66.666 MHz TCXO for KiwiSDR. Jamming/spoofing GNSS.
Please recommend me a 66.666 MHz TCXO for KiwiSDR. I suspect that there is GNSS jamming/spoofing in my region. Therefore, precise frequency trimming is impossible. Signals are often not decoded on any of the GNSS antennas. It just started recently. I searched the internet and couldn't find them with an accuracy of even 1 ppm. Thanx all.
Comments
The easiest thing to do in this situation is to keep the Kiwi in a relatively temperature stable environment and do a manual frequency calibration (see admin page, end of the "config" tab for instructions).
Yes, finding a TXCO around that frequency is pretty much impossible without a special order.
The other possibility is to use one of those cute Si5351-based synthesizers from AliEx that have the built-in STM32+TFT display so you can set the exact frequency for the Kiwi (66.672 MHz is ideal because it will give you an exact 12 kHz sample rate). They seem to be very inexpensive. If they don't use a TCXO then add one. I believe the common reference frequencies used by the Si5351 are all available as TCXOs.
Could a utility be implemented in the Kiwi that would allow one or more reference signals (such time signals WWV/WWVH) to be used to automatically calibrate the frequency?
Once every few hours or once a day, the utility could check for an offset on the reference signal(s) and make the correction. Could be designed so it only attempts a calibration if the signal strength or SNR is above a set threshold, and a stable PLL lock is established on the carrier to avoid erroneous calibration.
Might be a good alternative for many of those Kiwis that don't have the GPS antenna attached or have trouble receiving GPS signals.
I know a few Kiwi owners who have trouble reliably receiving GPS signals, and they don't bother re-calibrating the frequency each time the Kiwi gets shut down and restarted.
Good idea.
Then I always think to myself: Gee, who's going to do all this work? lol
Thinking about this some more (because I can't help myself). Higher frequency time stations are more useful because there is more relative frequency offset to visualize. At least when doing a manual calibration and you need to "eyeball" the offset in the waterfall (zoomed all the way in).
But HF time signals are more prone to having junk carriers close to the time station carrier (I've seen this) compared to LF time signals. But the later are not always present depending on antenna and Kiwi location. Hence the good SNR requirement mentioned by @nitroengine.
One thing we do have I remember now is the audio PLL associated with the SAM mode. So if SAM is able to achIeve a lock the exact offset can be determined rather than derived from, say, the number of waterfall bins which at z14 is only 1.76 Hz/bin (1.8 kHz span / 1024 bins). This is why the manual calibration instructions say to use the IQ extension for the ultimate fine tuning of the calibration.
Also needed is probably the more difficult part: Analysis of several different time signals at different frequencies and some sort of voting logic before there can be confidence in a solution.
Just a random thought; what about using WSPR receive mode, and comparing the signals received at the local station, versus a couple of nearby stations? Wouldn't that achieve pretty tight frequency calibration? (The WSPR signals should be less prone to false detection that ye olde time signal carriers, and you could try at 28MHz to start with).
73, Chris
You could have a list of fields on the Admin interface where the owner could input the frequencies of the signals they wish to use for reference. Could also have an option to auto-populate the fields with WWV/WWVH, CHU, BPM, etc. They could then omit certain frequencies where they know they have QRM or know their antenna doesn't do as well.
Another excellent idea!
I understand the reasoning behind this, but I'm slightly concerned that it may further discourage owners from bothering to install and use the GNSS antenna. This could in turn reduce the number of KiWi's available for things like TDoA runs.
It could be argued that there already plenty that can be used for TDoA purposes, but sadly, in practice, only about 10 to 20% of the 800+ KiWi's deployed worldwide provide good enough, and relatively interference free reception, and in turn, only a small proportion of these may have favourable propagation at any given time.
I think what is being proposed is a useful addition, but extra guidance may be required, to better indicate what it is intended to be used for, as a secondary option, if GNSS reception is problematic.
Just may thoughts, your milage may vary.
Regards,
Martin
Same argument can be made for people deciding if they should make their own Kiwi public or not.
Yes we have 800+ public Kiwi*. But, sadly, the vast majority of those are "less than satisfactory". Not only for reception quality reasons, but because they're always busy. Or they're in locations already well-covered by other public Kiwis.
The truth is we could use more, higher quality Kiwi* placed in underserved locations.
* I read something recently that said it's not correct to refer to the plural form of "Kiwi" as "Kiwis". So I'm going to try that. I always thought "Kiwis" just looked wrong. And of course I'm never quite sure about the grey areas when the use is not clearly 100% possessive requiring "Kiwi's". And I also read something that said when referring to "Kiwi the people" it should be Kiwis' which I think is just insane. Any linguists out there?
This was in a Radiogram on WINB 9265 moments ago, relating to WWV/WWVH:
This is Shortwave Radiogram in MFSK64
Please send your reception report to radiogram@verizon.net
From Phys.org:
New atomic fountain clock joins elite group that keeps the world on time
by Rich Press
National Institute of Standards and Technology April 28, 2025 Clocks on Earth are ticking a bit more regularly thanks to NIST-F4, a new atomic clock at the National Institute of Standards and Technology (NIST) campus in Boulder, Colorado.
This month, NIST researchers published an article in Metrologia establishing NIST-F4 as one of the world's most accurate timekeepers. NIST has also submitted the clock for acceptance as a primary frequency standard by the International Bureau of Weights and Measures (BIPM), the body that oversees the world's time.
NIST-F4 measures an unchanging frequency in the heart of cesium atoms, the internationally agreed-upon basis for defining the second since 1967. The clock is based on a "fountain" design that represents the gold standard of accuracy in timekeeping. NIST-F4 ticks at such a steady rate that if it had started running 100 million years ago, when dinosaurs roamed, it would be off by less than a second today.
By joining a small group of similarly elite timepieces run by just 10 countries around the world, NIST-F4 makes the foundation of global time more stable and secure. At the same time, it is helping to steer the clocks NIST uses to keep official U.S. time. Distributed via radio and the internet, official U.S. time is critical for telecommunications and transportation systems, financial trading platforms, data center operations and more.
NIST-F4 has improved time signals that are "used literally billions of times each day for everything from setting clocks and watches to ensuring the accurate time stamping of hundreds of billions of dollars of electronic financial transactions," said Liz Donley, chief of the Time and Frequency Division at NIST.
A special kind of clock
Cesium fountain clocks such as NIST-F4 are a type of atomic clock—a complex, high-precision device that extracts timing pulses from atoms. These clocks play a critical role in our globally connected society: They serve as "primary frequency standards" that work together to calibrate Coordinated Universal Time, or UTC (an agreed-upon system for keeping time using data from atomic clocks around the world, known as a time scale).
National measurement labs such as NIST produce and distribute versions of UTC using their own time scales; NIST's version, for example, is known as UTC(NIST). Those national time scales are then used to synchronize the clocks and networks we rely on in our daily lives.
In fountain clocks, a cloud of thousands of cesium atoms is first cooled to near absolute zero using lasers. Then, a pair of laser beams toss the atoms gently upward, after which they fall under their own weight.
During their journey, the atoms pass twice through a small chamber full of microwave radiation. The first time, as the atoms are on their way up, the microwaves put the atoms into a quantum state that cycles in time at a special frequency known as the cesium resonant frequency—an unchanging constant set by the laws of nature.
About one second later, as the atoms fall back down, a second interaction between the microwaves and the atoms reveals how close the clock's microwave frequency is to the atoms' natural resonant frequency. This measurement is used to tune the microwave frequency toward the atomic resonance frequency.
A detector then counts 9,192,631,770 wave cycles of the fine-tuned microwaves. The time it takes to count those cycles defines the official international second.
(That may change as early as 2030, when nations plan to consider redefining the second in terms of one or more different atomic elements used in so-called optical clocks that can measure time even more precisely than fountain clocks can. Even after that, cesium fountain clocks will still play an important, though diminished, role in timekeeping.)
Full text:
https://phys.org/news/2025-04-atomic-fountain-clock-elite-group.html