On Mar 17, 8:44�pm, wrote:

The advice to study an "All American Five" receiver, OTOH,
is very bad, for a number of reasons:

1) You want to build, not take apart. In theory you could take an AA5
all apart and put it back together again, but
that's not the same as building something new.

As a LEARNING experience it costs (almost always) nothing.

There must be tens of thousands still sitting around, doing
nothing.

2) There is a good chance that if you can find an AA5, it
will need to be fixed to make it work. While you can learn
a lot that way, it's still not the same as building something new.

I disagree. The only one I've seen "not working" was
already damaged beyond repair. :-)

I will repeat...it is a LEARNING experience. Since it is
working, one can work backwards from that to see what
makes it (or a stage within) NOT work.

3) The end result of any such effort is going to be a basic receiver
for AM broadcast. Not a transmitter or transceiver, and not a piece of
amateur radio or SW equipment. If amateur radio/SW is your interest,
it seems to me that your projects should be for amateur radio and SW,
not AM BC.

True enough, but such receivers still work by the same
principles that apply to HF or VHF or LF or VLF.

An advantage to using AM BC is the known "signal
sources" in the area. One doesn't absolutely need a
signal generator to check or compare its performance.

4) AA5 receivers are of transformerless, "AC-DC" design. Usually one
side of the AC line is directly connected to the chassis.

I have yet to see one that is so "directly connected to one
side of the AC line." They may exist, but all the ones
I've handled (maybe two dozen all told, different makes
and models) have always used a capacitor to chassis
from one side of the AC mains. As I recall, they all had
UL stickers on them.


... But in order
to work on one, you want it out of the cabinet and powered up.

Yes, but that applies to ALL such things, yes? :-)


Working on one requires a lot of extra precautions to avoid getting a
shock. *Better to focus on transformer-operated equipment whose
chassis can be directly grounded to minimize the shock hazard.

Tens of thousands of tinkerers have gone before you and
still survived without being "shocked." :-)

Electricians seem to survive just fine and some of them
work directly with "hot" circuits...at higher voltages than
a nominal 115 VAC. TV repair folks face 24 KV from
picture tube ultors (the final accelerating anode)...even
when the power is off and disconnected.

If all else is troublesome, a cheap 1:1 isolation transformer
can eliminate all those "hazards." Cost in the neighborhood
of $15-$20 for 50 VA. However, even if used, the "B+" is
still at 140 to 100 VDC and is always there when working.
Precautions are fine but let us use a little realism on
"advice" - tube based devices nearly ALL have lethal-
potential voltages present. The average solid-state
device tops out at +/-15 VDC or thereabouts, NOT a
lethal potential.

73, Len AF6AY

On Fri, 16 Mar 2007 21:26:15 -0700, gbowne1 wrote:
...
In an effort to help me learn more about electronics than I already
know, not a whole lot at this point, I am going to build something
with which I can use once I finally get my ticket.

I would concur with those who suggest you're shooting a bit high for a
first project(grin). Don't throw out that book - you'll be ready to build
that project soon enough - but you should start with something a bit less
ambitious. The "AA5" receiver idea strikes me as interesting but
completely 100% irrelevant to modern electronics, both from the design
standpoint and the implementation standpoint. Poking around an old
transistor radio, on the other hand, might be worthwhile.

Firstly, do you have soldering experience? If not, I would suggest buying
a bit of protoboard and a "grab bag" of electronic components for practice
purposes. You wouldn't be looking to make any circuit that actually
worked - just to develop the skills to reliably make good solder
connections. The perfect design isn't going to work if the components
aren't connected in the way the designer intended(grin) and solder joint
problems can be VERY frustrating to troubleshoot. The ARRL Handbook has a
section on soldering that includes pictures of proper joints.

(you really should have a copy of the Handbook)

After you're confident of your soldering ability (and I doubt it would
take more than a day or two to get it down right) I would look at a modest
kit as a starting point. Ten-Tec sells some direct-conversion single-band
receiver kits. They actually do something (grin), (indeed they really do
it pretty well) and are about the right size for a first construction
project. There are other similar choices out there. A kit like this will
also get you familiar with component identification.

When you're ready to start going after the transceiver project, do it in
modular steps. Try to work in such a way that you can test each section
after you complete it. For example, start with the receiver audio
amplifier; it should hum when you touch the input, even if the entire
remainder of the transceiver is missing. (i.e. you haven't built it
yet!) That way, if something doesn't work (and it won't!) you don't have
to search the entire radio for the problem; also, you'll get ego-boosting
results sooner!