++++++++++++++++++++++++++++++++++++++++++++ From: Charles Greene Subject: [Elecraft] K2 Freq "drift" When Using PSK31 Hey K2 Warblers, I think I know why the K2 apparently drifts when using PSK31. The symptom is that the other station is drifting because you have to reset your receive freq every time he turns it back over to you. However, it's the K2 that's changing freq. That's using Digipan 1.5 with the TX freq "not locked," or with "net" selected on most of the others. To investigate this effect, I tuned in WWV on 10 MHz and used Digipan to see how much their tones changed which would indicate a drift. I tuned in WWV on ant1 put a dummy load on ant2. I transmitted PSK31 into the dummy for a few minutes then switched back to ant1 when I went to receive. There is absolutely no drift. Another thing that could be happening is that the transmitter and receiver are not on the same frequency which would be the case if the RIT or XIT were enabled. These were both off, so it had to be something else. I had noticed when I set my filters, that the BFO freq is not the same on all filter bandwidths. I got the BFO the same on all the narrow bandwidths but as hard as I tried, I couldn't get FL1 (OP1) on the same freq. It's 10 to 20 Hz off, which is one or two of the minimum steps. So what I think is happening is that when I switch in FL2 or another narrow filter, the BFO freq shifts 10 or 20 Hz. The other station starts transmitting and he apparently is 10 to 20 Hz low because he had "net on" and his freq is on my transmit freq. The PSK31 program AFC won't capture a shift that great, so I have to click on the other stations freq, which shifts my receiver to his freq. I have "net on" so if he drifts, my transmitted tone will follow his tone. However when I go back to transmit, the difference in BFO freqs in the K2 between transmit and receive cause my transmitter to start transmitting down 10 or 20 Hz. The other station has to reset his freq to receive me, so we play hopscotch down (or up) the band. That's not the way it's supposed to work plus it irritates both of us because we have to reset frequency every time we turn it over to the other. So I'm going to go back and recalibrate the BFO and filters and see if I can get the BFO freqs to be the same on all filters. Any suggestions on how to do this? What I had done previously was to first set the BFO freqs the same then narrow the filters for FL2, 3 and 4. You might say, well just stay in OP1 all the time. That would be fine except for a few Pactor stations which come up and wipe out most all signals in the receiver band pass. I usually have the AF gain all the way up and adjust the level with the RF gain control. This reduces the K2 AGC and helps some. But the K2 filters are very effective in combating this - that's what they are for, and a valuable tool like the filters should be used if they can be made to work. That's one reason the K2 is better for PSK31 than most of the JA transceivers because you can't use their narrow filters on SSB. 73, Chas, W1CG +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Sun, 3 Dec 2000 19:58:11 -0800 From: "Ron D'Eau Claire" Subject: RE: [Elecraft] K2 Freq "drift" When Using PSK31 Chas, W1CG wrote: 1) " I couldn't get FL1 (OP1) on the same freq. It's 10 to 20 Hz off, which is one or two of the minimum steps. ... " 2) "The other station starts transmitting and he apparently is 10 to 20 Hz low because he had "net on" and his freq is on my transmit freq. The PSK31 program AFC won't capture a shift that great, so I have to click on the other stations freq, which shifts my receiver to his freq. I have "net on" so if he drifts, my transmitted tone will follow his tone." I don't believe that the K2 is capable of a BFO accuracy better than 20 Hz or so. It has to do with the resolution used in the DAC's that control the frequency. I generally use a narrow-band filter on PSK and tune with the receiver, not the computer. The idea of clicking on a waterfall display to select a signal is nice if there aren't any really strong signals in the bandpass that will trigger the AGC other than the one I want, but that generally is not the case. Waaaay back in the beginnings of PSK 31 it was suggested that only *one* station have the NET function enabled, to avoid the two of you 'walking' across the spectrum due to the inherent drift in rigs. It was suggested that the station calling CQ enable NET and the "calling" station be sure to turn it off. On the few occasions that I've noticed that we tend to be 'walking', I turn off NET even if I called CQ and it has always stopped the movement. I believe that a drift of 10 or 20 Hz over a period of time is perfectly normal for any high-quality rig. For me, that's why the AFC function in the software is so important. I usually run 'split' so I can twiddle with the main tuning to keep the signal in the bandpass without affecting my transmit frequency in any way. (Yes, I have worked some PSK sigs that threatened to drift out of my 100 Hz bandpass filter. Those are the ops who'd be grateful for a rig that only drifted 10 or 20 Hz in half an hour). Ron AC7AC ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ From: Wayne Burdick Subject: Re: [Elecraft] K2 Freq "drift" When Using PSK31 Charles Greene wrote: > > Hey K2 Warblers, > > I think I know why the K2 apparently drifts when using PSK31. Chas, On transmit, the K2 always uses BF1 (the BFO you set up for FL1), regardless of how many times you switch to other filters. So if you don't move the VFO, the TX freq won't change. However, 10 or 20 Hz of shift in *receive* frequency as you switch filters is very likely, and within spec. So the solution is to switch filters during receive as much as necessary, but use either RIT or the second VFO to re-tune the station you're working--not the primary VFO. That way, your TX frequency will never change. 73, Wayne N6KR ++++++++++++++++++++++++++++++++++++++++++++++++++++ From: "Gregg R. Lengling" To: , Subject: Re: [Elecraft] K2/100 and MFSK? Date: Thu, 6 Feb 2003 22:08:57 -0600 I've been running my K2 in this mode for the last month without any drift problems. I run at 20 or less watts...no reason to run 30 watts...(btw Elecraft did have a bulletin that continuous duty modes should only run 25 or less watts). I am using a real neat PSK31 program called PSK31 Deluxe v2.1 written by Simon Brown HB9DRV. it has some neat functions such as buffering of all streams. If you double click on a stream it replays the last 10 seconds or so....great for finding stations calling cq ect.... Gregg R. Lengling, W9DHI PSYCHOLOGY: The science of inventing words for things that do not exist. ----- Original Message ----- From: To: Sent: Thursday, February 06, 2003 9:34 PM Subject: [Elecraft] K2/100 and MFSK? > Is anybody else using a K2/100 with MFSK? I tried it today for my first > time (K2/100 serial #2838) running about 30 watts. Frequency drift seemed > to be more or faster than the IZ8BLY Stream program would tolerate, so > the station receiving me had to keep adjusting frequency and then when > I was receiving and the radio was cooling down I had to keep adjusting to > keep getting copy on him. > > I don't know if the solution is to improve frequency stability in the > K2 or to ask Nino to make the Stream program more agile. Trouble with > the latter is obviously the number of copies of the existing program > that are out there. > > Jim W6JVE +++++++++++++++++