[Amps] Decline of homebrewing?

[Jim Garland]

This interesting discussion about homebrewing techniques and safety 
brings to mind an experience I had a few years ago with my StationPro 
station controller. I designed the StationPro for myself, but it seemed 
to be a useful enough station accessory to warrant writing up the design 
in QST. After publication, I had a couple of offers to manufacture wired 
and tested versions, but ended up only making bare PCBs and enclosures 
available, primarily to encourage homebrew activity. (I've done this 
with other projects over the years.) The StationPro is a lengthy 
project, requiring nearly twenty hours of assembly time after the parts 
are collected. It's also not cheap, about $600, so it's a big investment 
in both money and time for most builders. That said, the assembly is not 
complex. Putting together the kit consists of following illustrated, 
step-by-step instructions. The builder stuffs five printed circuit 
boards (with a photo of each component), mounts them in two prepunched 
and silkscreened enclosures, and plugs them together with ribbon cables. 
Easy peasy, right?

As it turns out, no. What I didn't realize was how basic techniques that 
I took for granted were new and unfamiliar to many of my builders 
(roughly 350, to date). Simple stuff, that I'd never thought about: How 
tight should the mounting studs be on a DB25 connector? What's the 
difference between a machine screw and a self-tapping screw? Which way 
do you hold the resistor to read the color code? And no, it's not okay 
to use a 100W soldering gun on a 25 pin IC.

What really surprised me, though, was how things that seemed to be 
common sense to me, were things that some of my builders (not all, 
fortunately!) had never thought about: gathering the correct tools 
together before starting work; having a clean, uncluttered workspace, 
using a bright light to illuminate the work, keeping the cat in the 
other room, turning off the TV, being systematic and careful and 
checking your work.

Here's an example. Part of the StationPro assembly requires running 
short wires from two microphone connectors to carefully labeled solder 
pads on a PCB. What could be easier? Well, this part of the assembly 
turned out to be an exercise in frustration for several builders, to the 
point where I finally wrote up a little article for them, "W8ZR's Tips 
for Wiring Circuit Board Jumpers." You can read it here:
http://w8zr.net/stationpro/images/download%20files/Tips%20for%20Wiring%20Circuit%20Board%20Jumpers.pdf

My point is that one shouldn't take for granted, as I did, the 
importance of experience and practice in developing homebrewing skills, 
even for very simple projects. And just as important as skills is 
judgement and maturity. If you're going to be good at almost any craft, 
you can't be impulsive, or overconfident, or unaware of your 
surroundings, or easily distracted, or in a hurry, or unwilling to 
accept advice. And that's why I worry about teenagers undertaking 
projects involving lethal voltages. I'm sympathetic to the idea that one 
can be overprotective with young people, and that they'll never learn to 
be self-reliant if they're forever coddled and shielded from risk. And I 
agree that the pendulum may have swung too far in that direction in 
modern society. But I also believe that one has to crawl before one can 
walk. Ideally, one's parents or an elmer (or staff sergeant!) should 
provide guidance to beginners, but unfortunately that isn't always 
possible. It wasn't possible for me, and from some of the stories I've 
been reading about the past couple days, I'm not alone. Sorry, but I 
strongly believe hams should start with simple projects to acquire first 
the skills and wisdom required to build a high power RF amplifier. The 
stakes are too high to just plunge ahead and hope for the best.
73,
Jim W8ZR


On 1/7/2017 9:14 AM, Ward Silver wrote:
> > Excellent advice, Jim.
>
> Hear, hear!
>
> And another good piece of advice is to make sure you have an ac safety 
> ground connection on every metal enclosure.  With 12 Vdc being the 
> normal power supply voltage these days, we can get away with practices 
> that would really be hazardous for tube-based gear.
>
> >  A 50 uF capacitor charged to 4000 V holds a potentially deadly 400 
> Joules of energy
>
> In the defibrillator business of a few years ago, this was known as 
> the "rescue shock" of last resort.  This amount of energy can lift a 
> 200-pound person 1.5 feet.  When leveraged by muscle-and-bone, much 
> damage can be done.
>
> 73, Ward N0AX
>
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