Radio controlled clock question

I figure many guys in this group must have one of those "atomic clocks" set
by the Boulder radio broadcast.

Have any of you had problems with bogus signals -- someone intentionally
setting clocks wrong?

I live in La Mesa (near San Diego) and periodically find my clock to be
incorrect -- usually by exactly one minute or hour. I've even caught it
setting itself at times of the day it has no business resetting itself.
SOMEbody's messing, as far as I can tell -- and they've been doing it for
several years. Is that a common problem with these things?

(I see that NIST actually PUBLISHES the time signal format on their site,
which should make it very easy for radio-geeks to tamper.)

--cleve

Hi Cleve:

The NIST correction signal for digital clocks is transmitted on a very low
frequency (far below the AM broadcast band).

Although it's theoretically possible for somebody to transmit a VLF signal
to spoof your clock, putting together a VLF transmitter and antenna and then
putting out a signal of any appreciable power would be very, very difficult.

As a rule of thumb, the lower you go in frequency, the greater the natual
and manmade radio noise. Modern electrical and electronic equipment puts out
a LOT of radio crud in the VLF portion of the spectrum. This interference
goes long distances over power lines and electrical wiring. Worse, power
lines and wiring work as antennas and radiate this manmade crud.

My advice would be to try moving your clock to a different location in an
attempt to get it away from any interference. If you really want to get
serious, you can get a portable AM radio, tune it to an empty frequency, and
walk around the house and listen to the noise to determine where the
interference is minimal. When you find a quieter place, put your clock
there.

In addition to manmade interference is the problem of getting good reception
of the actual NIST correction signal. Houses in southern California
typically use metal foil-backed insulation in the walls and metal screen to
hold the stucco. The foil and screen really block radio signals. If your
clock uses a length of wire to receive the correction signal, try the
following:

- Make sure the wire is fully stretched out to its full length

- Once you've found a fairly interference free part of your home, drill a
tiny diameter (1/8 inch)
hole through the wall insert a small diameter brass tube from a hobby
shop through
the wall, and then put your wire antenna through the wall. Then string
up the wire in a straight
line.

I hope that helps.

Regards,

Brian Webb, KD6NRP
Southern California

"cleve" wrote in message
news:kDaDc.1358$6r1.499@fed1read06...
I figure many guys in this group must have one of those "atomic clocks"
set
by the Boulder radio broadcast.

Have any of you had problems with bogus signals -- someone intentionally
setting clocks wrong?

I live in La Mesa (near San Diego) and periodically find my clock to be
incorrect -- usually by exactly one minute or hour. I've even caught it
setting itself at times of the day it has no business resetting itself.
SOMEbody's messing, as far as I can tell -- and they've been doing it for
several years. Is that a common problem with these things?

(I see that NIST actually PUBLISHES the time signal format on their site,
which should make it very easy for radio-geeks to tamper.)

--cleve

On Sat, 04 Sep 2004 23:32:41 GMT, "Brian Webb"
wrote:

Hi Cleve:

The NIST correction signal for digital clocks is transmitted on a very low
frequency (far below the AM broadcast band).

Although it's theoretically possible for somebody to transmit a VLF signal
to spoof your clock, putting together a VLF transmitter and antenna and then
putting out a signal of any appreciable power would be very, very difficult.

As a rule of thumb, the lower you go in frequency, the greater the natual
and manmade radio noise. Modern electrical and electronic equipment puts out
a LOT of radio crud in the VLF portion of the spectrum. This interference
goes long distances over power lines and electrical wiring. Worse, power
lines and wiring work as antennas and radiate this manmade crud.

My advice would be to try moving your clock to a different location in an
attempt to get it away from any interference. If you really want to get
serious, you can get a portable AM radio, tune it to an empty frequency, and
walk around the house and listen to the noise to determine where the
interference is minimal. When you find a quieter place, put your clock
there.

You might also try hooking up a suction cup pickup (used for
recording off a phone handset) to a cheap (~$13) Radio Shack portable
hand-sized amplifier. Amazing noises, especially in the vicinity of
dimmer switches. Also fun on electric commuter trains.

In addition to manmade interference is the problem of getting good reception
of the actual NIST correction signal. Houses in southern California
typically use metal foil-backed insulation in the walls and metal screen to
hold the stucco. The foil and screen really block radio signals. If your
clock uses a length of wire to receive the correction signal, try the
following:

- Make sure the wire is fully stretched out to its full length

- Once you've found a fairly interference free part of your home, drill a
tiny diameter (1/8 inch)
hole through the wall insert a small diameter brass tube from a hobby
shop through
the wall, and then put your wire antenna through the wall. Then string
up the wire in a straight
line.

I hope that helps.

Regards,

Brian Webb, KD6NRP
Southern California

"cleve" wrote in message
news:kDaDc.1358$6r1.499@fed1read06...
I figure many guys in this group must have one of those "atomic clocks"
set
by the Boulder radio broadcast.

Have any of you had problems with bogus signals -- someone intentionally
setting clocks wrong?

I live in La Mesa (near San Diego) and periodically find my clock to be
incorrect -- usually by exactly one minute or hour. I've even caught it
setting itself at times of the day it has no business resetting itself.
SOMEbody's messing, as far as I can tell -- and they've been doing it for
several years. Is that a common problem with these things?

(I see that NIST actually PUBLISHES the time signal format on their site,
which should make it very easy for radio-geeks to tamper.)

--cleve

Thanks for the suggestions, guys.

I got a similar answer in alt.astronomy back in June. The guy who replied
also indicated that Japan broadcasts a similar but incompatable time
signal on the same frequency, and that might interfere here in CA.

I've relocated/reoriented the clock and I haven't had any problems for
awhile.

The oddest was shortly after I bought it a couple of years ago. Something
progressively "tested" the ability to set it during the course of one day:
first it was exactly one hour off; later, 10 minutes; then 1 minute; then 10
seconds. It seemed to be a systematic "test" -- not at all random -- as if
someone was testing their ability to set these clocks. Ever since then,
I've been highly suspicious whenever I find that clock to be in disagreement
with my standard clocks.

Thanks for your replies. I very much appreciate it.

--cleve


wrote in message
...
On Sat, 04 Sep 2004 23:32:41 GMT, "Brian Webb"
wrote:

Hi Cleve:

The NIST correction signal for digital clocks is transmitted on a very
low
frequency (far below the AM broadcast band).

Although it's theoretically possible for somebody to transmit a VLF
signal
to spoof your clock, putting together a VLF transmitter and antenna and
then
putting out a signal of any appreciable power would be very, very
difficult.

As a rule of thumb, the lower you go in frequency, the greater the natual
and manmade radio noise. Modern electrical and electronic equipment puts
out
a LOT of radio crud in the VLF portion of the spectrum. This interference
goes long distances over power lines and electrical wiring. Worse, power
lines and wiring work as antennas and radiate this manmade crud.

My advice would be to try moving your clock to a different location in an
attempt to get it away from any interference. If you really want to get
serious, you can get a portable AM radio, tune it to an empty frequency,
and
walk around the house and listen to the noise to determine where the
interference is minimal. When you find a quieter place, put your clock
there.

You might also try hooking up a suction cup pickup (used for
recording off a phone handset) to a cheap (~$13) Radio Shack portable
hand-sized amplifier. Amazing noises, especially in the vicinity of
dimmer switches. Also fun on electric commuter trains.

In addition to manmade interference is the problem of getting good
reception
of the actual NIST correction signal. Houses in southern California
typically use metal foil-backed insulation in the walls and metal screen
to
hold the stucco. The foil and screen really block radio signals. If your
clock uses a length of wire to receive the correction signal, try the
following:

- Make sure the wire is fully stretched out to its full length

- Once you've found a fairly interference free part of your home,
drill a
tiny diameter (1/8 inch)
hole through the wall insert a small diameter brass tube from a
hobby
shop through
the wall, and then put your wire antenna through the wall. Then
string
up the wire in a straight
line.

I hope that helps.

Regards,

Brian Webb, KD6NRP
Southern California

"cleve" wrote in message
news:kDaDc.1358$6r1.499@fed1read06...
I figure many guys in this group must have one of those "atomic clocks"
set
by the Boulder radio broadcast.

Have any of you had problems with bogus signals -- someone
intentionally
setting clocks wrong?

I live in La Mesa (near San Diego) and periodically find my clock to be
incorrect -- usually by exactly one minute or hour. I've even caught
it
setting itself at times of the day it has no business resetting itself.
SOMEbody's messing, as far as I can tell -- and they've been doing it
for
several years. Is that a common problem with these things?

(I see that NIST actually PUBLISHES the time signal format on their
site,
which should make it very easy for radio-geeks to tamper.)

--cleve