sidetone mod now works
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The sidetone mod by TF3MA was installed in my K2 right after Marti posted
it. I obtained a 47 mh inductor for this mod from Elecraft. The mod resulted in an improved sidetone, but left room for further improvement, especially at lower tones. Additionally there was an objectionable pin-prick sound at the make of the muting that was annoying to hear. Recently I decided to revisit this situation. I noticed in Marti's write-up that HIS 47 mh inductor had an internal resistance of 180 ohms. With the K2 apart, I measured the inductor I had received from Elecraft and sure enough, it had an internal resistance of only 40 ohms. This would entirely change the frequency response Marti's peaking high-pass filter. Elecraft is apparently using an 82 mh inductor in its mod, I obtained that, and found it has an internal resistance of 60 ohms which would seem to offer less than an ideal result. I put a 150 ohm resistor in series with the 47 mh / 40 ohm inductor originally used when I modified the radio some years ago. Folks, the difference is DRAMATIC !!! The sidetone is louder, clear, and is that way across its entire range from 400 to 800 cycles. Not only that, the tone is so much stronger that the slight pin-prick click from the make of the muting line is all but completely inaudible in the strength of the sidetone and no longer objectionable. A big thank you to Marti and to W3FPR who both stayed with me through my frustration trying to make this thing right. For a while they must have thought my hearing was the main problem because the radio seemed to have the right modifications in it to sound well. Maybe this will be helpful information for others. 73, Fred KT5X _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: sidetone mod now works
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I am curious about doing this sidetone mod on a K2 rev B. Elecraft changed the
sidetone circuit from serial number 3000 on, and wonder how effective the sidetone mod is on a rev B K2. My K2 is serial # 5093. The mod is described at http://www.raunvis.hi.is/%7Ematti/TF3MA/sidetone_tf3ma.html >From the schematic diagram it looks like L1 82mH is removed and inserted between U10 pin 7 and C33. A new capacitor is then installed at the old L1 position. From the charts on the mod page it looks like about 1 uF would be about right. My L1 82 mH inductor has a DC resistance of 62 ohms. This is quite different from the 180 ohm version used in the mod. Would a series resistor be desired as Fred indicates in the message below? I have 100 ohm, 120 ohm, and 150 ohm resistors on hand. Where is this resistor installed between U10 pin 7 and the inductor or between the inductor and C33? What type of capacitor would be best suited for this mod? My junk box only has 1 uF 100 V 5% metallized polyester or 2.2 uF 16 V 10% dipped tantalum capacitors. The polyester caps are rather large. A couple of the 2.2s in series would be 1.1 uF. Comments and recommendations? Darrell VA7TO K2#5093 On November 15, 2006 06:04 am, [hidden email] wrote: > The sidetone mod by TF3MA was installed in my K2 right after Marti posted > it. I obtained a 47 mh inductor for this mod from Elecraft. The mod > resulted in an improved sidetone, but left room for further improvement, > especially at lower tones. Additionally there was an objectionable > pin-prick sound at the make of the muting that was annoying to hear. > > Recently I decided to revisit this situation. > > I noticed in Marti's write-up that HIS 47 mh inductor had an internal > resistance of 180 ohms. With the K2 apart, I measured the inductor I had > received from Elecraft and sure enough, it had an internal resistance of > only 40 ohms. This would entirely change the frequency response Marti's > peaking high-pass filter. Elecraft is apparently using an 82 mh inductor > in its mod, I obtained that, and found it has an internal resistance of 60 > ohms which would seem to offer less than an ideal result. > > I put a 150 ohm resistor in series with the 47 mh / 40 ohm inductor > originally used when I modified the radio some years ago. Folks, the > difference is DRAMATIC !!! The sidetone is louder, clear, and is that way > across its entire range from 400 to 800 cycles. Not only that, the tone is > so much stronger that the slight pin-prick click from the make of the > muting line is all but completely inaudible in the strength of the sidetone > and no longer objectionable. > > A big thank you to Marti and to W3FPR who both stayed with me through my > frustration trying to make this thing right. For a while they must have > thought my hearing was the main problem because the radio seemed to have > the right modifications in it to sound well. > > Maybe this will be helpful information for others. > > 73, Fred KT5X -- Darrell Bellerive Amateur Radio Stations VA7TO and VE7CLA Grand Forks, British Columbia, Canada _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Cloud Runner-3
> My L1 82 mH inductor has a DC resistance of 62 ohms. This is quite
different > from the 180 ohm version used in the mod. Would a series resistor be desired > as Fred indicates in the message below? I have 100 ohm, 120 ohm, and 150 ohm > resistors on hand. Where is this resistor installed between U10 pin 7 and the > inductor or between the inductor and C33? > What type of capacitor would be best suited for this mod? My junk box only has > 1 uF 100 V 5% metallized polyester or 2.2 uF 16 V 10% dipped tantalum > capacitors. The polyester caps are rather large. A couple of the 2.2s in > series would be 1.1 uF. Darrell, I did the TF3MA sidetone mod some months ago on my K2 serial #2198 and I am very pleased with it. See my comments on http://www.ac6rm.net/mailarchive/html/elecraft-list/2006-12/msg01043.html where I wrote that "This mod really works wonders with the sidetone quality of the K2". I had done the sidetone upgrade to the 3000+ model previously, but this latest change still was very worthwhile doing. You should add series resistance to the inductor. If I understand your question right, the order, L+R or R+L, doesn't make any difference. I would try the 120 ohm resistor giving you a total of 120+62 = 182 ohms. Maybe the size I would probably have tried with the series combination of two 2.2 uF tantalum capacitors in order to avoid putting the large 1 uF capacitor in there. 73 Sverre LA3ZA Unofficial Guide to K2 Modifications http://www.qslnet.de/member/la3za/K2/mod.html -- I am using the free version of SPAMfighter for private users. It has removed 7471 spam emails to date. Paying users do not have this message in their emails. Get the free SPAMfighter here: http://www.spamfighter.com/len _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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I did the mod recently on my K2/100 serial 5545. It made a big
difference and now the sidetone is much more relaxing to listen to. I didn't enjoy txing on the K2 before this. This is what I did : 1 - Remove L1 and C33 2 - Solder a 2.2uF in place of L1 3 - Cut a small piece of holed circuit board to 23mm x 10mm 4 - Mount L1, a 120 ohm resistor and a 0.68uF capacitor on the board 5 - Cut appropriate tracks so that a series network is formed 6 - Solder two lengths of bare solid wire 1.5cms long to the board, coming out of the component side 7 - Solder the board into C33 holes, so that the components are facing the control board. This allows two things. One is that there is no track to cut and the other is that you can adjust the components on the small board easily if required I check before and after using Spectrogram and the sidetone harmonics have definitely been reduced. Chris G3SJJ Sverre Holm wrote: >> My L1 82 mH inductor has a DC resistance of 62 ohms. This is quite different from the 180 ohm version used in the mod. Would a series resistor be desired as Fred indicates in the message below? I have 100 ohm, 120 ohm, and 150 ohm resistors on hand. Where is this resistor installed between U10 pin 7 and the inductor or between the inductor and C33? What type of capacitor would be best suited for this mod? My junk box only has 1 uF 100 V 5% metallized polyester or 2.2 uF 16 V 10% dipped tantalum capacitors. The polyester caps are rather large. A couple of the 2.2s in series would be 1.1 uF. >> >> Darrell, >> >> I did the TF3MA sidetone mod some months ago on my K2 serial #2198 and I am >> very pleased with it. See my comments on >> http://www.ac6rm.net/mailarchive/html/elecraft-list/2006-12/msg01043.html >> where I wrote that "This mod really works wonders with the sidetone quality >> of the K2". I had done the sidetone upgrade to the 3000+ model previously, >> but this latest change still was very worthwhile doing. >> >> You should add series resistance to the inductor. If I understand your >> question right, the order, L+R or R+L, doesn't make any difference. I would >> try the 120 ohm resistor giving you a total of 120+62 = 182 ohms. Maybe the >> size >> >> I would probably have tried with the series combination of two 2.2 uF >> tantalum capacitors in order to avoid putting the large 1 uF capacitor in >> there. >> >> >> >> 73 >> >> Sverre >> LA3ZA >> >> Unofficial Guide to K2 Modifications >> http://www.qslnet.de/member/la3za/K2/mod.html >> >> Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: sidetone mod now works
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In reply to this post by Sverre Holm-2
I played a bit with this mod this evening. I can duplicate the results, but
I'd like to understand a bit more about this circuit. What is the purpose of RP5 pins 7/8 and pins 9/10? This grounds the audio signal via 940 ohms of resistance. Is this just to provide a DC bias for the electrolytic capacitors or does it have a role to play with the audio? -- Darrell Bellerive Amateur Radio Stations VA7TO and VE7CLA Grand Forks, British Columbia, Canada _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: sidetone mod now works (RP5, etc., explained)
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Darrell Bellerive wrote:
> I played a bit with this mod this evening. I can duplicate the > results, but > I'd like to understand a bit more about this circuit. > > What is the purpose of RP5 pins 7/8 and pins 9/10? This grounds the > audio > signal via 940 ohms of resistance. Is this just to provide a DC bias > for the > electrolytic capacitors or does it have a role to play with the audio? > Hi Darrell, There's some subtlety to this circuit. Among the various goals was to minimize component count. C32, on pin 8 of U9, is the AF amp's supply decoupling capacitor. It would normally be returned to ground, as shown in any LM380 datasheet. However, we played a trick here, using pin 8 as the sidetone injection point. In other words, we're treating pin 8 as a low-gain, single-ended third input to the amplifier. But C32 still needs a ground return path so it can perform its supply decoupling function reasonably well. L1, which is part of the sidetone shaping circuit, serves the ground-return function at low audio frequencies, but as F increases, the Z of the inductor does, too. This is where RP5 comes in. We had a couple of RP5 sections left over, so we put them in series to form about a 1K resistor that establishes a minimum ground-return impedance, ensuring stability of the AF amp's internal biasing. Of course this resistor also reduces the Q of L1, but not enough to impact its shaping function. We could have injected the sidetone at the amplifier's differential inputs, but doing this right (without AF artifacts) requires differential drive, e.g. more parts. 73, Wayne N6KR --- http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Bob Pease would be proud!!!
That is a really cool application - not to mention you taking time to explain it. 73s, Pete > > From: wayne burdick <[hidden email]> > Date: 2007/03/10 Sat AM 12:03:56 CST > To: [hidden email] > CC: [hidden email] > Subject: [Elecraft] Re: sidetone mod now works (RP5, etc., explained) > There's some subtlety to this circuit. Among the various goals was to > minimize component count. > > C32, on pin 8 of U9, is the AF amp's supply decoupling capacitor. It > would normally be returned to ground, as shown in any LM380 datasheet. > However, we played a trick here, using pin 8 as the sidetone injection > point. In other words, we're treating pin 8 as a low-gain, single-ended > third input to the amplifier. > 73, > Wayne > N6KR > > > --- > > http://www.elecraft.com > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > Pete Axson WD4LST 17901 NE 18th Ave Citra, FL 32113 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Sverre Holm-2
I did this mod yesterday to my S/N 4119 and am documenting it primarily for the parts number info. My unit had the REV B Control Board with the mod previously implemented by Elecraft (addition of 82 mH L1 across RP5 pins 7 and 10). The following applies only to REV B boards:
1. Remove L1 and insert a 2.2uF *non-polarized* capacitor in the same holes. I used a NICHION UVP1H2R2MDD1TD which fit nicely in the space for L1. I had to search for a suitable non-polarized capacitor so hopefully this will save time for others. 2. Cut the trace between C33 and C35. Check with a meter to make sure it's open. 3. Tack solder a 47 mH MURATA 22R476C between the pads for C33 and C35 (where the connecting trace was cut). This part is specified with internal resistance of 169 ohms which is key to the mod working properly (see below). I had to search quite a few different parts to find one with high internal resistance. 4. Lay the inductor on its side and be sure it is out of the way of the screw hole/standoff that attaches the Control Board. My K2 now has a very pure sidetone which will make zero beating much easier without harmonic distortion. 73, Bill W4ZV
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