On Sat, 16 Oct 2004 15:17:47 -0700, Roy Lewallen
wrote:



Many, or most, of the books oriented toward amateurs are written by
people who haven't developed the background or discipline to produce
reliable, repeatable circuits. Magazine articles are even more in this
category. Some circuits found in handbooks have perhaps never been
actually built or tested by the author, even in a quantity of one.
That's not a condemnation -- after all, this is amateur radio, most
offerings are free, and the designs are adequate for a lot of users.
Hopefully -- although I'm afraid a bit wishfully -- some builders at
least have enough technical know-how to take care of minor design flaws.
Nonetheless, it's really a treat when we're given a circuit or an
explanation by a truly professional engineer whose approach to circuit
design is one of making reliable, repeatable circuits. The chances of a
copy of the circuit working the first time, as predicted and claimed,
are much higher than for a design built once with little understanding
of how it works or what its limitations and weak points are. And the
deeper the designer's understanding of the fundamental principles
involved, the greater the chance that he's accounted for and designed
around potential problems in repeatability and operating environment.

That's one of the reasons I like and heartily recommend Wes' books and
other writings. I've known him as a friend and as an engineering
colleague for 30 years now. He's one of the very best, and we're lucky
to have access to a fraction of what he's learned.

When amateur constructors are mentioned, it is not only those who do
strange things. While many large telecommunication and instrument
factories like HP, Tektronic, Siemens, Wandel&Goltermann,
Rohde&Schwartz, LME, Philips, Telettra seem to have certain rules to
follow and you may even see certain ways the different factory solves
the problems, it is some very large companies in Norway, Great
Brittain and elsewhere who make rather strange solutions.

One Italian company forgot to put transient protection over a relay,
and the driver transistor was damaged ever so often. I've maintained
many different transmitters which were almost impossible to tune up
after replacing parts because the impedances changed a lot, adding a
resistor in the base circuit improved on this. A wellknown Norwegian
radiolink manufacturer designed local oscillators in 6-8GHz using
2N3866 with over 1.5W power consumption, a buffer with the same and
operated in class C, the next doubler to 200MHz in class C and a
2N3866 as well, and a 2N3375 in class C. The first and third
transistors were critical and had to be replaced every two years, and
the signal on 6cm was so noisy that SM6ESG couldn't find any beat
note. He modified the stages to class A, reduced the drive level on
all stages and the heat was considerable lower, and at least the
oscillator noise very much improved

So, one shouldn't only blame the amateurs for bad constructors, but
sometime the manufacturers may even be worse

73,
Jan-Martin
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm