--- "George, W5YR" <w5yr@att.net> wrote:
W5YR: ?Sadly, we have yet to see a true
"software-defined" radio from ANY manufacturer. We
have had *software-controlled* radios for years now,
but even with the Kachina, Pegasus, Jupiter, et al,
you cannot re-define or change a thing about those
radios that has not had software control capability
built into it.
Software upgrades can alter the manner by which
controllable things are controlled and the
circumstances, etc., but as for being able to
reconfigure the radio architecture and/or do anything
that the existing hardware and circuitry will not
permit, all bets are off. It is unfortunate that
manufacturers use such terminology in the interests of
product appeal when it really cannot be defended on
technical grounds.?
I?m not sure this is true, while Ten Tec may tout it?s
FLASH upgrade feature they generally haven?t tossed
the term ?Software Defined? about all that much.
Whether their radios fit some definition of ?Software
Defined? or not, doesn?t change the fact that they can
be updated by end users for new functionality up to
and including adding new modes. I also don?t think
that anyone is making claims that these radios can be
made to do everything that is possible by software
alone. These radios will always be bounded by their
hardware, but they can add functions and/or modes that
a non-FLASH (or equivalent) radio can never do.
W5YR: ?It is even more unfortunate that most of us
seem unable or unwilling to differentiate between true
sofware definition and software "control." ?
Yes they are truly different things, but to call or
imply that the firmware changes to the
Pegasus/Jupiter/RX350 capability are only changes to
?control? is a bit simplistic. Some of the changes to
date have directly affected signal demodulation and
generation on a DSP level. While Software Defined and
Control are indeed different they are however tightly
linked; one of the main points of using SDR technology
is to make heretofore control functions/feature that
were not possible, possible.
I spent some searching for the SINGLE ?true?
definition of "Software Defined Radio" (SDR) and came
up with none. The term is not in the least uniformly
defined; and there is also considerable debate as to
what constitutes a SDR. However many of the
definitions I found in various documents on the web
however contained these 3 main definition criteria
that I?ve distilled/paraphrased here:
1. That it uses A/D and D/A?s and digitally processes
the signal, whether it is done at RF, IF or baseband
is irrelevant.
2. The transmitted signal is generated using
techniques similar to the RX functions.
3. That radio allows for EASY changes to its functions
or performance via software changes alone. This
specifically applies to signal demodulation/generation
parameters/modes, not user control and interaction
parameters.
Based on these 3 key criteria the recent Ten Tec
offerings sporting FLASH ROM qualify. Radios such as
the Kachina are a bit murkier, because changes to it
required PC card changes. While the PC card is
hardware, it is not however a RF component but is
instead simply a software transfer/memory mechanism.
Other radios like the RX331/340 are even further
removed from the SDR definition because of their ROM
based firmware. And recent JA DSP IF radios are the
farthest because they don?t allow end user firmware
changes at all; whether its by policy or for technical
reasons.
W5YR: ?When we can place an A/D converter virtually on
the antenna terminals, doing nothing to the signal in
the process, and then execute every single step in the
reception and processing of an incoming signal by
software, then we will have a software-defined radio.
The more essentially fixed hardware and circuitry we
have between the antenna terminals and the A/D
converter the further away from that goal we are.?
No argument from me on this basic point, the less
analog stuff ?in the way? ahead of the A/D and DSP the
better. But A/D and DSP technology does not relieve
the radio designer from having to apply the best
techniques available for any remaining analog stages
there are, despite what some people may believe. Any
radio is only as good as its Analog RF components in
its front end; this applies equally to fully analog
designs as well as DSP IF designs. One thing new that
DSP brings to the design requirements table are
precision low noise A/D and D/A?s plus good DSP code
writing.
W5YR: ?Presently our DSP IF radios have significant
software configurable options potentially available.
Some manufacturers like TenTec have taken advantage of
this by effectively simplifying the design such that a
single firmware package can be used to upgrade and
make changes.
Others like Kachina intended that to be the norm, but
unfortunately they have left the marketplace. Recent
problems with an aftermarket firmware upgrade product
for the Kachina have underscored how fragile this
approach can be.?
Yes and part of the Kachina experience underscores the
EXTREME importance of persistent software development
efforts. If you want to play in this "software heavy"
radio game you better darn well be planning on writing
plenty of software, not just once but to continually
improve and expand upon it for some time. This will be
a key factor in determining which companies will still
be making radios 10 years from now and those who
won?t. And in terms of the user control functions, you
must aggressively support the 3rd party developers who
want to write control software for your radio. As a
manufacture you will never have enough resources to
write all of it yourself, simply because there will
always be somebody who is thinking of something that
they?ll want to do that you won?t think of. That is
why George?s point about having minimal radio specific
hardware ahead of the digital goodies is completely
true.
W5YR: ?Icom and most of the other JA manufacturers
seem to prefer a widely distributed control approach
with multiple ASIC and dedicated microprocessors such
that the firmware is distributed among several
processors and thus cannot practically be upgraded
after the fact.?
I?m not sure if this reflects a lack of forward
thinking on the JA companies part or a keen sense of
the end user market place and what they will actually
buy. I?m inclined to believe the later.
W5YR: ?So, the times they are a'changin' and we have
much in store for us!?
Indeed they are, and we?ve only entered into the very
beginning of what is already possible. I for one would
like to see the pace increase from the slow plodding
progress that we see today, it is not the technology
that is lacking today, it is instead the collective
?will? to apply it.
For those who are totally anti DSP etc need not worry,
there will always be variations of the traditional
analog designs available. Very much like you can still
buy a crystal detector or regenerative receiver to
this day. I also believe that there is still a place
for radios that employ the tube era Swans (and Atlas
210/215) VFO/mixer scheme. Apply some of the frequency
lock loop concepts posted on here on the reflector
earlier today and some of the Swan?s design
shortcomings can be rectified.
Believe it or not I?m not one for throwing a lot of
fancy technology at a simple problem, I believe in
only applying what is truly ?needed?. But for the
record it is not that I NEED this fancy DSP stuff, ???
I WANT it ;).
Duane
N9DG
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