Re: K3 FSK

[Julian, G4ILO]

AF4OX wrote

I am setting up my K3 for FSK.  I use Writelog for contest software.  I use PTT on COM1 and use COM2 to generate FSK, connecting through a NPN transistor interface to the K# FSK IN.  I am able to print fine via the MTTY plug in for Writelog.  However, when I transmit, the carrier from my K3 seems to be varying as indicated by the power output meter and if connected to my amp, the analog meter on the amp also indicates varying output as MARK-SPACE commands pass.  I am in DATA, FSK D.  I suspect that I have something else improperly configured or selected.  I can make contacts, but varying carrier level out is not normal compared to other radios I have used in FSK.  Any suggestions???

This was last discussed a couple of weeks ago. I think the reason for this is that the K3 does FSK by generating audio tones in the DSP. These audio tones must pass through the SSB filter and what you are seeing is the effect of ripple in the filter passband. Other radios, I guess, generate a FSK carrier the same way they do for CW and actually frequency shift it.

You could look back in the archives to see if there was any solution - all I can remember was the suggestion that the 8-pole filter has less ripple.

[KK7P]

> This was last discussed a couple of weeks ago. I think the reason for this
> is that the K3 does FSK by generating audio tones in the DSP. These audio
> tones must pass through the SSB filter and what you are seeing is the effect
> of ripple in the filter passband. Other radios, I guess, generate a FSK
> carrier the same way they do for CW and actually frequency shift it.

The K3 directly generates FSK tones in a phase-coherent manner at the 15 kHz
IF.  The output is then up-converted to 8.215 MHz, passes through the crystal
roofing filter, then converted to the final RF output frequency.  No audio
involved.

The "sidetone" audio for MON use is separately generated.

73,

Lyle KK7P/7 (Tucson AZ)
______________________________________________________________
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

[Julian, G4ILO]

KK7P wrote

The K3 directly generates FSK tones in a phase-coherent manner at the 15 kHz
IF.  The output is then up-converted to 8.215 MHz, passes through the crystal
roofing filter, then converted to the final RF output frequency.  No audio
involved.

Thanks for the clarification, Lyle. Mind you, to some of us, 15kHz *is* audio. :)

[AF4OX]

Thanks for your reply.

 

I did find a post supposing that the effect was related to 5 pole filter ripple, but I did not find any post with evidence that that this was the case or "solutions".  Your reply gave me an idea for some other searches and it seems like I probably do NOT have any wrong parameter settings causing this.

 

73 de Bob AF4OX

----- Original Message -----

From: [hidden email]

To: [hidden email]

Sent: Saturday, October 10, 2009 6:21 PM

Subject: Re: [Elecraft] K3 FSK

AF4OX wrote:

I am setting up my K3 for FSK.  I use Writelog for contest software.  I use PTT on COM1 and use COM2 to generate FSK, connecting through a NPN transistor interface to the K# FSK IN.  I am able to print fine via the MTTY plug in for Writelog.  However, when I transmit, the carrier from my K3 seems to be varying as indicated by the power output meter and if connected to my amp, the analog meter on the amp also indicates varying output as MARK-SPACE commands pass.  I am in DATA, FSK D.  I suspect that I have something else improperly configured or selected.  I can make contacts, but varying carrier level out is not normal compared to other radios I have used in FSK.  Any suggestions???

This was last discussed a couple of weeks ago. I think the reason for this is that the K3 does FSK by generating audio tones in the DSP. These audio tones must pass through the SSB filter and what you are seeing is the effect of ripple in the filter passband. Other radios, I guess, generate a FSK carrier the same way they do for CW and actually frequency shift it.

You could look back in the archives to see if there was any solution - all I can remember was the suggestion that the 8-pole filter has less ripple.

---

View message @ http://n2.nabble.com/K3-FSK-tp3801180p3801365.html
To unsubscribe from K3 FSK, click here.

[KK7P]

> Thanks for the clarification, Lyle. Mind you, to some of us, 15kHz *is*
> audio. :)

It was for me until about age 20 or so.  Now, I'm not certain if 6 kHz is
audio...

73,

Lyle KK7P/7 (Tucson AZ)
______________________________________________________________
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

[hf4me]

Listen to all you can now because later on it will not be the same.  Try
10db down up to 1500 Hz and 50 db down all above 1600 Hz.  Yes, 1500 Hz is
tops. Sometimes it isn't all bad.  My wife's voice is above that (mostly) hi
hi.

73, de Jim KG0KP

----- Original Message -----
From: "lyle johnson" <[hidden email]>
To: "Julian, G4ILO" <[hidden email]>; <[hidden email]>
Sent: Sunday, October 11, 2009 10:38 AM
Subject: Re: [Elecraft] K3 FSK

>> Thanks for the clarification, Lyle. Mind you, to some of us, 15kHz *is*
>> audio. :)
>
> It was for me until about age 20 or so.  Now, I'm not certain if 6 kHz is
> audio...
>
> 73,
>
> Lyle KK7P/7 (Tucson AZ)
> ______________________________________________________________
> 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
>

______________________________________________________________
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