Welcome to
Azur Electronics

The idea for this design has been around for some time and would fullfill two functions. The first is to provide a stable oven controlled frequency source and distribute this to all test equipment requiring external locking such as frequency counters. The second is to provide a central distribution point for any signal inputs/outputs that are located at the rear of test equipment and therefore difficult to access.

The HP 5342A Microwave Frequency Counter has a 10MHz Crystal Oscillator with Option 001 oven temperature control, which makes it my most stable frequency source. This can be used to provide an external clock to all my other Frequency Counters: HP 5316A; 2 x Thandar TF600; BlackStar Apollo 100 (all at 10MHz); and HP 8443A (divided down to 1MHz).

December 2008

Prototyping the circuit design on a Vero stripboard produced a 7400 buffer amplifier feeding 74128 50Ω line drivers for 10MHz outputs. The ÷10 utilises a 7490 decade counter and 74128 for 1MHz outputs. Also ÷2 circuits were included using 74175's to provide ÷2 5MHz and ÷4 2.5MHz outputs via 74128's.

Making use of spare gates, provides another frequency input to ÷2, ÷4, ÷10 outputs, again all on 74128 50Ω line drivers. After a few issues with crosstalk, all worked satisfactorily.

January 2009

A power supply of +5V @ 700mA dc approx is required. This uses a conventional linear design of mains transformer, bridge rectifier, smoothing capacitors, voltage regulator with heatsink and transient response circuit, which is capable of +5V at 1.5A dc max.

June 2009

This 'home grown' design makes use of a half-width HP case from a scrapped unit (see HP 3780A K01 PPTS Interface Unit) with modified front and rear panels, plus a new front escutcheon (thanks Glen).

The top row are the frequency references and dividers, the bottom row are signal distribution from other equipment rear panel connectors (still short of one BNC-BNC Adaptor). All tested and working ok.

January 2011

Received the missing BNC-BNC Adaptor (thanks Mike). Also need to fit a red LED on the front panel so I know if it is powered up or not. If not, none of my frequency counters work properly as no external clock. Sometimes it takes me a while to work out why they are not counting!

December 2016

Sometimes wasted time working out why test equipment using the 10MHz reference will not work. So added a red LED power indicator to the front panel. If the SDU106 is not powered up, the 10MHz reference is not distributed.