++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Wed, 18 Oct 2000 15:48:25 -0500 From: Tom Hammond =?iso-8859-1?Q?N=D8SS?= Subject: Re: [Elecraft] A few questions about C182 and the alignment of L34 Carl, et al: If you DO find that you have to change the value of C182, try to use a value which will STILL allow the signal a turn or two before you hit the top of the can. 73 - Tom Hammond N0SS +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Wed, 18 Oct 2000 09:01:23 -0700 From: Eric Swartz WA6HHQ - Elecraft Subject: Re: [Elecraft] A few questions about C182 and the alignment ofL34 > At 15:21 10/17/2000 -0700, Carl N5WN wrote: > >1. Is there any significant difference between a regular round NPO ceramic > >150pf 5% and the nice blue dipped capacitors that come with the kit? All of the blue caps supplied with the K2 are NPO monolythics and they have excellent Q. 73, Eric +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Subject: Re: [Elecraft] A few questions about C182 and the alignment of L34 At 15:21 10/17/2000 -0700, Carl N5WN wrote: >Hello, > >I have just finished the stage 2 alignment on SN # 1241 but my L34 is still >"broadly peaking" as the slug reaches the top of the can. I hear signals >on 40M and the peak >is clearly not reached with the slug at the top of the can. Carl, Experienced the same thing myself. Gary Surrency, AB7MY wrote an e-mail that sounds like what you are refering to. >7. If L34 does not have a definite but broad peak, then inspect C182 to >see if it is a 180pF cap. 270pF was used in the earlier kits, and in some >cases C182 must be lowered to 150pF or less. The peak is easiest to see >on a DMM, connected to the LM380N-8 side of R20 on the Control Board. Set >it for AC volts and tune to the 7.0MHz birdie. What I would recommend is tune the slug with A DMM. In addition to using what he said, try the following. Find the peak. Note the approximate position of the tuning tool blade. Tune past the peak, to a lower voltage, (5-10% of the peak should be adequate.) Note the new position, and number of turns if it was more than one. Tune back to the peak. Make sure it is in about the same place as the first time. Tune past the peak in the other direction, to the same voltage as you got above. Note again position and number of turns. Tune back to the peak, ensuring the peak is in the middle of the two "Shoulders" that you reached. I would recommend this before replacing the cap. I think you will find the peak is easier to spot in this manner then with your "earball." >1. Is there any significant difference between a regular round NPO ceramic >150pf 5% and the nice blue dipped capacitors that come with the kit? There can be behavior differences at different frequencies beween the different types of caps. This may be one of those areas. Good Luck. I am only a few terribleoids away from having #1383 in the fold as well. If I can just get the lawn mowed......... 73 de KA0OUV Timothy A. Raymer Missouri Department of Health +++++++++++++++++++++++++++++++++++++++++++++++++++ Sent: Wednesday, March 14, 2001 10:57 AM To: Elecraft Corporation Subject: [Elecraft] K2 S/N 1599 L34 peaking... Hi All- I've been finishing up the (hopefully final) re-calibration and alignment of K2 S/N 1599 by redoing/reviewing a lot of my previous tests and procedures. So far the rig is performing very well in all respects. A dozen or so CW QSOs on several bands seem to confirm this. However, my experience with peaking L34 (p.61 of the manual, IF Amplifier Alignment) still leaves me womdering whether it is performing as it should. (I wondered about L34 the first time I tuned it a couple of months ago, but at that time I decided to continue with construction and the re-visit the question later. Well...now is later!) As the manual suggests, I find that the internally-generated 7MHz tone DOES increase in acoustic level as the L34 slug is raised toward the top of the can from a lower position. Spectrogram also confirms this. However, there seems to be no real "peak" near the top of can--rather just a VERY gentle increase in tone level that never really peaks out. I have a nagging feeling that resonance with L34 is not occurring (if it's supposed to) in the IF strip before the received signal is passed onto the product detector. Does this seem to agree with others' experience with L34? Since I have no other receiver to make signal comparisons with, I hope someone can enlighten me so I can button up the rig--at least until I decide to do some more fiddling with it. Thanks for any feedback. Steve Banks K0PQ ++++++++++++++++++++++++++++++++++++++++++++++++++ Sent: Wednesday, March 14, 2001 10:57 AM To: Elecraft Corporation Subject: [Elecraft] K2 S/N 1599 L34 peaking... Hi All- I've been finishing up the (hopefully final) re-calibration and alignment of K2 S/N 1599 by redoing/reviewing a lot of my previous tests and procedures. So far the rig is performing very well in all respects. A dozen or so CW QSOs on several bands seem to confirm this. However, my experience with peaking L34 (p.61 of the manual, IF Amplifier Alignment) still leaves me womdering whether it is performing as it should. (I wondered about L34 the first time I tuned it a couple of months ago, but at that time I decided to continue with construction and the re-visit the question later. Well...now is later!) As the manual suggests, I find that the internally-generated 7MHz tone DOES increase in acoustic level as the L34 slug is raised toward the top of the can from a lower position. Spectrogram also confirms this. However, there seems to be no real "peak" near the top of can--rather just a VERY gentle increase in tone level that never really peaks out. I have a nagging feeling that resonance with L34 is not occurring (if it's supposed to) in the IF strip before the received signal is passed onto the product detector. Does this seem to agree with others' experience with L34? Since I have no other receiver to make signal comparisons with, I hope someone can enlighten me so I can button up the rig--at least until I decide to do some more fiddling with it. Thanks for any feedback. Steve Banks K0PQ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Fri, 16 Mar 2001 15:11:59 EST From: LHLOUSEK at aol.com Subject: [Elecraft] Interesting L34 Peaking info. I found that the peak of L34 depends on what you set the VFO to when listening to the internal 7MHz (or other) signal. Not too surprising really, when you think about it. I put my K2 on Spectrogram to check the peaking of L34. I found the that by setting the VFO so that the tone of the internal 7 MHz signal was at about 500Hz I was able to peak L34 at about 1.5 turns down from the top of the can. If I increased the frequency of the tone to 600 Hz the peak of L34 moved up in the can. At 750 Hz, which is what I use for my side tone, the peak was at the very top of the can. The peak is broad and the peaking level doesn't change much from 500 to 750 Hz but for that last little smidgen of tweakage you might want to peak L34 when the signal is beat to the side tone frequency you use. Luigi W7DZN +++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Fri, 16 Mar 2001 13:05:49 -0800 From: "Ron D'Eau Claire" Subject: RE: [Elecraft] K2 S/N 1599 L34 peaking... Steve, K0PQ asked: "However, there seems to be no real "peak" near the top of can--rather just a VERY gentle increase in tone level that never really peaks out. I have a nagging feeling that resonance with L34 is not occurring (if it's supposed to) in the IF strip before the received signal is passed onto the product detector." That's a question that has come up many times here. I call that peak "subtle" meaning "was there REALLY a peak there?". Gary from Elecraft published a note showing how to hook a DVM to the K2 and watch the peak directly. I cannot find that note! And looking all over the Elecraft "Builder's Resources" pages - if it's there I've gone blind!. Anyway, that procedure did show a definite peak and I noticed that I did NOT have mine tuned to the peak even though I was SURE I heard it (Yeah, and that was a 9UA down in the noise there answering my CQ too ).... Maybe Gary or someone will repost that procedure. Ron AC7AC K2 # 1289 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Fri, 16 Mar 2001 17:32:59 -0500 From: "Don Wilhelm" Subject: Re: [Elecraft] Interesting L34 Peaking info. Folks, Luigi makes a good point here. If you use a broadband noise source, tuning will not matter because there will always be some signal that produces the same tone as the pitch that you have set for the sidetone. OTOH, if you are using a single signal - like the internal 7MHz one - when the received pitch is different than your sidetone, you will end up trying to tune L34 to some frequency other than the center of the IF passband. I would think the bottem line should be - set L34 initially, then after setting up the filters and their BFOs, go back and re-peak L34 again for best performance (and make sure you are receiving the same frequency tone as your sidetone pitch). We did things by ear when we were working with the Field Test K2s. Things got easier with Gary's DVM tuning and the use of Spectogram for things like this. We all learn more as we progress. 73, Don Wilhelm -Chapel Hill, NC W3FPR home page: http://www.w3fpr.webprovider.com QRP-L # 485 K2 SN 0020 mailto: w3fpr at arrl.net +++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Fri, 16 Mar 2001 16:52:43 -0600 From: "Timothy A. Raymer" Subject: RE: [Elecraft] K2 S/N 1599 L34 peaking... Gentlemen, The message from Gary was originally titled: K2: 25 reasons for low RX sensitivity or low audio. I think it may still be up on the web site. Because of the length, I only sent the full text to Steve and Ron. Tim Raymer 73 de KA0OUV ++++++++++++++++++++++++++++++++++++++++++++++++++++++ NOTE: IT FOLLOWS AT THE BOTTOM !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Fri, 16 Mar 2001 20:20:24 -0800 From: "Ron D'Eau Claire" Subject: RE: [Elecraft] K2 S/N 1599 L34 peaking... Tim, KA0OUV wrote: "he message from Gary was originally titled: K2: 25 reasons for low RX sensitivity or low audio." That's not the one I recall. Gary's procedure was quite simple, running a couple of paragraphs. Working from memory, I suspect it was about the same as the ones described here by Luigi and others for adjusting L34 using Spectrogram. The only difference was that Gary hooked a DMM to a test point so you didn't have to use Spectrogram. Looking at my K2, I think the 'test point' Gary suggested was the 'hot' end of R 20 (the one nearest the IC) on the Control Board. That would have you measure the audio amplifier output voltage. It's been a couple of months (at least) since I did the procedure myself. As Luigi and Dave have pointed out, you must have a stable signal tuned in. It won't work on "noise". The procedure in the Elecraft manual uses the 7 MHz birdie. Ron AC7AC K2 # 1289 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Mon, 7 Aug 2000 15:12:36 -0700 From: gsurrency at juno.com Subject: [Elecraft] K2: 25 reasons for low RX sensitivity or low audio. (long) A number of people have commented their K2's audio seems a bit low. I have compiled a list of things to check that may help you resolve if there is a problem. Please forgive the bandwidth, as I have tried to include everything I have seen or could think of, that might go wrong. 1. Check the CAL FIL settings first, to be sure the BFO is set as closely to the optimum frequency as possible. Spectrogram is the best way to do this, so check our website for details on downloading and running this program. Carefully set CAL S LO and CAL S HI in the Menu. It is normal for these settings to change a little after the SSB adapter is installed, and they may vary due to the absolute BFO freq. relative to the center of the IF filter pass-band. The S-meter zero setting may also vary a bit between LSB, USB, and CW, because of the different BFO frequency of each mode. Careful and accurate adjustment of CAL FIL will minimize this, as will short leads in the BFO and SSB adapter circuits. 2. Check to see that the toroids at T6 and T7 are wound correctly and soldered well. T7 has been changed in recent kits from a 11:3 to 20:5 turn transformer to allow a little better coupling of the 4.915MHz IF signal into U12. The difference in transformer coupling is small, but might be helpful in rigs that suffer a little bit in sensitivity. Make sure T7's primary and secondary are not reversed, and that the correct color wires are inserted at T6 in the preamp stage of Q21. Be sure to use the correct core material for each toroid inductor or transformer. 3. Remove the SSB adapter if equipped, to isolate the problem to the K2 or to the SSB adapter. Remove the NB too, but remember the signals will normally be a bit stronger with it out, since the resistive pad was moved from the RF PCB to the NB PCB when we redesigned the NB to tolerate IMD and signal overload in the EU environment. Place jumpers across the appropriate connectors to complete the signal path. 4. Verify the band-pass filters are properly adjusted. I use less than 1 watt of TX output to peak these tuned circuits well. If there is no definite peak, then there is a problem with that filter. 5. See that the Preamp makes a noticeable change in the receiver hiss and noise when it is switched ON. This insures Q21 is working well. 6. See if changing the Menu setting for OPT=BAT to OPT=PERF makes a change in sensitivity and RX current draw. This insures Q22 is working well. 7. If L34 does not have a definite but broad peak, then inspect C182 to see if it is a 180pF cap. 270pF was used in the earlier kits, and in some cases C182 must be lowered to 150pF or less. The peak is easiest to see on a DMM, connected to the LM380N-8 side of R20 on the Control Board. Set it for AC volts and tune to the 7.0MHz birdie. 8. Sometimes the wrong value cap is installed in the RX signal path. I have seen this on several radios I have repaired, and the sensitivity will be greatly affected. Look for smaller than required caps in the series signal path, or smaller than specified bypass caps as well. Also check for larger then correct value caps to ground in the crystal filter areas of the SSB adpater and 2nd crystal filter. 9. The LM2930T-8 regulator voltage has been pretty high on many K2's. This will elevate the AGC Threshold at pin 5 of U12 (RF PCB), and cause premature reduction of gain on weak signals. If turning OFF the AGC causes the RX noise to increase significantly with no antenna connected, then you may need to reduce the size of U1 (51K) on the Control Board to something close to 33K to bring the AGC Threshold voltage lower. This works like increasing the RF gain a little further, than fully clockwise. 10. Some J310's in the Mute switch at Q6 and Q7 may not fully switch ON if the /Mute voltage on their gate lead is too low. Check this using a voltmeter with a high input impedance, since the 3.3M resistor from the gate to source leads of Q7 is the pullup resistor for the /Mute lead. The gate voltage should be very close to the voltage measured on the source of Q7. Change the J310's if necessary, or use a J309 or other JFET with a more tightly controlled Vp (pinch-off voltage) rating. You can temporarily jumper the source and drain leads of Q6/Q7 to see if the audio level improves noticeably. A leaky /Mute pin on the MCU at U6 pin 17 could cause problems by not allowing the /Mute line to rise adequately in receive. 11. Replace R18/R19 (1.5K) on the Control Board with jumpers, if they are not already jumper wires. I still use the 1.5K resistors in my K2, and it has good audio level. I prefer the audio characteristics of the /Mute circuit with the resistors installed, as it prevents the audio level from being so loud right off of the minimum setting. Your results may vary. Some rigs have 5K AF pots, where others may have 10K pots. There may be a small difference in maximum audio level as a result, but it should not be very significant. The J310 JFETS are more likely to be the cause of poor Mute switch operation. 12. Check to see if the 0.022 at C177 (on the output of the NE602 at U11, RF PCB) and C27 (on the drain leads of Q6/Q7). If these caps are too large in value, they will shunt too much audio level. Their function is to shape the AF pass band, and to remove the IF signal after the product detector. 13. Check to see if U9 on the Control Board, has the correct supply voltage on pin 7. R16 (10 ohms) is suspect if the voltage is too low. Also check the electrolytic caps polarity while you are inspecting the Control Board. 14. Check the supply voltages on Q21, Q22, U12 and U11, to be sure they are not below that given in the Troubleshooting Guide. 15. If there seems to be a large loss of signal through the crystal filter, you may have a defective crystal set. Be sure all of the crystals in the filter are marked 4915-20, *not* 4915 -S - which are BFO crystals. Do not mix crystals from one set (SSB) with another (variable filter set supplied with the K2). Check with us for recommendations and replacements if you suspect a filter problem. It *is* normal for some signal loss through the crystals, but it will be progressive between each crystal and will not be a large difference from one crystal to the next. 16. Low VFO injection to the TUF-1 diode ring mixer will reduce sensitivity. Most of the time, this will also lower the maximum possible TX output. An oscilloscope or RF probe should reveal any problem with the VFO output, which should be 300-400 mVrms or so. Check the VFO ALC circuit for errors. 17. A 1N4007 PIN diode that is not working correctly, or a PIN diode bias resistor that is incorrect, will lower the signal level. Moving an antenna or signal generator along the signal path will reveal if there is a sudden increase of signal level past a certain point in the receive signal path. 18. Shorting the heat sink of Q22 (the 2N5109 post-mixer amplifier) to ground may damage RFC11. Even if the DC collector voltage checks OK, RF signals may be lost through the defective RFC. One customer had this happen, and it surprised us both when a new RFC fixed the problem! 19. Note if the transmitter output is good on all bands. If one or more bands have less output, the receiver may also not work well on those bands. A problem in the low-pass filter or band-pass filter for that particular band would be likely. 20. A bad ZVN4424A Mosfet at Q2 (RF PCB) will not permit sufficient PIN diode bias at D3/D4. The voltage at Q2's drain lead should be quite small (less than 0.1V) in receive. Replace Q2 if necessary. 21. A properly working K2 will show a large increase in S-meter reading if a finger or tool is brought near jumper W3 or transformer T7. This is normal behavior due to BFO leakage being introduced into the high-gain IF stage of U12. I've only had to replace one U12 MC1350P IF amp IC in all of the K2 repairs I've done. IC's are extremely reliable once they are installed correctly. There is about 3.8 to 3.9 volts on U12's pin 5 when the AGC is not active on weak signals or no signal. More voltage than that is cause for concern. 22. Clean any excessive flux or dirt from around the receive signal paths. Always suspect toroid leads and poor solder connections, as a major cause of trouble. 23. The 2N5109 transistors used for Q21 and Q22 are pretty reliable and have good gain. Still, it is possible to have a bad one if there is not a good increase in signal level on the output side of these devices. The DC voltage tests on these transistors will usually determine if the transistor is bad. 24. Be certain the speaker plug at P5, and the external speaker jack are wired with the correct polarity. Otherwise, a large amount of speaker volume will be shunted to ground. 25. Use the correct impedance headphones of 30-40 ohms per channel if they are of the stereo type. Lower impedances headphones will produce lower volume. Reduce the resistance of, or replace R35/R36 if your preferred headphone impedance is very low. I hope this info is helpful to anyone who might be experiencing a lower than normal receiver sensitivity, or if your kit suffers low audio output. A properly working K2 has more than enough audio and senstivity. 73, Gary Surrency AB7MY Elecraft Technical Support support at elecraft.com +++++++++++++++++++++++++++++++++++++++++ Date: Thu, 22 Mar 2001 16:24:19 From: "Samuel Ramac" Subject: [Elecraft] L34 tuning I tried to tune L34 by following Gary's Aug 200 recommendation: 7. If L34 does not have a definite but broad peak, then inspect C182 to see if it is a 180pF cap. 270pF was used in the earlier kits, and in some cases C182 must be lowered to 150pF or less. The peak is easiest to see on a DMM, connected to the LM380N-8 side of R20 on the Control Board. Set it for AC volts and tune to the 7.0MHz birdie. Using the AC mode, I can't get any voltage reading. I tried measuring DC voltage but I get 6.8VDC which doesn't change as I tune L34. Am I missing something here? I have SSB and NB installed when I tried to do this. Thanks. ++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Thu, 22 Mar 2001 18:17:11 +0100 From: "Heyder, Norbert" Subject: [Elecraft] Re: L34 tuning "Using the AC mode, I can't get any voltage reading." Don't forget to increase the AF-Volume to a sufficient level! (been there, done that, hi) 72 de Bert, DL8BDF ++++++++++++++++++++++++++++++++++++++++++++++ Date: Thu, 22 Mar 2001 16:12:25 -0600 From: "Timothy A. Raymer" Subject: Re: [Elecraft] L34 tuning Samuel, In additon to setting the volume to a sufficient level, you need to be tuned to a signal, such as the birdy at 7.000.01 Mhz. Alternatively, you can key another transmitter into a dummy load, and use it as a reference. Good Luck. Tim Raymer At 16:24 03/22/01 +0000, Samuel Ramac wrote: >I tried to tune L34 by following Gary's Aug 200 recommendation: +++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Sun, 22 Apr 2001 16:08:27 -0500 From: "Joel Kluender, NF9K" Subject: [Elecraft] K2 #1874 UPDATE All, Thanks for the many excellent replies to my questions regarding peaking of L34 and the 40M BPF. They helped calmed me down and got me thinking in the right way. It turns out that I had no problem after all. My only problem was that I was trying to do the adjustments at 2:30 am, while tired, with a near dead band. I did find a QSO to work with but I think the signals were not strong enough. This afternoon, I set up my IC740 across the room with a dummy load, and this made all the difference. With the steady, strong signal from the IC740, I was able to peak both BPF and IF Amp. It also helped to turn the AF gain higher than I was initially. The louder volume made it easier to hear the "peaks". I think I'm ready to go on with construction. Thanks all for the help! 73, Joel NF9K K2 #1874 Builder ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Mon, 23 Apr 2001 08:32:00 -0700 From: "Ron D'Eau Claire" Subject: RE: [Elecraft] K2 1874 Progress & Question Joel, NF9K asked: "I don't seem to have the ability to really peak L34 in the IF Amp and L1, L2 in the 40M BPF. With the IF AMP, I do see a very broad peak but within that peak I can't hear much difference so I don't know where the "right" setting is. For L1 & L2, I cannot honestly say I heard any difference as I adjusted them, so I have no confidence that I have truly peaked the BPF....Please help de-panic me!" That's normal about L34. It's a very broad and subtle peak. Some ops use a sensitive a-c voltmeter on the speaker/phones output to see the peak while adjusting it listening to a weak signal (the 7 MHz "birdie" mentioned in the manual is great for this). If you have Spectrogram to align your filters, it makes a decent a-c voltmeter for this. Of course, you must adjust L34 listening to a signal centered in the i-f passband rather than just listening to 'white noise' like you do when using Spectrogram to align the filters. L1/L2 should produce a definite peak in transmitter output when they are adjusted properly as described in the manual. You mentioned 'hearing' any difference when adjusting them. These coils are set looking at the transmitter power output as described in the manual under "Alignment and Test, Part III". Are you getting the results the manual says when you adjust them according to the instructions? If so, they are fine. Ron AC7AC K2 # 1289 +++++++++++++++++++++++++++++ Date: Sun, 26 Aug 2001 11:39:29 -0700 From: lhlousek Subject: Re: [Elecraft] K2 IF amp alignment question I found when using Spectrogram and a CW note to peak L34 that the higher the note the higher the slug. At 600 Hz it was about 1 turn down. At 750 Hz it was right at the top and at 800Hz it was beyond the top. As has been said the peak is very broad. Lou W7DZN ++++++++++++++++++++++++++ Date: Sun, 26 Aug 2001 16:04:45 EDT From: N2EY at aol.com Subject: Re: [Elecraft] K2 IF amp alignment question In a message dated 8/26/01 9:14:47 AM Eastern Daylight Time, penzo at juno.com writes: > Need some advice. While performing the IF amp alignment, the signal at > 7100Khz is loudest with L34 at the top of the can. I have verified that > L34, C182 and other IF components are the correct values. I should also > add that the signal is quite strong (still hear it faintly with the af > gain all the way down and rf gain all the way up) but I can't confirm > that it's peaked since the slug is at the top of the can. > > Any ideas? Has this happened to anyone else? Should I consider a > different value for C182? K2 #2084 does this. When I get the proverbial "circular tuit" I'm going to try a slightly smaller capacitor. The gain went up quite a bit when I aligned it using an analog meter on the speaker terminals and AGC off. 73 de Jim, N2EY ++++++++++++++++++++++ Date: Thu, 03 Jan 2002 17:54:23 -0800 From: Wayne Burdick Organization: Elecraft To: Unifiedtx at aol.com CC: elecraft at mailman.qth.net Subject: Re: [Elecraft] L-34 Tuning Adjustment on K-2 I'd suggest you do the second crystal filter modification, which allows for a more optimal setting of L34 for CW while better equalizing USB and LSB center pitch. From my initial experiments with this mod, I recall that the peak is more defined as well. Sorry to leave off your name or call, but you didn't supply it! 73, Wayne N6KR Unifiedtx at aol.com wrote: > > My K-2 works fine in every respect, but the L-34 tuning adjustment haunts me. > I just left the slug one turn down from the top of the can (because I could > not find a peak). I would like to go back and find the peak with my DMM > connected to the LM380N-8 side of R20 on the Control Board set for AC volts > and tuned to the 7.0MHz birdie. If I do this, would it be necessary to go > back through a complete filter alignment with Spectrogram? If so, I think I > will just leave well enough alone. I would appreciate any feedback on this. --__--__-- ++++++++++++++++++ From: Unifiedtx at aol.com Date: Thu, 3 Jan 2002 20:54:11 EST To: elecraft at mailman.qth.net Subject: [Elecraft] L-34 Adjustment on K-2 Please excuse me. I did not give my name on previous posting on this subject. Roy W4WFB K-2 #2225 ++++++++++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: , Subject: RE: [Elecraft] L-34 Tuning Adjustment on K-2 Date: Thu, 3 Jan 2002 23:17:53 -0800 Ed, AC5DC asked: > Is this second crystal mod listed on the web page? I am also > interested in this and could not discern which mod you are > referencing. Yep. Go to "Builder Resources" on the Elecraft web site, then select "Mods" and choose "K2 2nd Stage Xfil Mod, for 'Flatter' SSB Filter Response" Very worthwhile mod, as in "no K2 should be without one..." . Hmmm... I see you have almost as much ac hum in your call as I do... Ron AC7AC K2 # 1289 ++++++++++++++++++++ Date: Wed, 23 Jan 2002 13:33:10 -0600 To: "Rick Shindley" , elecraft at mailman.qth.net From: Tom Hammond =?iso-8859-1?Q?N=D8SS?= Subject: Re: [Elecraft] K2 L34 tuning revisited Rick: >I retuned my K2's filters the other day. I made the filter flattening mod, >PSK-31 mod, and used a noise source and the latest tuning advice from the >Elecraft web site. I got to the part where L34 had to be adjusted for >lowest noise and maximum signal while listening to the birdie at 7 MHz. I >built the rig a year ago and anxiously moved through the adjustment >procedure. L34 was tough to set, but I forgot about it and moved on. This >time I wanted to be very careful and deliberate. ARRRRGGGH!!! > >I could not discern a point on L34 where the signal was more pronounced >relative to the noise. I finally used Spectrogram to display the audio >signal and found that no matter where I set the coil slug, the relative >difference between the noise and the audio peak remained the same. (The >manual indicates to adjust for max sig/noise.) I ended up peaking the slug >where the audio peaked without regard to the noise level, since it made no >difference. The slug ended up about one turn down from the top (not near the >bottom where my ears believed it belonged). > >I wonder if others see a relative change between signal and noise while >adjusting L34 using spectrogram? Since you have performed the SSB 2nd Xfil Mod, I think I'd urge you to use Spectrogram and to adjust L34 for the best 'flatness' between LSB and USB and to not worry about THAT much squeezing out the best S/N ratio. Well, that is unless SSB operation is anything more than just a passing thought. If you're a dedicated CW op, and will only use SSB periodically, then go for S/N ratio... however, there's a good chance you'll never really notice the actual difference, while you might well notice the diff between the two sideband settings if you don't tune L34 to equalize performance there. Tom Hammond N0SS +++++++++++++++++++ From: "Rick Shindley" To: Date: Thu, 24 Jan 2002 12:27:04 -0600 Subject: [Elecraft] L34 tweak help Thanks to Tom (N0SS) and the others that offered their advice for adjusting L34. There is apparently little relative difference between the signal and noise as the slug in L34 is adjusted. There is a signal peak that typically occurs about 1T down from the top, but that is unlikely to be the ideal setting for SSB filter flatness. Using Spectrogram, I found the ideal setting for my rig to be somewhere in the center of L34's adjustment range. Regarding filter flatness--"good" IF filters have ripple amplitudes of less than a db. This rig's filter typically has far more than that (mine does, anyway!) Ripple affects the amount of amplitude and phase distortion in both the transmit and receive audio. SSB audio is inherently primitive, so few care about significant IF passband ripple. (Regarding PSK-31; PSK-31 requires so little bandwidth, passband ripple is far less of an issue.) One last thing. I am not sure if this has been mentioned before, but there is a difference in audio fidelity between the speaker jack and the headphone jack. The latter has a filter that rolls off high frequency audio. The difference is noticeable when using Spectrogram. Consider using the speaker jack to drive Spectrogram (keep the volume low) to get a more realistic view of your rig's filter performance. Rick KC0OV (The cover is back on and I'm not messing with it any more!) +++++++++++++++++++ From: "Rich Lentz" To: =?us-ascii?Q?Tom_Hammond_NOSS?= Cc: "Elecraft Reflector" Subject: RE: [Elecraft] K2 L34 tuning revisited Date: Fri, 25 Jan 2002 19:15:45 -0600 I had set L34 as described in the manual and never touched it again. Noticed when using Spectrogram to set up the passband for each of the filters that the pasband had a slope similar to those shown in the graphics with the alignment method and thought that it was alright. I have seen the MODS for evening out the USB and LSB and thought that the USB/LSB mod. After reading Toms reply (below) I tried his method of tuning L34 for flatness of the passband. WOW - WOW - WOW !!! After making this simple adjustment my display looks as good as the graphics for the USB/LSB flattening MOD. It even increased the gain over the pasband and had negligible affect on the CW passband. Actually helped on the two lower bandpass filters. This technique is strongly recommended. Rich -----Original Message----- From: elecraft-admin at mailman.qth.net [mailto:elecraft-admin at mailman.qth.net]On Behalf Of Tom Hammond NOSS Sent: Wednesday, January 23, 2002 1:33 PM To: Rick Shindley; elecraft at mailman.qth.net Subject: Re: [Elecraft] K2 L34 tuning revisited Rick: >I retuned my K2's filters the other day. I made the filter flattening mod, >PSK-31 mod, and used a noise source and the latest tuning advice from the >Elecraft web site. I got to the part where L34 had to be adjusted for >lowest noise and maximum signal while listening to the birdie at 7 MHz. I >built the rig a year ago and anxiously moved through the adjustment >procedure. L34 was tough to set, but I forgot about it and moved on. This >time I wanted to be very careful and deliberate. -- snip -- +++++++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: Subject: [Elecraft] Simple way to set L34 Date: Sun, 29 Sep 2002 17:38:02 -0700 Gary Surrency posted a message here a year or so ago about setting L4 using a DMM rather than by "ear". Of course I lost it, but the next time I wanted to check the setting I recreated my own version of it (might even be the same) by remembering is general approach. The procedure is to tune the 7 MHz "birdie" and adjust L34 for maximum AGC voltage. Since the AGC voltage is a function of the amount of signal coming out of the IF amplifier, that assures you that L34 is on its "peak". I connect the DMM to the "hot" end of R2 on the Control Board. The Control board is the one attached to the front panel assembly that faces toward the inside of the K2. Looking down onto the board from the top with the cover removed, R2 is right next to U2 on the right end of the board near the top edge. The end of R2 nearest the top of the board is grounded. You must connect the test probe to the end of R2 furthest from the top edge of the board. Be sure you don't short to the adjacent component leads. Connect a dummy load to the rig. You must avoid picking up any outside signals or noise. They will mask the reading. Turn the K2 On. Turn the preamp On. Ensure the AGC is On Set RF Gain at maximum (fully clockwise). Tune in the 7 MHz "birdie". Use SPOT to be sure that you have it right on frequency. Now adjust L34 for MINIMUM voltage on the DMM. The setting is a bit broad, but I find a very definite "peak" indicated minimum voltage at one spot in the L34 adjustment. A DMM is required because the change in voltage is only a few hundredths of a volt with a little over 3 volts to ground. In mine the voltage sits at about 3.646 on the "sweet spot" rising to 3.647 or 3.648 1/8 to 1/4 turn off of the "peak" in either direction. That does it for me. Ron AC7AC K2 # 1289 =============================================== no9e wrote: >2. After doing 2nd XTAL mod, the sensitivity with FL2-4 is about 10 db >lower than with F1. Also, I feel that the CW sensitivity is lower. I >peaked L34 but the peak was not too sharp. Does the modification (inluding >removal of 10p), deteriorate CW sensitivity? I used BC337 instead of PN2222. kevin wrote: Finding the point of maximum signal with least noise is not an easy thing to do by ear alone. There is no sharp peak as you have found. I have a procedure for setting L34 using Spectogram but I haven't written it up yet. Its on my list of things to be done however. Hopefully soon. ++++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: Subject: RE: [Elecraft] Simple way to set L34 Date: Mon, 30 Sep 2002 18:10:36 -0700 Har... I left a word out: "I find a very definite "peak" indicated BY minimum voltage..." meaning the sought-after "peak" in the signal ... Good catch! Ron AC7AC +++++++++++++++++++ Date: Fri, 04 Oct 2002 16:01:56 +0200 From: Heyder.Family at t-online.de To: elecraft at mailman.qth.net Subject: [Elecraft] Tuning L34 on K2 - The 'Signal to Noise Ratio' method After the L34 thread popped up again, I decided to retune L34 once more, although I'm sure I did this a year ago, hi. I did almost every step in the procedure as it was suggested several times before: Nominal operational temperature, 7.0 Mc birdy, smallest CW filter, preamp on, AGC on, dummy load etc. Because I replaced R2 by a pot I measured the DC Voltage with a DMM at R4 instead. The signal behaviour must be the same there than at R2, except other levels. But since the absolute level is not so important it should be ok to have the testpoint there, both sides at R4 are ok to measure. My goal was to tune L34 for the best signal to noise ratio. (instead for simply just the biggest signal peak) When tuning in for the birdy signal (with the frequency dial) I used the smallest CW Filter setting (0.07) and the SPOT function too. When tuning out from the birdy (for pure noise measurement) I tuned the dial abt. 2 Kc off - let's say 7002.0Kc At first I tuned out from the birdy to measure the noise level over the whole tuning range of L34: I did this in small steps of 45 degrees, from L34 tuned completely out until the core was completely turned down. For each 45 degree step I noticed the according DC Voltage level in a tabel. After this I exactly tuned with the dial for the birdy at 7000.0Kc by using the SPOT function too. Then I repeated the procedure above with 45 degrees stepwise and noticed the according DC levels again in the tabel. After that was completed the tabel showed clearly the core position where the best signal to noise ratio occurred, which was simply the point with the biggest voltage difference between the signal- and the noise-level. I turned the L34 core for this required position and finally did a 'fine tune' on L34 by using the same principle. Should notice that I'm not so sure if it is really so important to be such accurate on this point here! Now my L34 core is abt. 2 turns down from the outmost position. Must say that I replaced C182 by 150 pF in earlier times. Of course if you have an o'scope the procedure to find the best signal to noise ratio will be much easier. gl + 72 de Bert DL8BDF K2 #433 +++++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: Subject: RE: [Elecraft] Tuning L34 on K2 - The 'Signal to Noise Ratio' method Date: Fri, 4 Oct 2002 08:21:25 -0700 Bert, DL8BDF, brings up a good point bout the L34 adjustment. The manual does say to tune for best "signal to noise" ratio. If the K2 tuned microwave frequencies, that would be a significant concern. Up in the VHF region and above we would be doing everything to improve the S/N ratio, since the internal noise in a receiver up on those frequencies is what limits the sensitivity - the ability to "hear" signals down at the noise level. That's not true on HF, however. Even up on 10 meters it's quite obvious that at minimum selectivity the noise being picked up by my antenna completely overwhelms any noise generated within the K2. So why the comment about setting L34 for best signal to noise rather than peak response? Ron AC7AC K2 # 1289 ++++++++++++++++++ Date: Fri, 04 Oct 2002 11:23:06 -0500 To: , From: Tom Hammond =?iso-8859-1?Q?N=D8SS?= Subject: RE: [Elecraft] Tuning L34 on K2 - The 'Signal to Noise Ratio' method Hi Ron: >Bert, DL8BDF, brings up a good point bout the L34 adjustment. The manual >does say to tune for best "signal to noise" ratio. > >If the K2 tuned microwave frequencies, that would be a significant >concern. Up in the VHF region and above we would be doing everything to >improve the S/N ratio, since the internal noise in a receiver up on >those frequencies is what limits the sensitivity - the ability to "hear" >signals down at the noise level. > >That's not true on HF, however. Even up on 10 meters it's quite obvious >that at minimum selectivity the noise being picked up by my antenna >completely overwhelms any noise generated within the K2. So why the >comment about setting L34 for best signal to noise rather than peak >response? I had the same (mental) question for quite a long time, but about 4-5 months ago I was dinking around with L34 (no recollection why), and even 'earballing' the adjustment, I did notice what I perceived to be a distinct drop in relative background at a point just inside the point of maximum received signal... maybe 1/2 turn (into the can) before reaching max signal. I was so surprised to hear it that I tried it several times, just to confirm that I was hearing what I thought I heard, and each time I noticed the same thing. So I now do believe that there was some thought behind the statement. NOTE that I have NOT (yet) performed any quantitative measurements to confirm my beliefs. 73, Tom N0SS +++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: Subject: RE: [Elecraft] Tuning L34 on K2 - The 'Signal to Noise Ratio' method Date: Fri, 4 Oct 2002 12:04:45 -0700 Tom, N0SS, wrote: ... I was dinking around with L34 (no recollection why), and even 'earballing' the adjustment, I did notice what I perceived to be a distinct drop in relative background at a point just inside the point of maximum received signal... maybe 1/2 turn (into the can) before reaching max signal. I was so surprised to hear it that I tried it several times, just to confirm that I was hearing what I thought I heard, and each time I noticed the same thing. So I now do believe that there was some thought behind the statement. NOTE that I have NOT (yet) performed any quantitative measurements to confirm my beliefs. ========== I've heard that too, but decided that it was an artifact of my hearing based on the frequency spectrum of the noise. Looking at the K2 audio spectrum I can see the noise peak produced by L34 move across the audio range as the coil is adjusted. This seems to a produce a subjective response in our ears (and in an voltmeter on the audio amplifier output) that makes the best signal-to-nose ratio appear when L34 is tuned off of its real peak. To see the effect on the background noise using Spectrogram requires me to turn the Attenuator On to put the 7 MHz birdie down near the internal noise level so I can see both the peak of the birdie signal and the noise floor on the display without driving the K2 into compression. It is important to turn the K2 AGC Off so it isn't trying to maintain an even audio output level as I make the adjustment. Then, as I adjust L34 I can see the "hump" of noise move back and forth in frequency as the spike of the "birdie" signal moves up and down in amplitude. To my ear, the background noise sounds lower when L34 is tuned to the low-frequency side of the peak. That produces the impression that the signal-to-noise ratio is better there, but it looks the same on Spectrogram. That is, the difference in dB between the signal peak of the birdie and the peak of the noise stays the same on the Spectrogram display. Only the frequency spectrum of the noise is slightly different. I found that trying to measure the "peak" with an audio voltmeter at the speaker jack produced a false peak when L34 is tuned off on the high-frequency side of the actual peak. The voltage the meter shows is the total voltage at all frequencies across the spectrum that is being amplified by the audio amp in the K2, and it appears that by detuning L34 to the "high frequency" side of the actual resonant point produces greater wide band noise for the meter to register, producing the false "peak". It seems to me that our ears, like that a-c voltmeter, are responding to a wide spectrum of noise that masks the actual "sweet spot". And, bottom, line, I can't see how that has any detectable effect on the K2's performance in the "real world" on the HF bands. These noise levels seen when doing the adjustment are WAY below what is coming in from my antenna in actual use. Still, it's a satisfying feeling to have the adjustment "peaked". Ron AC7AC K2 # 1289 +++++++++++++++++ Date: Thu, 24 Oct 2002 01:34:50 -0400 To: elecraft at mailman.qth.net From: Kevin Cozens Subject: Re: [Elecraft] Tuning L34 on K2 - Which Method? At 02:10 PM 10/03/2002 -0400, you wrote: >There appear to be several methods to tune L34. Two that I am familiar with >are: There is a third method I discovered. I have mentioned it on this list but haven't gotten around to writing down the procedure until now. You can call it method 0.5 if you like since I came up with it before method 1 and 2 you mentioned. :-) The procedure requires a computer capable of running the Spectogram program. In general, the procedure is as follows: Set up your K2 and computer as if you are getting ready to align the filters. The main difference is that you need to tune the K2 so that you can hear the birdie on the 40m band (usually found near 7MHz). Start with the slug in L34 near the top of the can. Turn the slug of L34 clockwise to lower it in to the can. As you do this you should see the strength (height of the birdie as seen on the Spectogram display) increase. Stop when you reach the point at which additional turning of the slug in L34 do not cause any further increase to the signal as seen in the Spectogram display. Turning the slug in L34 past the point at which no increase in signal strength is observed will just result in an increase in noise. It was reported on the Elecraft mailing list that the best signal to noise setting for L34 may be about 1/4 to 1/2 turn BEFORE you reach the point of maximum signal. This is not the only procedure for adjusting the slug in L34 but this should help make it easier than adjusting by ear alone. Don't forget to re-run CAL S Hi/Lo after making any adjustment to L34. Cheers! Kevin. (http://www.interlog.com/~kcozens/) Owner of Elecraft K2 #2172 |"What are we going to do today, Borg?" E-mail:kcozens at interlog dot com|"Same thing we always do, Pinkutus: Packet:ve3syb at ve3yra.#con.on.ca.na| Try to assimilate the world!" #include | -Pinkutus & the Borg +++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: Subject: RE: [Elecraft] Tuning L34 on K2 - Which Method? Date: Thu, 24 Oct 2002 10:17:03 -0700 It helps to turn the AGC OFF when doing the adjustment by measuring the audio output level. The function of the AGC is to keep the audio output constant as the signal level changes. That's exactly what you do NOT want in this case while tuning for the "peak". AGC doesn't actually prevent all change in the audio level of course, but the peak will be more apparent with it off. Ron AC7AC K2 # 1289 Kevin wrote: There is a third method I discovered. I have mentioned it on this list but haven't gotten around to writing down the procedure until now. You can call it method 0.5 if you like since I came up with it before method 1 and 2 you mentioned. :-) -- snip -- +++++++++++++++