Jerome,
This answer is for generic SDRs, since I don't have a KX3.
An SDR always must use both I and Q, even for CW. I and Q are two
streams of samples of the same signal. One of many advantages to i/q
sampling is the ADC's can run slower (cheaper). In the extreme and
ignoring the intrusion of real life components on sampling, a 10 kHz
wide signal could be sampled with I and Q ADCs running at 10 kHz.
Nyquist is satisfied because you have 2 streams, or 20 kHz sampling in
this example. Aliasing prevents you from using just I in that case.
The fact that Q is 90 deg from I, means we can plot them on axes 90 deg
apart. That allows re-appropriating the entire field of complex
mathematics to work with the samples. I and Q are both physical -
trying to avoid the word 'real'! - streams of samples, but I can be
called real and Q can be called imaginary. Using Euler's Formula, they
can be bundled into a concise exp(j phi) formulation to work with.
I/Q imbalance is always a concern. Maybe others can quantify it better
than me saying smaller is better. :-)
73 es GL!
Mike ab3ap
On 6/21/22 11:08 PM, JEROME SODUS wrote:
Hello,
Although I have asked some of these questions on another forum, here I have
expanded on them a bit.
When the KX3 transmits a CW-signal, are both I and Q used?
If so, why would that be necessary?
(My guess is only the I is needed.)
Same questions too for a SSB-signal.
But, for any digital transmission like RTTY, FT8, or Olivia, wouldn't both I
and Q would be active?
The LO is used for the "In Phase" and is delayed by 90 degrees for the
"Quadrature"; how is that delay done?
How much can the delay deviate from 90 degrees and still be useful?
My reason for asking is that I'm to give a talk to the Radio Club in August
about how a KX3 works and want to mention these details.
TIA for any replies.
73 jerry km3k....KX3#6088
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