[Elecraft] Survey and summary: Elecraft K3/K3S panadapter solutions

[Don Wilhelm]

Dave and all,

The answer to your assumptions depends on *your* definition of I and Q 
signals, and also your ability to separate analog I/Q concepts and 
digital I/Q concepts.

I believe the K3/K3S, KX3 and KX2 already qualify as SDR transceivers - 
but they do the DSP signal processing inside the box without any 
dependency on an external computer.  Some seem to think that to be an 
SDR, you must connect with a computer - I do not share those thoughts, 
an SDR is all about mathematical processing - study a bit on DSP, that 
is "what it is all about".

I and Q signals can be defined as 2 identical signals but 90 degrees out 
of phase - period (full stop there, anything more is what adds 
confusion).  One can do "magic" with those two signals, and create 
filters, demodulate, modulate - all by manipulating the signals in the 
digital world.  It can also be done in the analog world (examples, Rick 
Campbell's phasing receivers, and the old phasing SSB exciters)

The K3/K3S does have I/Q signals, but they are digital and are at 15kHz, 
not audio, so one cannot feed them to a computer soundcard.
The KX3 has I/Q signals (and I/Q outputs) because the I/Q signals are at 
baseband (audio frequency spectrum).  The onboard computer (MCU) inside 
the radios do the processing rather than depending on a computer 
soundcard and the computer MCU for the processing.  The KX2 is similar, 
but has no I/Q outputs.

While some want to add their favorite computer software application to 
do I/Q processing separate from that done by the K3/K3S or KX3 or KX2.

The current fact is that the K3 I/Q signals exist, but they are only in 
the digital world.  The P3 does extract them, but for purposes of the 
P3, they remain in the digital world.
Getting those signals into the analog world will take some work and 
design effort.  It is more complex than a digital to analog converter.

73,
Don W3FPR

On 7/27/2018 5:17 PM, Dave Fugleberg wrote:
>   As I understand it, the KX3, and the P3, both contain a software defined
> receiver, so the I/Q signals are already present.
> 
> That is not the case for the receiver in the K3 or K3S, so adding it there
> would involve adding a SDR.
> On Fri, Jul 27, 2018 at 2:21 PM Dick Dickinson <softblue at windstream.net>
> wrote:
> 
>> Ever the contrarian here, I note the KX3 has I/Q output.  Why not a module
>> for the K3/S rather than the P3..?