Hello:

I realize that everyone is going to probably write back and tell me I'm
crazy, but this is really driving me crazy, so let me ask, please.

I'm a retired engineer, but have never worked much with RF.

I have been putting up several models of Kidde and First Alert smoke
detectors in my new house recently.

Several different models, from both brands, both ionization and
photoelectric, some with the 9V battery, some with
the built in 10 year Li cell.

All exhibit the same performance:

About once every day or so, at totally random times, they give 3 or 4
Chirps, then nothing for approx another day or so.
This is not the indication that it gives for an actual fire; rather from the
skimpy instructions they include, an indication of needing a new battery, or
some internal fault the circuitry has discovered on its own.

All the batteries are brand new.

Here's what I'm leading up to:

About a quarter of a mile from my house, in a direct line, there's a Ham
operator with a massive mast of what must be pushing 100 feet in height.
Almost the kind you would see for a small commercial station. Has all sorts
of antenna and beams mounted to it.
I have no idea what freq's he operates at, and really don't want to ask him.

This is obviously a chap who takes his hobby seriously, and probably
radiates at the max allowable power levels, I would guess.

Is there any possibility that if he points his array at my house, it might
radiate enough power to cause my problem ?

If not, any thoughts on what else might be causing these chirps from two
different mfg's., and several models ?

Much thanks,
Bob

Robert11 wrote:
Is there any possibility that if he points his array at my house, it might
radiate enough power to cause my problem ?

Hams are usually pretty cooperative. Knock on his door,
explain the problem, and ask him to run a test for you.
--
73, Cecil http://www.w5dxp.com

"Robert11" wrote in message
. ..
Hello:

I realize that everyone is going to probably write back and tell me I'm
crazy, but this is really driving me crazy, so let me ask, please.

I'm a retired engineer, but have never worked much with RF.

I have been putting up several models of Kidde and First Alert smoke
detectors in my new house recently.

Several different models, from both brands, both ionization and
photoelectric, some with the 9V battery, some with
the built in 10 year Li cell.

All exhibit the same performance:

About once every day or so, at totally random times, they give 3 or 4
Chirps, then nothing for approx another day or so.
This is not the indication that it gives for an actual fire; rather from
the skimpy instructions they include, an indication of needing a new
battery, or some internal fault the circuitry has discovered on its own.

All the batteries are brand new.

Here's what I'm leading up to:

About a quarter of a mile from my house, in a direct line, there's a Ham
operator with a massive mast of what must be pushing 100 feet in height.
Almost the kind you would see for a small commercial station. Has all
sorts of antenna and beams mounted to it.
I have no idea what freq's he operates at, and really don't want to ask
him.

This is obviously a chap who takes his hobby seriously, and probably
radiates at the max allowable power levels, I would guess.

Is there any possibility that if he points his array at my house, it might
radiate enough power to cause my problem ?

If not, any thoughts on what else might be causing these chirps from two
different mfg's., and several models ?

Much thanks,
Bob


Possible.
Smoke detectors not supposed to be radio receivers. In other words, they
should be immune to RF interference. If they have wires going to them, they
work as antennas, pickup more RF and make things worse. Owner or
manufacturers should remedy the situation, usually bypass capacitor or
ferrite choke on the cables help.

Another solution, if there are no wires going to detector, is to insulate
portion of the circuitry with tape and wrap it in a aluminum foil, creates
the shielding and minimizes RF pickup.
Good luck.

Yuri, K3BU.us

I would approach ham and tell him about the problem. Most hams are decent
human beings and will try to sort the problem.

On Sat, 5 May 2007 08:11:40 -0400, "Robert11"
wrote:

Hello:

I realize that everyone is going to probably write back and tell me I'm
crazy, but this is really driving me crazy, so let me ask, please.

I'm a retired engineer, but have never worked much with RF.

I have been putting up several models of Kidde and First Alert smoke
detectors in my new house recently.

Several different models, from both brands, both ionization and
photoelectric, some with the 9V battery, some with
the built in 10 year Li cell.

All exhibit the same performance:

About once every day or so, at totally random times, they give 3 or 4
Chirps, then nothing for approx another day or so.
This is not the indication that it gives for an actual fire; rather from the
skimpy instructions they include, an indication of needing a new battery, or
some internal fault the circuitry has discovered on its own.

All the batteries are brand new.

Here's what I'm leading up to:

About a quarter of a mile from my house, in a direct line, there's a Ham
operator with a massive mast of what must be pushing 100 feet in height.
Almost the kind you would see for a small commercial station. Has all sorts
of antenna and beams mounted to it.
I have no idea what freq's he operates at, and really don't want to ask him.

This is obviously a chap who takes his hobby seriously, and probably
radiates at the max allowable power levels, I would guess.

Is there any possibility that if he points his array at my house, it might
radiate enough power to cause my problem ?

If not, any thoughts on what else might be causing these chirps from two
different mfg's., and several models ?

Much thanks,
Bob

I don't think you could trip a smoke detector with RF if you tried.

Those things work very well. Multiple sensors triggering means you
have a REAL PROBLEM!

There is either some connection smoldering (damaged wall switch?) or
some substance in the air being circulated by the ventilation system
that is triggering the alarms.

Unless you have an all electric house you need carbon monoxide sensors
as well.

Visit your local Fire Station and ask their advice. They will likely
take a serious interest in your problem.

Whatever you do, do not ignore the problem!

John Ferrell W8CCW
"Life is easier if you learn to
plow around the stumps"

On May 5, 5:11 am, "Robert11" wrote:
Hello:

I realize that everyone is going to probably write back and tell me I'm
crazy, but this is really driving me crazy, so let me ask, please.

I'm a retired engineer, but have never worked much with RF.

I have been putting up several models of Kidde and First Alert smoke
detectors in my new house recently.

Several different models, from both brands, both ionization and
photoelectric, some with the 9V battery, some with
the built in 10 year Li cell.

All exhibit the same performance:

About once every day or so, at totally random times, they give 3 or 4
Chirps, then nothing for approx another day or so.
This is not the indication that it gives for an actual fire; rather from the
skimpy instructions they include, an indication of needing a new battery, or
some internal fault the circuitry has discovered on its own.

All the batteries are brand new.

Here's what I'm leading up to:

About a quarter of a mile from my house, in a direct line, there's a Ham
operator with a massive mast of what must be pushing 100 feet in height.
Almost the kind you would see for a small commercial station. Has all sorts
of antenna and beams mounted to it.
I have no idea what freq's he operates at, and really don't want to ask him.

This is obviously a chap who takes his hobby seriously, and probably
radiates at the max allowable power levels, I would guess.

Is there any possibility that if he points his array at my house, it might
radiate enough power to cause my problem ?

If not, any thoughts on what else might be causing these chirps from two
different mfg's., and several models ?

Much thanks,
Bob

Hi Bob,

I've set off just about everything at one point or another by
transmitting, but so far, never a smoke detector. Doesn't mean it's
not possible though. I would do as Cecil suggested, and ask your
neighbor if he'd be willing to run a quick test. Chances are that
it's probably not the source, but if it is, he might be able to help
you find a solution to the problem.

Jim AC6XG

Although it's possible that RF is triggering the alarms, I think it's
highly unlikely in this case for the following reasons:

1. Battery operated alarms are physically small, so they make very poor
receiving antennas. That inherently makes them pretty immune to RF.

2. Although it's possible that one particular design might be
particularly sensitive, it's unlikely that several quite different ones
would be equally sensitive.

3. Typical amateur operating habits usually involve a comparatively long
period of operation at one frequency and direction. A few chirps per day
doesn't fit this pattern.

So I think you're looking in the wrong place for the problem. But I sure
don't know where you should be looking. I've had an ionization alarm
trigger from such things as steam from a nearby bathroom when someone
takes a shower, but I'd be surprised if it would get thick enough to
trigger a photoelectric alarm, or widespread enough to trigger multiple
alarms. But there are probably some resources on the web which can help
you sort it out. Good luck!

Roy Lewallen, W7EL

"Yuri Blanarovich" wrote in message
...

"Robert11" wrote in message
. ..
Hello:

I realize that everyone is going to probably write back and tell me I'm
crazy, but this is really driving me crazy, so let me ask, please.

I'm a retired engineer, but have never worked much with RF.

I have been putting up several models of Kidde and First Alert smoke
detectors in my new house recently.

Several different models, from both brands, both ionization and
photoelectric, some with the 9V battery, some with
the built in 10 year Li cell.

All exhibit the same performance:

About once every day or so, at totally random times, they give 3 or 4
Chirps, then nothing for approx another day or so.
This is not the indication that it gives for an actual fire; rather from
the skimpy instructions they include, an indication of needing a new
battery, or some internal fault the circuitry has discovered on its own.

All the batteries are brand new.

Here's what I'm leading up to:

About a quarter of a mile from my house, in a direct line, there's a Ham
operator with a massive mast of what must be pushing 100 feet in height.
Almost the kind you would see for a small commercial station. Has all
sorts of antenna and beams mounted to it.
I have no idea what freq's he operates at, and really don't want to ask
him.

This is obviously a chap who takes his hobby seriously, and probably
radiates at the max allowable power levels, I would guess.

Is there any possibility that if he points his array at my house, it
might radiate enough power to cause my problem ?

If not, any thoughts on what else might be causing these chirps from two
different mfg's., and several models ?

Much thanks,
Bob


Possible.
Smoke detectors not supposed to be radio receivers. In other words, they
should be immune to RF interference.

In a perfect world, yes. I had a problem with RF getting into a CO detector,
the plug-in AC powered kind. When I opened it up, I found there was only one
bypass cap on the circuit board, a 100 uF electrolytic. Adding a .1 to the
board, and a .01/1000V across the AC line fixed it. Somebody else with the
same problem ended up having to make a shield out of aluminum foil inside
the enclosure. His was AC, with a DC backup. Never had problems witj smoke
detectors, and the CO alarm is only affected at the 1KW power level. Also, I
am talking about less than 50 feet of separation here, not several blocks.

Tam/WB2TT


If they have wires going to them, they
work as antennas, pickup more RF and make things worse. Owner or
manufacturers should remedy the situation, usually bypass capacitor or
ferrite choke on the cables help.

Another solution, if there are no wires going to detector, is to insulate
portion of the circuitry with tape and wrap it in a aluminum foil, creates
the shielding and minimizes RF pickup.
Good luck.

Yuri, K3BU.us

I would approach ham and tell him about the problem. Most hams are decent
human beings and will try to sort the problem.

Robert11 wrote:
Hello:

About a quarter of a mile from my house, in a direct line, there's a Ham
operator with a massive mast of what must be pushing 100 feet in height.
Almost the kind you would see for a small commercial station. Has all sorts
of antenna and beams mounted to it.
I have no idea what freq's he operates at, and really don't want to ask him.

He would probably be quite happy to tell you.

This is obviously a chap who takes his hobby seriously, and probably
radiates at the max allowable power levels, I would guess.

Is there any possibility that if he points his array at my house, it might
radiate enough power to cause my problem ?

Yes it is quite possible.

As someone else said, ask him to run a test.

You could also test for RFI yourself by wrapping it in metal foil
(tinfoil). That would make a good Faraday cage and would stop any RF
reaching it - not only his of course.

Of course, that assumes you could hear the alarm.

However, if it is his transmitter that is causing your alarms to go off,
you can be 100% it is a fault on your alarm(s). They should not be
responding to the RF. Unfortunately, although things have improved over
the years, consumer items are not very immune to RF - it costs a few
cents more to add decent RF protection.

It would probably be fairly easy to harden one against RF. Covering the
solid parts of the case with metal paint would help a lot.

If not, any thoughts on what else might be causing these chirps from two
different mfg's., and several models ?

RFI seems quite a likely cause, but it could be very local, such as
something arcing in your house.

As I say, screening the alarms would tell you if its RFI.

Much thanks,
Bob




--
Dave (from the UK)

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