Today I was able to complete the oscillator module for my LF transverter. As per the previous post, last night I completed the 10MHz oscillator, but today I added the buffer stage to it. Therefore, now I'd consider it a nice self contained module that I can hook into the mixer module once I build that.
I've attached a couple of quick iPhone photos for you and another 'scope capture. You can see I've built the module with lots of space on a single small prototype board (47 x 72mm) from Rockby Electronics. I'm hoping that I can build each of the individual modules on their own board and then link them together. Plus, spacing it out (rather than aiming for miniaturisation) will allow me to – hopefully – modify and/or fix it. Further, at the larger scale, doing them as individual modules will allow me to easily test each module but also allow me to improve modules in the future – if I see fit.
The oscilloscope capture is interesting. First, we can see the wave form has come closer to a sine wave as opposed to that in the previous post. This could be due to me using a 12V battery this time, but unfortunately I didn't have time to compare it with the 9V battery. Hopefully I'll get a chance to try with a 13.8V power supply soon – just need time to do so. Also, the change in wave is also due to the addition of the buffer – plus I was taking the reading from the output of the buffer (the wave is rougher at the output of the oscillator's transistor).
Also interesting in that capture is that I've included the FFT graph. This excited me greatly, as it gave me an opportunity at hands on to see the theory I'd learnt for my license upgrade in action. The FFT confirms the 10MHz signal (centred) but also shows the presence of the harmonics (2nd thru 7th).
One thing also interesting was that I noticed the buffer transistor was getting rather hot – the oscillator transistor did not heat up at all. Maybe this is because currently it's not linked to the other modules, or maybe it's because I'm using 2n2222 rather than the 2n3904 (which I was struggling to get, but now have some ordered). But, I'll guess I'll just have to see what happens – just another opportunity to learn.
Anyway, things definitely now seem to be progressing, so hopefully soon I can move on to building the mixer – maybe the week-end, we'll see.