Elecraft

KX3 SDR

Classic

List

Threaded

13 messages Options

Enzo Adrian-Reyes

KX3 SDR

Hi All

Yes this topic might be a little bit more complicated than the title
suggest.

So I have the KX3 plugged into the audio input of my computer, and its
sending quadrature data (IQ) to the sound card, the sound card samples at
96Khz.

So my question is how I process this? Yes I know use a piece of software,
but I am trying to write this, I know the IQ data is coming through down
and if I use the right process on the IQ data I get base band data out. I
kind of know that however I dont understand the SDR data coming out, so for
example and I getting sample of IQ data at freq point Y, or is it a
circular buffer arrangement.

I guess what I am saying is, is the IQ data coming from teh KX3 data from
teh Centre Freq (+/-) the bandwith scope, or just the centre freq + some
additional side bands?

How are bandwith and sampling rate related? I mean if I am sampling at at
96Khz, with a band with of 48Khz does that mean I am only getting 2 samples
per second at perticular freq??? Or am I getting the entire band of 48Khz
at 96Khz.

Regards
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

tomb18

Re: KX3 SDR

Hi It's not that simple Basically you take the I and q signals, sample them with the sound card, convert them to a complex number, pop them in a fast Fourier transform, do a rectangular to polar conversion and then calculate the magnitude in dBm. Then plot them. There's a few more nuances but that's the overall idea. Check out the free book on the Internet called the scientists guide to digital signal processing.73 Tom va2fsq.com

Sent from my Samsung Galaxy smartphone.
-------- Original message --------From: Enzo Adrian-Reyes <[hidden email]> Date: 2016-07-27 7:16 PM (GMT-05:00) To: Elecraft List <[hidden email]> Subject: [Elecraft] KX3 SDR
Hi All

Yes this topic might be a little bit more complicated than the title
suggest.

So I have the KX3 plugged into the audio input of my computer, and its
sending quadrature data (IQ) to the sound card, the sound card samples at
96Khz.

So my question is how I process this? Yes I know use a piece of software,
but I am trying to write this, I know the IQ data is coming through down
and if I use the right process on the IQ data I get base band data out. I
kind of know that however I dont understand the SDR data coming out, so for
example and I getting sample of IQ data at freq point Y, or is it a
circular buffer arrangement.

I guess what I am saying is, is the IQ data coming from teh KX3 data from
teh Centre Freq (+/-) the bandwith scope, or just the centre freq + some
additional side bands?

How are bandwith and sampling rate related? I mean if I am sampling at at
96Khz, with a band with of 48Khz does that mean I am only getting 2 samples
per second at perticular freq??? Or am I getting the entire band of 48Khz
at 96Khz.

Regards
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Enzo Adrian-Reyes

Re: KX3 SDR

Hi Tom

I never thought it was simple :)

I am just trying to understand what is going on, so given by what you've
said I would push the IQ data coming from the KX3 into an FFT, that FFT
would then produce the circular buffer that would let me analyse what
signals are in that band?

But this would be in the frequency domain then, however I am not interested
in a band plot, I have a signal at Freq X, with the KX3 tuned at Y, (X=Y),
would I have to still pump that IQ data into the FFT to filter all the
other signals out, then inverse teh FFT to get the IQ data that I would
want?

Regards

On Thu, Jul 28, 2016 at 9:41 AM, tomb18 <[hidden email]> wrote:

> Hi It's not that simple
> Basically you take the I and q signals, sample them with the sound card,
> convert them to a complex number, pop them in a fast Fourier transform, do
> a rectangular to polar conversion and then calculate the magnitude in dBm.
> Then plot them. There's a few more nuances but that's the overall idea.
> Check out the free book on the Internet called the scientists guide to
> digital signal processing.
> 73 Tom
> va2fsq.com
>
>
>
> Sent from my Samsung Galaxy smartphone.
>
> -------- Original message --------
> From: Enzo Adrian-Reyes <[hidden email]>
> Date: 2016-07-27 7:16 PM (GMT-05:00)
> To: Elecraft List <[hidden email]>
> Subject: [Elecraft] KX3 SDR
>
> Hi All
>
> Yes this topic might be a little bit more complicated than the title
> suggest.
>
> So I have the KX3 plugged into the audio input of my computer, and its
> sending quadrature data (IQ) to the sound card, the sound card samples at
> 96Khz.
>
> So my question is how I process this? Yes I know use a piece of software,
> but I am trying to write this, I know the IQ data is coming through down
> and if I use the right process on the IQ data I get base band data out. I
> kind of know that however I dont understand the SDR data coming out, so for
> example and I getting sample of IQ data at freq point Y, or is it a
> circular buffer arrangement.
>
> I guess what I am saying is, is the IQ data coming from teh KX3 data from
> teh Centre Freq (+/-) the bandwith scope, or just the centre freq + some
> additional side bands?
>
> How are bandwith and sampling rate related? I mean if I am sampling at at
> 96Khz, with a band with of 48Khz does that mean I am only getting 2 samples
> per second at perticular freq??? Or am I getting the entire band of 48Khz
> at 96Khz.
>
> Regards
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Don Wilhelm

Re: KX3 SDR

In reply to this post by Enzo Adrian-Reyes

If you are writing your own software, you will have to become proficient
in Digital Signal Processing. The I and Q signals are simply baseband
signals that are 90 degrees out of phase - by themselves, they will do
nothing but audio signals, but with DSP processing, they can do most
anything that is possible in the math of digital signals - limited only
by your processing power and skills at DSP signal processing.

Run them through FFT transforms to convert them to digital signals, and
then do the math of your DSP algorithms to produce whatever you want -
panadapter display, demodulation, etc. You can add filtering and other
things like AGC, Noise Reduction, Noise Blanking, and a whole variety of
effects. It is all in how you choose to implement you DSP mathematical
functions.

Rather than write your own, there are several DSP applications available
for free or at nominal cost - try HDSDR or NaP3 or WIN4K3 as examples.
Once you see what is happening with those applications, you may be moved
to write your own DSP application to process the I and Q signals.

73,
Don W3FPR

On 7/27/2016 7:16 PM, Enzo Adrian-Reyes wrote:

> Hi All
>
> Yes this topic might be a little bit more complicated than the title
> suggest.
>
> So I have the KX3 plugged into the audio input of my computer, and its
> sending quadrature data (IQ) to the sound card, the sound card samples at
> 96Khz.
>
> So my question is how I process this? Yes I know use a piece of software,
> but I am trying to write this, I know the IQ data is coming through down
> and if I use the right process on the IQ data I get base band data out. I
> kind of know that however I dont understand the SDR data coming out, so for
> example and I getting sample of IQ data at freq point Y, or is it a
> circular buffer arrangement.
>
> I guess what I am saying is, is the IQ data coming from teh KX3 data from
> teh Centre Freq (+/-) the bandwith scope, or just the centre freq + some
> additional side bands?
>
> How are bandwith and sampling rate related? I mean if I am sampling at at
> 96Khz, with a band with of 48Khz does that mean I am only getting 2 samples
> per second at perticular freq??? Or am I getting the entire band of 48Khz
> at 96Khz.
>
>

Enzo Adrian-Reyes

Re: KX3 SDR

Hi

Yes, well I have used those in the past, hence my confusion, when I see
bandwith of a SDR at lets say 24Khz
and I am sampling at 48Khz. Does that mean I am sampling the whole bandwith
of 24Khz centered on freq X, or
am I a sampling some point Y at +/- from the center frequency.

I am trying to design a digital mode, and while I do understand the
concepts, could do it in GNU radio but it abstracts a lot of this away, and
I would like to do this in C/C++
So before getting there I have to know what is going on, especially what
data is coming from the device.

Thinking about it yeah it would have to be a stream of IQ signals coming
from the KX3 with a certain freq set, but I am guessing its in the time
domain. Not at the freq domain?

On Thu, Jul 28, 2016 at 10:26 AM, Don Wilhelm <[hidden email]>
wrote:

> If you are writing your own software, you will have to become proficient
> in Digital Signal Processing. The I and Q signals are simply baseband
> signals that are 90 degrees out of phase - by themselves, they will do
> nothing but audio signals, but with DSP processing, they can do most
> anything that is possible in the math of digital signals - limited only by
> your processing power and skills at DSP signal processing.
>
> Run them through FFT transforms to convert them to digital signals, and
> then do the math of your DSP algorithms to produce whatever you want -
> panadapter display, demodulation, etc. You can add filtering and other
> things like AGC, Noise Reduction, Noise Blanking, and a whole variety of
> effects. It is all in how you choose to implement you DSP mathematical
> functions.
>
> Rather than write your own, there are several DSP applications available
> for free or at nominal cost - try HDSDR or NaP3 or WIN4K3 as examples.
> Once you see what is happening with those applications, you may be moved
> to write your own DSP application to process the I and Q signals.
>
> 73,
> Don W3FPR
>
>
> On 7/27/2016 7:16 PM, Enzo Adrian-Reyes wrote:
>
>> Hi All
>>
>> Yes this topic might be a little bit more complicated than the title
>> suggest.
>>
>> So I have the KX3 plugged into the audio input of my computer, and its
>> sending quadrature data (IQ) to the sound card, the sound card samples at
>> 96Khz.
>>
>> So my question is how I process this? Yes I know use a piece of software,
>> but I am trying to write this, I know the IQ data is coming through down
>> and if I use the right process on the IQ data I get base band data out. I
>> kind of know that however I dont understand the SDR data coming out, so
>> for
>> example and I getting sample of IQ data at freq point Y, or is it a
>> circular buffer arrangement.
>>
>> I guess what I am saying is, is the IQ data coming from teh KX3 data from
>> teh Centre Freq (+/-) the bandwith scope, or just the centre freq + some
>> additional side bands?
>>
>> How are bandwith and sampling rate related? I mean if I am sampling at at
>> 96Khz, with a band with of 48Khz does that mean I am only getting 2
>> samples
>> per second at perticular freq??? Or am I getting the entire band of 48Khz
>> at 96Khz.
>>
>>
>>
>

tomb18

Re: KX3 SDR

In reply to this post by Enzo Adrian-Reyes

HiI have little experience in demodulation of the signals but I did do SSB and AM at one time. Basically once you have the samples in the fre1uency domain you will want to apply a bandpass filters and shift it down to baseband, do an inverse fft and then a Hilbert transform to demodulate the SSB signal.Again you best bet is the free online book I mention.73 Tom

Sent from my Samsung Galaxy smartphone.
-------- Original message --------From: Enzo Adrian-Reyes <[hidden email]> Date: 2016-07-27 8:04 PM (GMT-05:00) To: tomb18 <[hidden email]> Cc: Elecraft List <[hidden email]> Subject: Re: [Elecraft] KX3 SDR
Hi Tom
I never thought it was simple :)
I am just trying to understand what is going on, so given by what you've said I would push the IQ data coming from the KX3 into an FFT, that FFT would then produce the circular buffer that would let me analyse what signals are in that band?
But this would be in the frequency domain then, however I am not interested in a band plot, I have a signal at Freq X, with the KX3 tuned at Y, (X=Y), would I have to still pump that IQ data into the FFT to filter all the other signals out, then inverse teh FFT to get the IQ data that I would want?
Regards

On Thu, Jul 28, 2016 at 9:41 AM, tomb18 <[hidden email]> wrote:
Hi It's not that simple Basically you take the I and q signals, sample them with the sound card, convert them to a complex number, pop them in a fast Fourier transform, do a rectangular to polar conversion and then calculate the magnitude in dBm. Then plot them. There's a few more nuances but that's the overall idea. Check out the free book on the Internet called the scientists guide to digital signal processing.73 Tom va2fsq.com

Sent from my Samsung Galaxy smartphone.
-------- Original message --------From: Enzo Adrian-Reyes <[hidden email]> Date: 2016-07-27 7:16 PM (GMT-05:00) To: Elecraft List <[hidden email]> Subject: [Elecraft] KX3 SDR
Hi All

Yes this topic might be a little bit more complicated than the title
suggest.

So I have the KX3 plugged into the audio input of my computer, and its
sending quadrature data (IQ) to the sound card, the sound card samples at
96Khz.

So my question is how I process this? Yes I know use a piece of software,
but I am trying to write this, I know the IQ data is coming through down
and if I use the right process on the IQ data I get base band data out. I
kind of know that however I dont understand the SDR data coming out, so for
example and I getting sample of IQ data at freq point Y, or is it a
circular buffer arrangement.

I guess what I am saying is, is the IQ data coming from teh KX3 data from
teh Centre Freq (+/-) the bandwith scope, or just the centre freq + some
additional side bands?

How are bandwith and sampling rate related? I mean if I am sampling at at
96Khz, with a band with of 48Khz does that mean I am only getting 2 samples
per second at perticular freq??? Or am I getting the entire band of 48Khz
at 96Khz.

Regards
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Lyle Johnson

Re: KX3 SDR

In reply to this post by Enzo Adrian-Reyes

The signals at the IQ jack on the KX3 are analog, not digital. They are
centered approximately 8 kHz away from the dial frequency as the KX3
uses an internal offset of 8 kHz. Depending on the firmware release and
user settable options, that offset may be on either side of the center
of the IQ audio.

The rate at which you sample it in general will determine, and in any
case will certainly limit, the maximum bandwidth you can digitize for
further processing.

Internally, the KX3 samples the analog IQ signals at 48 kHz.

Externally you can sample at any rate you desire that your A/D
(soundcard) will support, as long as you take into account anti-aliasing
filtering and the bandwidth/response of the analog circuitry in the KX3
itself, and any similar limitations of the soundcard including its
analog circuitry and the characteristics of its ADC. For example,many
ADCs do noise shaping of their sampling systems to prefer 0 to 20 kHz at
the expense of internal noise humps above 20 kHz.

General information about the frequency rolloff of the KX3 analog IQ
signals have been discussed here in the past, and I think (but have not
checked) that they are in the Owner's Manual. You can also observe
them, perhaps using your proposed soundcard and the tools that gnu radio
provides for you to explore these topics.

73,

Lyle KK7P

On 7/27/16 5:43 PM, Enzo Adrian-Reyes wrote:
> Hi
>
> Yes, well I have used those in the past, hence my confusion, when I see
> bandwith of a SDR at lets say 24Khz
> and I am sampling at 48Khz. Does that mean I am sampling the whole bandwith
> of 24Khz centered on freq X, or
> am I a sampling some point Y at +/- from the center frequency...

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Joe Stone (KF5WBO)

Re: KX3 SDR

In reply to this post by Enzo Adrian-Reyes

Hi Enzo,

I'd recommend that you look at some of the Raspberry Pi / Elecraft KX3 panadapters,

http://twitter.com/giorgiofox/status/694969541521207296

https://github.com/Giorgiofox/panadapter

73's

Joe Stone
KF5WBO

James Austin

Re: KX3 SDR

In reply to this post by tomb18

Another free online DSP book, that I stumbled upon this evening is Signal
Processing for Communications. I have not gone much past the table of
contents, but it looks interesting.

http://www.signalprocessingforcommunications.org/
<http://www.signalprocessingforcommunications.org/index.html>

<http://www.signalprocessingforcommunications.org/index.html>Jim KA2RVO

On Wednesday, July 27, 2016, tomb18 <[hidden email]> wrote:

> Hi It's not that simple Basically you take the I and q signals, sample
> them with the sound card, convert them to a complex number, pop them in a
> fast Fourier transform, do a rectangular to polar conversion and then
> calculate the magnitude in dBm. Then plot them. There's a few more nuances
> but that's the overall idea. Check out the free book on the Internet called
> the scientists guide to digital signal processing.73 Tom va2fsq.com
>
>
> Sent from my Samsung Galaxy smartphone.
> -------- Original message --------From: Enzo Adrian-Reyes <
> [hidden email] <javascript:;>> Date: 2016-07-27 7:16 PM
> (GMT-05:00) To: Elecraft List <[hidden email] <javascript:;>>
> Subject: [Elecraft] KX3 SDR
> Hi All
>
> Yes this topic might be a little bit more complicated than the title
> suggest.
>
> So I have the KX3 plugged into the audio input of my computer, and its
> sending quadrature data (IQ) to the sound card, the sound card samples at
> 96Khz.
>
> So my question is how I process this? Yes I know use a piece of software,
> but I am trying to write this, I know the IQ data is coming through down
> and if I use the right process on the IQ data I get base band data out. I
> kind of know that however I dont understand the SDR data coming out, so for
> example and I getting sample of IQ data at freq point Y, or is it a
> circular buffer arrangement.
>
> I guess what I am saying is, is the IQ data coming from teh KX3 data from
> teh Centre Freq (+/-) the bandwith scope, or just the centre freq + some
> additional side bands?
>
> How are bandwith and sampling rate related? I mean if I am sampling at at
> 96Khz, with a band with of 48Khz does that mean I am only getting 2 samples
> per second at perticular freq??? Or am I getting the entire band of 48Khz
> at 96Khz.
>
> Regards
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email] <javascript:;>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email] <javascript:;>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email] <javascript:;>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email] <javascript:;>

Bob N3MNT

Re: KX3 SDR

Also be aware that many PC's ( especially laptops) do not have stereo line -in jacks. There is an excellent program written for the BeagleBone Black that does a Panadapter for the KX3. You can find it here. http://www.arrl.org/files/file/QST/This%20Month%20in%20QST/April%202014/Ewing.pdf

Lyle Johnson

Re: KX3 SDR

In reply to this post by Lyle Johnson

Sorry, I was thinking of the KX2 which always has the IF shift enabled.

In a KX3, the center of the IQ stream is approximately the dial setting.
I say approximately because some modes (AM, FM) or submodes (narrow SSB
using Weaver demodulation) there may be some offset regardless of the
setting of IF shift.

Thank you for your careful reading, Greg!

73,

Lyle KK7P

>> The signals at the IQ jack on the KX3 are analog, not digital. They
>> are centered approximately 8 kHz away from the dial frequency as the
>> KX3 uses an internal offset of 8 kHz. Depending on the firmware
>> release and user settable options, that offset may be on either side
>> of the center of the IQ audio.
> Do you mean always 8 kHz off, or is this only if the IF shift is
> enabled? I would expect a 0 offset without that.
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Phil Wheeler-2

Re: KX3 SDR

In reply to this post by Bob N3MNT

I built that one using a Raspberry Pi a couple of
years ago, pre-PX3. Worked fine for what it is,
but ergonomics are not even close to that of a PX3.

73, Phil W7OX

On 7/28/16 4:58 AM, Bob N3MNT wrote:
> Also be aware that many PC's ( especially laptops) do not have stereo line
> -in jacks. There is an excellent program written for the BeagleBone Black
> that does a Panadapter for the KX3. You can find it here.
> http://www.arrl.org/files/file/QST/This%20Month%20in%20QST/April%202014/Ewing.pdf
>
>
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Bob N3MNT

Re: KX3 SDR

Did not mean to imply that the Raspbery Pi or BBB panadpater was anywhere close to the PX3, but that looking at the code could help with OP's original question. Built mine while waiting for PX3 and yes they are day and night re functionality and ease of use. I love my PX3