[Elecraft] KX3 "Full" SDR

[Greg Troxel]

Don Wilhelm <w3fpr at embarqmail.com> writes:

> The KX3 is a "full SDR" radio (the K3 is as well).  By virtue of the
> modulation and demodulation all being done the firmware rather than in
> hardware.  Yes, the KX3 does have knobs which are used to pass
> parameters to the firmware - the "computer" is inside the KX3 and no
> external computer is required.
>
> There are some (maybe many) who believe an external computer is
> required for the radio to be a "full SDR" but I am not in that group.

There are several important questions that could be lurking behing "full
SDR", especially since Craig talked about hobby aspects of SDR -- people
often mistakenly equate SDR with "open-source SDR", blurring "functions
are controlled by software" with "user can control functions by
software".

1) Is the modulation/demodulation done in some sort of processor under
software control, from a wide IF (perhaps at 0, perhaps higher)?  This
is the normal definition, and indeed the KX3 meets it.

2) Is the user of the radio able to change the firmwmare, in order to
experiment or for other purposes?  One might call this "user-changeable
SDR".  Here, the KX3 does not meet that definition -- while Elecraft has
released updates and improvements and can be expected to keep doing so,
users cannot improve or even read the software.

2a) Can someone who changes the firmware share their improvements with
the world?  This is a further nuance, leading to "open-source SDR".
Flex used to be like this, but I understand (from speaking to a Flex rep
at Boxboro 2012) that the software used with their radios is now
proprietary rather than open source.  And, it is limited to Windows
only, which leads to an unreliable system (as described by a Flex user
who gave a talk at a local club).  Note that there is hardly any
discussion of KX3s locking up and being flaky and needing to be
rebooted.

Then there's a related question separate from SDR definitions, having to
do with packaging and interconnects:

3) Does the radio function without having to carry along an external
computer?  There is great merit in a small low-power box being
functional by itself.

Craig:

So it really depends why you think you want an SDR.  If you want to
understand the software and contribute towards a community of people
improving it, the KX3 won't let you do that, and I would suggest that
you look at GNU Radio and other open-source projects and their
associated hardware (some of which has open designs).  If you want a
radio which has features typically achievable in SDR, and that you can
expect to be improved by the manufacturer, and you don't mind not being
able to change it (and that others can't either), then the KX3 fits the
bill.

If what you want is to experiment with code to demodulate, the KX3 is
also a good choice because it provides I/Q output.  But I know of no way
to transmit custom signals (other than soundcard modes, which generally
are viewed as below the SDR definition).

My advice is to think about what you really want in terms of an
experimentation/learning platform vs. a really well designed useful
radio.  And if you are going to experiment with code, stay within the
open-source world, so that you can share your changes with everyone.


73 de n1dam