++++++++++++++++++++++ Date: Fri, 18 Jan 2002 13:56:33 -0800 From: Jay Hanawalt To: Dan Barker , Elecraft list Subject: Re: [Elecraft] This thing rocks! Dan- Try: http://www.elecraft.com/Apps/sinewave_sidetone_mod.htm The wheel has already be invented! -Jay, WB6SZE ++++++++++++++++++++++ Date: Fri, 18 Jan 2002 10:44:48 -0600 To: "Dan Barker" , elecraft@mailman.qth.net From: Tom Hammond =?iso-8859-1?Q?N=D8SS?= Subject: Re: [Elecraft] This thing rocks! Dan: >One bitch is the sidetone is ugly. Anyone got a cleanup for the nasty >harmonics on the sidetone? It's hard to zero-beat if it's not a clean tone. This one works... note that even if you don't have the EXACT values... even something relatively close will work. THANKS to Randy Hargenrader, WJ4P, for this one! From: "Randy Hargenrader" To: Subject: [Elecraft] SINEWAVE SIDETONE Date: Sat, 26 Feb 2000 02:26:53 -0500 K2'ers, Tonite I finally cracked the sidetone "nut"! I now have a pure sinewave from the sidetone circuit working in serial numbers 183 and 661. It's VERY easy. Here's the modification to the control board... 1) Add a 47 K ohm resistor to the position of C24, a .0027uF capacitor. Pull up one side of C24. It doesn't matter which side. I had to completely remove it first then extend one lead out from the body of the capacitor so that it would have one lead in a hole and one lead up in the air for a "flying connection". Add the 47K ohm resistor to the other hole, also standing on end. Tack solder the top of the 47K ohm resistor to the "top" lead of C24, making a "flying" connection. Note: If the only modification you make is to add the 47K resistor, the tone will smooth out enough that you WILL notice a difference (for the better) but the tone will not be a clean sine wave. The next step will give the sine wave. 2) Make sure C33 is a 2.2uF electrolytic capacitor. (If you made the previous modifications to the sidetone I suggested some time ago, you might want to use these new values.) Solder a 47mH inductor across pins 7 and 10 of RP5. Do not remove RP5, and there is no need to cut any traces. Just tack solder the 47mH inductor across pins 7 and 10 of RP5. Note: For those of you who prefer to run low frequency sidetones, the sidetone begins to become slightly distorted below 530Hz and loses the nice sinewave shape below that. To compensate, use a 4.7uF cap at C33 or tack a 2.2uF cap across it on the back of the board. The higher frequency side-tones will be nice but at a slightly lower amplitude which isnt really a problem since you can reset the level at will. Your done! Put your K2 back together and start enjoying the sweet sound of a sine wave sidetone! BTW, miniature 47mH chokes are available from Mouser Electronics - part number: 434-03-473J, at 800 346 6873. Approximate cost $1.36 each. Usual disclaimers... 72, Randy WJ4P 73 - Tom Hammond N0SS ++++++++++++++++ From: "Don Brown" To: "Kevin Cozens" , "Elecraft" Subject: Re: [Elecraft] Question re: sinewave sidetone modification Date: Sat, 2 Nov 2002 21:56:49 -0600 Hi The resistor is not a pull up it's in series with c24. You remove one sid= e of the cap and add the resistor from the board to the cap lead soldered= in the air. The R/C network helps to round of the square wave that cones= out of the DAC. The inductor finishes the job. =20 Don Brown KD5NDB ----- Original Message ----- From: Kevin Cozens Sent: Saturday, November 02, 2002 9:11 PM To: elecraft@mailman.qth.net Subject: [Elecraft] Question re: sinewave sidetone modification Greetings, all. I have a question about the WJ4P sinewave sidetone mod. The first part of= =20 the mod says to add a pull-up resistor to one side of C24. In the K2 manu= al =20 (Revision C) the schematic shows there is a pull-up consisting of RP7 (pi= ns =20 7 and 8) to 5A. Is an additional 47k resistor required or only the =20 inductor? The LA3ZA list of mods and the WJ4P page that provides details = on =20 the mod don't make it clear what serial numbers either require or could =20 benefit from making this mod. Cheers! Kevin. (http://www.interlog.com/~kcozens/) Owner of Elecraft K2 #2172 ++++++++++++++++ From: "Mike Harris" To: Date: Mon, 11 Nov 2002 18:09:51 -0200 Subject: [Elecraft] Sinewave Sidetone Mod Hi, One of the tasks completed this weekend was the installation of the 47k ohm part of the sidetone mod. The resistor was added without trouble and done with care can look neat and tidy. Before I did the mod I took a spectrum of the sidetone using the inevitable Spectogram under the following conditions: K2 audio source - KPA100 external speaker socket AF and RF gain fully CCW "Spot" activated - 700Hz tone. The tone was set to 40dB on the Spectogram (v7) display, K2 StL level set to 012. Before: 700Hz 40dB (reference) all other readings relative to 40dB 1400Hz -23.9dB 2100Hz -23.8dB 2800Hz -36.1dB 3500Hz -32.8dB After: 700Hz 40.0dB 1400Hz -31.1dB 2100Hz -26.7dB 2800Hz better than -40dB 3500Hz -38.3dB The sidetone is audibly cleaner and a beat with the 28MHz birdie was much easier to hear. Not a bad improvement for one resistor. I didn't fit the inductor 'cos I haven't got one. Regards, Mike VP8NO (IOTA SA-002) K2/100 #1400 ++++++++++++++++ Date: Mon, 11 Nov 2002 14:35:55 -0800 From: Wayne Burdick Organization: Elecraft To: Mike Harris Cc: Elecraft@mailman.qth.net Subject: Re: [Elecraft] Sinewave Sidetone Mod Mike Harris wrote: > > Hi, > > One of the tasks completed this weekend was the installation of the 47k ohm > part of the sidetone mod... Hi Mike, Both the resistor and the inductor are included in the updated K2 kit, and there will be an "official" mod kit for this available in a couple of weeks. The sidetone sounds much cleaner with the inductor included. 73, Wayne N6KR ++++++++++++++ From: Marteinn Sverrisson Date: Mon, 18 Nov 2002 10:18:39 +0000 To: elecraft@mailman.qth.net Subject: [Elecraft] Improved sidetone Improved Sidetone in K2... I have not been satisfied with the sound of the current side-tone in my K2. I have done the side-tone mod, using a 47mH choke. Looking at the circuit it is a High-Pass filter with some peaking in the 600Hz region but it does not attenuate the higher order harmonics of the side-tone. Why not make a Low-Pass filter using the same choke? I moved the 47mH choke (rs=180 Ohm) in series with C33 (the 2.2uF cap) and put a new 2.2uF cap across Rp5 pins 7 and 10, making a genuine LP filter. The internal resistance rs of the choke controls the Q of the filter. This makes a huge improvement of the side-tone sound, now it is soft and sweet :-). To make the mod I had to cut the trace from C33 leading to U10, I cut it next to C33 and inserted the choke across the gap, soldered it to the C33 pad and the pad for C35, this is done on the underside of the Control Board. Then solder a small 2.2uF cap between pins 7 and 10 on Rp5. Here are measurements of the side-tone harmonics before and after. The harsh sidetone is now gone and instead a softer tone is now generated, almost a pure sinewave. Side-tone at F0=600Hz, reference level 0dB. Before After 600Hz F0=0dB F0=0db 1200Hz F1=-16dB F1=-42dB 1800Hz F2=-27dB F2=-42dB 2400Hz F3=-54dB F3=-70dB 3000Hz F4=-47dB F4=-70dB Higher order harmonics not visible on the spectrum, with the new LP filter. Measurements done with "baudline" program running on Linux. 73's TF3MA ++++++++++++++++ To: elecraft@mailman.qth.net Date: Tue, 19 Nov 2002 15:09:49 -0500 Subject: Fw: Re: [Elecraft] side tone Mod From: Gilbert J Cross --------- Forwarded message ---------- From: Gilbert J Cross To: matti@raunvis.hi.is Date: Tue, 19 Nov 2002 14:57:01 -0500 Subject: Re: [Elecraft] sidetone -- baudline Hi, Matti. Just a line to tell you I made your side tone mod on my K2 and what a difference. It is a great mod. And I want to thank you very much for the info. 73 Gil K8EAG Tried sending this direct but mail was returned and so am putting it on the list hoping you will see this message. Thanks again Gil ++++++++++++++++ Date: Tue, 19 Nov 2002 21:36:59 +0000 From: dl1iaq@t-online.de (Martin) To: elecraft Subject: [Elecraft] Re: Improved Sidetone Hello all, just did the Sidetone-mod suggested by TF3MA. The sidetonetone really sounds much better. I didnīt have a 2.2uF cap, so I used 3.3uF. The result probably is a different low-pass-filter. There is a īplopī at the beginning of each dit and dah, will this be gone as soon as I replace the 3.3uF with 2.2uF? Martin ++++++++++++++++++ Date: Tue, 19 Nov 2002 19:09:38 -0800 From: Wayne Burdick Organization: Elecraft To: Martin Cc: elecraft Subject: [Elecraft] Re: Improved Sidetone Martin (et al), There are many ways to improve the sound of the sidetone, including the new one posted by TF3MA. The way we did it on the revision B K2, which is nearly identical to an earlier published app note, does not result in any type of "plop" or other audio artifacts. In our case we used an 82 mH inductor, the same one that we use in the KAF2. There's also a 47 k resistor involved in the mod. The quality of the resulting sidetone is excellent. The schematic of the Revision B Control board can be found in the Revision D K2 Owner's manual, posted on our manual download page. 73, Wayne N6KR +++++++++++++++ To: elecraft@mailman.qth.net Date: Fri, 22 Nov 2002 14:32:18 -0600 From: Jeremiah J McCarthy Subject: [Elecraft] Re: Elecraft digest, Vol 1 #349 - 24 msgs I just finished installing TF3MA's sidetone mod and I am very pleased with the sound...I wasn't comfortable with cutting the trace leading from C33 to U10-7, so I didn't...I had done the earlier sidetone mod and had changed C33 from 2.2mfd to 4.7mfd...While installing TF3MA's mod I wanted to change C33 back to 2.2mfd...Instead of mounting C33 in it's original position on top of the board, I mounted it on the bottom flat against the board and connected it in series with the 4.7mh choke...I soldered one lead from the choke into the "+" hole for C33 and bent the choke down against the board with it's top pointed toward the bottom edge of the board...I soldered the "+" lead of the new C33 to the other lead of the choke and soldered the negative lead of the new C33 into the negative hole in the board for C33...C33 is installed flat against the board with it's can pointing toward the top edge of the board, opposite to the choke...Then I installed a 2.2mfd cap across pins 7 and 10 of RP5 to finish the job... Thanks, Marteinn... Jerry, wa2dkg K2 # 2549 ++++++++++++++++++ From: "Dan Barker" To: "Elecraft (E-mail)" Date: Sun, 8 Dec 2002 19:21:22 -0500 Subject: [Elecraft] Sidetone mods I found the sidetone quality very annoying when my K2 first burped to life last Spring. I tossed a question on the reflector, and got directed to the "Sidetone Mod", which I performed. My sidetone got much better, but I still hear trash on the signal. Our outputs are pure sine waves, shouldn't our "inputs" be too? Months later, I saw TF3MA's post, saying in part, "I have not been satisfied with the sound of the current side-tone in my K2. I have done the side-tone mod. [...] Looking at the circuit it is a High-Pass filter. [...] Why not make a Low-Pass filter using the same choke?" His reasoning sounds good to me, because the sidetone originates as a square wave, and a square wave presents all odd harmonics when treated as an audio signal. The 1/3, 1/5, 1/9th etc. harmonics don't exist, and we want to filter the 3rd, 5th, 7th etc. out or the signal. However, his description of the modifications to a modification to a schematic from a PDF were more than I could follow. So, I decided to draw it out. Several days ago on this reflector, KO0B mentioned a PCB drawing program that was pretty slick, and free. I downloaded it, and low-and-behold, the PCB drawing program really works best if it has a schematic to go on (duh!). The (FREE I say) package came with a schematic drawing program too! And at a price I can afford, even this close to Christmas. So, I drew the Elecraft original circuit, copy/pasted it and applied the Sidetone mod, copy/pasted it and applied the TF3MA changes, and now I can see what's going on. Wayne posted a note that Elecraft had not adopted this version in the revision B K2, and I'm wondering why not. I'll wonder more after I do it myself, of course (or maybe less - doubt it). If you'd like to see the result, click http://www.visioncomm.net/images/sidetone.jpg and you can understand it too. For those of you who downloaded the Schematic software, my drawing is also available at http://www.visioncomm.net/images/K2sidetone.sch. For those of you who didn't download the PCB software, DO IT NOW! IT'S FREE! IT'S WORTH THE EFFORT. http://www.expresspcb.com/news.htm. Dan Barker / WG4S / K2 #2456 ps: No, I haven't done the KO0B mod yet, but his reported 42 db improvement sure beats the party-line 16 db improvement! I'll do it next! ++++++++++++++ Date: Sun, 08 Dec 2002 22:36:05 -0800 From: Wayne Burdick Organization: Elecraft To: Dan Barker Cc: "Elecraft (E-mail)" Subject: [Elecraft] Re: Sidetone mods Dan, The sidetone mod we used works very well, assuming you add both the resistor and the RF choke. Check the schematic in the revision D K2 manual. Many of those who have made the mod or who have used a rev B K2 have commented that it sounds very good, and it certainly is a huge improvement over the original minimal-parts audio filtering, which was provided by the op-amp. The new circuit functions like an L-C tank that resonates in the range of about 400 Hz. It looks like a high-pass filter at first glance. But since the op-amp's output impedance is quite low, the L and C function approximately as if they were in parallel. The signal is coupled into the tank at a low-Z point (the output of the op-amp), and the signal is picked off at a hi-Z point (the high side of the inductor) for injection into the AF amp. The low resonant frequency reflects our choice of inductor (82 mH, same value we use in the KAF2). It is very effective at rolling off high harmonics over the entire sidetone pitch range, although the amplitude will vary several dB depending on your selected pitch. 73, Wayne N6KR ++++++++++++++ From: "Bob - AG5Q" To: Date: Tue, 10 Dec 2002 12:46:10 -0600 Subject: [Elecraft] K1 sidetone mod The following mod has been found helpful to improve the sidetone in the K1: Lift either end of C72 (only one end). Add a 10K to 20K resistor in series with C72. One end of the cap and one end of the resistor will be sticking up in the air. No etch cutting is required. Then add a cap with a value in the range of 0.0047 to 0.01uf from RP3 pin 5 to ground. The exact values of the resistor and capacitor are not critical. This forms a low pass filter to reduce the amplitude of the harmonics from the tone circuit. This makes a noticeable improvement and it's a quick mod to implement :-) ======================== If anyone hasn't already modified their K2 sidetone, this simple mod can help it too. I put a 150K resistor in series with C24 and then placed a 0.022uf cap across RP7 pins 7 and 8. Using Spectrogram I found this reduced the 2nd harmonic by 17db and the 3rd harmonic by 11db. 73/ Bob - AG5Q +++++++++++++++ From: Eric Swartz WA6HHQ - Elecraft Organization: Elecraft To: Wilderman Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] K2 DC note modification The other operator was probably giving you a compliment. I get positive comments about my K2 CW signal almost every time I use it on the air. We designed the K2's CW TX wave form to have what we felt was an ideal rise/fall time characteristic on each dot and dash transition. This makes it sound extremely clean when someone hears your signal. I can also identify K2s on CW because I feel their characteristics are much more pleasant to listen to than most other rigs I hear. (Of course I'm a little biased.. ;^) (By the way, the mod you are referring to is to the side tone and will not impact your transmit tone. On rigs with s/n 3000 and above we added some additional parts to roll off harmonic components in the K2s CW sidetone generator, making it a little smoother to listen to when you send.) 73, Eric WA6HHQ Elecraft +++++++++++++++ Date: Sun, 5 Jan 2003 21:49:08 +0000 To: Elecraft Reflector From: David Pratt Subject: [Elecraft] K2 Improved Sidetone While I had my K2 #01583 control board out to increase the value of C42 from 10nF to 100nF as per Builder Alert #19, I decided to carry out the sidetone mod suggested by Marteinn Sverrisson TF3MA. I had already carried out the previously suggested sidetone mod by adding a 47mH choke across RP5 pins 7 and 10 and this mod did improve the sound of the K2 sidetone. The TF3MA mod involves cutting a PCB track and using the same 47mH choke in a low pass filter configuration. I reluctantly cut the track in the recommended place, repositioned the choke and fitted a 2.2uF capacitor. And, am I pleased that I did the mod? Yes I am! I am now getting a near sinewave sidetone which is very pleasing to the ear. Thank you TF3MA, your sidetone mod is highly recommended. David G4DMP +++++++++++++++++