++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Mon, 19 Mar 2001 06:55:06 -0500 From: Charles Greene Subject: Re: [Elecraft] K2 Transmit power question/problem At 09:50 PM 3/18/2001 -0700, Clif Squires wrote: >Ron: I am about to purchase a K2 and would be using it for PSK, SSB and CW in >that order. I was expecting to be able to have 10 watts available for all >modes. What does your statement mean: "and substantially less than 10 watts >when using high duty cycle digital modes to avoid overheating the finals"? > >What is your definition of "substantially less than 10 watts" so that I know >what the K2 will deliver. What would be the max output available on "digital" >PSK mode? >Tnx, >Clif, Elecraft recommends 5 watts PEP on PSK31. I have used my K2 on 6 watts PSK31 for extended periods without any ill effects, but it you go to 7 watts the IMD starts to increase. So 5 to 6 watts is a realistic limit. Actually, I defy anyone to tell the difference between 5 and 6 watts, and you would need an increase of 12 dB or an output of over 50 watts to equal 1 S unit. I have worked all over the country and some DX with 5 watts. On SSB and CW since they have a lower duty cycles 10 to 15 watts depending on the band is a realistic output to expect. On RTTY if you operate audio tones, you theoretically can get more output than on PSK31 as the final amplifier efficiency is greater, but you have to be careful that you do not drive the finals into non-linearity which I found just starts around 7 watts. In comparison, I have an old FT757 which overheats with PSK31 at 20 watts. It is rated at 100 watts SSB. My OMNI-VI overheats at 80 watts in PSK31, so I cut it back to 40 watts. It is rated at 100 watts 100% duty cycle for 30 minutes. My PSK20 operates at 2.5 watts and most operators are surprised at the power when I tell them. There is a good technical reason for the increase is heating which is the fact that the efficiency of the final amplifiers decreases from about 82% on CW to about 62% on PSK31, so more heat is dissipated in the final. 73, Chas, W1CG +++++++++++++++++++++ Date: Thu, 2 Jan 2003 14:00:17 +0000 From: "Julian (G4ILO)" Subject: Re: [Elecraft] Digital modes - need clarification To: "Elecraft List" Most of the seasoned operators of PSK who use 100W transmitters seem to run about 20W these days. It really isn't necessary to run more power than this on this mode, and in view of the reported problems of drift reported by K2/100 owners when the PA warms up I would think that it is particularly important to try to keep things cool. Assuming that you have a post SN 3000 K2 or have done the KI6WX mod to your KSB2 you can use the power control to limit the output power, then adjust the volume from the sound card until one bar of ALC is showing. Always operate close to the centre of the SSB filter passband because filter attenuation will reduce the drive at audio frequencies near the edge of the bandpass. 73, -- Julian, G4ILO. (K2 #392) Homepage: http://www.qsl.net/g4ilo jhaynes at alumni.uark.edu wrote: I read the document PSK31_2.PDF but I'm still unclear on setting transmit levels. I assume you set the K2/100 power level to 50 watts or less so as not to overheat on transmissions. Then how do you tell when you have the input level turned up enough? And what should the K2 mic gain be set at? ++++++++++++++++++++ Date: Fri, 3 Jan 2003 09:57:16 +0000 From: "Julian (G4ILO)" Subject: Re: [Elecraft] Digital modes - need clarification To: "Sandy W5TVW" , "Phil Wheeler" Cc: "Elecraft List" It doesn't help that many people work somebody with a poor signal and make no comment on it at all. I recently waited while 2 or 3 folk worked an Italian guy who was running an FT something or other and was claiming to be running 100 watts. He was about 1KHz wide! They all gave him 599 reports. When he eventually came back to me, I told him his signal was wide, he reduced power to 25 watts and was just as readable but clean as a whistle. You may be right that it is mainly the newbies who think they need more power. On the whole, I feel that I'm working more people now who are using only 20 or 25 watts, even a few using as little as 10 watts, when running a 100W transceiver. A couple of years ago everyone seemed to be running 40 or 50. I think that those who have used PSK for some time have come to realise that all that happens if you consistently use that much power is that you get a very warm transceiver that probably drifts noticeably during an over. 73, -- Julian, G4ILO. (K2 #392) Homepage: http://www.qsl.net/g4ilo ==== Original message ==== Sandy W5TVW wrote: [snip] > The second thing is "newbies" running overloaded rigs/sound cards > causing wide and/or > dirty signals with many "sidebands" or numerous "spurs". Takes away all > the > advantages of the narrow mode. In properly operated 25 watters, one > cane see a dozen > stations on in a 1.5-2 khz slice of bandspace! Amazing mode only IF > operated > properly. Lots of fun ++++++++++++++++++ Date: Sun, 19 Jan 2003 17:55:43 +0000 From: "Julian (G4ILO)" Subject: Re: [Elecraft] K2 & PSK-31 To: "Elecraft List" Rod, I take it you don't have the KIO2 installed, nor the updated firmware? Otherwise I'd enable the RTTY mode, which allows you to set up separate narrow filters optimised for data, and also disables the compressor. If you are forced to use USB or LSB, then you want to disable compression (SSBC). The SSBA setting can stay the same is it usually is: the trick is to make the attenuator in the cable from the computer to the mic socket so that it generates about the same level of audio as your microphone, then you can fine tune the audio level using the computer mixer settings. If the power is quickly jumping from 0 to 5 watts as you advance the slider from zero then I guess either you don't have an attenuator at all, or its effect is too small, or possibly RF is getting in to the microphone socket. I can't remember the value resistors I used in my attenuator, unfortunately, but I guess they won't be far different from the values recommended by G3PLX in the help file to his original PSK program, which is 100K in series with the audio and 1K down to ground. Unfortunately, I don't think it is possible to use VOX to control the TX/RX switching in the K2. In my experience, the K2 VOX is too insensitive, with the result that you have to set the audio input too high for a clean signal in order for the VOX to trigger. (BTW, I'd really love to see a KSB2 MkII with greater input sensitivity and a more sensitive VOX.) There's really no excuse for not using DTR or RTS to control the PTT, as the circuit only involves one resistor, one general purpose diode and one general purpose NPN transistor and can easily be built to fit inside the D-shell on the PC serial port. If you have done the KI6WX modification to the KSB2 then one ALC bar is acceptable for a clean signal. Prior to that, I used to set the K2 power control to 10 watts and then control output power entirely using the computer mixer settings, so that there was no ALC action at all. I measured an IMD of -34dB in that configuration, with an output power of 4 watts. 73, -- Julian, G4ILO. (RSGB, ARRL, G-QRP, K2 #392) G4ILO's Shack: http://www.qsl.net/g4ilo Rod N0RC wrote: Folks, I read the PSK app note: http://www.elecraft.com/Apps/PSK31_2.PDF but still have questions about setting the TX audio level. I'm using a cable as described in the appnote, and I am using VOX (0.4 setting) for TX/RX mode switching; software is Digipan; Pout is set for 5W; SSB A = 2; SSB C = 2:1. With the K2 in RF out mode: As I advance the soundcard volume the power quickly jumps from 0 to 5 watts, I believe this behavior is a result of the tracking ALC of the K2. With the K2 in ALC mode: As I advance the soundcard volume I can adjust for 1 ALC bar or 2 ALC bars. I can even set the audio so that the second bar is flickering somewhat. Is there a more refined way to set the K2 for good PSK performance? Based on reports received from others, I believe this config to be optimal: Pout <= 5W SSB A = 2 SSB C = 2:1 Audio-in level set so that the second ALC bar flickers Is there something I've not accounted for? 73, Rod N0RC Elecraft CC: 0 of 100, started 05-Jan-2003 ++++++++++++++++++ Date: Sun, 19 Jan 2003 16:35:26 -0500 Subject: Re: [Elecraft] K2 & PSK-31 From: Dave Gingrich K9DC To: Elecraft at mailman.qth.net On Sunday, Jan 19, 2003, at 13:42 America/Indianapolis, Rod N0RC wrote: > > Why? It seems to work just fine. Like I said I'm getting good on > air results. KSB2 manual says 2:1 compression is OK to use. The KSB2 Manual was written before the dedicated RTTY settings were available in the firmware. Leaving the compression at 2 is a compromise for those that want to run voice with some compression, but also use PSK. Remember, PSK is *simulated* by running a steady state, very clean audio signal into a SSB transmitter. Anything that detracts from the purity, i.e. adds distortion is a bad thing. Included in that is compression and ALC. Having ALC bars show up is a worst case scenario for PSK. If you can get the appropriate power out with no ALC bars, your signal will be cleaner (and more likely to stay legal) > So it stand to reason that if 1-3 bars is good for voice, it > should work just fine for PSK-31. Not true. Voice is a signal that varies widely in amplitude. Compression helps to narrow the spread between the peaks. With PSK you start out with a steady state signal that should not vary at all in amplitude, therefore if you are into compression, including ALC, all it can do is add distortion. If you limit the ALC to 1-2 bars, then things will still be reasonably narrow. But in this case, less is better. +++++++++++++++ From: "Rod N0RC" To: "Dave Gingrich K9DC" , Subject: Re: [Elecraft] K2 & PSK-31 Date: Sun, 19 Jan 2003 15:08:13 -0700 Dave, Good stuff [technically] makes a lot of sense I'll give the RTTY settings and compression-off a good trial. Thanks. 73, Rod N0RC Elecraft CC: 0 of 100, started 05-Jan-2003 +++++++++++++++++ Date: Sun, 19 Jan 2003 23:08:21 +0000 From: "Julian (G4ILO)" Subject: Re: [Elecraft] K2 & PSK-31 To: "Rod N0RC" , "Elecraft List" Rod, > I do not have the KIO2, I do have the updated FW. I want to use > narrow filters. I like the wide waterfall of digipan. I'm assuming you meant to say you DON'T want to use narrow filters. That's your prerogative, of course. However I'm personally of the view that Digipan is a flawed approach to PSK that may be appropriate when using dedicated radios such as the PSK20 which have (I assume) a broad filter covering the whole of the band where PSK signals are to be found, and also (I assume) no AGC. Trying to work PSK using the standard SSB filter on the K2 is fine if the band is quiet, but when there is a lot of activity (and there is ALWAYS a lot of PSK activity these days) strong signals will activate the AGC reducing the percentage copy from the wanted station unless it is a strong one. I don't think it is possible to disable the AGC in the K2, only change it from FAST to SLOW. Because of this, it is really valuable to be able to use a narrow filter when working PSK. Many a time I have lost a signal completely when a strong station came on nearby, until I switched in the narrow filter. I'm also convinced Digipan is responsible for some of the weird signals I see, where one side of the PSK signal is much stronger than the other. I guess that this occurs because people are working on an audio frequency that's on the steep part of the SSB filter passband. If you use narrow filters, you get accustomed to tuning the wanted station to a frequency in the center of the passband, so that's never a problem. > Why? It seems to work just fine. Like I said I'm getting good on > air results. KSB2 manual says 2:1 compression is OK to use. Compression is never going to do any good to the IMD of a PSK signal. Perhaps the K2 manuals have changed since 1999, but I don't think there is any reference to recommended settings for PSK operation in *my* manual at all. I don't think you can rely on on-air reports as a measure of signal quality. Only a couple of days I worked a guy who was so overmodulated that even his CW ID had multiple IMD products. I pointed this out, but he took no notice. A few minutes later I noticed him asking his next contact what his signal was like and the reply was "excellent signal, no problem." It's so frustrating... > I'm using the cable as described in the Digipan Help files. It > works fine. The cable plus the sound card control enable me to > set the audio just fine. The issue is setting it with a tracking > ALC, In my 746, using the exact same cable, I can vary power > output evenly from 0 to Max_Pout_setting. From the KSB2 manual: > > "Tracking ALC: SSB transceivers use Automatic Level Control (ALC) > to reduce transmit drive if output exceeds a desired level. Many > transceivers require that you adjust the mic gain manually until > the ALC indication is in a certain range. The K2's ALC is > different: the drive level is automatically adjusted, over time, > to keep ALC close to the optimal level. This tracking ALC (TALC) > eliminates the need to adjust mic gain in most cases. You can > set the POWER control, mic gain, or speech compression to any > level, and the ALC level will average between 1 and 3 bars (in > ALC meter mode) as you talk." > > So it stand to reason that if 1-3 bars is good for voice, it > should work just fine for PSK-31. I don't think that is true, because any extra distortion added to a PSK signal by ALC action is much more evident than it would be on an SSB transmission. I think you need to read KI6WX's explanation of his modification to the KSB which changes the ALC time constant. With that modification in place, some ALC action won't noticeably worsen the IMD on a PSK31 signal. Without it, your signal is wider than it need be. PSK31 is a narrowband mode whose potential is being wasted because of the number of overmodulated signals that interfere with reception on several hundred Hz either side of the frequency. It's in everyone's interest to take the steps to ensure our signals are as narrow as they can be, even if it means paying more attention to the audio drive levels instead of just letting the transceiver take care of it. By the way, with my cable I CAN adjust the power output smoothly using just the mixer level control, if I so wish, so if your cable isn't delivering too much audio to the mic input I can't think of any other reason why you should find the power increase so sudden. Unless (DING! Light bulb goes on) the reason is that TX only happens once there's enough audio for the VOX to kick in, of course... > [VOX] Works fine at the 0.4 setting, That seems to be on the assumption that up to three bars of ALC is acceptable. I didn't consider that to be acceptable, and on my K2 I could not get the VOX to trigger with the amount of audio necessary to just reach 5W output *without* any ALC action (this was before KI6WX came up with his mod, so I didn't consider *any* ALC to be conducive to a clean signal.) > Many new laptops don't have a serial interface, mine is one of them. I > use VOX on my Icom 746pro, I also used a homebrew VOX circuit on a > PSK-20. Now with the K2, never a problem, works great. The other reason for not using VOX is the ease with which it is possible to broadcast Windows sound effects and other audio when people forget they have their radios connected to the computer. Many people are using USB - serial converters. However, I take your point. I guess it *may* be acceptable on the newer K2s or those with the KI6WX mod to use VOX and drive the rig to one or two bars of ALC without unacceptable widening, but personally I'd like to get the OK from Wayne and Eric, and see some figures on the effect of the K2's ALC on the IMD of a PSK signal, before trying it. On most transceivers, driving them into ALC is responsible for the many lousy signals we see, which is why I'm so strongly against it. 73, -- Julian, G4ILO ++++++++++++++++ Date: Sun, 19 Jan 2003 18:19:50 -0500 Subject: Re: [Elecraft] K2 & PSK-31 Cc: "Elecraft List" To: "Julian (G4ILO)" From: Dave Gingrich K9DC On Sunday, Jan 19, 2003, at 18:08 America/Indianapolis, Julian (G4ILO) wrote: > I don't think it is possible to disable the AGC in the K2, only change > it from FAST to SLOW. Press the AGC and PRE/ATT buttons together to turn off AGC. =========================== +++++++++++++++++ From: "Rod N0RC" To: Subject: Re: [Elecraft] K2 & PSK-31 Date: Sun, 19 Jan 2003 17:26:27 -0700 Thanks all for the thoughtful replies and analysis. Man I've got a lot to learn about these "modulation modes" and the equipment...etc. You see what happens when a died-in-the-wool CW OP steps out of his "comfort" zone. :-) But life is no fun unless you're learning and moving from one adventure to the next. So, now it's off to config the RTTY filters and make another attempt at getting things "good". I don't want my call associated with a crummy looking signal 73, Rod N0RC Elecraft CC: 0 of 100, started 05-Jan-2003 ++++++++++++++++++ Date: Mon, 20 Jan 2003 09:34:48 +0000 From: "Julian (G4ILO)" Subject: Re: [Elecraft] K2 & PSK-31 To: Hank Kohl K8DD , "Elecraft List" Thanks Hank, and everyone else who pointed out how turn the K2's AGC off. I wish this function was on the AGC button. Is there a knack to doing this? I did see the word OFF appear once on the display, but mostly I just toggled the preamp, attenuator and AGC time-constant! 73, -- Julian, G4ILO. (RSGB, ARRL, G-QRP, K2 #392) G4ILO's Shack: http://www.qsl.net/g4ilo ==== Original message ==== To disable, or turn off, the AGC simultaneously press AGC and > PRE/ATT +++++++++++++++ From: "Rod N0RC" To: "Julian (G4ILO)" , "Elecraft List" Subject: Re: [Elecraft] K2 & PSK-31 Date: Sun, 19 Jan 2003 11:42:15 -0700 > Rod, > I take it you don't have the KIO2 installed, nor the updated > firmware? Otherwise I'd enable the RTTY mode, which allows you > to set up separate narrow filters optimised for data, and also > disables the compressor. I do not have the KIO2, I do have the updated FW. I want to use narrow filters. I like the wide waterfall of digipan. > If you are forced to use USB or LSB, then you want to disable > compression Why? It seems to work just fine. Like I said I'm getting good on air results. KSB2 manual says 2:1 compression is OK to use. > (SSBC). The SSBA setting can stay the same is it usually is: > the trick is to make the attenuator in the cable from the > computer to the mic socket so that it generates about the same > level of audio as your microphone, then I'm using the cable as described in the Digipan Help files. It works fine. The cable plus the sound card control enable me to set the audio just fine. The issue is setting it with a tracking ALC, In my 746, using the exact same cable, I can vary power output evenly from 0 to Max_Pout_setting. From the KSB2 manual: "Tracking ALC: SSB transceivers use Automatic Level Control (ALC) to reduce transmit drive if output exceeds a desired level. Many transceivers require that you adjust the mic gain manually until the ALC indication is in a certain range. The K2's ALC is different: the drive level is automatically adjusted, over time, to keep ALC close to the optimal level. This tracking ALC (TALC) eliminates the need to adjust mic gain in most cases. You can set the POWER control, mic gain, or speech compression to any level, and the ALC level will average between 1 and 3 bars (in ALC meter mode) as you talk." So it stand to reason that if 1-3 bars is good for voice, it should work just fine for PSK-31. > Unfortunately, I don't think it is possible to use VOX to > control the TX/RX switching in the K2. In my experience, the > K2 VOX is too insensitive, with Works fine at the 0.4 setting, > There's really no excuse for not using DTR or RTS to control > the PTT, as the circuit only involves one resistor, one > general purpose diode and one general purpose Many new laptops don't have a serial interface, mine is one of them. I use VOX on my Icom 746pro, I also used a homebrew VOX circuit on a PSK-20. Now with the K2, never a problem, works great. 73, Rod N0RC Elecraft CC: 0 of 100, started 05-Jan-2003 ++++++++++++++++++