A Stratum1 Server at home?

In my former article about the VNWA, I quicky explained that I had acquired a GPS Disciplined Oscillator, as I wanted a precision clock for calibration and measurement. I had ordered LeoBodnar’s GPSDO device able to output 2 signals from 450Hz to 800MHz, with an astonishing precision.

As stated on the documentation, the specs are impressive:

Manufacturered by Leo Bodnar LTD, the Low-jitter GPS-Locked Precision Frequency Reference Oscillator can be programmed to two output frequencies between 450 Hz up to 800 MHz with a stability of better than 1e-9 (1 part per billion (ppb) within 1 minute after achieving lock to the high accuracy GPS Satellite Network which is controlled by a Caesium Clock with accuracy approaching 1e-12

USB powered, this instrument is the ideal frequency standard for supplying an external reference clock signal to the DG8SAQ Vector Network Analyzer to make Frequency and Frequency Difference measurements with accuracy  approaching 1e-10 and frequency  measurements (dF) in the mHz (milli Hertz) and even down to the uHz (micro Hertz) region.

The device is autonomous but can also be connected to a PC to program the frequencies. This is quite useful when measuring precise components or playing with radio frequencies. It is now part of my mobile electronic measurement shelf.

I couldn’t resist to see what was inside. Indeed, the quality is there.

As we can see, there is an uBlox GPS processor on the upper left, and the OXCO is physically isolated on the upper right, to ensure thermal stability.

The board itself looks simple, but neatly done. And I admit it’s nice.

LeoNTP

LeoBodnar also created a Stratum-1 NTP server based on quite the same architecture. After years of wondering if it was worth, I couldn’t resist and ordered one. LeoNTP is not cheap, but has really advantages compared to the typical Raspberry+GPS shield that we can often see. As it’s totally dedicated to only serving NTP requests, its attack surface is low. The embedded firmware boots really fast as it’s not running an Operating System such as Linux, and the GPS acquisition time is around 30s.

The device looks quite similar to the GPSDO, but is larger, embeds an oled screen and a PoE RJ45 ethernet connector.

As the manufacturer, LeoBodnar, has experience in precision clocks, the stability of the receiver, even in the case of signal loss, is still <4ms per day. In normal operation, however, the NTP accuracy is below 1µs, which makes it a reliable Stratum-1 server.

As for the GPSDO, I couldn’t resist opening the case to see how it was designed. The board is quite simple, making it easy to understand the different parts. The RJ45 upper part is the voltage adapter from 48V to 5V and PoE extractor. The center left part manages the Ethernet data, the lower-part in the shielded box is the uBlox GPS receiver, there is an Atmel CPU to process everything, a battery on the bottom, and the oled display on the right, along with the push-button encoder. Quite simple, but for me it’s the right application of the KISS principe. This devices just does one thing, but it does it well.

LeoNTP is also able to output a PPS or a 10MHz signal on the BNC output, which can be used to synchronize other equipment.

Among the advantages of having such a simple design, are the electrical power, less than 1W ; the boot time which is quasi immediate ; stability and reliability, performance (it can handle over 100k requests per second without issues, also meaning it can’t be DDoSed) and a very reduced attack surface because there’s no OS and no open ports except NTP. That’s why we can see LEONTP directly on the wild, serving Internet NTP pools.

In summary, both devices are really nice. As all LeoBodnar products, their design is good and made with quality components. And no, I didn’t get sponsored for this article, it’s just because I like nice products.

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Bruno Kerouanton on août 24th 2020 in Electronics

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