Army interferes with garage doors.

[Reed]

Today on the news I heard that a big bunch of electronic garage door
openers weren't working in Churchville Maryland because the govt. at
the Aberdeen Proving Grounds was doing something with a satellite or
something. Tomorrow their going to do the same thing around Aberdeen.

People are paying techs to change the freqs, but some may have paid
for other repairs by mistake, one would assume.

Someone in charge admits he didn't get the word out well enough.

1) Don't they assign frequency ranges to things so that this sort of
thing doesn't happen?

2) How could the use of a frequency mess up the garage door openers?
Even if the govt. signal was stronger, why wouldn't the opener still
work? If the govt. signal was picked up by the opener, how come the
doors didn't open or shut. (Apparently they didn't since they would
surely have mentioned that.)


If you are inclined to email me
for some reason, remove NOPSAM

read here:
http://www.ddc.dla.mil/news/2005_02_15_FCC_Garage_Door.pdf

 

[Arfa Daily]

Today on the news I heard that a big bunch of electronic garage door
openers weren't working in Churchville Maryland because the govt. at
the Aberdeen Proving Grounds was doing something with a satellite or
something. Tomorrow their going to do the same thing around Aberdeen.

People are paying techs to change the freqs, but some may have paid
for other repairs by mistake, one would assume.

Someone in charge admits he didn't get the word out well enough.

1) Don't they assign frequency ranges to things so that this sort of
thing doesn't happen?

2) How could the use of a frequency mess up the garage door openers?
Even if the govt. signal was stronger, why wouldn't the opener still
work? If the govt. signal was picked up by the opener, how come the
doors didn't open or shut. (Apparently they didn't since they would
surely have mentioned that.)

Front end swamping ?

Garage door openers are coded so that your remote doesn't open every door in
the street ??

Arfa

 

[PeterD]

Today on the news I heard that a big bunch of electronic garage door
openers weren't working in Churchville Maryland because the govt. at
the Aberdeen Proving Grounds was doing something with a satellite or
something. Tomorrow their going to do the same thing around Aberdeen.

People are paying techs to change the freqs, but some may have paid
for other repairs by mistake, one would assume.

Someone in charge admits he didn't get the word out well enough.

1) Don't they assign frequency ranges to things so that this sort of
thing doesn't happen?

No, they don't. Shared and the primary user (military) has priority,
all non-primary users much accept any interference generated by the
primary user.

2) How could the use of a frequency mess up the garage door openers?

Well, if two signals could occupy the same frequency, we'd only need
televisions with one channel, right?

Even if the govt. signal was stronger, why wouldn't the opener still
work?

OK, so your car's FM radio picks up a given station. It picks up the
strongest station, in fact if that strongest station were to suddnly
stop transmitting (say a power or equipment failure) you'd then
probably pick up the next strongest station on the same frequency...
Strongest wins, in this and in fighting.

If the govt. signal was picked up by the opener, how come the
doors didn't open or shut. (Apparently they didn't since they would
surely have mentioned that.)

Huh? So the military signal overpowers the remote... How's it going to
work?

 

[clifto]

If the govt. signal was picked up by the opener, how come the
doors didn't open or shut. (Apparently they didn't since they would
surely have mentioned that.)

For the same reason that all garage doors don't open when you push the
remote for one.

 

[Percival P. Cassidy]

Today on the news I heard that a big bunch of electronic garage door
openers weren't working in Churchville Maryland because the govt. at
the Aberdeen Proving Grounds was doing something with a satellite or
something. Tomorrow their going to do the same thing around Aberdeen.

People are paying techs to change the freqs, but some may have paid
for other repairs by mistake, one would assume.

Someone in charge admits he didn't get the word out well enough.

1) Don't they assign frequency ranges to things so that this sort of
thing doesn't happen?

2) How could the use of a frequency mess up the garage door openers?
Even if the govt. signal was stronger, why wouldn't the opener still
work? If the govt. signal was picked up by the opener, how come the
doors didn't open or shut. (Apparently they didn't since they would
surely have mentioned that.)

Garage door openers (and a bunch of other household electronic devices
(e.g., cordless phones, computers, wireless networking systems, wireless
remote temperature/humidity sensors) are unlicensed devices governed by
Part 15 of the FCC regs. They must not interfere with licensed services
but must put up with any interference from licensed services. So if your
garage door opener interferes with your ham-radio neighbor's
communications, it's your responsibility to fix the problem (e.g., by
replacing or refraining from using the offending device). Similarly, as
long as your ham-radio neighbor is operating within the terms of his/her
license and you keep hearing him/her in your cordless phone, that again
is your problem -- although he/she ought to be willing to assist you in
finding a solution to the problem (but is under no obligation to
actually fix the problem or pay for somebody else to fix the problem).

Perce

 

[[email protected]]

1) Don't they assign frequency ranges to things so that this sort of
thing doesn't happen?

As someone else stated the front end of the garage door openers
receiver is being swamped by a strong signal. This signal need not
be the same frequency. It only has to be very strong and dilute the
remote so that it can not be picked up.

 

[Kurt Ullman]

As someone else stated the front end of the garage door openers
receiver is being swamped by a strong signal. This signal need not
be the same frequency. It only has to be very strong and dilute the
remote so that it can not be picked up.

Sorta like what happens when you are trying to use FM channels to
listen in your car to the portable iPod or satellite radio. You get a
strong station even a couple of channels over and you have to retune,
often to the other end of the spectrum.

 

[mm]

Today on the news I heard that a big bunch of electronic garage door
openers weren't working in Churchville Maryland because the govt. at
the Aberdeen Proving Grounds was doing something with a satellite or
something. Tomorrow their going to do the same thing around Aberdeen.

People are paying techs to change the freqs, but some may have paid
for other repairs by mistake, one would assume.

Someone in charge admits he didn't get the word out well enough.

1) Don't they assign frequency ranges to things so that this sort of
thing doesn't happen?

2) How could the use of a frequency mess up the garage door openers?
Even if the govt. signal was stronger, why wouldn't the opener still
work? If the govt. signal was picked up by the opener, how come the
doors didn't open or shut. (Apparently they didn't since they would
surely have mentioned that.)


If you are inclined to email me
for some reason, remove NOPSAM

 

[Sjouke Burry]

Today on the news I heard that a big bunch of electronic garage door
openers weren't working in Churchville Maryland because the govt. at
the Aberdeen Proving Grounds was doing something with a satellite or
something. Tomorrow their going to do the same thing around Aberdeen.

People are paying techs to change the freqs, but some may have paid
for other repairs by mistake, one would assume.

Someone in charge admits he didn't get the word out well enough.

1) Don't they assign frequency ranges to things so that this sort of
thing doesn't happen?

2) How could the use of a frequency mess up the garage door openers?
Even if the govt. signal was stronger, why wouldn't the opener still
work? If the govt. signal was picked up by the opener, how come the
doors didn't open or shut. (Apparently they didn't since they would
surely have mentioned that.)


If you are inclined to email me
for some reason, remove NOPSAM

I have used these openers for datatransmission, and the type I used
had 8 tri_state codeswitches.
If the code does not fit, nothing happens, when some outside transmitter
intervenes.
The codestring contained about 42 bytes in total, and it is difficult to
trigger that with some random signal.
In case of interference, you just have to get closer to your receiver,
for it to work.

 

[EXT]

Garage door openers (and a bunch of other household electronic devices
(e.g., cordless phones, computers, wireless networking systems, wireless
remote temperature/humidity sensors) are unlicensed devices governed by
Part 15 of the FCC regs. They must not interfere with licensed services
but must put up with any interference from licensed services. So if your
garage door opener interferes with your ham-radio neighbor's
communications, it's your responsibility to fix the problem (e.g., by
replacing or refraining from using the offending device). Similarly, as
long as your ham-radio neighbor is operating within the terms of his/her
license and you keep hearing him/her in your cordless phone, that again is
your problem -- although he/she ought to be willing to assist you in
finding a solution to the problem (but is under no obligation to actually
fix the problem or pay for somebody else to fix the problem).

Perce

This is the same sort of problem that some Chrysler cars had in the 90s. If
you drove by a powerful radar installation, and the beam hit your car, it
would stall due to interference with the electronic ignition/computer
components in the car. The car manufacturer had to come up with a
modification to harden the engine's controls to the radar signal.

 

[S. Barker]

sounds like some bs to me.

s

 

[aemeijers]

Today on the news I heard that a big bunch of electronic garage door
openers weren't working in Churchville Maryland because the govt. at
the Aberdeen Proving Grounds was doing something with a satellite or
something. Tomorrow their going to do the same thing around Aberdeen.

People are paying techs to change the freqs, but some may have paid
for other repairs by mistake, one would assume.

Someone in charge admits he didn't get the word out well enough.

1) Don't they assign frequency ranges to things so that this sort of
thing doesn't happen?

2) How could the use of a frequency mess up the garage door openers?
Even if the govt. signal was stronger, why wouldn't the opener still
work? If the govt. signal was picked up by the opener, how come the
doors didn't open or shut. (Apparently they didn't since they would
surely have mentioned that.)


If you are inclined to email me
for some reason, remove NOPSAM

Must be a slow news day in Maryland- this has been going on for years,
at multiple bases, and even at some civil airports. Like others in the
thread have said, homeowners are legally SOL- low-power non-licensed
consumer devices are not protected. Megawatts versus milliwatts, the
big-ass transmitter will simply overpower the tiny one. Sometimes
repositioning or changing the length of the antenna pickup wire attached
to the opener can help. Sound like the local garage door companies have
their shears out.

Did the article say if the base was working with the locals, to maybe
fine-tune reality a tad, and move their transmitter to a freq that would
cause less problems, or reorient the transmitting antenna? They aren't
obligated to, but base commanders <hate> having the locals all pissy
with them. They have done that at some bases, to include providing the
local media with how-to guides about moving the antenna wire in the
garage and such.

aem sends...

 

[Arfa Daily]

sounds like some bs to me.

s

Why ??

Arfa

 

[Dave Platt]

Today on the news I heard that a big bunch of electronic garage door
openers weren't working in Churchville Maryland because the govt. at
the Aberdeen Proving Grounds was doing something with a satellite or
something. Tomorrow their going to do the same thing around Aberdeen.

People are paying techs to change the freqs, but some may have paid
for other repairs by mistake, one would assume.

Someone in charge admits he didn't get the word out well enough.

1) Don't they assign frequency ranges to things so that this sort of
thing doesn't happen?

Not really. The garage door openers are "Part 15" devices - they
don't have a reserved frequency allocation. Instead, they (and other
low-power devices) are allowed to use a wide range of frequencies that
are primarily allocated for other radio services.

2) How could the use of a frequency mess up the garage door openers?
Even if the govt. signal was stronger, why wouldn't the opener still
work? If the govt. signal was picked up by the opener, how come the
doors didn't open or shut. (Apparently they didn't since they would
surely have mentioned that.)

A lot of unlicensed (Part 15) devices such as garage door openers and
car-alarm keyfobs use frequencies around 433.920 MHz.

The primary usage allocation for this frequency band is government
echolocation (radar). Ham radio operators have a secondary allocation
(i.e. they can use it as long as they don't interfere with government
radar). Unlicensed users are tertiary, and have *no* legal protection
against interference from licensed, or other unlicensed users.

The transmitters for these Part 15 devices use very low power, by
design and law. The receivers for them are, well, let's say
"inexpensively made" - they tend to be reasonably sensitive (so that they
can pick up the weak signals from the transmitters) but are not at all
selective.

Strong signals from other transmitters, on the same or nearby
frequency bands, can overload (saturate) the RF front end circuitry in
these receivers - a phenomenon known as desensitization or "desense".
When this happens, a strong transmission can completely block the
weaker one, even if the actual frequencies of the two transmissions
don't overlap at all. It's sort of like trying to hear a low-pitched
voice speaking quietly in the next room, when somebody is blasting
your eardrums with a piccolo

 

[noespaem]

Did the article say if the base was working with the locals, to maybe
fine-tune reality a tad, and move their transmitter to a freq that would
cause less problems, or reorient the transmitting antenna? They aren't
obligated to, but base commanders <hate> having the locals all pissy
with them. They have done that at some bases, to include providing the
local media with how-to guides about moving the antenna wire in the
garage and such.

aem sends...

the base is under no obligation to do anything. some base commanders
have chosen to create more trouble for themselves by attempting to
accomodate the "locals". they then discover the cost associated with
any "mitigation" strategy to be cost prohibitive.

there is no one single "transmitter". there are several - these are
Motorola digital APCO P25 trunking systems. a "control channel" is
continously transmitting 24/7. the other transmitters will key up
to carry voice traffic as needed (as assigned by the central controller,
the "brains" of the system).

it is NOT a simple process to modify the frequency bandplan due to
the domino effect on the rest of the system. trunking central controllers
would need to be reprogrammed, databases changed, subscribers (ie. the
hundreds of portable walkie talkies and mobiles in the field) would need
to be bought in and reprogrammed, and RF transmit combiners would need
to be retuned. These are NOT simple tasks !

"reorienting" an antenna is not going to work either. the coverage
on these systems is OMNI directional (ie. we strive to provide a perfect
circle, if possible). the typical goal is >95% coverage for a portable.
in practice, we can usually achieve numbers greater than that.

now, if a spineless base commander wants to pay the several hundred
thousand dollars to do a new engineering study and then the actual
man hours involved in implementing a frequency change (that they are
under ZERO obligation to do), then i'm sure the vendor (Motorola) would
be more than happy to accomodate them - just show them the money !

however, it's unlikely any new frequency within the assigned govt.
spectrum will solve the problem. you're always going to have some
part 15 device affected.

the answer is better engineering on the consumer side (ie. move the
devices to another frequency band, and tighten up the front end
selectivity on the receiver).

 

[aemeijers]

the base is under no obligation to do anything. some base commanders
have chosen to create more trouble for themselves by attempting to
accomodate the "locals". they then discover the cost associated with
any "mitigation" strategy to be cost prohibitive.

there is no one single "transmitter". there are several - these are
Motorola digital APCO P25 trunking systems. a "control channel" is
continously transmitting 24/7. the other transmitters will key up
to carry voice traffic as needed (as assigned by the central controller,
the "brains" of the system).

it is NOT a simple process to modify the frequency bandplan due to
the domino effect on the rest of the system. trunking central controllers
would need to be reprogrammed, databases changed, subscribers (ie. the
hundreds of portable walkie talkies and mobiles in the field) would need
to be bought in and reprogrammed, and RF transmit combiners would need
to be retuned. These are NOT simple tasks !

"reorienting" an antenna is not going to work either. the coverage
on these systems is OMNI directional (ie. we strive to provide a perfect
circle, if possible). the typical goal is >95% coverage for a portable.
in practice, we can usually achieve numbers greater than that.

now, if a spineless base commander wants to pay the several hundred
thousand dollars to do a new engineering study and then the actual
man hours involved in implementing a frequency change (that they are
under ZERO obligation to do), then i'm sure the vendor (Motorola) would
be more than happy to accomodate them - just show them the money !

however, it's unlikely any new frequency within the assigned govt.
spectrum will solve the problem. you're always going to have some
part 15 device affected.

the answer is better engineering on the consumer side (ie. move the
devices to another frequency band, and tighten up the front end
selectivity on the receiver).

Don't know about the current case, but the ones previously written up
were NOT LMR systems, trunked APCO p25 or otherwise- they were radar r&d
sites. One of my duties at work is buying LMR systems, so I do
understand how those work. (or in the case of the local public safety
LMR, NOT work.) I've never heard of a trunking control channel causing
problems for garage door openers- the repeaters just aren't that
powerful. I suppose it is possible, but reorienting the antenna for the
part 15 device usually would fix that.

No, a base commander is not gonna break his budget or compromise mission
capability to keep the locals happy. But since 'having a good working
relationship with local civil authorities' is one of the things he gets
rated on, he isn't gonna tell them to eff off, either. Having a senior
tech and a PR flack give a few tours, and provide info to local media,
can go a long way.

aem sends...

 

[Michael Kennedy]

I have used these openers for datatransmission, and the type I used
had 8 tri_state codeswitches.
If the code does not fit, nothing happens, when some outside transmitter
intervenes.
The codestring contained about 42 bytes in total, and it is difficult to
trigger that with some random signal.
In case of interference, you just have to get closer to your receiver,
for it to work.

Or get a signal amplifier, although I'm sure that is not legal.

Mike

 

[clifto]

Or get a signal amplifier, although I'm sure that is not legal.

That's it, a garage door opener transmitter with a 500-watt linear amplifier.

 

[noespaem]

Don't know about the current case, but the ones previously written up
were NOT LMR systems, trunked APCO p25 or otherwise- they were radar r&d
sites.

the new system at Eglin AFB ran afoul of some locals in the
developments nearby (who discovered their garage door openers
were being hit with the equivalent of a jammer - the emitter
being the control channel of the new trunking system).

there have been other reports of similar spectrum issues at
other installations.

now in a different reverse case, the military is claiming
amateur radio repeaters are interfering with some PAVE PAWS
radar sites. which the ARRL is cooperating with them to
address the issues.

One of my duties at work is buying LMR systems, so I do
understand how those work. (or in the case of the local public safety
LMR, NOT work.)

is "MA/COM" in that scenario ?

I've never heard of a trunking control channel causing
problems for garage door openers- the repeaters just aren't that
powerful.

typical output on a licensed transmitter is approximately 55 watts
out of the transmit combiner to, say a 100' high, 7 db gain antenna. so
anyone can do the math here. a nominal receiver sensitivity number
for receiver 5% BER (on the subscriber side) is probably about -120 dbm
of signal.

the "average" part 15 consumer device is hard of hearing to begin
with (compared to a $4000 high end Motorola unit). so it has some
attenuation hearing it's intended signal (the remote) to begin
with. flooding the area with the control channel signal only adds
to the noise mask the garage door receiver would need to struggle
against.

also keep in mind, these systems operate in the spectrum slots
assigned to US federal govt users. so, it's not going to be the
800 mhz, or 450-512 band slices.

the remote manufacturers rolled the dice (on operating on frequencies
that could be reclaimed by the govt at anytime), and they lost.
unfortunately the consumer is caught in the middle. of course,
the manufacturers specifically have wording in their manuals that
address the possibility of interference and disclaim all liability
for same.

I suppose it is possible, but reorienting the antenna for the
part 15 device usually would fix that.

see above, maybe, maybe not - probably not.

No, a base commander is not gonna break his budget or compromise mission
capability to keep the locals happy. But since 'having a good working
relationship with local civil authorities' is one of the things he gets
rated on, he isn't gonna tell them to eff off, either. Having a senior
tech and a PR flack give a few tours, and provide info to local media,
can go a long way.

agreed, most CO's are politically savvy (unfortunately so in some cases,
but we won't go there).

 

[DerbyDad03]

Today on the news I heard that a big bunch of electronic garage door
openers weren't working in Churchville Maryland because the govt. at
the Aberdeen Proving Grounds was doing something with a satellite or
something.  Tomorrow their going to do the same thing around Aberdeen.

People are paying techs to change the freqs, but some may have paid
for other repairs by mistake, one would assume.  

Someone in charge admits he didn't get the word out well enough.

1) Don't they assign frequency ranges to things so that this sort of
thing doesn't happen?

2) How could the use of a frequency mess up the garage door openers?
Even if the govt. signal was stronger, why wouldn't the opener still
work?  If the govt. signal was picked up by the opener, how come the
doors didn't open or shut. (Apparently they didn't since they would
surely have mentioned that.)

If you are inclined to email me
for some reason, remove NOPSAM  

re: some may have paid for other repairs by mistake, one would
assume.

You know what happens when one assumes...