1.? The audio section is lacking in gain, for some reason, and it just may be the
reason why Doug Hendricks, KI6DS, and Steve Weber, KD1JV, switched to an LM386
in the kit version.? I'll ask Doug when I see him sometime later.
So the delay is going to be a sidebar where I build two audio amps on
<> designed by Diz, W8DIZ <sk>,
and the second one by Robert Cerreto, WA1FXT.? One of these may replace
the original design, so the workbench is covered with stuff.
2.? I have three VFO kits.? A uni-VFO from KitsAndParts, another from the
QRPGuys and the last from QRP-Labs.
SMD Learning curve.? So, I thought I'd take an hour and learn how to do
SMD.? Went to my favorite URL, YouTube, and looked at some videos.? Went
to several sites for solder paste and looked at the curves.? I had ordered
a 6" cast iron skillet yesterday off amazon and it got here at 6am.
I took a small hot plate in the garage and run two tests.? One with the
temp control at max and a second run at medium.? With the solder paste
manufacturers curve and my data, the graph is shown below.? Having
learned that the manufacturers curve is really determined by the
thermal properties of the FR-4 material in the PCB and not so much
the solder paste.
Last year, we had work done on a fridge.? O*(*&P(*)( things are the worst
appliance in the house, but the most important.? The kid left behind a
Milwaukee 10:1 IR temperature gun.? Valued at $90 from HomeDepot. If
the kid every calls he can have it back and I'll buy my own.
The skillet curve means the job will take about twice and long, but
should be well within the parameters of the FR-4 board material and
the 450 deg F limit recommended by the paste guys.
I fired up the setup from a cold start with the control set at medium.
I used the gun to let the system get to 365 deg F, shut off the power,
waited 30 seconds or so and removed the skillet from the plate and
removed the board to a pyrex glass plate.? Second photo is the results.
Had two solder bridges on the big chip.
Didn't have copper braid, so heated the first bridge and dropped the
board (on purpose) on the desk and the solder exited the board. For
the second bridge I wasn't as lucky and the solder stuck between
the two resistors R1 and R3 and cap C3 in the bottom center.? So
fixed that we are good to go.
Note, the Si5351A 10-MSOP package came out perfect.? I just have to
perfect the syringe application to keep from getting too much in places
so that bridges don't occur.? You experts can see that this work is
way below par, but shown here for getting ideas on where I went wrong.
I'm no longer scared to tackle a SMD kit, but then fools rush in.
3.? Going back to the Manhattan project.? I was talked out of doing a
DC receiver.? The thought being that the project would be too simple
and too boring and just a toy.
I watched the latest version of SolderSmoke and the status of the
DC receiver challenge.? I'm thinking that 50 built is way too low.
Can I possibly interest a group of you to take on the challenge
and show that qrptech has the best group of builders on the planet?
I really looks like a fun project and not too serious and not too
complex.? Let the world know you exist.? What?? 4-6 hours max?
You have the parts.
chuck, aa7fo
