[Elecraft] PX3

Sat Apr 5 20:53:32 EDT 2014

Yes, the I/Q signal from the KX3 goes through an analog buffer directly 
into a two-channel analog to digital converter.  All processing is then 
done digitally by the DSP.  Correcting the frequency response is a 
simple matter of multiplying the frequency points by the correct number 
before they are displayed.  It's a good example of something that would 
be complicated using analog circuitry but is trivial with a DSP.

Alan N1AL

On 04/05/2014 04:13 PM, Barry LaZar wrote:
> I was hoping to get a hint from the manual as well as answer a few other
> questions, But it isn't on line yet.
>
> The I&Q data coming out of the KX3 is analog. It could be that they are,
> in fact, feeding an A/D converter directly. The rest would be just some
> software and a look up table. I guess I agree with you that would be the
> way to go. It's straight forward.
>
> 73,
> Barry
> K3NDM
>
>
>
> On 4/5/2014 7:35 PM, Walter Underwood wrote:
>> I bet they digitize it as early as possible, then use an FIR filter to
>> reshape it. Or scale the values after they FFT, since that is already
>> in the frequency domain. The scale values would be a vector of
>> constants, so it would be really fast and wouldn't even add delay (the
>> bane of FIR filters).
>>
>> wunder
>> K6WRU
>> On Apr 5, 2014, at 6:26 PM, Barry LaZar <k3ndm at comcast.net> wrote:
>>
>>> Yep. That what I was questioning. I, too, remembered those words. I
>>> also know it will take more than just inserting an amplifier with
>>> inverse gain characteristics. I know it can be done. However, that
>>> doesn't sate my curiosity as to how they did it. I just hope the
>>> solution isn't proprietary.
>>>
>>> 73,
>>> Barry
>>> K3NDM
>>>
>>> On 4/5/2014 7:14 PM, Walter Underwood wrote:
>>>> Yes. I posted the text from the manual two days ago in the KX3 list.
>>>>
>>>> "The RX I/Q outputs from a receiver are not “flat” over an infinite
>>>> frequency range; the signal-conversion process results in some slope
>>>> (decrease in gain) as you move farther from the center frequency. In
>>>> the case of the KX3, the signal will be reduced by about 2.5 dB at
>>>> +/- 24 kHz, 4 dB at +/- 48 kHz, and 7 dB at +/- 96 kHz. The spectrum
>>>> amplitude on the display, including the apparent noise floor of the
>>>> receiver, will “roll off” by these amounts."  (page 26)
>>>>
>>>> I would not be surprised if they corrected for this in the PX3.
>>>>
>>>> wunder
>>>> K6WRU
>>>>
>>>> On Apr 5, 2014, at 1:55 PM, Barry LaZar <k3ndm at comcast.net> wrote:
>>>>
>>>>> Good question. I have run at 192 KHz. with the sound card I have, a
>>>>> Steinberg UR22. The display I see using NaP3 shows a non-flat
>>>>> response. In fact, there are some words about this in the KX3 manual.
>>>>>
>>>>> 73,
>>>>> Barry
>>>>> K3NDM
>>>>>
>>>>>
>>>>>
>>>>> On 4/5/2014 1:07 PM, Uwe Hermanns wrote:
>>>>>> Hi,
>>>>>>
>>>>>> is the frequency responce of the KX3-IQ really flat over 250 kHz?
>>>>>>
>>>>>> 73 de Uwe, DL4AC
>>>>>> ---------- Weitergeleitete Nachricht ----------
>>>>>> Von: "Allen Patterson" <allenp at cryptosafe.com>
>>>>>> Datum: 05.04.2014 19:03
>>>>>> Betreff: [Elecraft] PX3
>>>>>> An: "Elecraft at mailman.qth.net" <Elecraft at mailman.qth.net>
>>>>>> Cc:
>>>>>>
>>>>>> When is the PX3 going to be available for shipping?
>>>>>>
>>>>>> You mentioned several software-firmware updates for the PX3 that are
>>>>>> planned.
>>>>>> What is the general schedule for each of these updates after initial
>>>>>> product shipment?
>>>>>> When is the manual for the PX3 going to be available?
>>>>>>
>>>>>> 73
>>>>>>
>>>>>> Allen Patterson, KC7SYR
>>>>>> Allenp at cryptosafe.com
>>>>>> ______________________________________________________________
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>>>>> ______________________________________________________________
>>>>> Elecraft mailing list
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>>>> --
>>>> Walter Underwood
>>>> wunder at wunderwood.org
>>>>
>>>>
>>>>
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>>> ______________________________________________________________
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>> --
>> Walter Underwood
>> wunder at wunderwood.org
>>
>>
>>
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>
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