John Smith wrote:

gb:

Well, we certainly need to examine the "bottle neck" and remove it... before
we are doomed...

If we can't institute this "radical" idea here, we need to look at Canada,
Mexico, So. America, China, India, etc...

When there are as many functional radios (or "cards") hitting the dumpster
as there are functional computers and related equip. (replaced with
upgrades) we will know the right idea has prevailed and radio has come
home...

I would think there must be some EXCELLENT argument/reasoning serving as a
road block, or else, others are simply going to pass us by...

John

I've considered this sort of a radio before. There are a few problems,
however:

First, there is a fundamental difference between digital systems and
analog systems that prevents this sort of thing working with the success
of a PC.

The basic difference is that with a digital system you either end up
with a clean signal or a useless signal. In an analog system the
character and purity of the signal must be carefully guarded, at least
until you manage to digitize it. This means that there will be a much
greater chance that adding a new card to the radio will degrade not only
the function of the new card, but the function of all the other cards.

Second, the PC market is a huge one, with great advantages to be derived
from common equipment and software, and much smaller advantages to be
derived from commonality. This is the exact obverse of the radio
market, including homebrew radios. To make a "card" radio would be to
define a basic radio architecture, probably down to the IF frequency (or
at least to the point of forcing you to match your IF and front end).
While improvements could be made within this structure an independent
experimenter couldn't play around with such things as direct-conversion,
different IF schemes, etc., without extensive modification.

In this way the radio market is more like the market for computing
devices as a whole. The PC market doesn't account for the most
processors sold, or even the most dollars of all computing devices. The
largest segment of the market is in embedded computing devices ranging
from things as visible and obvious as your PDA, through cell phones, and
down to burglar alarms and TV remotes. Take apart a new home thermostat
or TV remote and there's a good chance that you'll find a processor that
implements most of its functionality in software -- but a very slim
chance indeed that its PC compatible!

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com