From: "Tim Shoppa" on 17 Mar 2007 18:10:32
-0700

wrote:

but, for the last 30 years or so, "radios" ARE using more and
more "computer" parts.

And I think that's fine. I personally find those parts as detracting
from what is interesting about homebrewing, up until you get to say a
Software-Defined Radio, or maybe some hamshack accessories that let
you use a computer to do clever things with your rigs.

To paraphrase from an old film, "we have a failure to
communicate?"

A PLL subsystem is essentially ALL digital with the exception
of the VCO itself. It uses "computer parts" and it can take
the place of a dozen or hundreds of quartz crystals, using only
one crystal as THE reference. All the parts are legacy and have
been so for at least two decades.

A DDS SOC (System On a Chip) can do the same, yet yield a much
finer frequency increment, still with quartz crystal stability
and control. It is all digital inside that SOC.

I do feel it's pointless to build computerized gadgets when perhaps an
already existing desktop PC can do the same job.

Why tie up a desktop PC to do things that can be done in a
small, dedicated assembly? A PIC microcontroller can be a
stand-alone frequency indicator...as witness to Neil Hecht's
fine products over on AADE. Or, how about a vector wattmeter
such as Larry Phipps' (N8LP) LP-100 unit that will also read
the complex impedance of the load? Or the Palstar ZM-30
antenna analyzer as a self-contained Z-R-X box to 30 MHz?
All enabled with "computer parts." All small, easy to apply
or portable with self-contained batteries.

Most digital modes
beyond CW are really used much more effectively with a CRT than with
little microcontroller-based LED displays etc.

"Effective?" Using a desktop or laptop as an I/O device, and
the internal sound card as an extra digital processor and
A/D, saves BUILDING the equivalent. But, otherwise the PC
has only a larger viewing area and color display capability.

This is the HOMEBREW newsgroup and is about BUILDING at home.

I was trying to focus on the LEARNING aspect of getting
acquainted with the various stages of radios. I picked the
ordinary old table model radio as a representative of such
a LEARNING device for several reasons: There are thousands
of them sitting around in storage, unused, replaced by
newer BC receivers; the "All-American-Five" variety has
every basic stage in it...rectifier, mixer-oscillator,
gain-controlled IF amplifier, audio voltage and output
amplifier, plus tuned circuits; it can be forgiving if one
changes some parts values to see what happens; the RF and
IF stages have frequencies low enough to view with most
modern oscilloscopes. The theory part is very legacy and
can be found in dozens of basic text books. If they are
unused for BC listening now, few will complain if a beginner
tinkers around with it.


Again, I tried to encourage him to go into SDR's as the cutting-edge
of homebrewing.

I still disagree. Someone who is only a couple steps up
from crystal detector sets jumping into Software Defined
Radios is making MANY quantum leaps in theory just to get
the PROGRAM working. That program is the heart of SDR...
once there is a processor SOC that can work with the
right frequencies...or A/Ds that work at higher IFs.

Yes, modern cell phones HAVE such things and ICs ARE available
to do RF-to-baseband software-controlled receiver functions.
Ever try to USE one of those in a lab environment? It is
NOT for beginners.

"Begin with a simple regenerative receiver?" I say a resounding
NO to that.

You do have a point, the OP had a pretty kick-ass all-mode SW receiver
already. Perhaps a simple rock-bound CW transmitter that could be used
once he got his ticket would be a much more interesting project.

Naturally using CW now that NO US amateur license requires
a code test? :-(

But you do correctly deduce that my first ham-band receiver was a
regen built by me in 5th grade :-).

It's irrelevant WHEN anyone BEGAN getting into the guts
of radios to find out how they worked. The real point
is the HOW of learning, the methods used. Everyone was
a beginner at first.

I built a SW BC regenerative back in 1947 as a teen-ager.
Out of an article in Popular Science. Outside of what
the article text gave, I didn't learn anything but how
to assemble one and solder (which I already knew from
middle-school shop class). I tried "quantum jumping" in
theory on different electronics-radio things back then
but didn't get focussed until entering the US Army and
getting into the Signal Corps. But, that is a personal
experience and isn't for everyone nor even recommended.


Considering that a complete working multimode multi-band (but used) HF
ham rig can be bought for not much more than what the ARRL handbook
costs new, homebrewing a complete rig is a non-starter for even those
who've been doing simpler projects for decades!

Sorry, but I'll say that is wrong...unless the ARRL suddenly
changed its prices for Handbooks by an order of magnitude.
"Multimode" beyond CW-only? Nah.

So, thinking it over again, I'd like to advise the OP to find a simple
CW QRP transmitter project that can be used with his existing receiver
after he gets his ticket.

It can be checked out BEFORE getting any license...using
it on the bench with a dummy load. That will allow lots
of inspection and playing around with parts values before
connecting it to an antenna. One can do the same with an
AM mode transmitter or FM mode voice transmitter (FM is the
simplest but has to be on VHF and above)...although AM DSB
is frowned upon by the "gentlemen" who occupy the HF bands.

73, Len AF6AY