+++++++++++++++++++++++++ See also K2 CW Filter Mods +++++++++++++++++++++++++ Date: Fri, 08 Jun 2001 12:10:29 -0500 From: "George, W5YR" Subject: Re: [Elecraft] Mod to K2 CW Filter To Improve Rejection Depends upon what you are doing with the program, etc., John. For example, 6.0.8 has Peak Hold which is invaluable for some applications and unneeded for others. There are a number of other differences - but again their merit depends upon what you are using the program for and how you are using it. Used properly, you should NOT get different results with the various program releases for the same input data. What you *do* get is an increased feature set with added capabilities. SpectroGram now compares, within its capabilities, very favorably with SpectraPLUS which is a multi-hundred$$$ commercial program. Previous to 6.0.8. this was not the case. 72/73, George W5YR - the Yellow Rose of Texas QRP-L 1373 NETXQRP 6 Fairview, TX 30 mi NE of Dallas in Collin county EM13qe Amateur Radio W5YR, in the 55th year and it just keeps getting better! Icom IC-756PRO #02121 Kachina #91900556 IC-765 #02437 "John Grebenkemper, KI6WX" wrote: > > I used both versions 6.0.8 and 5.1.6 and found no difference in their > performance and results. I'm not convinced that it makes any difference > which version you use. If someone has a definitive comparison of both > versions getting different results with the same input, I'd be very > interested in hearing about it. > -John > KI6WX +++++++++++++++++++++++++ Date: Sat, 15 Sep 2001 13:02:55 -1000 From: John Buck Subject: [Elecraft] KAF2 comments and Test of CW Filter Rejection Mod. per KO0B/KI8WX Finished the KAF2. It tuned as advertised and really does a good job eliminating residual noise outside the desired passband. This filter is a must have for both CW and SSB modes. The listeners noise fatigue is greatly reduced. While I had the system open I decided to incorporate the KO0B/KI8WX shielding suggestions to improve the basic CW filter. K2 #1242 has all currently available options and significant mods, such as XFIL, Sine sidetone and PSK 31 installed. I made the best measurements I could using Spectrogram 6.2.3 The measurement system had a 70db below signal capability using the 90 db range. No Spectrogram or receiver setting changes (except for filter selection) were made during the modification and test process. I used a broadband noise generator as the signal source. Careful measurements were made three times: 1. Before modification; 2. After the crystal ground wires were modified by soldering to the side of the cans; 3. After the addition of the .1uf surface mount capacitors per KI6WX with the Gull Wing shield wires per KO0B. I printed the Display plots for each of the 3 measurements for each of the four filter settings. OP1, 700Hz, 400Hz and 100Hz. FL2, 3, and 4 are centered on 750Hz sidetone choice. When the plots were overlayed using a light box so I could see any differences, the following the conclusions were reached. A. There was no harm of any type due the the changes. I did not see any evidence of the slight broadening of the top of the filter response curve reported by one of the authors. In all cases, each sucessive plot coincided with or fit within the previous plot. B. As expected, the FL1 OP1 filter showed no significant changes. (KSB2 installed) C. The FL2 700 Hz filter shows 2 to 3 db improvement in the 1500 to 2000Hz area. Almost all of the improvement is from the crystal can grounding change. No effect from the gull wing and capacitor additions is seen. D. The FL3 400 Hz filter also shows 2 to 3 db improvement in the 2000Hz area with noticable improvement starting in the 1000Hz region. The gull wing plot is almost identical to the grounding plot but there is a db or so in the 2000Hz area. E. The FL4 100 Hz filter shows about 5 db in the 1800/2000Hz region. About 2 db is due to the gull wing mod. About 1 db overall improvement starts as close as 1000 Hz. Was it worth it? Probably. My K2 now has even better close in rejection of strong signals than before. Knocking down a signal 400 Hz above the center of my filter by another db or two or a signal 1000 Hz higher by 5db could make a real difference. Then I can turn on the KAF2 audio filter for even more help! Who said that K2 does not have bells and whistles? I have .jpg files of the plots on my system if someone really wants to analyze my data. I did not make the .txt spreadsheet readable files however. I freshly downloaded Spectrogram for this effort and did not discover that feature until I was almost done. Aloha, John KH7T +++++++++++++++++++++++++ Date: Sun, 16 Sep 2001 20:09:10 -0700 From: Vic Rosenthal Subject: Re: [Elecraft] KI6WX/KO0B filter mod "David A. Belsley" wrote: > > (A) Does this > really make any difference in the effect of the filter? and (B) is there > greater danger in soldering to the side of the case? I soldered mine at the bottom, and it seemed to me that you would have to be a real klutz to heat it up enough to damage the seal. Just to be sure, I did it this way: 1) Polished up the place I was going to solder to with a relay burnishing tool, 2) Tinned the wire and the crystal, and then 3) Soldered it quickly with a clean, hot iron. I don't know if it makes a difference in performance, since I didn't try it the other way. But it seems to me that it will make a big difference in the reactance of the path to ground, so if this is what you are trying to achieve, then shorter is better. I also pushed the varactor diodes all the way down to the board, and the mod made a big difference in filter blowby. 73, Vic, K2VCO Fresno CA +++++++++++++++++++++++++ Date: Mon, 17 Sep 2001 15:39:12 -0600 From: "Ferguson, Kevin" Subject: [Elecraft] re. CW Filter Rejection Mod. per KO0b/KI8WX et al Here is the complete article on the mod. http://www.rt66.com/~hypoxic/K2stuff/ultreject.html There are functional links to many of the pro and con comments, and also some test data. I like the dead quiet performance between signals. The mod may slightly increase the insertion loss of the filter...I don't recall if any of those resuldts made it into the comment files. since the article was written, I modified my rig to ground all the crystals at the base of the can, on both sides...I also grounded the cans on the SSB adapter and the 2nd xtal filter as close to the board as possible. This made a slight improvement, but nothing like the origional work. 73, ko0b ++++++++++++++++++++++++ Date: Tue, 18 Sep 2001 09:07:24 -0500 From: "Timothy A. Raymer" Subject: Re: [Elecraft] Test of CW Filter Rejection Mod. per KO0b/KI8WX et al Sverre, I have discussed that with several people in person and via e-mail, and the general agreement is that you reach a point of diminishing returns at some point in time. I however, being a stubborn purist at heart, am planning to find out. I have my K2 ready to test each modification, each step of the way, to see if it can be quantified how much change the mods make. In the following, the crystal designations I am referring to are from the schematic for the K2 RF Board Rev B, dated 4/12/2001. In general, I have to agree with those I have discussed this with. The problem with coupling in the main filter was primarily to do with coupling through the filter stages from the cans. X7-X11 are unique in there placement and coupling into the radio. Changing the way the cans of those units are grounded has a profound effect on how the K2 performs. In addition to the grounding changes recommended by KI6WX or KO0B, the bypass capacitors discussed, as well as the additional shielding with the leads proposed by KO0B, has some additional help. In reviewing the information, and the letters posted, the KI6WX mod may be the simplest approach to improvement. John said it best in his documentation: >The basic modification improves the crystal grounding with a change >that should take 5-10 minutes. A second change improves the bypassing to >the varactor bias circuit using chip caps, but there is no proof that this >change makes any further improvement and most people should skip doing it. What grounding X6 and X5 in the 2nd XTAL Filter, along with the grounding or X3 and X4 in the BFO section, is much more subtle, and not as clearly documented or explored. If you refer to the schematic, C182 and C180 are both components involved with being removed or altered in the assembly of the radio. These components, along with and X6 and X5 and the famously strange L34, couple the output of the IF Amp int the Product Dect. stage of the radio. Changing the grounding of X6 and X5 COULD have some impact on the shape of the bandpass of the radio, or the tuning of L34. In an ideal configuration, L34 would tune closer to the middle of its range, and the bandpass of all the filters would be Razor flat on the top of the filter bandpass curve. Many of the changes that diddling with C182 and C180 were for was to improve the shape of the bandpass filter. In theory, changing X6 and X5 could improve both as well. X3 and X4 in the BFO PROBABLY won't be changed much, but a better coupling of their shield with a shorter ground connection may alter the noise floor of the radio, or make a stage work just a bit better. IN sum, and to be sure I answered your question: Maybe! If you are able to use Spectrogram in the procedure documented in the KI6WX mods, let me know what your results are. I will do the same, and we will see what we find. Tim Raymer K2 #1383 At 23:13 09/17/01 +0200, Sverre Holm \(LA3ZA\) wrote: >Both of the filter mods refer to better grounding and shielding of X1-X5. >Is there any point in doing something similar to the second IF filter, X6 >and X7? > >Just wondering. > >Sverre > >LA3ZA, Oslo, Norway. Timothy A. Raymer Missouri Department of Health and Senior Services +++++++++++++++ Date: Thu, 28 Feb 2002 12:52:59 -0800 From: Vic Rosenthal Organization: Transparent Software To: Mark Rozmilowski Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] filtering Mark Rozmilowski wrote: > > I like my K2 very much. However we must be objective. There is a problem with filter "blow by" > when you tune off very strong signal and this takes place on CW and SSB. I consider this a major > problem, > which we should try to eliminate perhaps with help from Eric or Wayne. See for a simple mod reduced leakage around the filter IN MY K2 to a negligible amount. 73, Vic, K2VCO Fresno CA +++++++++++++++++++ Reply-To: "Ron D'Eau Claire" From: "Ron D'Eau Claire" To: "Elecraft-list" Subject: Re: [Elecraft] RFI: KI6WX K2 XTAL filter mod Date: Sat, 8 Jun 2002 18:14:50 -0700 > I can't seem to find this on the Elecraft site lately. Has it fallen > from grace? > > 73, Rod N0RC You can find the mod on the Elecraft WEB site under Builder's Resources, Modifications, "2nd Stage Xfil Mod for a Flatter SSB Response." As for its value, I questioned Wayne about that recently and here's what he replied: "Let me be unequivocal on this, as I always have: the 2nd XFIL mod makes a HUGE improvement in USB/LSB matching, and simultaneously allows L34 to be set close to its optimal CW setting. "I strongly recommend that everyone make the mod. It is so important that I will be adding it to the K2 RF board the next time it is revised.." Ron AC7AC K2 # 1289 ++++++++++++++++++++ From: "Rod N0RC" To: "Elecraft-list" Subject: Re: [Elecraft] RFI: KI6WX K2 XTAL filter mod Date: Sun, 9 Jun 2002 06:08:05 -0600 Thanks to all for help and assistance. I have located the article. Turns out it was NOT on Elecraft's site, it WAS on John's site: http://home.pacbell.net/johngreb/KI6WX.html 73, Rod N0RC ----- Original Message ----- From: "Rod N0RC" To: "Elecraft-list" Sent: Saturday, June 08, 2002 6:12 PM Subject: [Elecraft] RFI: KI6WX K2 XTAL filter mod > Folks, > > I can't seem to find this on the Elecraft site lately. Has it fallen > from grace? ++++++++++++++++++++ From: "Don Brown" To: "Elecraft" Subject: Re: [Elecraft] K2 CW Filter Grounding mod... Date: Wed, 11 Sep 2002 09:17:42 -0500 Hi I have built several K2's and I ground the crystal cans by soldering the = wire to the board then running the wires up both sides close to the can a= nd flowing solder quickly on the side of the can. I solder only one side = of each can, allow them to cool then solder the other side. Any excess wi= re is then clipped flush with the top of the can so as to not interfere w= ith the SSB module. This technique seems to work for me. As was stated in= the original mod description adding the shield wires to the bottom of th= e board and chip bypass capacitors do not really help all that much so I = don't do that part of the mod. The mod does work and it's effect is measurable with Spectrogram so I thi= nk it is worthwhile to do. Elecraft has not approved it probably because = of the possibility of damage to the crystals. If you are careful (and qui= ck) you can do the mod safely. You can always buy another set of crystals= if you screw it up. I have never had a problem with it and I have built = 4 K2's and 3 K1's using the same method. =20 I have seen crystals with grounding wires spot welded to their cans as an= option from the manufacturer. Maybe Elecraft could look into obtaining t= his type of crystal and then we would not have to risk damaging a crystal= by overheating it. =20 All of the other mods should be done after the radio is completed except = this one. It is much easier to do this mod when building the radio than g= oing back and reheating and moving the wires (much safer for the crystals= also) Don Brown KD5NDB ----- Original Message ----- From: Tom HammondN=D8SS Sent: Wednesday, September 11, 2002 8:28 AM To: George, W5YR; elecraft at mailman.qth.net Subject: [Elecraft] K2 CW Filter Grounding mod... Sorry folks, last message carried an INappropriate Subject line. Trying again... _____________________ GM George: At 12:05 AM 9/11/02, you wrote: >Is the delta improvement obtained from grounding at the base instead of = the >top due to the lowered inductance of the shorting wires? And/or their >parasitic capacitance to other circuit components? I cannot knowledgeably answer this. However, I suspect that it it due to =20 the added lead length, which would tend to imply the first of your two =20 choices, above. >Is it acceptable to ground the crystal cases both at the top and the >bottom? If you ground on both sides of the xtal can, as suggested, I don't think =20 there'll be any additional available holes for grounding at the top as we= ll. >Would there be any merit to fashioning some sort of shield can around th= e >filter components? I believe I recall that this has been tried and found to be lacking. >Getting a K2 in a few days and this mod seems to be of such importance t= hat >I want to do it right . . . Were it me, I'd follow the grounding at the bottom recommendations and be= =20 done with it. 73, Tom N0SS +++++++++++++++++++ Reply-To: "Indy" From: "Indy" To: Date: Fri, 14 Mar 2003 21:33:14 -0700 Subject: [Elecraft] crystal grounding How i DID it!!! by young Frankenstein ;-) Your mission, ground them twice with the thickest and shortest wire = possible while not destroying the crystal in the process. this is how I = did it, no guarantees if anyone else were to do it... no vises, no fancy = tools, just a little thought 1) 600 grit sand paper, sanded the side of the crystals. i did not tin = them. Once scruffed up they tin instantly anyway. 2) soldered vertical bare wires in the circuit board ground holes 3) soldered crystals in place on circuit board 4) pushed top of wire toward crystal until it touched, but it won't = stay against the crystal, springs back a little 5) slid screw driver down wire from the top, while pushing it against = crystal, now it stays in contact with the crystal. made sure that the = grounding wire on the SSB board side is at least an eighth of an inch = down from the top of the crystal, then it won't interfere with SSB board 6) solder the top of the wire to the crystal 7) then, in one swift motion, draw iron and solder down the side of the = crystal along wire and off of it. iron is in contact low on the crystal = for tenths of a second at most. grounding wire ends up well shorter than a quarter of an inch. this is a high point of the entire build. My filter skirts are straight = down to the noise floor, no convex dish at all, and thank you to the two = engineers who pioneered this approach to get rid of the blow-by, KI6WX = and the other was Kevin, but I forget his call, thank you guys for so = improving the performance of these filters! they deserve the credit GL Fred KT5X W5YA/qrp K2 # 700 ++++++++++++++++++++