved.
>>GPS receivers use this technique to recover the weak satellite signals.
>
> But, by definition "spread-spectrum" is not "on the same frequency".
I understand that Dave. I was just pointing out there are techniques to get
around being jammed by a stronger signal. The ICs developed for GPS may
make it feasible to use that approach for mid-price automation products.
While not totally jam proof, such a system could be much more resistant to
external interference.
Jeff
Robert Green
> "Robert Green" <ROBERT_G...@YAH00.COM> wrote:
>
> >I don't need no stinkin' Powermids to run X10 RF! I've had enough
problems
> >with them recently (too much RF on the 418MHz band, I wonder?) that I am
> >going to retire them for a $100 system that Smarthome sells. The are at
> >least 10, if not 20 years old, so I got my money's worth. I'm monitoring
> >for some feedback at their site since some IR gear appears to get
completely
> >flummoxed by interference from plasma TV's. I'll try to remember to post
> >the URL when I make up my next order.
>
> What Smarthome system? It probably uses 418MHz - almost all of the IR
> extenders do.
Sorry, I was unclear. The Smarthome unit is a 4 or 6 drop hardwired system.
I can't recall which at the moment.
--
Bobby G.
Robert Green
RG>> Right now, my admittedly limited understanding of radio
RG>> transmissions tells me that a stronger transmitter will completely
RG>> drown out a weaker one on the same frequency.
> There is a technique that uses spread-spectrum and correlation between a
> received signal and a pseudo-random pattern.
Sounds interesting. But as Dave notes, when you are talking about
spread-spectrum techniques, you've strayed outside the limits of my original
words "same frequency."
I am sure that by using multiple frequencies and high levels of redundancy
that a delayed radio message can be sent intact through heavy interference.
It will always take longer than a straight-up message sent on a single
frequency because of the reconstitution required. It would be nice to know
if Lutron Radio RA use such a method . . .
> It is possible to recover a weak signal even in the presence of jamming
with this
> method. Bandwidth is limited, and it takes time to search until a pattern
match is
> found. But it amazing how that signal pops out of the noise when
correlation is
> achieved. GPS receivers use this technique to recover the weak satellite
signals.
Would it work if more than one of those frequencies were deliberately
jammed?
From your description it sounds like it relies more on the weak signal
appearing just slightly more coherent in the face of random background noise
of the same general signal level. My guess is that if there are spread
spectrum transmitters there are spread spectrum jammers. And if the
Pentagon is afraid that terrorists will use GPS info against them, you can
be pretty sure they are already in the field. (-:
--
Bobby G.
Robert Green
<stuff snipped>
> And meanwhile it's nothing but unsubstantiated FUD claiming it's
"possible".
> Shit, ANYTHING is possible. You want proof it can't be interferred with,
> well, show me one that has suffered from interference. Otherwise you're
> just spewing "chicken little" style nonsense. Meanwhile PLC continues to
be
> fraught with perils, often not within it's realm of control, that will
> further hamper it's uptake into the residential market.
This discussion didn't occur ex nihilo. It was a response to similar RF
transmitters, apparently operating on the same frequencies as RA, being shut
down by recent military tests. If it did come out of nowhere, you'd be
right, it's just FUD. But it didn't come out of nowhere. There have been
persistent, credible, nationwide reports of RF jamming of very similar
equipment by military signals. Signals that obviously weren't being
transmitted as strongly as they are now when RA was designed.
The question of RadioRA's resistance to a jamming signal is perfectly
germane in light of the very recent experience of 100's and maybe 1,000's of
garage door owners. As I've noted before, there are probably so few RA
users *nationwide* that finding any that have had a problem is not going to
be easy. But that doesn't mean that they don't exist. Nor does it mean
that system is designed to reject such interference. In fact, it's becoming
more and more clear that it can't, just on technical, and not anecdotal
evidence. Why would they have a replacement frequency in the wings, as Marc
suggested, if they were immune to interference, as you suggest, or if they
used a spread spectrum design?
> In the context of this thread I'm merely less than sympathetic to the
> "problem" of the garage door openers being interfered with because the
> vendors have known about this for YEARS.
If you really wanted to convince me, a testimonial from an RA user in one of
the known affected areas would be nice. A thousand units operating happily
away in the absence of interference isn't any proof. There are tens of
millions of garage door openers operating normally. Despite those millions,
the ones near Elgin, AFB and Quantico (so far) don't work.
We haven't had any personal reports from any of the affected 100's or
1,000's of garage door owners. So why on earth would you expect to hear
about Lutron RA problems from a much, much smaller set of users? And yet,
without any members *personally* reporting the problem here in CHA, we know
it exists. A similar Lutron problem could just as readily exist and from
the technical discussion so far, appears TO exist.
What's the worst case scenario? Probably that you have to pull all your
gear and return it for a re-fit. Not the end of the world, but a pain. I
believe people considering LutronRA living next to military bases should be
alerted to any potential problems. They also should find out what Lutron
will do for them if they need to switch to a new frequency. That doesn't
seem like FUD to me as much as getting the facts straight for someone that
might be thinking of buying Lutron. Let's see, what's the inverse of FUD?
HCS: Happiness, certainty and surety.
Or is there something wrong with potential Lutron RA purchasers knowing
whether the system is immune to interference already plaguing some home
control RF users? Is there anything wrong with knowing what Lutron will do
for their customers should a jamming transmitter fire up in their
neighborhood, either?
--
Bobby G.
Jeff Volp
>> received signal and a pseudo-random pattern.
>
> Sounds interesting. But as Dave notes, when you are talking about
> spread-spectrum techniques, you've strayed outside the limits of my
> original
> words "same frequency."
>
> I am sure that by using multiple frequencies and high levels of redundancy
> that a delayed radio message can be sent intact through heavy
> interference.
> It will always take longer than a straight-up message sent on a single
> frequency because of the reconstitution required.
Spread-spectrum not as complex as you may think. It does not involve
multiple transmitters running on different frequencies. The pseudo-random
digital pattern is used to modulate a single transmitter, causing its output
to look a lot like noise. The receiver has a copy of the pseudo-random
pattern, and uses that as an input to the correlator. When the patterns
exactly line up, the correlator produces a valid output. All you get is
noise if just one bit off. As I recall, the P-code bit rate is 10.23MHz, so
each bit is only 98nS. Data is modulo-2 added to the pseudo-random code,
and the result modulates the transmitter. So, when the codes are aligned at
the receiver, the data pattern comes out the correlator.
Jeff
Dave Houston
>> What Smarthome system? It probably uses 418MHz - almost all of the IR
>> extenders do.
>
>Sorry, I was unclear. The Smarthome unit is a 4 or 6 drop hardwired system.
>I can't recall which at the moment.
They have an 8-drop hard-wired system for $110.
Dave Houston
Philips uses a simpler method with their RF-capable Prontos. They modulate
the 418MHz carrier with both the bit pattern and with ~36kHz. The receivers
use an Atmel U2538B chip to demodulate the 36kHz after the RF receiver
demodulates the 418MHz. It's similar to how Consumer IR distinguishes a
signal from ambient IR. But I suspect it, as well as the method you
describe, could be jammed by a sufficiently strong RF signal just as
Consumer IR fails in a strong ambient IR field (e.g. fluorescent lights).
AFAIK RadioRA doesn't do anything out of the ordinary. At least, they don't
mention it in their literature or FAQs. I believe their repeaters repeat in
(near) real-time (as opposed to the sequential repeaters used by Z-Wave).
The slight smearing this causes would probably preclude using the method you
describe.
Robert Green
JV>>Spread-spectrum not as complex as you may think. It does not involve
JV> >multiple transmitters running on different frequencies. The
pseudo-random
JV> >digital pattern is used to modulate a single transmitter, causing its
output
JV> >to look a lot like noise. The receiver has a copy of the pseudo-random
JV> >pattern, and uses that as an input to the correlator. When the
patterns
JV> >exactly line up, the correlator produces a valid output. All you get
is
JV> >noise if just one bit off. As I recall, the P-code bit rate is
10.23MHz, so
JV> >each bit is only 98nS. Data is modulo-2 added to the pseudo-random
code,
JV> >and the result modulates the transmitter. So, when the codes are
aligned at
JV> >the receiver, the data pattern comes out the correlator.
There are a number of spread spectrum techniques. The one I am familiar
with:
http://en.wikipedia.org/wiki/Frequency_hopping
clearly switches between frequencies. They go on to say that "Adaptive
Frequency-hopping spread spectrum (AFH) (as used in Bluetooth) improves
resistance to radio frequency interference by avoiding using crowded
frequencies in the hopping sequence." That's a question I was asking
earlier - does Lutron "switch around" channels when it determines they have
high levels of interference?
I was trying to find out some more information about the subject and came
across the FCC rules about frequency hopping:
http://www.fcc.gov/oet/info/rules/part15/part15-2-16-06.pdf
and reading through that makes it clear that in spread spectrum
communications, more bandwidth is required. I assume that means multiple
frequencies, although, as you point out, not multiple transmitters.
The most interesting tidbit I found at Wikipedia was this:
"The most celebrated invention of frequency hopping was that of actress Hedy
Lamarr and composer George Antheil, who in 1942 received patent number
2,292,387 for their "Secret Communications System." This early version of
frequency hopping used a piano-roll to change between 88 frequencies, and
was intended to make radio-guided torpedoes harder for enemies to detect or
to jam."
DH> Philips uses a simpler method with their RF-capable Prontos. They
modulate
DH> the 418MHz carrier with both the bit pattern and with ~36kHz. The
receivers
DH> use an Atmel U2538B chip to demodulate the 36kHz after the RF receiver
DH> demodulates the 418MHz. It's similar to how Consumer IR distinguishes a
DH> signal from ambient IR. But I suspect it, as well as the method you
DH> describe, could be jammed by a sufficiently strong RF signal just as
DH> Consumer IR fails in a strong ambient IR field (e.g. fluorescent
lights).
Which gets us back to the original question. Can RadioRA be jammed with the
same sort of signal that is affecting garage and car door openers near Elgin
AFB and Quantico? Its clear spread spectrum techniques may help make
communications more immune to the standard "noise soup" in the modern RF
environment. That could simply be a result of the FCC allowing SS
transceivers to operate at higher powers than single frequency devices.
Spread-spectrum clocking distributes the energy so that it falls into a
large number of the receiver's frequency bands, without putting enough
energy into any one band to exceed the statutory limits, at least according
to Wiki. But there's no telling whether the door openers in question had
such enhancements and still failed or whether Lutron RA will fail if
operating in the same geographical area.
An interesting comment at:
http://en.wikipedia.org/wiki/Spread_spectrum
says:
"The usefulness of spread spectrum clocking as a method of actually reducing
interference is often debated, but it is probable that some electronic
equipment with sensitivity to a narrowband of frequencies will experience
less interference, while other equipment with broadband sensitivity will
experience more interference."
DH > AFAIK RadioRA doesn't do anything out of the ordinary. At least, they
don't
DH> mention it in their literature or FAQs. I believe their repeaters repeat
in
DH> (near) real-time (as opposed to the sequential repeaters used by
Z-Wave).
There's a good selling point - "we're *much* faster than Z-wave!" That's
like MS's advertising of XP: "much more reliable than previous versions!"
DH> The slight smearing this causes would probably preclude using the method
you
DH> describe.
Part of the reason RA may(?) work so well is that they are very conservative
about the radio range, saying that the units work for 30' in any direction a
worst case scenario with lots of metal in the walls. If your transmitters
and receivers are close, they are more immune to noise. But those low
limits mean (according to them) a 10,000 sq. ft. home will require the
maximum of 4 repeaters. Even so, there's still a maximum of 32 loads and
that's just not enough for me so it doesn't really matter to me if it works
during an EMP blast from an airburst neutron bomb. LutronRA comes up short
in other places, at least for me, no matter how reliable it's claimed to be.
--
Bobby G.
Jeff Volp
spread-spectrum technique I described earlier is used by millions of people
every day in their GPS receivers. Here is the reference:
http://www.navcen.uscg.gov/pubs/gps/sigspec/gpssps1.pdf
It uses a pseudo-random sequence to modulate the transmitter, and receives
through correlation with that exact pattern. Knowing what we had to do in
those early GPS recievers, I find it amazing how cheap they are today. The
wonders of commercialization...
The other technique uses a number of discrete frequencies, and the RF link
hops between those frequencies based on some sequence. This is an easy
system to impliment with digitally tuned synthesizers.
As our RF environment becomes more polluted every day, techniques like this
will become more commonplace in our attempt to achieve reliable
communication.
Jeff
Dave Houston
>There are a number of spread spectrum techniques. The one I am familiar
>with:
>
>http://en.wikipedia.org/wiki/Frequency_hopping
>
>clearly switches between frequencies.
I believe Jeff was describing DSSS (Direct Sequence Spread Spectrum) which
does use only one carrier frequency but is still subject to jamming. See...
http://rfdesign.com/images/archive/0900McCune90.pdf
Jeff Volp
>
> I believe Jeff was describing DSSS (Direct Sequence Spread Spectrum)
> which does use only one carrier frequency but is still subject to
> jamming. See...
>
> http://rfdesign.com/images/archive/0900McCune90.pdf
>
That looks like an excellent reference document.
Yes, GPS uses DSSS. While not immune to jamming, it does tolerate moderate
power narrow-band signals within its bandpass. Its resistance to jamming is
a function of the data rate. From the summary:
"If there are narrowband interferers of moderate level, then a DSSS system
that will completely reject them may be designable. Should there be large
interfering signals, then a DSSS link may completely fail while FSSS is
likely to continue operating even though the interference is not complete
rejected."
The difference is that a jammer may totally block of the discrete
frequencies in the frequency hopping link, so that information is lost. The
integrator in the DSSS link can reject the jammer until its energy dominates
the summation.
Jeff
Robert Green
>
> >There are a number of spread spectrum techniques. The one I am familiar
> >with:
> >
> >http://en.wikipedia.org/wiki/Frequency_hopping
> >
> >clearly switches between frequencies.
>
> I believe Jeff was describing DSSS (Direct Sequence Spread Spectrum) which
> does use only one carrier frequency but is still subject to jamming.
See...
>
> http://rfdesign.com/images/archive/0900McCune90.pdf
We're veering off into one of the semantic excursions that often obscure the
much simpler, original question: Can a system like RadioRA be jammed by a
transmitter of much greater power at the "same frequency?"
The system that Jeff's talking about, DSSS, is described at Wikipedia:
"This noise signal is a pseudorandom sequence of 1 and -1 values, at a
frequency much higher than that of the original signal, thereby spreading
the energy of the original signal into a much wider band."
Band of what? (-:
"As this description suggests, a plot of the transmitted waveform has a
roughly bell-shaped envelope centered on the carrier frequency, just like a
normal AM transmission, except that the added noise causes the distribution
to be much wider than that of an AM transmission."
Distribution of what? (-:
Certainly spread spectrum can performed in a variety of ways, and though
these technologies obviously provide greater *resistance* to jamming than
simple radio designs, nothing I've read so far suggests that any one of them
is *immune* to jamming.
They seem best suited for rejecting the low power interference created by
other, similar devices. DSSS seems especially adept at recovering very weak
signals (like satellite transmissions) from a sea of *normal* radio noise.
It also seems quite useful in providing synchronization information between
multiple transmitters, a great asset to
GPSs. But the military can jam civilian GPSs and they even admit to that
capacity openly, along with the ability to keep military GPSs in operation
while they do it.
******************************************************************
http://www.newscientist.com/article.ns?id=dn3474
The Pentagon has told New Scientist it will not implement a global GPS
blackout for civilian users if war starts in Iraq, as seems increasingly
likely.
"We would not create a global problem for transport out of spite for
Saddam," says a spokesman at the US Department of Defense. However, he
admitted that the US military does have the capability to jam civilian GPS
signals regionally, and did not rule this option out.
. . .
"A GPS expert at the University of New Brunswick in Canada, Richard Langley
says "the civilian GPS signal relies on a so-called "coarse/acquisition
code" (c/a), which enables a receiver to determine the distance to the
satellite. But the US military relies on the "precise code" (p). The p code
is transmitted over a much wider bandwidth than the c/a code explains
Langley: "So you can jam the narrower c/a code without jamming the wider
signal."
******************************************************************
Simple brute force would probably knock out a lot of gear right near the
jamming source. A much larger radius could be achieved if the pseudorandom
sequence of 1 and -1 values of DSSS or the frequency map of a frequency
hopping system were known.
There have been a number of situations I know of where radio traffic shot up
so much in such a short time that communications broke down nearly
completely. 9/11 and the recent tidal wave come to mind. A lot of radio
gear that's never active simultaneously otherwise comes on line and it all
fails. I'm not sure what can be done to address those issues but a lot of
problems resulted from the breakdown of communications at a time when
communications were critical. So there's still room for progress in radio
comm.
Of course, this will be more of an issue when HA switches all have embedded
GPS receivers to detect sinkholes or landslides or other tectonic activities
. . . (-:
--
Bobby G.
Richard Revis
> Would it work if more than one of those frequencies were deliberately
> jammed?
<delurk>
It depends on how expensive your kit is.
Assuming you have a suitably powerful* frequency agile transmitter then
jamming problem is not easy.
You can either:
Jam every frequency the transmitter is using; If there are up to 20
frequencies you need 20 times as much power as jamming a single frequency
for example.
Hop jamming frequencies when you detect that he has changed transmitting
freqnecy, which means that he can transmit in the interval required for you
to catch up. If the hopping is fast enough you may never catch up.
Attempt to guess which frequency he will use next. If this is essentially
unguessable - usin a cryptographic RNG or sufficiently complex (and
unrepeated) predetermined pattern for example - then it's very unlikley you
can do this.
If you would like to put in an RFQ for an unjammable garage door opening
device I'm sure we could come up with something - but it might not fit in
your car. (I should point out that neither crypto nor jamming nor
transmitters feature in my job and I am in no way connected to the people
who work here who do that kind of thing, nor am I talking for my employer,
myself, the church, state or any other body with sufficiently deep pockets
to cause me to regret any statement I have made regardless of it's accuracy
or otherwise.)
*In relationship to the reciever, bear in mind the power square law, you
don't need megawatts to get a high recieved power at 5 feet compared to a
transmitter at 5 miles.
</>
Nomen Lapetos
"Richard Revis" <richar...@baesystems.cREMOVEm> wrote in message
news:45f13815$1...@glkas0286.greenlnk.net...
> "Robert Green" <ROBERT_G...@YAH00.COM> wrote in message
> news:WoSdnfla97CuGXXY...@rcn.net...
>
>> Would it work if more than one of those frequencies were deliberately
>> jammed?
>
> <delurk>
>
> It depends on how expensive your kit is.
>
> Assuming you have a suitably powerful* frequency agile transmitter then
> jamming problem is not easy.
>
> You can either:
>
> Jam every frequency the transmitter is using; If there are up to 20
> frequencies you need 20 times as much power as jamming a single frequency
> for example.
>
> Hop jamming frequencies when you detect that he has changed transmitting
> freqnecy, which means that he can transmit in the interval required for
> you to catch up. If the hopping is fast enough you may never catch up.
>
> Attempt to guess which frequency he will use next. If this is essentially
> unguessable - usin a cryptographic RNG or sufficiently complex (and
> unrepeated) predetermined pattern for example - then it's very unlikley
> you can do this.
you don't have to do any of that, there are other ways, knowledge of a
specific frequency is un-necessary, just the band.
Robert Green
<stuff snipped>
> And meanwhile it's nothing but unsubstantiated FUD claiming it's
"possible".
> Shit, ANYTHING is possible. You want proof it can't be interferred with,
> well, show me one that has suffered from interference. Otherwise you're
> just spewing "chicken little" style nonsense. Meanwhile PLC continues to
be
> fraught with perils, often not within it's realm of control, that will
> further hamper it's uptake into the residential market.
While I can in no way vouch for the accuracy of this claim, while looking
for something else (Uniden 5.8 phones) I did come across this thread:
http://www.avsforum.com/avs-vb/archive/index.php/t-704373.html
and this message:
audiblesolutions 10-07-06, 03:57 PM
[QUOTE=DAP]I do not have any other wireless equipment operating at 5.8 GHz,
but I am sure it is not interferance since the noise does not appear when
using the intercom mode.
[/QUOTE]
<<How have you determined this fact? Just because you have no equipment you
have purchased that uses the 5.8 GHz spectrum does not mean that there are
no other devices also broadcasting at that frequancy that might lead to
issues in your system. I have been on jobs, especially in crowded urban
enviorments, especially high rise aprartment buildings, where all sorts of
external interference caused some system to operate poorly. One famous
example was Lutron's Radio Ra in NYC. It turned out a government agency was
operating on the exact frequancy it was using which caused it not to work
reliablly. They had to bring a spectrum analyzer on to the site to figure
out what was causing the problem. As Newtonian physics still operate and
matter cannot exist in the same space at the same time, how have you
determined that your issues are product related and not enviormental? --
Alan>>
So I cranked up Google to search for "RadioRA NYC problems" and that led to
another document at:
http://www.radiora.biz/technical_info/pdf/RFwhitepaper.pdf.
That described how, in 1999, they added a second frequency to their RadioRA
equipment. From the description of techniques they examined and discarded,
I'm confident that they are not using any spread spectrum encoding
techniques to transmit their signals. I'd say we know exactly how they
intend to deal with any interference on their "A" band at 418MHz. They say:
**********************************************************
RadioRA “B” Frequency 434 MHz – one channel (AM)
In nearly a decade—and with over 1 million devices sold—only one isolated
area in North America has interfered with our one channel RadioRA system—New
York City. The “B” frequency was developed to address this situation.
**********************************************************
That was in 1999, before the WTC and 9/11 and the tests at Elgin, AFB and
Quantico, CA so it's hard to say whether the assumptions they made in that
design whitepaper are still valid.
--
Bobby G.
Robert Green
news:45f13815$1...@glkas0286.greenlnk.net...
> news:WoSdnfla97CuGXXY...@rcn.net...
>
> > Would it work if more than one of those frequencies were deliberately
> > jammed?
>
> <delurk>
A delurk AND a X-post to sci.crypt where I am out of my league, so I see
your X-post, and raise you with a further X-post to a radio newsgroup . . .
hmm . . are there really over 500 newsgroups with the word 'radio' in them?
. . . hmmm. OK. We'll leave the radio folks out of this because I've
answered the primary question in another message in this thread. You win
this hand!
> It depends on how expensive your kit is.
>
> Assuming you have a suitably powerful* frequency agile transmitter then
> jamming problem is not easy.
Ah yes, but in this case, the whole issue revolves around the asterisk. The
question was whether LutronRA, a low power RF home automation switching
system with a stated reliable operational radius of 30 feet, could be jammed
by a much stronger signal. The miracle of spread spectrum, at least IMHO, is
that it allows low-powered devices to communicate with each other as well as
receive signals from great distances. The problem of the garage door
jamming incidents is that it puts low-powered transceivers up against a
transmitter probably powered by a military 500kVA truck-mounted generator
set.
> You can either:
>
> Jam every frequency the transmitter is using; If there are up to 20
> frequencies you need 20 times as much power as jamming a single frequency
> for example.
What happens to the signal if you jam 10 of those channels? Does the
message still get through? What about 5 channels? It all depends, I
assume, on the redundancy present in the transmitted message. What if you
set up your jammer to randomly transmit on the 20 frequencies? Will that be
as effective in jamming the signal as flip-flopping between two of 20 known
frequencies?
Wouldn't you only need to jam as many channels as it would take to destroy
the signal integrity of the tranmission? Bad static in a voice transmission
might not be as a serious as data packets that are corrupted. Wouldn't a
lot depend on the redundancy (if any) built into the distribution of the
signal into different frequencies?
> Hop jamming frequencies when you detect that he has changed transmitting
> freqnecy, which means that he can transmit in the interval required for
you
> to catch up. If the hopping is fast enough you may never catch up.
Of course, you may never have to if you manage to step on enough of the
transmission often enough to prevent its reconstruction at the receiving
end.
> Attempt to guess which frequency he will use next. If this is essentially
> unguessable - usin a cryptographic RNG or sufficiently complex (and
> unrepeated) predetermined pattern for example - then it's very unlikley
you
> can do this.
Agreed. But this sort of technology is not likely to be found in garage
door openers. Those devices do use some pretty sophisticated rolling code
techniques but it's to prevent bad guys from recording and playing back the
opening signal and not to precent jamming.
> If you would like to put in an RFQ for an unjammable garage door opening
> device I'm sure we could come up with something - but it might not fit in
> your car.
(-: Already covered. Pan and tilt mount automatically-aligning laser
sender with line of sight to the garage receiver. When your GPS senses
you're close to home, the laser sender deploys and begins searching for the
receiver. Nothing short of a supernova or a direct atomic blast should be
able to interrupt the transmission.
> (I should point out that neither crypto nor jamming nor
> transmitters feature in my job and I am in no way connected to the people
> who work here who do that kind of thing, nor am I talking for my employer,
> myself, the church, state or any other body with sufficiently deep pockets
> to cause me to regret any statement I have made regardless of it's
accuracy
> or otherwise.)
Shucks, no one would *ever* sue anybody for something they posted on the
net, would they? <deep sarcasm!>
> *In relationship to the reciever, bear in mind the power square law, you
> don't need megawatts to get a high recieved power at 5 feet compared to a
> transmitter at 5 miles.
I wonder exactly how strong the transmissions were that knocked out 100's of
garage door openers and whether we're likely to be seeing more or less
interference on these bands in the future.
--
Bobby G.
Dave Houston
>So I cranked up Google to search for "RadioRA NYC problems" and that led to
>another document at:
>
>http://www.radiora.biz/technical_info/pdf/RFwhitepaper.pdf.
>
>That described how, in 1999, they added a second frequency to their RadioRA
>equipment. From the description of techniques they examined and discarded,
>I'm confident that they are not using any spread spectrum encoding
>techniques to transmit their signals. I'd say we know exactly how they
>intend to deal with any interference on their "A" band at 418MHz. They say:
>
>**********************************************************
>RadioRA “B” Frequency 434 MHz – one channel (AM)
>
>In nearly a decade—and with over 1 million devices sold—only one isolated
>area in North America has interfered with our one channel RadioRA system—New
>York City. The “B” frequency was developed to address this situation.
>
>**********************************************************
>
>That was in 1999, before the WTC and 9/11 and the tests at Elgin, AFB and
>Quantico, CA so it's hard to say whether the assumptions they made in that
>design whitepaper are still valid.
That's about equal parts puffery and technical and seems to be more their
response to ZigBee than anything else. Their critique of "RF standards" and
mesh networks would apply equally to Z-Wave.
They use 418MHz ASK/OOK which is also used by almost all of the IR extenders
(e.g. Powermid) and most of the RF-capable high-end touchscreen remotes
(e.g. Pronto). In Europe, all of the above as well as several RF based
lights/appliance systems use 433.92MHz (i.e. their "B" frequency) and, if
RadioRA sells in Europe they are also required to use 433.92MHz.
Any nearby ~418MHz transmitter will jam their "A" frequency" and any nearby
~434MHz transmitter will jam their "B" frequency.
In this specific case the military frequency was far enough away from 418MHz
that it was not likely to affect any RadioRA but, in general, their
"immunity" from interference is more a matter of miniscule market share than
technical prowess.
For those who reacted by blaming the garage door makers, a glance at FCC
frequency allocations shows that nearly the entire spectrum allowed for
low-power unlicensed use under FCC Part 15 is also allocated for some type
of licensed use. I doubt there's any easy way to determine what particular
sub-band might avoid some future problem like this - it goes with the
territory.
http://www.ntia.doc.gov/osmhome/allochrt.pdf
http://www.panix.com/clay/scanning/frequencies.html
Robert Green
> "Robert Green" <ROBERT_G...@YAH00.COM> wrote:
>
> >So I cranked up Google to search for "RadioRA NYC problems" and that led
to
> >another document at:
> >
> >http://www.radiora.biz/technical_info/pdf/RFwhitepaper.pdf.
<stuff snipped>
> That's about equal parts puffery and technical and seems to be more their
> response to ZigBee than anything else. Their critique of "RF standards"
and
> mesh networks would apply equally to Z-Wave.
Interesting. Zigbee probably would be their main competitive concern.
Proprietary protocol vendors always fear open system designs the most and
with good reason. Let me count the proprietary schemes that have fallen
over dead. Microchannel PC cards. Microsoft's HELP file format.
> They use 418MHz ASK/OOK which is also used by almost all of the IR
extenders
> (e.g. Powermid) and most of the RF-capable high-end touchscreen remotes
> (e.g. Pronto). In Europe, all of the above as well as several RF based
> lights/appliance systems use 433.92MHz (i.e. their "B" frequency) and, if
> RadioRA sells in Europe they are also required to use 433.92MHz.
>
> Any nearby ~418MHz transmitter will jam their "A" frequency" and any
nearby
> ~434MHz transmitter will jam their "B" frequency.
From what I could decipher they based their design decisions on that band
being restricted to some very narrow "on time" broadcasting parameters, i.e.
no continuous or automated traffic on that band as opposed to 2.4GHz's
wireless phones, LANs and cameras. Lutron says they based their design on
their analysis of the RF environment but that environment is already out of
date if I recall their timeline correctly. There's really no telling if
they're really future proof. There's more and more wireless equipment
coming on line each day. Many millions of Homeland Security $'s have gone
into the purchase of emergency radios and other goodies. Who knows what
band they'll be transmitting on and for what? I think the only thing one
can say about the RF spectrum 20 years from now is that it will be a lot
noisier, all over the world.
Some poor radio astronomer out there probably knows precisely how much
earth-generated RF is floating around and how much it increases each year.
This site:
www.ofcom.org.uk/static/archive/ra/smag/papers/smag02-12.doc
says:
"These tiny communication devices will in many cases be disposable items and
are likely to give rise to a general increase in overall background r.f.
signals"
So it seems to me the RF spectrum is going to get as nasty as home
powerlines have become in the thirty years or so that X-10's been around.
RA's reliability may simply come from the conservative 30 foot radial
distance rating of the RadioRA units. As RR pointed out, moving transmitter
and receiver closer even slightly results in significantly more transmitter
power reaching the receiver. Couple that power to the transmission speeds
RA uses, and it's a vast improvement over X-10's PLC abilities. I'm
assuming RA could try/retry a complex 100+ digit command string at least 100
times before either of us could blink. (-:
> In this specific case the military frequency was far enough away from
418MHz
> that it was not likely to affect any RadioRA but, in general, their
> "immunity" from interference is more a matter of miniscule market share
than
> technical prowess.
Probably. But I haven't seen many failure reports at all and they claim to
have 1 million somethings sold (installations, clients, switches,
something - sorry but I can't remember what the million things were but I
was surprised it was that many!) Still, I wouldn't mind seeing a "shootout"
at a trade show to see exactly how it stacks up against other transceivers
in that band.
> For those who reacted by blaming the garage door makers, a glance at FCC
> frequency allocations shows that nearly the entire spectrum allowed for
> low-power unlicensed use under FCC Part 15 is also allocated for some type
> of licensed use. I doubt there's any easy way to determine what particular
> sub-band might avoid some future problem like this - it goes with the
> territory.
The experience with the door openers also indicates that if the military or
the government owns the frequency (or perhaps just wants to borrow it for a
while), low power users might not be on the "need to inform" list. (-: I'd
expect to see more jamming incidents as the military configures itself to
fight against IEDs for the next war, which, if military history is any
indicator, will have nothing to actually *do* with IEDs. But we will be
ready for it. Just like we were prepped to fight either a jungle war or a
Baltic war in the 80's but ended up fighting in the desert. I just wish
Congress could fast-track some troop and vehicle armor the way they do trade
agreements. )-:
> http://www.ntia.doc.gov/osmhome/allochrt.pdf
> http://www.panix.com/clay/scanning/frequencies.html
Lots and lots of gummint bands in dem dere lists!
What I'd really like to know is how Lutron's customer service dealt with the
situation. What did it cost their NYC customers to switch to channel B?
Were the units field upgradeable? Even better, could they be upgraded
without being pulled? With radio modules as cheap as they are these days,
what would it have cost them to design a switch with complete different fall
back frequency, in other words, both A and B in the same switch with either
a DIP or some other way to switch them? Perhaps even auto-hopping if the
switch can't get through on the primary channel.
--
Bobby G.