++++++++++++++++ From: "Don Wilhelm" To: "David Steere" , Subject: Re: [Elecraft] K1 carrier rise/fall times unequal? Date: Mon, 21 Apr 2003 12:58:32 -0400 David, I don't have a K1 that I can measure, but I would not be overly concerned about the explicit fall time. The keying waveshape is not really a true square wave, so to me the most important factor is the presence of any overshoot tendencies which are an indication of keyclicks (I assume you see none on the keying waveshape). I do know that the keying in the Elecraft rigs has been described as "chrisp" and "nice to listen to", so perhaps the short damped fall time is the mechanism that produces this chrispness. As far as bandwidth of the signal goes - the waveshape alone does not tell the whole story because the keying speed is also a primary factor - a 10 wpm CW signal is more narrow than a 30 wpm CW signal and so on. I also trust that when you plan to operate to within the last kHz of your allocated band you would have more accurate measurement capability than the readout on your transceiver dial (I personally would not trust ANY transceiver to provide that accuracy without frequent reference to a known standard, and I do not intend any disparity toward an Elecraft product or any other product by making that statement). 73, Don W3FPR ----- Original Message ----- > > While researching the basic accuracy of my new K1's accuracy display, I > discovered with an oscilloscope that my unit transmits with about a 5 ms > carrier rise time, but with a carrier fall time of only about 1 ms. Having > learned that the bandwidth of the transmitted signal is a function of the > keyed carrier's rise and fall times, I'm wondering now whether a 1 ms fall > time is normal. According to Figure 12.21 of the ARRL Handbook (2003) in > the chapter on modulation sources, a 5 ms rise time signal will have a 150 > Hz bandwith, but a 1 ms fall time corresponds to a rather large 700 Hz > bandwith. This signal bandwidth, plus the basic accuracy of the K1's > displayed frequency, affect just how close to a band's edges I would want to > set my frequency when transmitting. > +++++++++++++++ Date: Mon, 21 Apr 2003 11:28:37 -0700 From: Vic Rosenthal Organization: Transparent Software To: Don Wilhelm Cc: David Steere , elecraft at mailman.qth.net Subject: Re: [Elecraft] K1 carrier rise/fall times unequal? Don Wilhelm wrote: > As far as bandwidth of the signal goes - the waveshape alone does not tell > the whole story because the keying speed is also a primary factor - a 10 wpm > CW signal is more narrow than a 30 wpm CW signal and so on. Actually, this is incorrect. It is true that the faster you send, the harder the keying needs to be (otherwise the elements start to run into each other), so faster CW requires harder keying, which makes the signal wider. But speeding up or slowing down does not change the actual bandwidth that the signal takes. The bandwidth is dependent on the rise and fall times of the elements. To the original poster: Having said that, I suspect that it's a little more complicated. You can have different shaped leading and trailing edges with the same overall rise/fall time, so just looking at a scope is not sufficient to determine whether your signal is clean. I suggest using a second receiver with a sharp IF filter. Adjust it so the signal from your K1 is S9 and carefully tune across the signal. If you hear clicks for more than about 500 Hz above or below the signal itself, then perhaps it is too wide. Note that you cannot determine if a signal is too hard by listening ON the frequency of the signal, because the receiver's filter will soften what you hear. What you are listening for is clicks on make and break when you do NOT hear the tone of the signal. By the way, if you do have excessive clicks, you may be interfering with other band users even if you are well within the band, so if there's a problem you have to fix it! 73 Vic K2VCO +++++++++++++++++ From: "George, W5YR" To: "Vic Rosenthal" , "Don Wilhelm" Cc: "David Steere" , Subject: Re: [Elecraft] K1 carrier rise/fall times unequal? Date: Mon, 21 Apr 2003 13:59:12 -0500 Organization: W5YR Vic is entirely correct on this one, guys. I know that there are all sorts of formulas for bandwidth that seem to involve code speed only, but they make a lot of assumptions and do not really give correct answers most of the time. In addition to the rise and fall time aspects of keyed bandwidth, there is another more subtle cause involved. That is the manner of the transition from carrier off to the leading edge; from leading edge to full amplitude; from full amplitude to trailing edge; and finally from trailing edge to full off. Those four transitions can be anything from very abrupt to very gentle. It has been found that waveforms with abrupt transitions have wider bandwidths than the rise and fall times would predict, even at a fixed speed. I know from measuring the waveforms on my IC-765, two PROs and the K2 that there is a wide variation in how these four transitions are accomplished. Each radio does the four transitions differently. My K2 has fairly short rise and fall times - about 3 msec for the rise time and about 1.5 msec for the fall time. But the off-to-risetime is abrupt while the risetime-to-on is very smooth and gentle. Similarly the on-to-falltime is very abrupt while the falltime-to-off is less so. So, the keying is pretty hard on my K2, but careful receiver monitoring does not reveal that excessive bandwidth is involved with clicks. My PRO2 has adjustable rise and fall times from 2 to 8 msec. Two msec is very hard and clicky while 8 is rather soft and narrow. I use either 4 or 6 and like the sound. I mentioned this to Wayne and sent him a photo of the K2 envelope of a dot and he agreed that it was pretty sharp. I think that the final arbiter is performance. If the keying is not offensive to your band neighbors and sounds good to you and is easily read when the going gets tough, then it is doing its job. But first principles tell us that the time-domain characteristics of each keyed element determine its spectrum, not the repetition rate of a string of elements, as Vic reminds us 73/72, George Amateur Radio W5YR - the Yellow Rose of Texas Fairview, TX 30 mi NE of Dallas in Collin county EM13QE "In the 57th year and it just keeps getting better!" +++++++++++++ From: "Guy Olinger, K2AV" To: "George, W5YR" , "Vic Rosenthal" , "Don Wilhelm" Cc: "David Steere" , Subject: Re: [Elecraft] K1 carrier rise/fall times unequal? Date: Mon, 21 Apr 2003 16:44:06 -0400 Think possibly that the CW contest scenario defines the needed bandwidth. Short version: K2 keying needs to be shaped well enough that an MP, tuned up or down 500 hz with matched INRAD 400's in the 2nd and 3rd IF, does not hear any clicks. K2 has significant clicks with this test. Long version: At this date, CW stations calling CQ in a contest will align themselves about every 500 hz up and down the band. This means every calling station will be listening their frequency plus/minus 200 hz or plus/minus 150 hz. Stations farther away calling are mostly likely to be someone calling the station up or down from you. Hearing the station up or down 200 hz calling you just as well as you hear dead on is required. Easily half the calling stations are not dead on frequency. The CQing stations are frequently running max power and 20 or 30 over S9. At the same time the station up or down 500 hz is 20/30 over, the station calling on frequency may not even kick the s-meter lights or even be substantially in the noise. Even S1 key clicks from the station up or down can cover such a weak station calling on frequency. The weak station scenario happens a lot (one growing reason is DX stations running K2's with limited antennas, e.g. loaded whip on a balcony!). Them who cannot work the QRP guys with limited antennas are not going to work as many QSO's. The serious contester MUST work the QRP layer. An example of the best filter arrangement for this separation is an MP with matched 400hz INRAD filters in second and third IF's. Listening to my K2 (1239) at S9 in the MP using aforementioned filters, with the MP tuned up or down 500 hz from the K2's frequency, the clicks are S1 or S2. If I tune up or down 1000 hz, the clicks are almost gone. If the test setup is set for the K2 to be 30 over, the clicks at plus/minus 500 are very loud. Doing the same test with the transmitter an MP modified to reduce clicks, the clicks cannot be heard tuned up or down 500 hz. The transitions ARE too sharp. This is also shown in a spectrum analyzer plot on the INRAD web site that shows a NUMBER of rigs, including the K2. Those of us who want to operate a contest with the K2 high power with a 1.5 KW amplifier behind, to get the benefits of the receiver, will need to soften the CW keying transitions, the same way our MP's need their transitions softened. Any clue as to what to modify? I had been looking at the schematic but haven't figured it out yet. 73, Guy. ++++++++++++++ Date: Mon, 21 Apr 2003 14:28:27 -0700 From: Vic Rosenthal Organization: Transparent Software To: "Guy Olinger, K2AV" Cc: "George, W5YR" , Don Wilhelm , David Steere , elecraft at mailman.qth.net Subject: Re: [Elecraft] K1 carrier rise/fall times unequal? Guy Olinger, K2AV wrote: > Those of us who want to operate a contest with the K2 high power with a 1.5 KW amplifier behind, to get the benefits of the receiver, will need to soften the CW keying transitions, the same way our MP's need their transitions softened. I personally would prefer slghtly softer keying on my K2. Say 4-5 ms rise/fall instead of the current 2-3. Let me add, though, that it is MUCH better than an unmodified MP and many other rigs. I often hear stations clicking 3 KHz off frequency. I suspect this is handled in firmware and Wayne would have to give up valuable memory resources to make it adjustable! Vic K2VCO +++++++++++++++ To: vic at rakefet.com, w3fpr at peoplepc.com, elecraft at mailman.qth.net, dls_1946 at hotmail.com Date: Mon, 21 Apr 2003 14:41:58 -0700 Subject: Re: [Elecraft] K1 carrier rise/fall times unequal? From: k6se at juno.com Don, W3FPR wrote: "As far as bandwidth of the signal goes - the waveshape alone does not tell the whole story because the keying speed is also a primary factor - a 10 wpm CW signal is more narrow than a 30 wpm CW signal and so on." ---------- Keying speed would be a primary factor only if the CW signal is click-free. The ARRL defines the bandwidth of a clean CW signal as approximately BW (in Hz) = WPM times 2. I.e., a 10 wpm signal has a BW ~20 Hz and a 30 wpm signal has a BW ~60 Hz. ========== Vic, K2VCO wrote: "I suggest using a second receiver with a sharp IF filter. Adjust it so the signal from your K1 is S9 and carefully tune across the signal. If you hear clicks for more than about 500 Hz above or below the signal itself, then perhaps it is too wide." ---------- I agree with Vic. If you hear clicks outside of the passband of the receiver's narrow filter, then the offending transmitter needs improvement. Many modern rigs have clicks as much as +/- 2.5 kHz from the transmitted frequency. The clicks are not necessarily caused by overshoot of the keying waveform but rather because of the risetime and/or falltime being too short. 73, de Earl, K6SE +++++++++++++++ Reply-To: From: "Sverre Holm - LA3ZA" To: "'Guy Olinger, K2AV'" Cc: Subject: RE: [Elecraft] K2 carrier rise/fall times unequal? Date: Tue, 22 Apr 2003 20:54:52 +0200 Some of the CW waveform control must be in hardware as the K2 manual says: "U10A and associated circuitry are used to accurately control power output as well as provide CW waveform shaping". Looking at that circuitry, there is an RC time constant for rising amplitudes (R21, C31) of 0.47ms, and one for falling slopes (RP2, C31) of 3.9ms. Could these be the ones that determine CW waveform? All others (C34, RP3) and (R98, C168) are in the 2-5 us range and should be negligible. 73, Sverre ------------------ Sverre Holm, LA3ZA www.qsl.net/la3za ++++++++++++++++++ Date: Thu, 01 May 2003 22:00:02 -0700 From: Eric Swartz WA6HHQ - Elecraft Organization: Elecraft To: k6se at juno.com Cc: w5yr at att.net, elecraft at mailman.qth.net Subject: Re: [Elecraft] Re: K2 vs OMNI V keying waveform? Hi guys, Over the past three years, prior to when the recent spate of MP key click discussions and mods hit the ham community, we have never received a report from our customers of key click complaints. This with many running high power to large antennas. The K2 is in the same category (or better) for keying spectrum width as almost every other commercial ham rig out on the market today (756 PRO, Omni 6, 6+, TS850, TS2000, TS570s etc. (with unmodified MPs slightly worse..). Also note that comparative test result differences of 3 to 5 dB (less than an S unit) are essentially the equal since you can see that much variance when repeating tests on different days and on different serial numbers of the same rig. In my many times running the K2/100 into my 87a at 1.5KW I have -never- received a complaint of key clicks. And I've had people actually check each side of me to confirm all was OK. When I worked Earl, K6SE, when he was using his K2/100 in eQP he was +30 or more on my K2, by far the loudest signal on the band, yet I didn't notice him until I tuned very close to his frequency.. We also did extensive testing for key clicks and for on frequency keying when we designed the K2, hence its excellent reputation when running CW. We made sure it was equal to or better than anything on the market at the time. Please also remember that the limited receive dynamic range and poor phase noise of most commercial ham rigs will make another strong transmitter (especially on in the same shack), regardless of how clean it is on CW, appear to be much wider than it actually is, due to receive overload and its internal RX phase noise. (Noise blankers don't help either ;^). To be honest, using a ham rig to evaluate the keying width of another transmitter is not an accurate lab test method since it is impossible to determine if the artifacts you are hearing are generated by the transmitter or by the phase noise and IMD products of the receiver. The only way to accurately test transmit bandwidth is with a low phase noise spectrum analyzer. This is the method used by George at International Radio and by Elecraft. That said, the recent mods to the MP have certainly made an improvement to that radio and have raised the hopes of many users. Can the K2 be made even better? I wouldn't be surprised. We will certainly take a look at the keying of the K2 and if we can improve the keying spectrum you can bet we will release the mod to you immediately via an application note. Its awfully good now, but as many have noticed, we never give up trying to improve the K2 :^) In the mean time I have no fear of being accused of being a 'clicker' ;^) 73, Eric WA6HHQ http://www.elecraft.com ++++++++++++++++