+++++++++++++++++++ Date: Wed, 7 May 2003 09:33:50 -0700 (PDT) From: Daniel Reynolds Subject: Re: [Elecraft] K2 Power indication, CW vs SSB question To: k6iii at juno.com, elecraft at mailman.qth.net Although I may be wrong - my understanding is that you are dialing up 5 W PEP when you set your K2 to 5 W. If you want to operate 10 W SSB, you'll need to turn the power up to 10 W. I guess most folks consider the 10 W SSB to be comparable to 5 W CW because of the lower 'duty cycle' of SSB voice. - Daniel/AA0NI --- k6iii at juno.com wrote: > A trivial question re K2 Power Out indication, CW vs SSB. > > In contesting activities, the published rules typically indicate some > maximum power out to operate in a particular entry catagory. For example, > 5-watts is the usual QRP max power. Some SSB mode contest rules may even > say 10w PEP. > > My practice has been to dial up 5 with the POWER knob and let her rip. I > am trusting that this is 'close enough' and have no other means of > measuring my actual power out. > > So the question I raise is..... Is this dialed up '5' a DC power (i.e. > CW mode) and what about SSB mode... would the '5' indicate PEP power, or > am I actually running some other power out value in SSB? What would I > dial up if I wanted to run SSB, say, 10-w PEP? > > Inquiring minds want to know... > de Jerry/k6iii > San Jose, CA > K2 #500 +++++++++++++++ From: "Gregg R. Lengling" To: , Subject: Re: Re: [Elecraft] K2 Power indication, CW vs SSB question Date: Wed, 7 May 2003 12:16:20 -0500 I aligned my radio and calibrated the output power meter using my IFR1200S....I found that it reads actual carrier power in CW and when watching SSB signals, it is showing PEP power. So 5 watts is 5 watts on CW and 5 watts is 5 watts PEP on SSB. Gregg R. Lengling, W9DHI, Retired K2/100 SN 3075 http://www.milwaukeehdtv.org ----- Original Message ----- From: To: Sent: Wednesday, May 07, 2003 12:06 PM Subject: Fw: Re: [Elecraft] K2 Power indication, CW vs SSB question > > Thanks for your input, Daniel. I am aware that CW and SSB power are > typically measured differently... SSB is usually expressed as P.E.P. (and > sometimes Peak-to-Peak) and CW is usually Peak power. (Then, of course, > there is Average Power and RMS Power - just to confuse the discussion!). > But I don't know what the K2 power indication is actually measuring. Thus > the question I posed. I suspect there may be several differing opinions > and am hoping Wayne will jump in on this one. > 73 de Jerry/k6iii ++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: , Subject: RE: [Elecraft] K2 Power indication, CW vs SSB question Date: Wed, 7 May 2003 10:24:18 -0700 The confusion seems to come out of a decision by the ARRL to consider 10 watts PEP equivalent to 5 watts CW for "QRP" power levels.=20 I believe that the QRP ARCI defines QRP as 5 watts our less output = either PEP or CW.=20 When you set the power output on your K2, you are requesting either CW = or PEP, depending upon the mode. The bargraph shows you the PEP output in = SSB, and you will see that the 5 watt bar will just flicker on occasion when = you transmit SSB with the power set to 5 watts. If you want to run 10 watts = PEP, set the POWER control for 10 watts.=20 The difference is 3 dB or half an S-unit. By itself that's an almost insignificant difference. That difference can matter when striving to = work "by the rules" or when digging for every dB of system performance. To paraphrase the old saying, "A dB here, a dB there and pretty soon we're talking about a real power!" Some ops are pretty... uh... "rigid" about setting the power output to exactly 5 watts. In the "real world" out there, a power difference of a couple of dB is undetectable on the air. Dedicated QRPers, wanting to = know that they won their awards and scored the points in the contest in the = true tradition of "5 watts or less!", tend to err on the low side. They often hook up the best power meters available and set the power a closely as = they can to 5 watts, being very careful not to go a milliwatt over 5 watts output.=20 Other ops look at the 5 watt limit rather like some automobile drivers = look at the speed limit on a road with no police around. And that's a good analogy. It's a matter of doing "what's right" that agrees with our = sense of personal ethics. Where's the joy in a high contest score or a QRP award = if, when we look in the mirror we see someone who knows that we cheated?=20 I'd have a very hard time if any one complained that I wasn't running = "QRP" when I had the K2 power output set to 5 watts on the bargraph. That = metering is accurate to 20% or better... and that's a difference of only 1 = watt.... or less than 0.8 dB.... or only about 1/10th of one "S" unit!=20 Very few "Ham" wattmeters are more accurate than that. Many are a good = deal worse. And who is to say that if the meter is off by 20% that I am not actually running 4 watts rather than 6 watts? Ron AC7AC K2 # 1289 ++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: Subject: RE: [Elecraft] Power Readout Discrepency Date: Sun, 18 May 2003 09:51:47 -0700 I've played with the 1N5711 RF detection circuits too. While they are superior to the 1N34 germanium diode that has been commonly used as an = RF detector for many years, the 1N5711 is NOT absolutely flat across the HF spectrum and their characteristics do vary somewhat from diode to diode. = You got my curiosity up so I plugged my K2 into two external devices: an = RF ammeter and an external wattmeter. The ammeter uses a current sensing transformer. It is a lot "flatter" in its response than the old = thermocouple ammeters. The wattmeter is quite flat up to the vicinity of 500 MHz. = They both agreed to within a couple of hundred milliwatts. With the K2 set = for 10 watts out on the display, here's what my external meters indicated: 160 meters: 9.7 watts 80 meters: 10.1 watts 40 meters: 11.5 watts 30 meters: 11.3 watts 20 meters through 10 meters: 10.6 watts If you have two meters spec'd at 10% accuracy such as the Oak Hills unit = and the internal meter in the K2, they may show a comparative error of up to = 20% of course. It does get a little curious if, when using three = instruments, two agree closely and the third appears to be off by a large margin. But that's not definitive if the total error is less than the sum of the possible errors. =20 Wasn't it Murphy who decreed that all errors add in the most damaging = (or confusing) way possible?=20 Ron AC7AC K2 # 1289 -----Original Message----- My K2, #2636 has always had a large discrepancy in the displayed power = vs what I see on other, external wattmeters, including units from Oak Hills = and Diamond. I know these are not lab quality devices, but I still think = things should agree a little better. I talked to Eric about this yesterday at Dayton. I get the idea that non-linearities in the rf detector D9 could = be a factor. Has anyone had any experience with this? I'm thinking of replacing D9 just to see if that's the problem. Below are my = K2-indicated power levels for 10 watts out, measured through a Diamond wattmeter connected to a commercial dummy load. Bands progress from 160 through = 10 meters, respectively. I see similar non-linearity at lower powers = through the WM-2 wattmeter. 8.2, 8.5, 8.8, 8.4, 6.2, 6.8, 8.6, 11.0, 11.0 I would appreciate any comments on this. I've confirmed that I have the correct diode at D9 and solder joints are good. Parker WD8JOL ++++++++++++++++ From: "Parker Buckley" To: "Ron D'Eau Claire" , , "Don Wilhelm" Subject: Re: [Elecraft] Power Readout Discrepency Date: Sun, 18 May 2003 17:28:52 -0400 Don and Ron, here's some better data. I had made my previous comparisons with the dummy load at the far end of an internally bypassed Palstar antenna tuner, a coax switch, a homebrew tuner-tuner, and the Diamond wattmeter. Hard to say what all that does to the poor K2 trying to push a few watts through it. With the dummy load right on the back of a WM-2 wattmeter and a short piece of coax from the rig straight to the wattmeter, shown below is the displayed power on the K2 to get 10 watts on the WM-2. I get very different values now, and for the most part they are within 10%! Sometimes I have to do this to myself. Sorry to drag everyone else through it. :) Here's the data from 160 to 10 meters for 10 watts on the WM-2: 8.5, 9.4, 9.9, 9.9, 10.8, 10.8, 11.7, 12.2, 12.2 According to the WM-2, the Diamond wattmeter, the tuner tuner, and the coax switch each provide an impedence bump resulting in some reflected power. Thankfully, the Palstar tuner switching is not a problem. I am about to eliminate a few accesssories and/or rely on the WM-2 for power settings; not the K2 display. I think I've learned enough this time, and will just go look for a QRP contact somewhere. Thanks for all your patience. Parker WD8JOL +++++++++++++++ From: "Robert Boerhorst" To: , Subject: Re: [Elecraft] Elecraft K2 Power Readout Discrepency Date: Mon, 19 May 2003 21:34:49 +0200 Ron, Thanks for your quick response and advice. I will measure the output of the 5 V regulator and go from there. As I said in my earlier message I have lived happily with the situation as it is for more than a year now, but reading the message from Parker I thought I have te same experience. I have not opened the K2 since the last time I adjusted the CW filters with Spectrogram now more than a year ago. The K2 is the best rig I ever worked with. I try to make at last one or more CW QRP QSO's with the rig daily with the object to reach QRP DXCC (95 entities sofar). I am familiar with the site of Sverre Holm, LA3ZA, but forgot to look at it for existing mod's on K2 power readout. 73/72, Robert, PA0RBO K2 # 2406 ----- Original Message ----- From: "Ron D'Eau Claire" To: "'Robert Boerhorst'" ; Sent: Monday, May 19, 2003 5:56 PM Subject: RE: [Elecraft] Elecraft K2 Power Readout Discrepency > If the power indication is uniformly off across the bands, you probably > don't have a problem with the diode. The usually manifestation of diode > issues is that the metering accuracy varies a lot with frequency. > > There is a voltage divider (R67/68) in the circuit that sets the output > level to "calibrate" the system. You can change the value of R68, or replace > R68 with a small pot, to make the K2 power meter agree with the external > wattmeter and then, as our friends in England are fond of saying: "Bob's > your uncle!". > > It's very likely that in your case the 5 volt regulator used by the A/D as a > reference is slightly "off" the nominal value. The accuracy of the > calibration is dependent upon that voltage being exactly 5 volts. > > There's more on tweaking the power monitoring circuit at: > http://www.elecraft.com/Apps/RF_Det_application_note.htm > > PLUG FOLLOWS: > > Looking up the above application note, it occurred to me that a lot of newer > folks might not know about the fantastic job Sverre Holm, LA3ZA, has done > collecting and cataloging the documentation on mods, application notes, > builder alerts and other general information about the Elecraft rigs. If you > haven't done it already, bookmark: > http://www.qsl.net/la3za/K2/mod.html > > It's a great resource! > > Ron AC7AC > K2 # 1289 ++++++++++++++++ From: "Don Wilhelm" To: "Parker Buckley" , Subject: Re: [Elecraft] Power Readout Discrepency Date: Sun, 18 May 2003 16:09:49 -0400 Parker and all, I trust you are not confusing the "power requested" indication that is displayed when you turn the POWER knob with the actual power output. The actual power output may fall quite short of the requested power because of a number of things - including the actual load impedance - the RF detector arrangement in the base K2 is quite unsophisticated and great accuracy should not be expected from it. If you have installed one of the Elecraft automatic tuners, the story is quite different again because the tuners include a real wattmeter (which you can calibrate) rather than the simple RF detector included in the base K2. 73, Don W3FPR ----- Original Message ----- > My K2, #2636 has always had a large discrepancy in the > displayed power vs what I see on other, external wattmeters, > including units from Oak Hills and Diamond. I know these > are not lab quality devices, but I still think things should > agree a little better. ++++++++++++++++++