New clock accurate to within 1s every 300 million years

14PML013_f2_jefferts_heavner_LR

NIST physicists Steve Jefferts (foreground) and Tom Heavner with the NIST-F2 “cesium fountain” atomic clock, a new civilian time standard for the United States. Credit: NIST

The U.S. Department of Commerce’s National Institute of Standards and Technology (NIST) has officially launched a new atomic clock, called NIST-F2, to serve as a new U.S. civilian time and frequency standard, along with the current NIST-F1 standard.

NIST-F2 would neither gain nor lose one second in about 300 million years, making it about three times as accurate as NIST-F1, which has served as the standard since 1999. Both clocks use a “fountain” of cesium atoms to determine the exact length of a second.

NIST scientists recently reported the first official performance data for NIST-F2,* which has been under development for a decade, to the International Bureau of Weights and Measures (BIPM), located near Paris, France. That agency collates data from atomic clocks around the world to produce Coordinated Universal Time (UTC), the international standard of time. According to BIPM data, NIST-F2 is now the world’s most accurate time standard.**

NIST-F2 is the latest in a series of cesium-based atomic clocks developed by NIST since the 1950s. In its role as the U.S. measurement authority, NIST strives to advance atomic timekeeping, which is part of the basic infrastructure of modern society. Many everyday technologies, such as cellular telephones, Global Positioning System (GPS) satellite receivers, and the electric power grid, rely on the high accuracy of atomic clocks. Historically, improved timekeeping has consistently led to technology improvements and innovation.

Read more and watch video …

Read background information about how NIST F-2 Works and watch animation …

From my Twitter feed: Ontario Science Center demos ham radio

VA3XPR
Ontario Science Centre Demonstrates Ham Radio Digitally Remastered http://t.co/sU2HgoYO

K5PO
My catch-phrase! RT @K5KVN: New meme! @K5PO says: Put A Ferrite On It! http://t.co/CxrqFIMY

wa5ray
Amateur Radio Quiz: A Log of dBs: By H. Ward Silver, N0AXn0ax@arrl.netI f there is a single unit of measurement b…http://t.co/lkdKX9cb

A look at the radio spectrum

Someone e-mailed this today to a list I’m on. It is a bit simplified, but this chart is meant to introduce people to the concept of electromagnetic radiation. Click on it to get a slightly larger version of the chart.

EM Spectrum

UPDATE 12/8/12:

Here’s another from Fred, W8ZLK:

Extra Class question of the day: system noise; electrical appliance noise; line noise; locating noise sources; DSP noise reduction; noise blankers

Noise is often a real problem for radio amateurs. Fortunately, by understanding how noise is generated and how to reduce or eliminate it, noise can be tamed.

Atmospheric noise is naturally-occurring noise. Thunderstorms are a major cause of atmospheric static. (E4E06) There’s not much you can do to eliminate, but you can often use a receiver’s noise blanker to help you copy signals better. Signals which appear across a wide bandwidth (like atmospheric noise) are the types of signals that a receiver noise blanker might be able to remove from desired signals. (E4E03) Ignition noise is one type of receiver noise that can often be reduced by use of a receiver noise blanker. (E4E01)

One undesirable effect that can occur when using an IF noise blanker is that nearby signals may appear to be excessively wide even if they meet emission standards. (E4E09)

Many modern receivers now use digital signal processing (DSP) filters to eliminate noise. All of these choices are correct when talking about types of receiver noise can often be reduced with a DSP noise filter (E4E02):

  • Broadband white noise
  • Ignition noise
  • Power line noise

One disadvantage of using some types of automatic DSP notch-filters when attempting to copy CW signals is that the DSP filter can remove the desired signal at the same time as it removes interfering signals. (E4E12)

While filters can be very effective at reducing noise, it is often better to figure out what is  generating the noise and taking steps to reduce or eliminate the amount of noise generated in the first place. For example, one way you can determine if line noise interference is being generated within your home is by turning off the AC power line main circuit breaker and listening on a battery operated radio. (E4E07) If by doing this you determine that an electric motor is a problem, noise from an electric motor can be suppressed by installing a brute-force AC-line filter in series with the motor leads. (E4E05)

All of these choices are correct when it comes to the cause of a loud roaring or buzzing AC line interference that comes and goes at intervals (E4E13):

  • Arcing contacts in a thermostatically controlled device
  • A defective doorbell or doorbell transformer inside a nearby residence
  • A malfunctioning illuminated advertising display

Sometimes your own equipment may be the cause of received noise. A common-mode signal at the frequency of the radio transmitter is sometimes picked up by electrical wiring near a radio antenna. (E4E08)

The main source of noise in an automobile is the alternator. Conducted and radiated noise caused by an automobile alternator be suppressed by connecting the radio’s power leads directly to the battery and by installing coaxial capacitors in line with the alternator leads. (E4E04)

Personal computer and other digital devices can also generate noise. One type of electrical interference that might be caused by the operation of a nearby personal computer is the appearance of unstable modulated or unmodulated signals at specific frequencies. (E4E14) All of these choices are correct when talking about common characteristics of interference caused by a touch controlled electrical device (with an internal microprocessor) (E4E10):

  • The interfering signal sounds like AC hum on an AM receiver or a carrier modulated by 60 Hz hum on a SSB or CW receiver
  • The interfering signal may drift slowly across the HF spectrum
  • The interfering signal can be several kHz in width and usually repeats at regular intervals across a HF band

Noise can even be generated by the most unlikely things. For example, it is mostly likely that nearby corroded metal joints are mixing and re-radiating the broadcast signals if you are hearing combinations of local AM broadcast signals within one or more of the MF or HF ham bands. (E4E11)

Extra Class question of the day: modulation methods; modulation index and deviation ratio; pulse modulation; frequency and time division multiplexing

In FM modulation, the two primary parameters of interest are deviation ratio and modulation index. Deviation ratio is the ratio of the maximum carrier frequency deviation to the highest audio modulating frequency. (E8B09) The deviation ratio of an FM-phone signal having a maximum frequency swing of plus-or-minus 5 kHz when the maximum modulation frequency is 3 kHz is 1.67. (E8B05)The deviation ratio of an FM-phone signal having a maximum frequency swing of plus or minus 7.5 kHz when the maximum modulation frequency is 3.5 kHz is 2.14. (E8B06)

The term for the ratio between the frequency deviation of an RF carrier wave, and the modulating frequency of its corresponding FM-phone signal is modulation index. (E8B01) The modulation index is equal to the ratio of the frequency deviation to the modulating frequency. The modulation index of a phase-modulated emission does not depend on the RF carrier frequency. (E8B02)

The modulation index of an FM-phone signal having a maximum frequency deviation of 3000 Hz either side of the carrier frequency, when the modulating frequency is 1000 Hz is 3. (E8B03) The modulation index of an FM-phone signal having a maximum carrier deviation of plus or minus 6 kHz when modulated with a 2-kHz modulating frequency is 3. (E8B04)

Some amateur radio communications are pulse-width modulated. That is to say that the information being sent is proportional to the time the carrier is on. When using a pulse-width modulation system, the transmitter’s peak power greater than its average power because the signal duty cycle is less than 100%. (E8B07)

Some signals are pulse-position modulated. That is to say, what is significant is when the pulse occurs. The time at which each pulse occurs is the parameter that the modulating signal varies in a pulse-position modulation system. (E8B08)

Frequency division multiplexing is one method that can be used to combine several separate analog information streams into a single analog radio frequency signal. (E8B10) When a system uses frequency division multiplexing, two or more information streams are merged into a “baseband,” which then modulates the transmitter. (E8B11)

When a system uses digital time division multiplexing, two or more signals are arranged to share discrete time slots of a data transmission. (E8B12)

Oriole on a tower and other links of interest

Oriole on a tower

Google sent me a link to this photo. I love orioles, and thought I’d share it with you. In her post, the photographer writes, “My son built the tower, which is 120 feet tall. Not sure how high the oriole was, but he was up there.”

Here are a couple of other links:

Minimum Discernible Difference. This is an attempt by AB7E to “quantify the difference in readability between two signals of comparable, but unequal strength.” The goal was to determine if it’s really worthwhile to modify an antenna to gain say 1 dB or 2 dB of signal strength. Very interesting discussion.

Build your own 100W,  20m, end-fed, half-wavelength antenna. Most end-fed, half-wavelength (EFHW) antenna designs that you see are for QRPers. The reason for this is that the voltages at the end of a half-wavelength can be quite substantial, even at QRP levels. This design, however, is rated at 100W. I have all the parts to do this, except for the enclosure, and plan to try this soon.