We need to hone the definition of a SDR radio.
That doesn't seem that hard to me but I am probably using it more
broadly than some. I think that most people want to use the
definition where they pump broadband signals into an A:D and then do
all the filtering and detection in software (DSP). This allows the
receiver to be used at any frequency below the Nyquist frequency (1/2
the sampling rate). The state-of-the-art right now is something like
60Msps at 16bits of depth. That implies a radio that can cover all of
the HF spectrum, i.e. 0-30MHz, all at once and have a dynamic range
of 96dB.
OTOH, I am willing to broaden this definition to include some analog
bits, e.g. preamp, first mixer, first IF with roofing filters, second
mixer, A:D at second IF of up to about 200KHz with about 20 bits
(120dB) of dynamic range. All modulation and demodulation takes place
in software following the A:D. There is no conventional demodulator,
e.g. product detector.
OTOH some might consider the second mixer to actually be a product
detector and the second IF to be 'audio'. Since demodulation takes
place in software and the software also generates some or all of the
AGC signal used to reduce the gain of the analog components, I
consider this "audio" to actually be IF. If the software then
controls all of the other functions of the radio and every aspect of
the analog functioning is also under the control of the software, I
would say that this constitutes an SDR.
I do recognize that this is a rather open interpretation but I also
think that it is the best that we can do today at HF given the SOTA
(sorry, state-of-the-art) of A:D, D:A, and DSP. I suspect that will
will achieve greater flexibility in the not-too-distant future as A:D
gets deeper (bit depth) and faster (sample rate).
We need to hone the definition of User Interface
That one is dirt simple. It is how the person using the device
controls the device. The knobs and switches on a standard radio form
one form of user interface. The screen, keyboard, mouse, and software
of the standard PC along with the software forms another kind of user
interface. The steering wheel, throttle, brake pedal, and dashboard
of a car form yet another user interface.
The problems of user interface have to do with how easy it is to
learn and how easy it is to use. These are NOT the same. The average
"desktop" metaphor used with most computer systems is relatively easy
to learn and a pain-in-the-butt to use because you end up having to
make lots of monkey-motion to get even the simplest task
accomplished. Contrast that with the command-line interface of Unix
which is the polar opposite: daunting to learn but amazingly powerful
and simple to use.
Here is another example I think almost everyone can relate to: the
average 2M HT. Back in the days of the venerable Icom IC-2AT things
were dirt-simple: dial in the frequency (precious little training
needed there), set the offset, and key the mic. Then along came the
microprocessor. Programmers discovered they could do all SORTS of
clever things inside the HT, most of them useless to a person using
the hand-held. This required them to come up with all sorts of arcane
key sequences, menus, and 'soft keys' to control the device, all of
which were done badly and painfully. Sure you can spend the evening
programming all the memories but now I want you to hop in your car,
drive out of your normal operating area, and just manually enter a
new repeater as you drive along. Better still, manually scan for a
local repeater and get on it. Painful, isn't it? Now imagine an
IC-2AT that just adds one more thumbwheel -- CTCSS tone -- and
imagine how it would be. Add one more feature, a read-out of received
CTCSS tone, and you can probably get on any repeater you can find and
hear.
The point is, the user interface on almost every device with a
microprocessor SUCKS! Notable exceptions are those things with single-
function switches and knobs.
Now think about your average hard-wired HF transceiver. Not a lot of
differences. I can sit down at most HF transceivers and make them
work ... up until they started added microprocessors. HW101? KWM2?
FT-101E? No problem. IC-706? Not without a manual in front of you you
won't. But add the switches on the front panel back in and it becomes
easier. A toggle switch labeled "speech processor" and another
labeled "VOX" is a no brainer, as is a rotary switch labeled "IF
bandwidth 6.0k 2.7k 1.8k 800 500 200".
And then there is the concept of customization. Puh-leeze! Why do we
need 49 different ways to do the same thing? All that accomplishes is
to ensure that no one else can use your device.
Sorry. I got carried away.
Bottom line, single-function knobs and switches have a very nice
quality. I can look at them and know what they do. Maybe we can move
some (all?) of that into software and put it on a screen. If so, do
not give me only 10 buttons and interminable menus. It may seem
elegant at first but when you are trying to use it for real, it gets
old quickly.
(I am saying I LIKE the UI on the K3. OTOH, I can see needing a way
to add too it at some time. To this I *don't* have an answer. LEGO-
block switches and knobs anyone?)
We need to look under the hood to see the technology and how that
impacts performance
That too.
73 de Brian, WB6RQN
Brian Lloyd - brian HYPHEN wb6rqn AT lloyd DOT com
_______________________________________________
Elecraft mailing list
Post to: [email protected]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
