Almost finished but not really.

I think I can say that the lpf/mar6 circuit is finished. All’s left to do is documentation.  Making some more changes so the prototype has all the components that will be in the final product, had me add in an 8volt regulator.  Of course when I started this board it had not been decided as to what voltages would be available so I went ahead and fed the MAR-6 with 12v.

To accommodate the regulator, I had to think up some way of fitting it in.  No room on the board that was easy so I came up with the idea to insert the regulator in-between molex connectors. I soldered the pins onto the regulator and inserted the load side into the molex connector mounted on the pcb.  The input of the regulator in soldered directly to a connector and the original 12v feed plugs into that.  Worked out pretty nicely and I didn’t short anything out. Pictures below detailing this.

Interestingly the most important thing that came out of this session was making rf measurements.  This topic rears its head every one and a while and this time I took the opportunity to dig into it a little more.

Making measurements during this project became very frustrating. Noisy signals along with measurements that did not agree on repeated tests been the primary cause.  Hand/body placement or nudging the probe was enough to drastically alter the readings.

Of course it pretty much came down to the ground lead on the oscilloscope. Reading up on the subject and most importantly, viewing Alan’s, W2AEW, video on this was most informative.  Alan describes a spring or a wire wrapped around the ground contact on the probe as an effective way to minimize ground lead induced problems.  Going through the bag of items that came with my new scope revealed such a device. 

So as much as I hated the thought of more testing, I was curious to see the difference in making measurements with it.  Big difference. The signals were now much clearer with less noise, making those measurements easier.  Only problem now is figuring out a way to make a probe socket to mount on prototype boards to make the measurements easy.  So here we are again, a project driving the need for another project.

 73, Peter