On Mar 16, 10:13�pm, "Tim Shoppa" wrote:
gbowne1 wrote:
* I'm interested in homebrewing. *I've been a SWL since 1986, and I'm
a newcomer to amateur radio, although I have been interested in that
since then too, and will be getting my ticket during the course of the
following year. *I now own a Yaesu FT-757GX which I use as my HF Gen
coverage receiver so I can still listen to SW, and practice code and
then get my ticket, while working on building the rig and slowly
learning still. *Mind you, I also have a Fluke 8050A DMM too that I
bought last year which will help me. (Still learning how to use it)

* 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.

* In search for helpful documentation, I found a book by Randy L.
Henderson, titled
"Build Your Own Intelligent Amateur Radio Transceiver". *While now 10
years old, the book has many outdated components, and other errors in
the book. *While a good design idea, I think it could be improved on
to 2006/2007 standards in many ways.. which I will attempt to do. *The
rig is based on the 80C31 / 8051 family with a 27C64 EPROM in with a
7805 regulator, and 74LS373 on the computer board. *The computer board
also listed as having: a 1N4001, a 1N4148, a 2N2222A, a 2N2907, and
lastly a SK3444. *It also featured a 100,000uF memory backup capacitor
and a 6.2v Zener.

* My basic dimensions for the chassis are 16.1875" W x 6.1875" H x 15"
D.. so that will be the working envelope of whatever design I end up
with. *That's a pretty big space, and I like having space to work
inside.

* Well, anyhow this is my introductory post, and I'd love to hear your
comments, suggestions, etc.

My catchphrase of advice: "If you don't know how to do it, you don't
know how to do it with a computer".

I don't know much about the book in question and the radio it builds,
but the parts you name are all computer parts, not radio parts. My gut
advice would be that you not build a computer but a radio :-)

Tim, I don't want to sound demeaning about a "clever" response,
but, for the last 30 years or so, "radios" ARE using more and
more "computer" parts. The main frequency-determining
components of modern receivers, transmitters, transceivers in
amateur radio ARE "computer sub-systems." PLLs and DDSs
ARE "digital" and the last part of the "IF" in the newer receivers
ARE "digital." So is voice-frequency shaping and compression-
expansion and noise reduction.

"Begin with a simple regenerative receiver?" I say a resounding
NO to that. All that will be "learned" is assembly and how to
fuss around with trying to keep it from becoming a transmitter.
NOT a good place to start to "learn" despite the political-
correctness and "all the old-timers say that." Nonsense. I'm
one of those old-timers and "been there, done that, got lots
of T-shirts" in many ways in radio-electronics.

To "begin learning" I would suggest getting an ancient TUBE-
type "All American Five" AM BC receiver. There must be tens
or hundreds of thousands of those things sitting around unused
in attics, basements, etc. It is a basic superheterodyne
receiver with simple power supply, a local oscillator (think of it
as a "VFO-to-be"), a Mixer, a gain-controlled IF amplifier, a
diode detector, and a two-stage audio (low) power amplifier.
All the basic building blocks in there on one chassis.

EXAMINE each stage and its interrelationships, play with
changing things as clues come into mind from textbook
explanations. The "signal sources" are plentiful and no
signal generator is needed until the examination gets very
detailed. Make a mistake fussing around with one? Not a
serious problem. They can be had for nothing from neighbors
or family that accumulates old stuff...for nothing usually. Get
two or three if possible...old parts for them are getting scarce.

Need progress towards a transmitter? The Hartley oscillator
in an All-American Five is an introduction to oscillators and
modern "computer age" oscilloscopes can monitor the wave-
forms in it. One heckuva lot better than, for example, I had
it over 50 years ago. Add a simple, low-power Class C tube
amplifier (parts out of a second AM BC receiver) and one has
the basic MOPA transmitter (Master Oscillator Power
Amplifier). From there it is messing about with crystal
controlled oscillators and various keying schemes for OOK CW
and old-timer's beloved morse code. :-)

One of the VERY LAST things a beginner should avoid is to
jump in with plans to build some kind of state-of-the-art
digital transceiver. NOT from it being "made of computer parts"
but because what happens INSIDE the "digital" devices is so
enormously COMPLICATED that it can present a very steep
cliff in a learning curve about "radio." Unless one has a very
good theoretical grounding in MANY DIFFERENT circuits and
schemes that have led up to such "digital radio" designs, the
best way (to me) is to start with a KIT and learn assembling
the parts. The design has already been worked out. Those
few who bother going into WHY it woks can do so with something
that works after assembly.

Doing what "everyone else" did some 30 to 50 years ago sounds
all nice and homey but is NOT "the best" way to approach radio
in this new millennium. WE are IN the "digital age" and have been
for decades...but the analog circuits are still blended in. We
have
to know how they all interface and the characteristics of all to
make
a whole system work.

73, Len AF6AY





My feeling is that if you want to do something that is a mix of analog
and digital to do something interesting in radio, go through the SDR
("Software-Defined Radio") route. Google "software defined radio"
along with ham to see some links to stuff that's been published in QEX
and other sources the past couple of years.

But I'd encourage you to also build some really, really simple regen
receivers before doing anything that has a computer in it. The
learning curve will be so much less steep, and you'll learn so much
more about radio (as opposed to computers) by doing so.

More generically, also consider investing in the ARRL Handbook and
Horowitz and Hill's _The Art of Electronics_. Neither are abstract
academic texts, they are all about hands-on stuff. Together they will
cost more than a good used ham rig, though they will pay off much more
in the long run!

Tim.