Obscure RTTY bug?
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Preparing for the ARRL RTTY Round-Up this weekend, I ran into a strange problem. Using "AFSK A" mode, feeding transmit audio into the K3's line in from the computer running MMTTY (also tried with DM780, with the same result), I would get a crackling noise along with the RTTY tones in the K3's monitor audio. I don't know if the crackling is transmitted, or just in the monitor. Levels are set for 5 bars on the ALC meter, and the problem occurs in "TX TEXT" mode. After lots of tearing my hair out (well, at least tearing my cables out and trying other ones), I observed two things that make it go away: 1) Changing to USB ("REV DATA") 2) Turning *off* "TEXT DEC" I recorded the probleml, from line-out, with text decode on and off: http://www.dseven.org/k3/ Why the text decode would cause crackle in the monitor audio, and why not in "REV" mode, I'm not sure... but I would like to be able to have the decoder turned on... ~Iain / N6ML _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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I am experiencing the same issue and have been for a while. It occurs for me without being in the text mode. Lyle says he is aware of it and is working on a solution. I think it has gotten worse in recent releases. I tried this morning turning the drive down to two or less bars, which used to fixed it, but now I can't get rid of it if there is any drive at all. 73 Doug N3QW ----- Original Message ----- From: "Iain MacDonnell - N6ML" <[hidden email]> To: "Elecraft" <[hidden email]> Sent: Wednesday, December 31, 2008 5:39:34 PM GMT -05:00 US/Canada Eastern Subject: [Elecraft] Obscure RTTY bug? Preparing for the ARRL RTTY Round-Up this weekend, I ran into a strange problem. Using "AFSK A" mode, feeding transmit audio into the K3's line in from the computer running MMTTY (also tried with DM780, with the same result), I would get a crackling noise along with the RTTY tones in the K3's monitor audio. I don't know if the crackling is transmitted, or just in the monitor. Levels are set for 5 bars on the ALC meter, and the problem occurs in "TX TEXT" mode. After lots of tearing my hair out (well, at least tearing my cables out and trying other ones), I observed two things that make it go away: 1) Changing to USB ("REV DATA") 2) Turning *off* "TEXT DEC" I recorded the probleml, from line-out, with text decode on and off: http://www.dseven.org/k3/ Why the text decode would cause crackle in the monitor audio, and why not in "REV" mode, I'm not sure... but I would like to be able to have the decoder turned on... ~Iain / N6ML _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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On Dec 31, 2008, at 2:54 PM, [hidden email] wrote: > I am experiencing the same issue and have been for a while. It > occurs for me without being in the text mode. Lyle says he is aware > of it and is working on a solution. I think it has gotten worse in > recent releases. I tried this morning turning the drive down to two > or less bars, which used to fixed it, but now I can't get rid of it > if there is any drive at all. I have just sent Iain a couple of screenshots of the waveform from his "crackle" recording and they definitely show up as envelope glitches. 73 Chen, W7AY _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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The odd thing is that the glitches in Iain's recording appear to occur
a cycle or two before a frequency shift. It almost appears to be due to an improperly windowed FIR filter, but it could be caused by anything else... If you have an audio editing program, you can see the envelope glitches quite clearly in Iain's wav file. There is one at 2.9235 seconds into the recording, and another at 3.253 seconds into the recording, for example. You can see the frequency shift about 2 or 3 msec following those glitches. 73 Chen, W7AY _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Iain MacDonnell - N6ML-2
Hi Iain:
I was curious to see where this thread was going. I too noticed crackling monitor audio on AFSK A mode. But in my case it was present when the dual passband filter was engaged and disappeared when I was listening with the normal filter. I'm not bothered by the crackling I just hope it is not going out in the transmitted signal. 73, Mike K2MK [Elecraft] Obscure RTTY bug? Iain MacDonnell - N6ML Wed, 31 Dec 2008 14:40:25 -0800 Preparing for the ARRL RTTY Round-Up this weekend, I ran into a strange problem. Using "AFSK A" mode, feeding transmit audio into the K3's line in from the computer running MMTTY (also tried with DM780, with the same result), I would get a crackling noise along with the RTTY tones in the K3's monitor audio. I don't know if the crackling is transmitted, or just in the monitor. Levels are set for 5 bars on the ALC meter, and the problem occurs in "TX TEXT" mode. After lots of tearing my hair out (well, at least tearing my cables out and trying other ones), I observed two things that make it go away: 1) Changing to USB ("REV DATA") 2) Turning *off* "TEXT DEC" I recorded the probleml, from line-out, with text decode on and off: http://www.dseven.org/k3/ Why the text decode would cause crackle in the monitor audio, and why not in "REV" mode, I'm not sure... but I would like to be able to have the decoder turned on... ~Iain / N6ML _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Iain MacDonnell - N6ML-2
This sounds exactly like the problem I report to the reflector on 11/23 titled "K3 AFSK RTTY overdrive - no ALC". Everyone on the reflector poo-poo'd it as it being a problem on my end. I'm glad to see others come out of the woodwork with the same problem. I haven't tried RTTY since upgrading to the latest firmware to see if it's gotten worse, but the "ticking" sound would go away when I only used about 2 bars of ALC, but then it was difficult to get the full 100W output. Mine, too, was present in TX TEST mode, so I knew it wasn't a RF issue.
In listening to the signal on another receiver the ticking/crackling seems to make the TX signal wider, but that's only by ear....I don't have a scope. Chad WE9V
On Wed, Dec 31, 2008 at 4:39 PM, Iain MacDonnell - N6ML <[hidden email]> wrote:
_______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Obscure RTTY bug?
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In reply to this post by Kok Chen
Kok Chen wrote: > The odd thing is that the glitches in Iain's recording appear to occur a > cycle or two before a frequency shift. It almost appears to be due to > an improperly windowed FIR filter, but it could be caused by anything > else... It does seem like something like that, but what I can't get past is the fact that turning off the text decoder makes the problem go away (for me, at least). BTW, occasionally I can start transmitting with the text decoder on, and the problem will not occur, and doesn't seem to start during a transmission, but if I stop and restart, the problem comes back right away. I've also reproduced it at different mark ("PITCH") frequencies. I wonder if it could be some sort of resource contention between the decoder and the DSP.... or something? ~Iain / N6ML _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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