K3 AFSK RTTY overdrive - no ALC
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I'm no stranger to soundcard RTTY or to my K3, but today I decided to mix the two and fire up MMTTY on the K3. The first thing I noticed is that there was a very strange ticking sound in the monitor. While it was difficult to hear on frequency on another radio, you could hear clicking off-frequency.
Long story short, I guess it was due to overdriving. If I backed the mic gain WAY down, or the soundcard output way down, the clicking went away. (I'm using FP.L - the same connection as I do for soundcard SSB.) Upon further investigation, I need to set the MIC gain to light up only 2 bars on the ALC meter. Anything less and I'm not getting full output power. Anything more and I'm getting the ticking sound (assumed to be overdrive). I can't get nowhere near 5 bars of ALC, and this setting is very touchy...a fine line between full output power and distortion. I've used this same soundcard and homebrew interface for many, many years, on several different radios. It does include isolation transformers and works fine on SSB. I've also listened to the monitor while in TX TEST mode, and the same problem exists, so it's not an RF issue with the station. It's definitely audio related. I've tried FP.L, RP.L, and LINE, all with the same results. For the LINE, I had to crank up the soundcard to max output and MIC all the way up to 40 (of 60) just to get 2 bars of ALC and nearly full output power. Any further and again I hear the ticking/distortion. I got the the latest SW (well, prior to 11/18 it was the newest), 2.63/1.95. Any ideas out there? I'd like to run this thing with a few more ALC bars and have it so it's not so touchy between having distortion and getting full output power. I've seen emails from others saying they are able to run 5 ALC bars. Not sure why I can't. 73 and thanks, Chad WE9V _______________________________________________ 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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Radio is in DATA operating mode, with DATA MD set to AFSK A.
Not sure what you mean by soundcard setting. I'm using the stereo line out, with isolation transformers on each channel, with left channel going to K3 and right channel going to FT-1000. Audio is fine on FT-1000 TX. Swapping the L/R so that the FT-1000 audio channel is driving the K3 has the same ticking/overdrive issue on the K3, at least until MIC gain is set to only 2 bars. Reducing the soundcard output and then compensating with MIC gain also has the same results. Only 2 ALC bars are allowed, beyond which the ticking sound begins. Chad WE9V On Sun, Nov 23, 2008 at 12:10 PM, Greg <[hidden email]> wrote:
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Re: K3 AFSK RTTY overdrive - no ALC
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In reply to this post by Chad WE9V
On Sun, 23 Nov 2008 11:37:17 -0600, Chad WE9V wrote:
>Any ideas out there? Lots. http://audiosystemsgroup.com/HamInterfacing.pdf 73, Jim K9YC _______________________________________________ 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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Jim,
Thanks. I've seen and read your document previously. Is there something specific you are referring me to in your document that I already haven't covered? Let me recap and add a couple points of clarification: * It's not an RF problem, as it still exists in TX TEST mode. * I do not have a hum/buzz problem. * I've used this setup on microphone inputs of other radios, no problem. (FT-920,990,1000) * I am using audio transformers. "Expensive" solution, but it's worked in the past. * I am using a ~20dB pad between the soundcard output and iso transformer. (5600/560ohm) * Duplicate 20dB pad/iso xfmr are on both channels, other channel driving FT-1000 no problems. Swapping L/R channels has problem follow K3, not cable. * I have 1.25" braid bonding K3>computer>FT-1000. * I can turn the soundcard output down very low (<20%), but I have to turn up the K3 MIC to get any power output. * Using my Heil headset directly into the K3, I use a MIC setting of 15 on SSB to get 5-6 bars ALC with 0 CMP. Using this same MIC=15 setting, I adjust my soundcard output so that both the Volume Control and Wave control are both 50%. At this setting, I have no ALC and <50W output power (with PWR set to 100). I can increase MIC to about 21, where I'll have nearly 100W output, but only 2 bars ALC. If I back of MIC only one step, to 20, I'll be one bar less than 100W, and only one bar ALC. If I increase MIC to 23, I get 3-4 bars ALC and the ticking noise. This seems very sensitive, and a difficult tradeoff between getting 100W output and having the ticking sound (which I'm guessing is some sort of clipping/distortion). Others have mentioned being able to use 5 bars ALC with AFSK RTTY. I can't get anything close to that. I'd like to reduce the MIC/ALC/output power tradeoff sensitivity. I've typically left the MIC gain alone on my rigs, and when running AFSK RTTY, I would adjust the soundcard output to get full ALC reading with no compression. It seems that I can't do that with my K3, only getting 2 bars ALC, and there's a fine line (about 2-3 'clicks" on the MIC gain) between full output power and ticking/distortion. So I ask again, is there some specific idea you'd like me to try that I haven't covered? Chad WE9V On Sun, Nov 23, 2008 at 3:19 PM, Jim Brown <[hidden email]> wrote: On Sun, 23 Nov 2008 11:37:17 -0600, Chad WE9V 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 |
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Just wondering, why not use the line in instead of the microphone input?
vy 73 de toby _______________________________________________ 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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Because I use the same mic input during SSB operation, keeping the configuration the same regardless of what radio is in that position. The K3 is the only radio that has a line in. And, I did try using the line in to troubleshoot this problem. Due to the 20dB attenuator that I'm using, I had to crank up the sound card output to max, and turn the LINE IN gain up to a whopping 40 (60 is max). Even then, the same problem existed. Very low ALC and not 100W power, and turning it up just a hair more to get 3-4 bars ALC resulted in the ticking/distortion.
Chad WE9V On Sun, Nov 23, 2008 at 6:09 PM, Toby Deinhardt <[hidden email]> wrote: Just wondering, why not use the line in instead of the microphone input? _______________________________________________ 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: K3 AFSK RTTY overdrive - no ALC
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In reply to this post by Chad WE9V
Chad, Start by unplugging the RS-232 (CAT connector). It us likely that the ticking is the computer polling the radio. You will find that is due to ground loop ("pin 1") problems. Read K9YC's stuff again very carefully ... connect a jumper from pin 5 of the RS-232 connector to the shell (to bypass a choke in the RS-232 return) and consider putting a jumper across L4 (the rear panel "mic" return) on the KIO3 AF board. You would also be better served to remove the 20 dB pad and connect your soundcard interface to the Line input. The K3 will select inputs independently for data modes. By increasing the audio drive for digital modes (and reducing the gain of the K3 input) you make it much less sensitive to the RS-232 "spike." Remember, RS-232 is a +/- 10V (or more) signal. If even a small amount of that signal flows through the "ground" lead of your mic input (normally < 10 millivolts) you will have a serious "pin 1 problem." 73, ... Joe, W4TV > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Chad WE9V > Sent: Sunday, November 23, 2008 6:08 PM > To: Jim Brown; [hidden email] > Subject: Re: [Elecraft] K3 AFSK RTTY overdrive - no ALC > > > Jim, > > Thanks. I've seen and read your document previously. Is > there something specific you are referring me to in your > document that I already haven't covered? Let me recap and > add a couple points of clarification: > > * It's not an RF problem, as it still exists in TX TEST mode. > * I do not have a hum/buzz problem. > * I've used this setup on microphone inputs of other radios, > no problem. (FT-920,990,1000) > * I am using audio transformers. "Expensive" solution, but > it's worked in the past. > * I am using a ~20dB pad between the soundcard output and iso > transformer. (5600/560ohm) > * Duplicate 20dB pad/iso xfmr are on both channels, other > channel driving FT-1000 no problems. Swapping L/R channels > has problem follow K3, not cable. > * I have 1.25" braid bonding K3>computer>FT-1000. > * I can turn the soundcard output down very low (<20%), but I > have to turn up the K3 MIC to get any power output. > * Using my Heil headset directly into the K3, I use a MIC > setting of 15 on SSB to get 5-6 bars ALC with 0 CMP. Using > this same MIC=15 setting, I adjust my soundcard output so > that both the Volume Control and Wave control are both 50%. > At this setting, I have no ALC and <50W output power (with > PWR set to 100). I can increase MIC to about 21, where I'll > have nearly 100W output, but only 2 bars ALC. If I back of > MIC only one step, to 20, I'll be one bar less than 100W, and > only one bar ALC. If I increase MIC to 23, I get 3-4 bars > ALC and the ticking noise. This seems very sensitive, and a > difficult tradeoff between getting 100W output and having the > ticking sound (which I'm guessing is some sort of > clipping/distortion). > > Others have mentioned being able to use 5 bars ALC with AFSK > RTTY. I can't get anything close to that. I'd like to > reduce the MIC/ALC/output power tradeoff sensitivity. I've > typically left the MIC gain alone on my rigs, and when > running AFSK RTTY, I would adjust the soundcard output to get > full ALC reading with no compression. It seems that I can't > do that with my K3, only getting 2 bars ALC, and there's a > fine line (about 2-3 'clicks" on the MIC gain) between full > output power and ticking/distortion. > > So I ask again, is there some specific idea you'd like me to > try that I haven't covered? > > Chad WE9V > > > > On Sun, Nov 23, 2008 at 3:19 PM, Jim Brown > <[hidden email]> wrote: > > On Sun, 23 Nov 2008 11:37:17 -0600, Chad WE9V wrote: > > >Any ideas out there? > > Lots. > > http://audiosystemsgroup.com/HamInterfacing.pdf > > 73, > > Jim K9YC > > _______________________________________________ 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: K3 AFSK RTTY overdrive - no ALC
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On Sun, 23 Nov 2008 19:54:24 -0500, Joe Subich, W4TV wrote:
>It us likely that >the ticking is the computer polling the radio. You will find that >is due to ground loop ("pin 1") problems. Ah! That's a source I hadn't thought of, but it's a perfect example of a "pin 1 problem" -- you inject noise at a shield contact associated with one circuit and it shows up somewhere entirely unexpected! I've never heard it, since my serial cable is wired with signal returns to the shells on both ends. :) Yes, I agree with all of your advice -- use the line input, run the sound card about 6 dB below it's max output, adjust the line in gain accordingly. Thanks! Chad -- I still don't understand why you want to use the mic input for data. I like to leave my mic plugged into the front panel and the sound card plugged into the rear panel. The only change for data modes is that I'm feeding Line Out back into the sound card so that MMTTY can decode it. An important difference between the MP and the K3 is that the K3 has a 20 dB pad in front of the Line In transformer. As Joe observes, an additional 20 dB pad outside the radio is too much. When I'm doing SO2R on SSB, I plug my mic (an EV RE11) into the computer and let N1MM keep track of where it should go. It works quite well here. 73, Jim K9YC _______________________________________________ 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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Okay, all good suggestions. Thanks Jim and Joe.
I didn't stop at just removing the RS-232 cable. I removed EVERY cable to the K3 other than the single cable for audio in. (I kept the grounding braid and antenna, but still tested using the TX TEST mode, no RF.) Tried the FP mic connector. Same behavior. Shorted out the series resistor on the 20dB attenuator and connected to the LINE IN on the K3. Cranked up the soundcard output, turned the LINE IN gain to around 5. Same problem. Monitor audio sounds fine at 2 bars ALC with no hint of ticking. Increase either the soundcard output or K3 input gain to get 3 bars ALC and ticking begins. Goes from no ticking to ticking with only one "click" of the K3 mic/line in gain. No setting of soundcard output and K3 input gain results in 3 bars more more of ALC without the ticking sound. No hint of ticking at 2 bars ALC. Soundcard is an ol' favorite, a Creative Labs PCI 128 CT4750...been working great for years and scores the 7F on Writelog. Works fine at any output level with any other radio. Continues to work FB with FT-1000D. On Sun, Nov 23, 2008 at 7:13 PM, Jim Brown <[hidden email]> wrote:
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One other thought. Are you using the line out to drive your soundcard?
And if so, is your monitor level turned up on the K3? And if so, is anything in your computer, digital mode software, allowing the incoming sound card audio to be mixed with the outbound audio? Each software package and audio card combo is different. There is the possibility that your setup is looping audio back to the K3. If this is happening, it would be hard to figure out where the feedback frequency is, and that could be tripping the K3 audio limiters. Pull the line out cable on the K3 while you have the problem, and see if it disappears. tom bosscher k8tb _______________________________________________ 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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All cables were removed, other than the LINE IN into the radio, including the line out. Headphones were worn to listen to the monitor audio. (Okay, so I didn't mention the headphones, but they are electrically isolated from everything else.)
Chad WE9V On Sun, Nov 23, 2008 at 9:41 PM, K8TB <[hidden email]> wrote: One other thought. Are you using the line out to drive your soundcard? And if so, is your monitor level turned up on the K3? And if so, is anything in your computer, digital mode software, allowing the incoming sound card audio to be mixed with the outbound audio? Each software package and audio card combo is different. There is the possibility that your setup is looping audio back to the K3. If this is happening, it would be hard to figure out where the feedback frequency is, and that could be tripping the K3 audio limiters. _______________________________________________ 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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