Frequency Standard System: TCXO 10Mhz Mk1

This is part of my Frequency Standard System.

Oscillator VEB Narva 10Mhz

The 10MHz TCXO itself is from east Germany made by NARVA. According to the data sheet it has a tolerance of ±2e-6, an aging of ±1e-6 and a thermal precision of ±3e-6. Given the timestamp of 1983 on it, it will have a deviation of approximately 3.7e-5 at this point.

The TCXO power circuit consists of a 555 timer with an ON-delay of a couple of seconds to ensure the supply has stabilized. It is then heavily filtered through inductors and low-ESR capacitors.

Pulse Amplifier

The pulse amplifier uses a BC547 and a BF254 transistor both in an AC couples configuration. The first stage using the BC547 amplifies the 50μVp-p signal from the oscillator to around 1Vp-p. The second stage with the BF254 offsets the signal to DC, such that it is within 0-5V and amplifies it to 0.7-4.7V, this is enough to trigger 7400 series TTL chips.

Currently I’m using a 74HC08 as an output buffer, this is not the fastest TTL chip available but it was the best I had around. The rise time of the output pulses is longer than I would like but it works for now.

The finished module

Front Panel


According to my Philips PM6666 frequency counter, it’s virtually spot on to the precision of the counter itself.

Philips PM6666 showing 10Mhz