+++++++++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: "ZOOM" , "Elecraft" Subject: RE: [Elecraft] Audio Improvements on a K2 Date: Sat, 13 Apr 2002 12:35:57 -0700 Robert, VE3RPF wrote: > I really like my K2 but would like to improve on the SSB audio. My K2 is > unmodified and I would like to hear from the list which improvements you > have made to make the K2 sound better in SSB reception. I have done the > spectrogram and my K2 has all the options except the RS232 option. I know > there are several mods out there for this rig but I only want to > do the ones > that are essential to improve audio. For good RECEIVE audio, the "2nd Filter Flattening Mod" shown under Builder's Resources is ESSENTIAL and recommended by Elecraft. According to Wayne, it is due to become a part of the basic K2 when they next revise the r-f board. Without this mod, a tilt in the bandpass of the 2nd i-f filter (this is the "cleanup filter at the output of the i-f amp) emphasizes the low frequencies on one sideband, making it sound bassy or 'muddy', and emphasizes the high frequencies on the other sideband, making it sound 'tinny'. The mod greatly flattens the 'tilt' in the bandpass, providing consistent good quality on both sidebands. Note that this mod affects RECEIVED audio only. > > My second question is that i am using a radioshack mike and am told my > transmit audio is too much on the high side. What mike seems to work well > with the K2 and give a nice signal? Although I do not do a LOT of SSB work, I have gotten a number of excellent audio reports with my Radio Shack 21-1172D microphone. I have also heard K2's with GHASTLY audio quality, including some using the Elecraft Heil Microphone. I suspect that your problem, like theirs, is in the transmit filter alignment. First of all, be SURE you have the OPT1 filters set up as instructed by Elecraft. If you are going to deviate from their instructions at all for the OPT1 filters (e.g. use Spectrogram, etc.), be sure that you check your own audio quality after you tinker with them. The OPT1 filters are the ones used for transmitting, regardless of which filter you have selected for receive. If you want to change the filter setup for receive to better suit your preference in listening, change one of the filters other than OPT1 and leave OPT1 as specified by Elecraft. As you will see in the SSB module setup instructions, Elecraft suggests that TINY changes in the BFO frequency might be made in the OPT1 filter to get the best quality. But these should only be done if you can check your audio quality after you have done it. I checked my audio quality by hooking my K2 to a dummy load, and then tuning in my signal on a second receiver. If you listen to yourself talk while listening to the second receiver in your headphones, you can tell when you have the auxiliary receiver exactly on frequency. Then hook up a tape recorder and RECORD some of your audio on the auxiliary receiver and play it back to assess its quality. It is not possible to hear what your audio really sounds like when talking and listening in the phones. Audio, particularly the bass range, conducts through the bones of your head and it's impossible to separate that sound from what you are hearing in the phones. The sound of your audio will be very different when you stop talking and play back the tape. In general, the low frequencies will be a lot weaker. Of course, if you have a helper, you have him/her talk into the mic while you listen on the phones. Ron AC7AC K2 # 1289 ++++++++++++++ Date: Sat, 13 Apr 2002 14:26:33 -0500 From: "George, W5YR" Organization: AT&T WorldNet Service To: ZOOM Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] Audio Improvements on a K2 While I do not (yet!) own a K2, I had the pleasure of borrowing one for a couple of weeks recently. While I had it, I ran spectral plots of the band noise response of the receiver for all modes and all filters. I used the same procedure and equipment that I used to plot the IF/audio response curves for the Icom IC-765 and IC-756PRO which may be seen at http://www.qsl.net/ab4oj I have assembled these plots into a rather large but informative ZIP file containing 19 plots which I will be happy to send to anyone who requests it. It is about 880K in size. This particular K2 was built by a resident "expert" builder (not me!) and I am confident that it represents typical if not above average performance. My subjective impression upon listening to the K2 on SSB with the same outboard audio mixer, EQ and power amp/speaker system that I use with my other receivers was that the audio response did sound rather constricted, probably due to the response function of the crystal filter. The lack of low-frequency response seemed to aid intelligibility for weak signals but made the stronger signals sound somewhat thin. The lack of high-frequency response reduced the hiss and higher frequency band noise components, and thereby helped with weaker signals, but again with strong SSB signals there was a tendency toward a slight muffled sound. Please keep in mind that what the plots show is fairly accurate "science;" what I say it sounded like to me is conpletely subjective and unsupported by anything scientific. <:} 73/72/oo, George W5YR - the Yellow Rose of Texas Fairview, TX 30 mi NE of Dallas in Collin county EM13qe Amateur Radio W5YR, in the 56th year and it just keeps getting better! QRP-L 1373 NETXQRP 6 SOC 262 COG 8 FPQRP 404 TEN-X 11771 I-LINK 11735 Icom IC-756PRO #02121 Kachina 505 DSP #91900556 Icom IC-765 #02437 ++++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: Subject: RE: [Elecraft] Audio Improvements on a K2 Date: Sat, 13 Apr 2002 14:58:48 -0700 George W5YR wrote: > ...listening to the K2 on SSB with the same > outboard audio mixer, EQ and power amp/speaker system that I use with my > other receivers was that the audio response did sound rather constricted, > probably due to the response function of the crystal filter. > > The lack of low-frequency response seemed to aid intelligibility for weak > signals but made the stronger signals sound somewhat thin. The lack of > high-frequency response reduced the hiss and higher frequency band noise > components, and thereby helped with weaker signals, but again with strong > SSB signals there was a tendency toward a slight muffled sound. I certainly agree with George's assessment of the K2 audio in my case. That's why I have been listening, when I run across a K2 on the air, to see how the Elecraft/Heil mics and others compare to my Radio Shack mic. What I am getting from my K2 is what we called, back in the 50's at least, "excellent communications quality", which means speech shaped for best intelligibility, not fidelity. So far, I haven't heard a K2 that could be accused of producing anything approaching a "high fidelity" audio - meaning the sort of sound you usually hear on the AM or FM Broadcast band. I agree with George that the filter design probably precludes getting any sort of sound like that. My voice has been compared to "dragging an empty garbage can up a gravel road" with lots of base rattle and rumble. But that was by people listening to me speak live, not through a radio. So for the limited phone work I have done I take care to strike something of a balance between the rumble and the higher frequencies essential for the sibilant sounds. The K2 with the RS mic seems to do that well, but it is nothing that I'd call "high fidelity" by any stretch of the imagination. It is more like the quality we expected from a telephone 50 years ago. Quite intelligible, certainly recognizable, but that's about it. Ron AC7AC K2 # 1289 +++++++++++++++++ Reply-To: "Don Wilhelm" From: "Don Wilhelm" To: , Subject: Re: [Elecraft] Audio Improvements on a K2 Date: Sat, 13 Apr 2002 20:55:15 -0400 Ron and all, Having just set up a K2 for SSB, I can directly relate to what you are saying - the filter bandwidth of the SSB filter (OP1) is about 2300 Hz wide (or at least the ones I have worked with) - and you just can't get hi fi through that tight a bandpass, but it certainly can be quite effective for communications clarity. This slightly narrow SSB bandpass does bring up a valid point that you have mentioned several times - it is important that the USB and LSB BFOs are set properly - especially if you have a voice that has a lot of energy in either the low or the high end of what is considered to be the 'normal' communications speech frequencies (300 to 3000 Hz). I personally use Spectogram to set the OP1 filter for SSB, and in doing so I set markers at 300 and 2300 Hz, then adjust the BFO so that the displayed passband fits evenly between those markers with particular attention at the low frequency end (I look at the slope) - it works for most voices, but an individual can adjust slightly higher or lower if one needs to compensate for his/hers particular voice. 73. Don Wilhelm - Wake Forest, NC W3FPR home page: http://www.qsl.net/w3fpr/ QRP-L # 485 K2 SN 0020 mailto: w3fpr at arrl.net *** Life is what happens when you're making other plans -- Mike Cross *** ++++++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: Subject: RE: [Elecraft] Audio Improvements on a K2 Date: Sat, 13 Apr 2002 20:15:22 -0700 > ...I personally use Spectogram to set the OP1 filter for SSB, and in > doing so I > set markers at 300 and 2300 Hz, then adjust the BFO so that the displayed > passband fits evenly between those markers with particular > attention at the > low frequency end (I look at the slope) - it works for most voices, but an > individual can adjust slightly higher or lower if one needs to compensate > for his/hers particular voice. > Don Wilhelm Very interesting info, Don. Since I always prefer speak from recent personal experience with the K2 when I answer a question, I fired up mine into a dummy load and listened on an auxiliary receiver to tinker with the SSB BFO settings today. It had been a year or so since I last looked at them anyway. Then with the K2 set up for the best audio quality for my voice, I plugged in Spectrogram and compared what I saw with your message. You won't be surprised when I say that the bandpass is nicely centered between the 300 and 2300 Hz markers, Hi! By the way, I went back and looked at my BFO frequency settings when all was done. They were right on 4913.5 for the lower sideband and 4916.3 for the upper sideband - the EXACT frequencies Elecraft says to use in the SSB module instructions. So all of my fiddling and testing simply validated Elecraft's recommendations. I heartily recommend a "real world" audio check as the final test to anyone adding the SSB module to their K2, regardless of whether they set the frequencies to what Elecraft recommends and leave them there or if they use some other procedure to arrive at the "best" settings. Ron AC7AC K2 # 1289 ++++++++++++++++++ From: "Dave Johnson" To: Cc: Subject: Re: [Elecraft] Audio Improvements on a K2 Date: Sun, 14 Apr 2002 21:40:59 +0100 Hi Robert I've done the 2nd filter mod and it makes quite a difference to the dull sounding SSB audio. My microphone is a low cost Kenwood MC-43S and that works just fine. The links are just to adjacent pins in the K2 front panel and can be made with the "computer jumpers" for a real neat job. There are "before" and "after" Spectrogram images and a comparison image of a home brew transceiver with a 2.4 KHz filter at: http://www.astromag.co.uk/k2/filter.html 73's Dave, G4AON K2 #1892 K1 #1154 ++++++++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: Subject: RE: [Elecraft] Audio Improvements on a K2 Date: Mon, 15 Apr 2002 00:01:54 -0700 > Are these observations of the K2 SSB audio with or without the KAF2 audio > filter installed? > > Mike, KD5QPF > > p.s. while the bug bit a while ago it finally got the best of me and I > ordered a K2 & KSB2 today. In my case it is WITHOUT the KAF2 filter and WITH the 2nd filter flattening mod installed. Ron AC7AC K2 # 1289 +++++++++++++++++++++ Reply-To: "Don Wilhelm" From: "Don Wilhelm" To: "ZOOM" , Subject: Re: [Elecraft] Audio Improvements on a K2 Date: Mon, 15 Apr 2002 06:00:15 -0400 Robert and gang, One thing in addition to the SSB Flattening Mod that helps for many K2s is to remove C180 (the 10 pf cap in the 2nd xtal filter circuit). I have not seen this mentioned much lately, but Wayne Burdick began suggesting it as early as November 1999, and I saw it mentioned in a post reporting information from Gary Surrency in mid-February this year. (I am curious why it is still included - but then Wayne and Eric have been busy with other things too!) Note that after removing C180, L34 should be re-peaked. Also if you install the SSB Flattening Mod and want to do some additional 'tweaking', one can experiment with the value of the 120 pf capacitor that is added with the mod - I recall I ended up with something like 115 pf in my K2, but then I just finished building a K2 for another ham and 120 pf worked out really great so YMMV. 73, Don Wilhelm ++++++++++++++++++ From: "Don Brown" To: "Elecraft" Subject: Re: [Elecraft] Audio Improvements on a K2 Date: Mon, 15 Apr 2002 12:34:49 -0500 Hi Yes you are right. Except the transmit circuits are not affected because = the second Xfilter is switched out when transmitting. The 120 pf cap is s= witched in when OPT1 is selected, but only matters on receive. Don Brown KD5NDB ----- Original Message ----- From: lhlousek Sent: Monday, April 15, 2002 12:03 PM To: elecraft at mailman.qth.net Cc: w3fpr at peoplepc.com Subject: Re: [Elecraft] Audio Improvements on a K2 Don wrote: <<>> It is my understanding that removing C180 IS the filter flattening mod. = The 120 pf cap that is added is only switched in when the OPT1 filter is selected (always for TX and when OPT1 is used = for RX). Right? Lou W7DZN ++++++++++++++++++ To: elecraft at mailman.qth.net Date: Mon, 15 Apr 2002 13:13:51 -0700 From: Gary L Surrency Subject: [Elecraft] K2 CAL FIL: Setting the BFO for the best sounding SSB TX signal. Some folks have noticed their RX and TX SSB audio is not as good as it could be. The easiest way to resolve these problems, is to first use Spectrogram to set the filters up well for RX. See our website for details on how to do this: http://www.elecraft.com/Apps/new_fil_docs/filter_apps.htm Then, go back and tweak FL1 or the bF1txxx settings for the most natural sounding TX audio. Wayne and I have found that the optimum TX BFO setting is often 50-200Hz different than the best sounding RX BFO settings. Monitoring the K2's SSB TX signal on another rig is the best way to determine this. I use headphones on the other rig to prevent audio feedback, and then compare how my voice sounds on the headphones to how I really sound in person. Exposing one ear by removing that side of the headphones, and cupping a hand between the mouth and exposed ear helps you compare the real and transmitted audio - just as you have seen some singers (on TV or film) do in the recording studio. The BFO settings in CAL FIL can then be best determined for your particular voice and mic characteristics. A tinny or bassy sounding mic can also be improved with a little effort and time spent in CAL FIL. For example: In LSB, moving the BFO *lower* in freq. (further from the center of the IF passband) will enhance the treble or higher voice characeristics. Moving the BFO *higher* in freq. (closer to the center of the IF passband) will make the audio sound more bassy. In USB, do just the opposite to the BFO freq. for the same effect. Always use a lower band (such as 80m or 40m) when doing this, to avoid the confusing reversal of BFO settings that occurs on bands from 15m to 10m. The point here is, that although the KSB2 SSB filter may be a little on the narrow side, some attention to how well the CAL FIL BFO settings are done can optimize the way the rig sounds in both SSB RX and TX. Note that the FL1 or bF1txxx settings are always used for transmitting, regardless of which filter FL2-FL4 is selected. This allows you to have custom BFO settings for RX and TX. This is why we recommend you set FL2=OP1 in CAL FIL, and then set this filter up for the most pleasing SSB RX audio and use it for all normal SSB operations. The BFO setting for FL1 that have been customized for the best sounding SSB TX audio, will be automatically selected when you transmit. One advantage of a narrow SSB filter is that more power is concentrated into a smaller bandwidth TX signal, maximizing the punch of the QRP power level. For the best sounding RX SSB audio, you should also perform the 2nd FIL mod that allows the LSB/USB and CW settings of L34 to be optimized. See: http://www.elecraft.com/Apps/new_fil_docs/k2_2nd_xfil_ssb_mod.pdf This mod takes four commonly available parts and about 15 minutes to do. It will likely be phased into the next K2 revision. This mod affects ONLY the SSB RX audio, and has no direct affect on the SSB TX audio. Gary Surrency AB7MY For Elecraft Technical Support, please use: support at elecraft.com ++++++++++++++++++ Date: Mon, 15 Apr 2002 19:05:55 -0600 From: Clif Squires To: rondec at easystreet.com, elecraft at mailman.qth.net Subject: [Elecraft] Audio Improvements on a K2 Ron: I have had a ton of trouble with the KSB, mine died with no way to null the carrier. So on to a second KSB. SSB in xmit still didn't work until I saw your post about the filters. I had changed the BFO settings while using Spectragram including settings on FL1. Is FL1 used the xmit mode and when I changed factory recommended settings, all went wrong? After changing back to recommended settings, my voice sounds *near* normal and the mic works again. Can I tweek current setting on FL1 to optimize sound? The spectragram mod only allow one to change FL2-4, not FL1 and now I am seeing why. TIA & 73, Clif W7ECS +++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: "Clif Squires" , Date: Mon, 15 Apr 2002 20:04:57 -0700 Subject: [Elecraft] RE: Audio Improvements on a K2 > Ron: >I had changed the BFO settings while using > Spectragram including settings on FL1. > > Is FL1 used the xmit mode and when I changed factory recommended > settings, all went wrong? > > After changing back to recommended settings, my voice sounds *near* > normal and the mic works again. Can I tweek current setting on FL1 to > optimize sound?... > TIA & 73, > Clif W7ECS Hi, Clif: Yes, OPT1 is used for SSB transmit when you have the SSB module installed. The OPT1 filter is the one built onto the SSB module and you cannot change its bandwidth. When you installed the SSB module, you assigned the OPT1 filter to the FL1 position. When you switch to FL1 you will see "OPT1" instead of a bandwidth. (By the way, people have asked if there is an OPT2 and Wayne or Eric answered, "Not Yet..." Hi! They apparently called it OPT1 to allow for the possibility of other special filters in the future.) So FL1 (OPT1) is ALWAYS used in SSB transmit, no matter which filter you have selected to use in receive, AND the BFO settings for FL1 are ALWAYS used for transmitting, no matter which filter you have selected. So you want to set up FL1 using the OPT1 filter for the best TRANSMIT audio. I found it best to start with the frequencies Elecraft recommends. As I mentioned in my earlier post, after I set up my K2 for the "best sounding" audio as heard on another receiver, I found that spectrogram showed my bandpass well centered between 300 and 2100 Hz. That may not be exactly the case for every filter. I recommend that you use the Elecraft BFO frequencies and adjust them by listening to yourself in another receiver to please your ear. A good final check might be to use spectrogram to see how the bandpass looks, but I would not rely on it alone. Indeed, I have set up my BFO frequencies using only spectrogram and while the plot looked good, my voice did not sound good. For me, my ability to interpret the spectrogram display was not 'precise' enough to see the best BFO frequency to use. My ear did a much better job. That done, you might want to use slightly different BFO settings for receive. You can choose OPT1 in FL2 position, then change the BFO settings to please your ear on receive. That will NOT affect the transmit signal since only the FL1 BFO settings are ALWAYS used on transmit regardless of which filter position you have selected for receiving. Indeed, I think it was Wayne who suggested a while back using several different BFO settings on the OPT1 filter in FL 2, 3 and 4 positions to provide a sort of rudimentary "passband tuning" affect. I hope that helps! 73, Ron AC7AC K2 # 1289 +++++++++++++++++++++ Reply-To: "Don Wilhelm" From: "Don Wilhelm" To: "lhlousek" , "Elecraft List" Subject: Re: [Elecraft] Audio Improvements on a K2 Date: Mon, 15 Apr 2002 23:31:12 -0400 Lou and all, As far as I know, the REAL filter flattening mod is the one that adds the transistor switch and the 120 pf cap. Yes, it only works in RX when the OP1 filter is selected. It is not active during transmit. Removing C180 indeed can have some flattening effect, but the amount is not significant as far as I have experienced. 73, Don W3FPR ----- Original Message ----- > > It is my understanding that removing C180 IS the filter flattening mod. The 120 pf cap that is added is only switched > in when the OPT1 filter is selected (always for TX and when OPT1 is used for RX). Right? ++++++++++++++++++++++ Date: Wed, 17 Apr 2002 10:46:17 -0400 To: From: Bill Coleman Subject: [Elecraft] K2 - Tip using CAL FIL to get good sounding audio on SSB I wanted to pass this along. My K2 is "finished" (until the KPA100 comes out), and I've been tweaking it. One thing I didn't like was different pitch of the background noise when switching from USB to LSB. My TS-430S does this, and I compensate with a bit of IF shift when in LSB. Also, signals seem to shift around a bit as I picked different filtersmodes. Here's some things I discovered to get everything to sound good. * Get the SSB option. The variable-bandwidth filter is awfully asymmetrical at wide bandwidths. The OP1 filter is much nicer. * Do the 2nd XFIL mod. Cleans up the symmetry of the OP1 filter. * Get the KAF2 option. Even if you never turn AF1 or AF2 on, the default low-pass filter takes out a lot of hiss. * Use Spectrogram or similar program. The default setup suggested in the manual sounded really wacky. I used MacCRO (Think Different!). These programs can really help you get things close, although there is a bit of leeway where several BFO positions will produce very similar spectrum plots. * In CAL FIL, listen to the audio in LSB from a noise generator like you used with Spectrogram. Switch to USB (use CW REV for this). Go back and forth and pick the BFO frequencies that give you the least pitch change. Note that the "color" of the noise will differ slightly, due to filter asymmetries. But you should be able to get them close. * Get a radio with an AM detector. Tune to a strong 40m SWBC station. Tune the K2 to the same station in LSB. Tune so that the audio pitch from the K2 matches the AM detector. Switch to USB (use CW REV). If the audio pitch differs, go back to CAL FIL and adjust until you get the same audio pitch from both modes to match the AM detector on one frequency. * Check the variable-bandwidth filters on SSB. Make sure you don't have any audio pitch changes when selecting these filters. Adjust the BFO frequency accordingly. I used these techniques to tweak up my filters, and I'm real happy with the results. The BFO changes were really minor, and didn't make a whole lot of difference in the spectrum plots, but it certainly sounds great. Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr at arrl.net Quote: "Not within a thousand years will man ever fly!" -- Wilbur Wright, 190 +++++++++++++++++ Reply-To: From: "Ron D' Eau Claire" To: "Nicholas Lokuciewski" , Subject: RE: [Elecraft] increasing mic gain Date: Fri, 26 Apr 2002 14:03:18 -0700 > I understand that by changing some resistors on the SSB board > allows the mic > gain to be increased. Any suggestions? Just to note, I am using a moving > coil microphone and have not had any bad audio reports except 'could be a > little louder'. > > 73/72 2E1LOK / M3LOK Nicholas K2 #2448 Increasing the value of R14 on the SSB Module will usually improve the audio level quite a bit, Nicholas. Values of between 5 and 10 k have been used. A while back some ops swapped R14 and R2 on the SSB module board to accomplish this AND to provide slightly more signal to the Balanced Modulator. There were some concerns voiced that doing so might over-drive the Balanced Modulator. I don't know if anyone ever investigated that possibility further, but a number of operators reported good results after switching the two resistors. Don't forget to turn up the "compression" a bit if you want more "punch" too (SSBC on the menu: 1= no compression, 4= maximum compression). If you are getting at least one bar with the K2 "meter" in ALC mode (press and hold RF/ALC button) you have all the audio input from the mic that the K2 can use. Ron AC7AC K2 #1289 ++++++++++++++++