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I wanted to get a distribution amplifier for my 10 MHz lab reference signal from my GPSDO to feed my equipment, like my timer/frequency counter, signal generator, and other stuff. I also needed a way to distribute a 1 PPS signal from my Trimble GPSDO to my NTP servers and other clocks and monitoring systems. The Trimble only got two 10 MHz outputs and one 1 PPS signal output, so I needed to add more, especially for experimentation. I saw this video by Gerry Sweeney where he modifies an Extron 300MX video distributions amplifier, adding a rubidium reference standard and was intrigued. But I changed the modifications to fit my needs and here is the result. ...

Warning: as of yet, there is no official support for overclocking the Raspberry Pi 3, so you could damage your small computer. Just a reminder. Update: I’ve managed to make a DIY heatsink for the Raspberry Pi 3 for $4, and it’s running stable at 1.5GHz. Click here to read. The new version of Raspberry Pi 3 was released yesterday, so I naturally had to get two. I’m using two as Stratum-1 NTP servers, and with the old Raspberry Pi 2, I had hit the roof when it came down to getting better time resolution. So when I read that a new 50% faster version had been released, I raced to the nearest store and got a couple. I have one experimental NTP server that isn’t handing out time on the internet and another one that is the primary server, connected to the NTP Pool Project. I installed the experimental Raspberry Pi 3 first, so I could test performance and try to overclock it. And it went very well. ...

Update: You can download the Eagle PCB files for the PPS Pulse Width Extender here. The PCB is made to fit the Hammond 1455C802BK enclosure. I have two Stratum-1 NTP servers using Raspberry Pi 2’s as servers. But the two setups are entirely different. My primary NTP Stratum-1 server is available at ntp.jacken.se, but it is also in the .se pool of ntp.org. It’s a Raspberry Pi 2 I use a Raspberry Pi 3 that I have connected a U-Blox Neo-7 GPS receiver. But I’m not using the 1 PPS signal coming out of the U-Blox. I have a Trimble GPSDO that I bought from eBay. The unit has two 10 MHz lab reference outputs and one 1 PPS output. But after measuring the signal coming out from the GPSDO, I realized that the timing speed for the seconds “Tick” was only 10 µsec which is way to fast for the Raspberry Pi to pick up as an interrupt on one of the GPIO pins. So I built a pulse extender, making the pulse around 250 milliseconds instead. And now the Raspberry Pi picks up the pulse without problems. Some GPSDO units can set the pulse width by programming the unit via a serial port, but I can’t find that feature on this unit (which is poorly documented and was OEM made for some other manufacturer), so I had to do it with hardware. So how does it look when crunching the numbers on it? ...

Generator functions and Python. Doing your administrative stuff faster. Often when I need to monitor something on one of my linux servers, I always gravitate towards these papers. I always forget how to use them, so putting them here is for me as much as it is for you. Go though the PDF presentation about Python Generators for System Administrators. and fiddle around with the example code. I’m pretty sure you can find stuff you need to to and you will be amazed of the speed of the code. It took a while for me to wrap my thick head around it, but the end result is great!

The last couple of weeks I’ve been busy building a Raspberry Pi 2 Raspberry Pi 3 connected to my Trimble GPSDO using the 1 PPS output. The Trimble unit synchronizes with the atomic clocks onboard the GPS satellites, and the precision is fantastic! I bought the GPSDO to get a 10 MHz lab reference for my measure equipment, but after reading an article about Time-Nuts, people obsessed with measuring time as accurately as possible, and one of my friends showed me pictures of their new Stratum-1 NTP server rack he helped design, I was hooked. ...

Upgrading a Philips-Fluke PM6665 Frequency Counter with an Oven Controlled Crystal Oscillator - Up and Running! I needed a frequency counter for my little lab at home. Naturally, I wanted an HP Agilent 53132A or similar, but it’s way too expensive for my modest use. So I browsed around eBay and found an old Philips-Fluke PM6665 frequency counter with the optional 1.3GHz add-on board. With a 10 second gate time, I can get down to 0.1 Hz at 10 MHz, so that’s more than I need. It didn’t have the option of a better crystal, unfortunately. When I tested the PM6665 against my Trimble 10 MHz GPSDO reference, the unit was off by 200.1 Hz. Without a calibration sticker on the instrument, I’d say that’s pretty good for a device manufactured in the late 80s. I tried to trim it, but it uses an adjustable capacitor, and you only needed to look at it for it to change settings. ...

Speeding up your SPI MAX7219 LED displays when using Arduino and LedControl Library In preparation for the arrival of my GPSDO[1], I’m doing a quick build of an “Atomic Clock” display to have above my lab equipment. I’m using a cheap, small eight digit red LED SPI-controlled display. It uses the MAX7219 controller that I got from eBay for next to nothing. I plan to parse the RS232 information from the GPSDO unit and display the exact time. I’ll also post error messages if the GPS signal lock gets lost. I’ve done a quick prototype using an Arduino Uno, but I plan to try to get an Attiny85 to work as the controller when I’ve finished the parser and the rest of the software. After doing some research, naturally, there was a library available to connect to my LED display called LedControl. It’s part of the standard Arduino libraries (in the download section). But when I checked the code, it uses the Arduino routines to shift out the SPI data to the display. It’s great if you want to be able to use any pins to connect to the screen, but using Arduino’s bit manipulation tools for “bit-banging” the display is slow. ...

I’ve finished the OCXO upgrade. Read about it here While browsing on eBay for my new lab at home (I’m getting into electronics again), I came across a Philips PM6665 Frequency Counter, an old but functional unit so I couldn’t resist, I had to buy it. So I downloaded the Users Manual and Service Manual for the frequency counter and started to check the schematic. As usual the unit, when new, could be bought with several options. One of them was a better crystal oscillator, an MTCXO that can be automatically calibrated using a 10 MHz external reference, giving an accuracy of 3*10-8 but my unit doesn’t have that option, unfortunately. This will be fixed though. But it does have a 70 MHz to 1.3 GHz optional input! So here’s what I plan to do… ...

Running LTspice IV on Mac OS X Before I start testing a new idea for an electronic circuit and building it on a breadboard, I usually want to check it with LTspice. It’s a fantastic piece of software for testing almost any kind of component. Nearly all manufacturers have a spice equivalent for most of their parts. But there’s a snag. The Mac version of LTspice is a piece of crap. Having to run a virtual PC or reboot using BootCamp feels unnecessarily slow and convoluted. But there’s a way of running it as a “normal” Mac application. Here’s how to do it. ...

I got myself a four channel 50MHz oscilloscope to be able to do some measurements. The Rigol DS1054Z. It’s expensive in Sweden if you buy it from a local retailer, but I ordered mine from Batronix in Germany and thanks to being part of the EU, there’s no customs and extra taxes added to the price. The oscilloscope is easily hacked to 100MHz and a lot of other functions like serial protocol decoding and also more memory depth. RS232/UART, I2C and SPI decoding, advanced trigger functions like RS232/UART, I2C, SPI, Runt, Windows, Nth edge, Delay and Timeout trigger. Search for “Rigol DS1054Z hack,” and you’re on your way to transform your scope to a much more expensive version. But don’t enable the 500µV option. The oscilloscope doesn’t support it in hardware, so you will run into bugs if enabled. I’ve been delighted with my purchase, except for the occasional bug. But today it went into a total haywire mode. When trying to start it up, it hangs on boot. Either by just showing the Rigol boot screen, or show the standard display but remain immune to any input from the controls. Panic! But thankfully I found a solution to my problem. ...