digital clock near cable box always gaining minutes per month-- any way to remedy?

Have you tried swapping the clocs around, so you know if it is the clock or the location which is the source of the problem?

Most inexpensive clocks count the cycles (frequency) of their power source. Excessive noise on the line can cause extra cycles to be counted. The power supply in the cable box could be adding noise to the power line. If so, a filter can help with that. Technically, it would be a low pass filter (as you said) because it lets through the

I don't doubt that you can come up with an example, but I think it's unlikely that the average digital clock works that way.

I think it's unlikely that the cable box is interfering.

If the clock synchronizes with WWVL, the location may interfere with acquiring that signal.

I'd wager the clock is busted. Move it and see.

I think only a smal fraction of clocks work that way, "In 2011, NIST estimated the number of radio clocks and wristwatches equipped with a WWVB receiver at over 50 million.[3]"

I have 12 clocks and watches and if the average person has only 4, that's 1.2 billion in the US alone, 50+ million of which use WWVB.

Dang newfangled devices, mom had the same clock on the kitchen wall for

I am not talking about "atomic clocks". I am talking about regular old clocks like people sit on their nightstands. Most of them sync to the power line frequency. By most, I mean over 90%. Many have battery backup and keep lousy time when running on battery.

WWVL has been off the air over 40 years ago. I think you mean WWVB. But, the OP never mentioned it was that type of clock. However, if it is, use are right about location and RF noise being the likely problem.

Which is not consistent with a steady loss or gain.

... Phil

Exchange either of the working clocks with the one in the living room and see if the problem remains with the clock or the location. Repair by substitution is a well known technique.

Nope. Cable modems operate at 50-1000 MHz at signal levels that are unlikely to interfere with your unspecified maker and model of digital clock. Similarly, the signals on the cable system are much higher than the 50/60 Hz clock frequency used by the clock. Were it possible for a cable box to radiate a signal sufficient to affect a digital clock, it would never pass FCC incidental radiation testing.

I think you'll find an AC extension cord to be a useful tool for testing.

Certainly. You can accurately disclose the maker and model number of the various clocks and nearby devices so that we can better guess what you have happening.

That might be a good fix AFTER you determine if it's the location of the specific clock that's the problem. The fix usually follows the diagnosis, not the other way around.

For AC power, there are two types of radiation, conducted and radiated. Your clock might be overly sensitive to either or both.

Conducted noise and signals arrive via the AC power line, which then drives the counter in your digital clock. This noise and spurious signals come from any device plugged into the AC power line. Motor noise is most commonly known to cause clocks to miss or add a few beats. Powerline intercoms, switching power supplies, ferroresonant line regulators, DC desk lamps, light dimmers, electronic ballasts, and other powered devices that might inject noise, signals, or distortion onto the 50/60 Hz power line, can all be potential culprits.

It might also be radiated noise and signals. For example, some AC transformers have a substantial radiated field. I had an antenna rotator control box that was good for adding about a minute to a nearby digital clock while it was turning the rotator. It might also be that your unspecified model clock is more sensitive to these fields that your other clocks. Try moving the clock away from anything with a power supply or wall wart.

There are various pieces of test equipment and procedures that can be used to identify potential sources of noise or interfering signals. I don't want to recommend anything with so little information as it will surely be a waste of time. However, if you want to go sniffing, borrow or rent a "power quality meter" and see what's on your AC power line. If you see glitches like these: on your AC power, there's your likely culprit.

If the clock is in a box that plugs into an outlet (oven, microwave, TV, VCR back in the day), odds are that it counts cycles of the power line.

It's easy to tell; just set it precisely and then monitor it for a few weeks. If it keeps "perfect" time, it uses the power line; if it slowly drifts ahead or behind, it's using a crystal for a time base.

Isaac

Unless the clock is unable to synchronize, and therefore are free-running.

My digital radio-controlled clocks are only sync'ing once every 24 hours, usually at 3am, where the radiowaves supposedly travel the best and the noise is the lowest.

Btw, I've had an analog (i.e. with hands, not digits) clock. It's funny to see it change time in and out of DST; the hands spin around like crazy, moving either 1 or 11 hours ahead in a few minutes.

Leif

I had to move an atomic clock because the clock couldn't sync with WWVB in that location. Don't know whether it was interference or plain old loss of signal...and I didn't care. I moved the clock.

I know what you mean. My mother had a clock that also had a 60 minute timer since before I was born. Maybe when it was 50 years old it stopped working but I found the motor part (that say between the two poles of the electromagnet, copper colored with a cupola on one side and one simple gear coming out the other side. I replaced that, cleaned everything on the face of the clock, cleaned the dirt out of the grooves on the knob, and it looked and worked good as new. I have it now but I'm not using it.

I don't know what I'm waiting for. The microwave has a timer but it beeps so quietly I can't hear it when the tv or radio is on, and one always is. Nor can I use the timer when I'm cooking in the microwave.

The stove has a timer too, analog, but harder to read and harder to set.

Orientation is important, at least when you're out near the limits of coverage. I thought it mattered to be near a window, but sometimes I've forgotten to take my watch off and so long as I orient it properly at the bedside, it syncs up fine.

I have four clocks and 1 watch, and I can't think of a time when they all missed the signal the same night.

Michael

WWVB is at 60KHz because groundwave reception is very wide. So transmission is generally reliable, unlike higher frequencies that might vary with time.

The clocks have generally picked 3am because with most people asleep, a lot less local electronics is on. It would be mostly sleeping power supplies, rather than the equipment turned on.

My Casio Wavecepter starts checking the time at midnight, and will try on the hour until it gets a signal. SO long as I have taken it off and put it on its stand early enough, it generally syncs up at midnight, though if it misses, it has other chances still. The clocks do only seem to do it at 3am, so they can miss the sync.

Michael

Probably a mixture of both. Switching power supplies that operate around 60 KHz can cause problems. Positioning of the WWVB receive antenna is also somewhat critical. If you're in a bad signal area, you might have problems getting updates. Mine has to be across the room from the computers or it doesn't work. You can check if your area is having signal strength problems at: (Java required).

Mine always starts checking at 4:00 am. 99% of the time, the last synced time is 4:03AM on the day I am checking. I wonder why mine is different than yours. Does it vary by time zone? I am in the eastern time zone so at 4:00 am, it is well past midnight along the entire signal path.

Pat

Ya, when I went home one Christmas and saw the clock was gone, I was disappointed, I would have attempted a repair, just because. Mikek

Then it can't be timezone. I'm in the east too. I recall the manual even stating it starts checking at midnight.

Try watching it at midnight, there will be an indicator that it's checking. Maybe you have local noise so it doesn't sync up until 4am. It will check on the hour until it does sync (well I dont' think it keeps checking after a certain hour, but I don't know when it stops).

Mine is 8 or 9 years old, I got it for $20 at a department store. Maybe they've changed the design in more recent times. WWVB has changed it's format, so now one can get the time signal with a non-AM format of modulation. Newer receivers are supposed to use the newer format.

Michael

I have a Philips DVDR** with a terrible clock. A digital video disk recorder with a hard drive. It has 3 setting, auto, manual, and off.

Auto is supposed to sync to some signal on educational tv stations, or maybe I mean public tv stations.

But what could be the difference between manual and off???? Do you or anyone else here know?

No matter what the setting, the clock is often wrong, and I have to set the timer to start a minute in advance and end a minute late. This usually works, but of course doesn' if I want to record a program that starts right after another on a different channel ends.

My friend bought a very similar machine, now sold under the name Magnavox, and it too has a clock that works like mine, badly.