kx3 vs k3

[KC6CNN]

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[Don Wilhelm-4]

You may have to do some study on both analog receivers and SDR receivers
to understand and appreciate the differences, but let me try to give an
answer in the way I understand it (others can correct me if I am wrong
in any area).

The K3 down-converts first to an 8 MHz IF, then converts to a 15 kHz IF
signal that is passed to an ADC and the digital output is processed by
the DSP before being converted back to analog audio signals which are
amplified and sent to the headphones or speaker.

OTOH, the KX3 down-converts direct to baseband (audio range) as I/Q
signals (each with its ADC) and the DSP processes those quadrature
signals and then sends the output to a DAC to obtain audio which is then
amplified.

That means that the KX3 will be more like other SDR receiver designs
than the K3 (which is also technically an SDR).

Which is better?  That is a difficult question to answer.  The 8 MHz IF
of the K3 allows crystal roofing filters to be inserted in the path to
keep strong signals which are out of the filter passband from
overloading the ADC (which would result in garbage data out).
The KX3 can have roofing filters, but they will be active filters in the
audio range - they will do the same thing, but I expect the dynamic
range of the KX3 will not be as great as that if the K3.
There are advantages for both approaches.  The K3 design is more
complex, but allows more controls in the analog IF system (note both
analog and DSP Noise Blankers for one example).

I do not expect the KX3 to have performance characteristics that are
equal to the K3, but it may be close.
You might want to think of the KX3 as a "full SDR" as opposed to the K3
which is a combination of analog and SDR - both of which are complete
receivers without the addition of a computer, and that is different than
most other SDRs on the market.

73,
Don W3FPR

On 9/4/2011 5:24 PM, KC6CNN wrote:
> The KX3 and K3 have different engineering for the receive.
> Can someone explain the difference and which one would be better?
>
> Thanks.
>
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[drewko]

One feature the KX3 will have that the K3 does not is dual watch
capability.

73,
Drew
AF2Z


On Sun, 04 Sep 2011 14:24:53 -0700 (PDT), KC6CNN wrote:

>The KX3 and K3 have different engineering for the receive.
>Can someone explain the difference and which one would be better?
>
>Thanks.

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[wayne burdick]

drewko wrote:

> One feature the KX3 will have that the K3 does not is dual watch  
> capability.

The KX3 will have "dual watch" over a limited range, possibly as small  
as 10 kHz, though we'll aim for something wider. This would be enough  
for CW split operation. Filter bandwidths and certain other features  
will have different constraints in this mode.

The K3, of course, has a fully independent sub receiver. This provides  
completely flexible "dual watch," as well as simultaneous receive on  
two different bands and diversity receive. The latter is not possible  
on rigs with only dual watch, because it requires two antenna inputs.

73,
Wayne
N6KR


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