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
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