[Elecraft] Understanding the KX3 Block Diagram

[Tony Estep]

On Wed, Mar 7, 2012 at 10:20 PM, Wayne Burdick <n6kr at elecraft.com> wrote:
>...This is a substantial departure from other SDRs.....
----------------
Yep, for sure. And the biggest departure from the typical ham SDR is
the fact that the computer is inside the radio box. There are various
commercial and non-commercial SDRs in use on the ham bands, but nearly
all of them rely on the PC to do filtering, detection, and other
stuff. At first this had a certain irresistible gadget-lover's appeal,
but when you stop to think about it, it's not surprising that it opens
up a can with a nearly infinite number of worms.

The processing inside the PC introduces latency which is aggravated by
delayed procedure calls, an operating-system process that happens when
certain interrupts happen at certain times. This can mess up
performance both on receive and transmit.

Moreover, the programming involved is complicated. To replicate all
the functions of a competitive ham transceiver, a lot of code is
required. When that code has to run in an environment where an unknown
mix of other resource-hogging code is running, in an operating system
not designed for real-time application, the complexity multiplies. The
result can be an endless bug-squashing process, which has to start
over every time there's a big change in the running environment (e.g.
a new OS version).

I sorta think that in the medium term the future of SDRs in ham radio
will be those like the KX3, wherein the computer is completely devoted
to the radio, using its own real-time OS, and handing off ancillary
functions like the pan display to an external client. I don't think
the KX3 is the last word by any means, because with a bigger CPU and
different A/D gizmos you could obtain much wider bandwidth and more
gadgetry. But at the moment, it's the thought-leader in the SDR
sweepstakes.

Tony KT0NY





----------
http://www.isb.edu/faculty/facultydir.aspx?ddlFaculty=352