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Two new products. Frequency Standard and Calibrator.

I just finished the first batch of two new products that complements each other and is a great addition to any lab or RF experimenters toolbox.

Frequency Standard

The first product is an ovenized quartz oscillator with a fixed frequency of 10MHz.

It's intended use is as a time base for instruments. Many Instrument has an input for a 10 MHz reference at the back that can be used to improve frequency accuracy. With this small box you can feed four instrument as it has a small distribution amplifier built in and four outputs.

I calibrate these on my bench against my Rubidium standard so they should be accurate to at least 10ppb E.g the 10MHz output is accurate down to 100 milliHertz or better.

The inside houses a Japan made OCXO from the company NDK. The OCXO are new-old-stock of a now obsolete product so I have been able to source them at a good price that I pass on to you.

The Frequency standard is powered from an micro USB input and comes with a cable but no power supply. Use a computer or a phone charger to power it. Takes about 500mA at warm-up.

I have broken out the Voltage adjustable trim input to a SMA connector that can be used to GPS discipline it or for use in a PLL application. Manual re-calibration can be performed from the front using the 20 turn potentiometer.

For re-calibration you need a source to compare it against and that's were the second product comes in.

Frequency Calibrator

The second product is a GPS based oscillator that can output any frequency from 1Hz to 10MHz. It has a GPS module with an internal oscillator that is being kept synchronized to the Cesium clocks in the GPS satellites. The output is pretty jittery so it's not great to use for a Frequency standard on it's own but what it's lacks in low jitter it makes up for in frequency accuracy. If the output is averaged for a few seconds or more the precision is very good, better than 1ppb.

The GPS is controlled from an on-board Arduino that runs Open Source software and I have written a PC program that communicates with it to set the output Frequency and save it in EEPROM for use at next boot.

The PC software also calculates and displays a pretty useful GPS signal quality meter. It is based on the Signal to Noise Ratio from the four strongest satellites. For best performance you should try to get 75% or better quality.

Once you have configured what output frequency you want, it will output it as soon it has a good position fix.

To use the Calibrator for frequency calibration one can either use it as a reference on a frequency counter by inputting it to the counters external reference (Se picture below) or you can use an oscilloscope for calibration and instead of measureing you simply compare two signals.

Using a frequency counter has the advantage that a frequency of interest can be measured while the calibrator provides a known good time base on the external input.

The jitter on the Calibrator signal will case the counter values to jump around a bit, this can be minimized by increasing the counter time to several seconds. If for example the counter is counting for 10 seconds it is possible to measure to a high precision, how much is depending on the frequency counter.

The Oscilloscope method compares instead of measuring the signals. One inputs the Calibrator on one input and the oscillator on the other input.

You will set the trigger to trigger on one input and then adjust the oscillator until there is no sideways drift on the display. The calibrator don't need to be on the same frequency as the oscillator under calibration, as long as they have a fixed relationship.

In the picture below the Calibrator is outputting a 2MHz signal (yellow trace) and the oscillator is running at 10MHz. (Blue trace). In this example the scope is triggering on the yellow signal so that is always stationary.

If the 10MHz signal is off then the blue trace will drift to either side. The 10MHz oscillator will be adjusted until no drift is seen. It is quite easy to calibrate to a few ppb of precision using this method.

If you find any of these product interesting you can find more information my documentation pages. They are available for purchase in the shop in a first small batch.


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