++++++++++++++++++++++++++++++++++ Date: Mon, 25 Jun 2001 12:56:56 -0700 From: "John Clifford" Subject: [Elecraft] K2 & Digital Modes... Greetings Fellow Elecrafters, A quick question on running digital modes with a K2: Why do audio cables ONLY work great with some computers, and not so great with others? For example, on my desktop system if I use two shielded patch cables, one from my K2 headphone jack to my soundboard MIC jack, and one (I made up) from my soundcard SPKR jack to my K2's microphone jack, I can work PSK31, etc., just fine via adjusting the volume on my K2 and on my computer's Volume Control control panel applet. This also works great with the Toshiba L50CT. However, on the Libretto 100CT I cannot successfully operate: when transmitting I get an awful feedback even at extremely low soundcard volumes and the K2 stays 'stuck' in transmit mode until I go and turn the POWER pot down to 0.1 and then back up again. I'm operating in VOX mode (0.4), with compression turned off. I've been hesitant to buy a rig-to-soundcard adapter a la RigBlaster NOMIC, etc., but maybe it's necessary for the problem computer due to some sort of feedback problem (?). Would one of these pretty much guarantee hassle-free digital mode operation? I've read the app notes on PSK31, and why do some people put a 100k resister inline with the computer-to-K2 mike connection? Is this just to drop the soundcard volume so that it is more easily adjustable, and would this most likely fix my problem? Any input would be appreciated. - jgc John Clifford KD7KGX ++++++++++++++++++++++++++++++++++ Date: Mon, 25 Jun 2001 15:37:58 -0500 From: "George, W5YR" Subject: Re: [Elecraft] K2 & Digital Modes... Always make sure your MIC input is muted to prevent its signal from appearing in the speaker output circuit and thence to the transmitter where it could cause feedback. Your Libretto may not be muted while the others are. 72/73, George W5YR - the Yellow Rose of Texas QRP-L 1373 NETXQRP 6 Fairview, TX 30 mi NE of Dallas in Collin county EM13qe Amateur Radio W5YR, in the 55th year and it just keeps getting better! Icom IC-756PRO #02121 Kachina #91900556 IC-765 #02437 ++++++++++++++++++++++++++++++++ Date: Mon, 25 Jun 2001 14:13:38 -0700 From: "Ron D' Eau Claire" Subject: RE: [Elecraft] K2 & Digital Modes... John, KD7KGX, asked: > A quick question on running digital modes with a K2: Why do audio cables > ONLY work great with some computers, and not so great with others? > >...on the Libretto 100CT I cannot successfully operate: when > transmitting I get an awful feedback even at extremely low > soundcard volumes > and the K2 stays 'stuck' in transmit mode . > > I'm operating in VOX mode (0.4), with compression turned off. > > I've read the app notes on PSK31, and why do some people put a > 100k resister > inline with the computer-to-K2 mike connection? Is this just to drop the > soundcard volume Does it have a 'built in' mic? Sometimes they stay active until you go in to the audio setup, select 'record' and mute it. I've not heard of anyone successfully using VOX mode with most digital modes. One problem with doing that seems to be that you have to drive the K2 into ALC action before the VOX will recognize the signal, and to keep the digital signal as clean as possible, they usually set the POWER control to 10 watts, then run the audio input to the K2 to produce a maximum of 5 watts. That avoids overheating the finals (since the digital modes have much higher duty cycles than CW or SSB) and keeps the r-f level below that at which the ALC starts to controls the power output. You are "right on" about the mic input. The output of your computer - even using a 'line' output - is many many times greater than the mic input if the K2 wants to see. Turning down the computer sound level often doesn't work because the sensitive mic input sees the small amount of residual noise in the computer audio output as an overwhelming blast of noise coming in. The resistor serves as an attenuator. I prefer to put a 1k resistor between the mic input and ground to properly terminate the microphone input, then use a series resistance to bring the amount of audio down to 'normal' at the K2 with the computer sound card volume at about mid range. By reducing the input level to the mic connection that way, the signal-to-noise ratio and audio distortion at the computer sound output is going to be just about as good as they can get. The K2 has a resistor to ground in the input circuit so it is not really necessary to have another one to ground at the input, but on some rigs failing to terminate the mic input properly can also cause trouble. You can also buy from Radio Shack and "attenuator cable" specifically designed for this service. They sell them to folks who want to connect the headphone output of a player to the microphone input of a recorder. I haven't bothered with an interface circuit any more exotic than the microphone input attenuator. I do see some slight traces of hum in PSK receive - they show up as very faint vertical lines on the waterfall display - but the transmit is clean. So I haven't bothered to do anything more exotic than that. Ron AC7AC K2 # 1289 ++++++++++++++++++++++++++ Date: Mon, 25 Jun 2001 19:58:51 -0400 From: Charles Greene Subject: Re: [Elecraft] K2 & Digital Modes... At 12:56 PM 6/25/2001 -0700, John Clifford wrote: >Greetings Fellow Elecrafters, > >A quick question on running digital modes with a K2: Why do audio cables >ONLY work great with some computers, and not so great with others? > >For example, on my desktop system if I use two shielded patch cables, one >from my K2 headphone jack to my soundboard MIC jack, and one (I made up) >from my soundcard SPKR jack to my K2's microphone jack, I can work PSK31, >etc., just fine via adjusting the volume on my K2 and on my computer's >Volume Control control panel applet. This also works great with the Toshiba >L50CT. > >However, on the Libretto 100CT I cannot successfully operate: when >transmitting I get an awful feedback even at extremely low soundcard volumes >and the K2 stays 'stuck' in transmit mode until I go and turn the POWER pot >down to 0.1 and then back up again. > >I'm operating in VOX mode (0.4), with compression turned off. > >I've been hesitant to buy a rig-to-soundcard adapter a la RigBlaster NOMIC, >etc., but maybe it's necessary for the problem computer due to some sort of >feedback problem (?). Would one of these pretty much guarantee hassle-free >digital mode operation? > >I've read the app notes on PSK31, and why do some people put a 100k resister >inline with the computer-to-K2 mike connection? Is this just to drop the >soundcard volume so that it is more easily adjustable, and would this most >likely fix my problem? > >Any input would be appreciated. Sounds like your sound cards have different output levels. I use a 50k pot between the sound card and the K2 mike input. I experimented with fixed resistors and found if the K2 mike gain is in low, a 1k resistor works fine. If the K2 mike gain is in high, a 4.7 K resistor gives the same level. I have used a 100K ohm resistor on my Yaesu FT-757GX where the mike gain is very high impedance in comparison to the K2. On my desktop, the AC hum level is much higher than on my Lap Top. With the K2 and using the CAT control for PTT, or using an opti-isolator 4N25 to key CW, I don't need an isolation transformer for the audio to/from the computer. However, on the desktop, I use two isolation transformers, one for audio in and one for audio out to the sound card. Without them the AC hum is over powering. I guess the point is that what works on one computer may not work well on another because of differences in sound cards, AC supplies, grounding systems, and other variables. So do what works for you. It may take a bit of experimenting to find this out. 73, Chas, W1CG +++++++++++++++++++++++++++++++++ From: "Don Wilhelm" To: "David Walker" , Subject: Re: [Elecraft] OPT1 Filter Adjust... Date: Sun, 6 Apr 2003 20:10:09 -0400 Dave, You can do just about anything you want with the BFO settings associated with the OP1 filter - just don't do it in SSB FL1 which is the filter setting that the K2 uses for transmit of SSB. Don't forget that the K2 includes an additional set of 4 filter settings if you activate the RTTY mode. You will find the means to activate it in the secondary menu (assuming you have version 2.x firmware). The other advantage of using the RTTY mode is that compression can be turned off so the transmitted signal is a lot cleaner. 73, Don W3FPR ----- Original Message ----- I want to play with RTTY and AMTOR using the K2. Using MMTTY I see the filter won't allow for audio signals to pass the required tones. I can't adjust the filters to pass the tones either. All the audio is on the low end of waterfall display even using the OPT1 filter. Anyone got any ideas? Is it possible to adjust the opt1 filter without mucking up my BF1 T filter? ++++++++++++++++++