Sunday, 10 August 2014

OCM

It is like those snacks - you know, the ones that come in a cardboard tube - "once you pop, you can't stop". Once you've made one plug-in module, you just have to make another.

Apparently it is called "Obsessive, Compulsive Moduling", OCM for short.

I was still playing with my cheap 'n dirty SSB experiments, using this hideous, mal-formed 8 MHz filter...


I wanted to switch to 12 MHz - and the obsession took hold.

Here's the resulting module -


Once again, it is the now standard 12 holes wide - that way it perfectly straddles the "blocks" on my solder-less breadboard, using up real-estate in the most efficient way possible.

As soon as I had the crystal filter, I needed to be able to put a local oscillator in just the right place to be able to use it in either an upper- or lower-sideband application, so I built a little circuit that would allow me to pull a crystal a few kHz. [Editor's Comment: That's a dumb idea - why doesn't somebody have the good sense to use a DDS in this role?]

I prototyped it straight onto the solder-less breadboard but I soon realised that this would be a useful "standard module" to have as a "keeper".

Once again the OCM took hold and I ended up spiraling out of control into module construction...


As you see, the VXO module has a socket to allow the crystal to be changed and a trimmer capacitor to set the frequency.

Here are the new modules joining the existing ones on the breadboard...


There's even a 5V regulated PSU plug-in already there, providing evidence that my OCM is a long-standing disorder and not some new affectation!

...-.- de m0xpd


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