+++++++++++++++++++++++++++++++++ Date: Wed, 25 Apr 2001 19:36:30 -0400 From: "Steve and Anne Ray" Subject: [Elecraft] Checking KNB2 I recently completed the noise blanker for my K2 and fortunately I live in a electrically quiet neighborhood. I wanted a way to see what it could do, so I wired up a old 24VDC relay as a buzzer (power to normally closed contact, armature to one side of coil and power return to the other side of coil). On testing this lash up with a 4 foot hunk of wire to feed the buzzer and act like an antenna I could hear the NB was doing it job and playing with the threshold on the NB I could hear the NB1 and NB2 and Hi and Lo Threshold effect on the receiver. Naturally being curious I then hooked up my trusty Tek 454A and used the spike in the power line feeding channel A and trigger A and hooked the audio output of the K2 to channel B. I did not see a significant difference in the audio on the scope. (Noise went down a by about 20 percent with the NB on. Yet, I could see a difference in the noise that drove up the level of the S Meter with the NB on the S meter reading was two or more S Units less, then with the NB off. I was concerned that maybe the NB wasn't that great, then it dawned on me, maybe the NB is good and it is the AGC being on. I then turned off the AGC and could see the difference. It really cuts down the noise with the AGC off. Well that does make sense. Just thought I would pass this on to anyone who wants to see how the NB is working. Wayne and Eric you did good again. OK, Wayne and Eric now I have praised the K2 again, I even ordered the shirt. So Wayne and Eric what are you going to show us at Dayton I want to build that computer interface and 100 W final or any other K2 goodies. 72, Steve Ray K4JPN ex K1VKW HW-101, HW-8, Elecraft K2 1422 HeathKit fan EM82fp Warner Robins GA +++++++++++++++++++++++++++++++++++++++++ Date: Wed, 7 Nov 2001 23:44:17 -0800 From: "Ron D' Eau Claire" Subject: RE: [Elecraft] K2 Noise Blanker problem Ken wrote: > Just got around to building the "Rev D" K2 noise blanker that I > bought back > in March.. > It does turn on & off according to the front panel display.. but try as I > may, it makes zero difference to buzzing noise. It takes a really high noise level at the blanker to make it work. There was a thread here a while back in which a number of ops were debating what kind of noise was best to test it on. A 'doorbell buzzer' was high on the list of recommendations, apparently being what one of the major receiver manufacturers has used in the past. I've noticed two things. 1) Cheap lamp dimmer buzz is ideal for the NB to clean up. 2) The r-f gain of the K2 must be far higher than I normally run it to make the blanker work. On 40 and 80 meters I often turn on the pre-map to make the NB work - even with 'low threshold' enabled. I know that it's crazy to run a preamp on 80 or 40 - it only reduces the dynamic range capabilities of the receiver on those bands and does absolutely nothing to improve the weak signal reception. But I don't have any obvious overload problems so that's what I do. Turning on the preamp can make the difference between a very loud signal-covering buzz and a signal out in the clear. If you have a cheap dimmer lamp, try it. And then tune in on 80 meters and turn up the r-f gain with the AGC on and then, if the noise is still there, turn on the preamp and see if that doesn't make the noise suddenly disappear. If that doesn't do it, you may well have a defective Noise Blanker... Ron AC7AC ++++++++++++++++++++++ ate: Thu, 08 Nov 2001 06:49:36 -0800 From: Wayne Burdick Subject: [Elecraft] Re: K2 Noise Blanker Ron D' Eau Claire wrote: > > Ken wrote: > > Just got around to building the "Rev D" K2 noise blanker that I > > bought back > > in March.. > > It does turn on & off according to the front panel display.. but try as I > > may, it makes zero difference to buzzing noise. > > It takes a really high noise level at the blanker to make it work. Ken, Ron made some good points. But it should not always take a high-level noise signal to activate the KNB2. All it takes is a fast rise-time signal that is above the ambient noise level. For example, the blanker is very effective on broadband power-pole noise, especially on the higher bands where the background atmospheric noise is low. The KNB2 should be triggered properly even if such noise is only S1 or S2. As Ron noted, turning on the preamp lowers the threshold at which the blanker will turn on. Note that the RF GAIN control actually controls the I.F. gain, as is true of many receivers. Since all noise blanking happens prior to the I.F. amp, the RF GAIN control will have no effect at all on noise blanking performance. If your KNB2 doesn't work as I described above, chances are it is not functioning correctly, or the buzzing noise you hear may be narrow-band rather than broad-band. In a typical shack, there are lots of ugly buzzing sounds coming from things like monitors and switching power supplies. Most of these are frequency-specific, i.e. if you tune around the band, they will appear in many places but not everywhere. Such noise is narrow banded, at least by the standards of a pulse-type noise blanker. Multiple-conversion receivers may have an advantage here, because they can place the blanker at the second I.F. with a 15-50 kHz roofing filter ahead of it; in this case, some noise that is not truly broadband will still trigger the blanker. The K2 is single-conversion, so we focused strictly on broadband noise suppresion in the KNB2 design (not to mention avoiding having the NB degrade RX performance). For testing noise blankers, I use a broadband line noise simulator: an IC squarewave oscillator followed by a small capacitor to generate very fast rise/fall-time edges at a repetition rate of 60 Hz. I then inject this signal directly into the K2's antenna jack. An NE555 timer IC can be used to generate the squarewave, followed by a very high-speed/high-current Schmidt-trigger-input buffer to improve rise/fall times. Building the noise simulator on a PC board with very low-impedance paths to ground will eliminate ringing and make the simulation more effective. A 100-ohm pot should used at the output to form a differentiator with the small cap and allow the noise injection level to be varied. (The actual circuit is left to the reader as an excersize ;) 73, Wayne N6KR +++++++++++++++++ Date: Thu, 08 Nov 2001 15:48:23 -0800 From: Wayne Burdick Subject: Re: [Elecraft] Re: K2 Noise Blanker Dave Gingrich K9DC wrote: > While we're on the NB topic perhaps you could respond to a related question. > > Given the same noise source, why would the KNB2 perform better on some > bands than others? Occasionally I have a severe noise problem at my > location. Usually the KNB2 takes it out completely on 80 meters, but > sometimes doesn't touch it at all on the higher bands. This is not unique > to the K2 as I have had the same situation with other rigs. Dave, Your antenna system and the K2's filters "shape" the noise, so that by the time it gets to the noise blanker may look quite different on every band. Not only that, the noise itself may have different components, each with different amplitudes. As a result, highest peak in the noise pulse train may trigger the blanker, while another might be too low, so that it gets through. The NB2 setting has a longer blanking time and might help if the pulses are close together, but it's pretty unpredictable. Another possibility is a shaped pulse that has a slower rise time on some bands, so that part of the noise envelope is blanked, but not all of it. At such times it might be helpful to have a more sensitive threshold control on the blanker; we provided two levels (LO and HI). There's a fine line betwee providing enough blanking and too much. If the noise detector is too agressive, it will cause intermodulation, actually raising the noise floor. 73, Wayne ++++++++++++++++++ Date: Fri, 9 Nov 2001 18:18:58 EST From: Unifiedtx at aol.com Subject: [Elecraft] KNB2 Does it work or not? when I completed the noise blanker board and installed it, I did not think it was working. However, I couldn't find any random noise. I asked Gary Surrency how I could tell if the blanker is working, and he told me to turn the blanker on and gently rub a metal screwdriver across Q21. If it is working you will hear a "singing" noise from this transistor. Q21 is the round metal transistor in the middle of the RF board. I heard the "singing" he described and was satisfied my blanker was working. I have lately experienced a lot of random noise, and my blanker works great. Roy Morris W4WFB K2 #2225 ++++++++++++++++++++ Date: Mon, 07 Jan 2002 17:40:29 -0600 To: "rich a." , elecraft at mailman.qth.net From: Tom Hammond =?iso-8859-1?Q?N=D8SS?= Subject: Re: [Elecraft] capacitor substitution & other problems Hi Rich: You wrote: >While assembling my KNB2 noise blanker I dropped, then stepped on and >broke C4, a 100pf blue mono cap. I've got a disk cap marked 101J, which >I think is also 100pf. Can I use it or do I need the blue mono cap? You should be able to use it, at least temporarily... I think I'd still consider replacing it later, just for aesthetic reasons. -- snip -- Good luck, Tom Hammond N0SS +++++++++++++++++ Reply-To: "Ron D'Eau Claire" From: "Ron D'Eau Claire" To: Subject: Re: [Elecraft] Rx comparison test with the K2 Date: Mon, 27 May 2002 10:17:49 -0700 > Frankly, I haven't been very impressed by > the K2's blanker either, but not sure I've had a chance to test it under > really noisy conditions. When thunderbumpers were hovering 50 miles away, > I've seen QRN levels 20db over S-9. The FT-1000D's blanker would usually > reduce it to S2 or 3. > Ed, W5EJ Quite right! The K2's noise blanker is designed to handle high-amplitude impulse noise such as auto ignition - pulses with a very fast rise-time. It doesn't do a thing to help with typical "atmospheric" QRN. Ron AC7AC K2 # 1289 +++++++++++++++++++ From: "JohnCrux" To: Date: Tue, 28 May 2002 18:06:30 +0100 Subject: [Elecraft] Elecraft Digest Vol 1 #159 K2 Noise Blanker I rarely find the KNB-2 useful here because I do not usually suffer from = pulse noise. Its not designed for any other semi-continuous noise, like = thunderstorms, thermostat arcing etc. But when operating in ZS6 from a = location completely surrounded by vicious electric fences (mostly = energised 24/7) , the K2 blanker completely took them out ... and I mean = completely. Without it, operation was hopeless. If you have continuous = local noise a canceller is a better bet.=20 John G3JAG ++++++++++++++++++ Date: Tue, 04 Jun 2002 15:50:54 -0500 To: "Van W1WCG" , From: Tom Hammond =?iso-8859-1?Q?N=D8SS?= Subject: Re: [Elecraft] KNB2 Noise Blanker Problem? Van: >Just finished the Noise Blanker for the K2. In trying it out, I can't see >that NB1 makes any appreciable difference >to a high AC-type noise level, although the NB in my FT-1000MP knocks it >out fairly well. NB2 somewhat attenuates >signals and noise about equally. Changing the threshold makes no apparent >difference. I'm afraid there may be >a problem with the KNB2. I've checked all the solder joints (reflowed a >couple of 'em) and made sure components >were properly placed and oriented. Question: is it normal for the the >NB-2 mode to somewhat attenuate everything? Has >anybody else had the same type of problem and found a fix for it?? Unless the TS-2000 uses DSP to accomplish it's DSP function, I'd expect the KNB2 to be AS effective as just about any other type of NB. The KNB2 in my K2 worked better than the NBs in either my TS-930S or my TS-950SD, and I always thought THEY worked pretty darn well. NB2 may appear to attenuate things a bit more than NB1, because NB2 has a longer-duration blanking interval. Tom N0SS ++++++++++++++++++ Reply-To: "Ron D'Eau Claire" From: "Ron D'Eau Claire" To: Subject: Re: [Elecraft] KNB2 Noise Blanker Problem? Date: Tue, 4 Jun 2002 17:23:21 -0700 Just finished the Noise Blanker for the K2. In trying it out, I can't see that NB1 makes any appreciable difference > to a high AC-type noise level, although the NB in my FT-1000MP knocks it out fairly well... > Van, W1WCG > K2 #2634 I assume you mean something like a lamp dimmer or other source of big spikes. I have found that to get my Noise Blanker to work in many situations, I must use the Preamplifier. Setting Low Threshold doesn't do it either. But turning on the preamp will cause the noise to virtually disappear. Ron AC7AC K2 # 1289 ++++++++++++++++++++ To: n4in at iolky.com, Elecraft at mailman.qth.net Date: Wed, 5 Jun 2002 13:35:29 -0700 Subject: Re: [Elecraft] KAF2 performance??? From: k6se at juno.com David, N4IN wrote: "Just got through using the KAF2, audio filter, working a few QSO's on 30M and noticed that my KAF2 performs better in AF1 than AF2 and that it is also performing better with the wider xtal filter settings of 1.6kHz and 0.7kHz. Does this sound right or do I need to do some more aligning of the audio filters with the xtal filters." ========== No, it doesn't sound right. AF2 should be slightly narrower. It also should be slightly louder because it introduces a couple of dB gain where AF1 does not). It works on all filter bandwidths, of course. When turned off, it even helps a bit on SSB (as opposed to not being installed). I adjusted R1 and R2 on my KAF2 using a steady signal in CW mode (the "birdie" at 7000 kHz with the antenna disconnected is ideal) tuned in at the same pitch as my sidetone for loudest audio while AF2 is selected. The R1 & R2 peaks are slightly broad, but they are definitely there. Another (better) way would be to monitor the same signal using Spectrogram with a frequency mark at your sidetone pitch and the signal tuned in to coincide with that frequency mark. Adjust R1 & R2 while AF2 is on for max amplitude at the frequency mark. Spectrogram will also show you if you have the BFO set correctly for each CW filter bandwidth (i.e, with the received signal; tuned in at your sidetone pitch, centered in the passband of each filter BW). The KAF2 does a great job of enhancing CW signals, especially those weak ones. 73, de Earl, K6SE 68 countries with K2 #2622 and counting..... +++++++++++++++++ To: "David E. Shelton" , "Elecraft" From: "Timothy A. Raymer" Subject: Re: [Elecraft] KAF2 performance??? David, I would venture to guess a bit of tweaking will help the CW filters do what you want. If you haven't used Spectrogram and an RF noise source, I would recommend it. But the two filters do different things. So, another way of answering your question is: It depends. The audio filter reduces hiss, and AF1 and AF2 are different audio bandwidths. The CW filters limits the amount of RF that flows through the rest of the radio by restricting the amount of RF energy that flows through the narrow bandpass of the filter. Some on the forum have reported variations in Crystal filter settings that can change with how warm the temperature of your K2 is. Hope this helps a bit. Should spark a few additional comments from others that have seen the same thing you have. Tim Raymer K2 #1383 +++++++++++++++++++ Date: Fri, 21 Jun 2002 15:52:46 -0500 To: elecraft at mailman.qth.net From: Tom Hammond =?iso-8859-1?Q?N=D8SS?= Subject: [Elecraft] K2 Noise Blanker (KNB2) Demo Hi Folks... Over the last couple years, there have been several discussions about how effective the K2 Noise Blanker (KNB2) really is. Well, this morning, on 15M (21.025) I found the best demonstration of it's effectiveness that I've EVER experienced. K1LIK was working an SV (Greece) station. Neither station was terribly strong, and I had a pretty bad line noise problem at that time. In desperation, I turned on the KNB2... and the noise just DISAPPEARED! I didn't believe it... I tried it again... and again it was like night and day. I was so impressed that I made a 1:30 WAV file of part of the QSO and I now have it (UNedited, except to limit the length of the file) on my web site at: http://home.earthlink.net/~n0ss/knb2_demo.zip There are a lot of other items out there as well, so feel free to rummage through the DOWNLOAD page at: http://home.earthlink.net/~n0ss/ (also at http://fantasia.galaxynet.com/~casey/k2/knb2_demo.zip thanks to Kevin ve3syb) You CANNOT listen to the file on-line! It is too large a file (nearly 2MB) and it would eat up my monthly download quota in a heartbeat. However, I have ZIPped it into an 814kB ZIP file which you can download by going to the URL shown above. Once you have it on your PC, THEN you can play it. If anyone is interested enough to pull the file and upload it to THEIR server, for others to access, that would be just fine with me. If you do, PLEASE publish the address and I will then remove it from my site, to make room for other items of possible interest. Enjoy. 73, Tom Hammond N0SS P.S. Yes, I know, there ARE some types of noise which the KNB2 will not address. But for those that it WILL address, it usually handles them quite well. ++++++++++++++++++ From: "Rod N0RC" To: , =?iso-8859-1?Q?Tom_Hammond_N=D8SS?= Subject: Re: [Elecraft] K2 Noise Blanker (KNB2) Demo Date: Fri, 21 Jun 2002 15:35:52 -0600 WOW! What a difference. Here is a link to how it looks in Spectrogram: http://www.radioactivehams.com/~n0rc/pics/nb_demo.jpg Very dramatic improvement. +++++++++++++++++++++ Date: Sat, 22 Jun 2002 00:02:25 -0400 To: elecraft at mailman.qth.net From: Kevin Cozens Subject: Re: [Elecraft] K2 Noise Blanker (KNB2) Demo At 03:52 PM 06/21/2002 -0500, you wrote: >I was so impressed that I made a 1:30 WAV file of part of the QSO and I >now have it (UNedited, except to limit the length of the file) on my web >site at: [snip] >If anyone is interested enough to pull the file and upload it to THEIR >server, for others to access, that would be just fine with me. If you do, >PLEASE publish the address and I will then remove it from my site, to make >room for other items of possible interest. To save Tom from exceeding his bandwidth for the month, I have uploaded a copy of the file to a server I manage. The file can be found using the following URL: http://fantasia.galaxynet.com/~casey/k2/knb2_demo.zip Its amazing what difference the KNB2 made with the type of noise Tom had to deal with during that QSO. It starts to make me think I may go for a KNB2 for those times when I can't use my DSP unit. 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 +++++++++++++++++++++ Date: Tue, 09 Jul 2002 14:11:28 -0700 From: Wayne Burdick Organization: Elecraft To: BlandRanch at BlandRanch.net Cc: elecraft Subject: [Elecraft] Re: Noise Blanker Hi Chuck, The situation we were trying to avoid was having someone turn on the NB, then forget that it's on, possibly compromising receiver performance later under strong-signal conditions. We had to weigh this against the inconvenience of turning it on each time you power up the K2. Look at the bright side: you get to test your noise blanker (and your Blazer's engine) every time you turn on the rig. 73, Wayne N6KR Charles Bland wrote: > > I have been doing a bunch of mobile operating. > > I presume it is by design that the noise blanker (essential when the > engine in my Blazer is running) reverts to OFF when the K2 is first > turned on. Stated another way, I have to turn on the noise blanker > every time I turn the radio on? > > Why would I want it to be this way? I would prefer the noise blanker > remain in the condition I left it at powerdown. ++++++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: Subject: RE: [Elecraft] Noise Blanker Date: Sat, 28 Sep 2002 07:44:25 -0700 The Noise Blanker does a GREAT job with high amplitude, fast-rise-time impulse noise. It counts on a very sharp leading edge on the noise pulses to 'trigger' it. That's how it discriminates between noise and signal. A lot of noise lacks the fast rise time needed to trigger it. Auto ignition noise is a great example of the sort of noise that it will kill effectively, although I've found that a lot of what sounds like "hash" on the lower bands is also handled by the KNB2 very nicely. It's not always obvious what noise has the requisite waveform just by listening to it. The noise blanker literally punches "holes" in the signal path, turning off the signals for a brief period during each noise pulse. That sort of action creates artifacts of its own that can show up as other forms of noise and distortion. That's why Elecraft cautions users to leave the noise blanker OFF whenever it is not needed. I'm not certain that is what is causing your odd sounds, but it's something to consider. Does the KNB2 add the noise with a dummy load connected to the K2 antenna input? Ron AC7AC K2 # 1289 ----------------------------------------------------------------- "Postal Guy" wrote: Although I'm still very impressed and satisfied with my new K2, I've yet to notice much of a difference in using the Noise Blanker. I could 'see' a slight difference using the Spectrogram program but could not hear much of one. Switching to hi or low threshold did'nt change much of anything either. I just thought that maybe there was'nt any electrical noise to filter out around here. Unrelated to the KNB2, after seeing the suggestion about swapping out the R1 resistor (control board), I changed mine to 49k and heard some improvement, (and still found little use for the KNB2), so I changed it again to 39k and can hear even more of an improvement. However, now when I try the KNB2, it actually ADDS interference noise. In hi-threshold, it adds some clicking/popping sounds; in lo-threshold, it adds a "roaring hiss" sound. Not that I really found a need to use it anyway, but has anyone else experienced this? So far I dont mind the trade-off, but I would like to see a remedy for this, other than going back to the 51k value. ++++++++++++++++++++ Date: Sat, 28 Sep 2002 11:07:43 -0400 From: W3SZ Subject: RE: [Elecraft] Noise Blanker To: 'postal_guy' , elecraft at mailman.qth.net Hello, All! The K2's noise blanker is the most effective noise blanker I have ever heard on a commercial amateur radio transceiver. I use my K2 for weak signal VHF/UHF/microwave work, including 144 MHz EME. I have a location filled with pulse noise and the K2 outperforms all of the commercial rigs I have tried, up to and including the FT-1000MP, which has a very highly regarded receiver. If I am doing EME or other weak signal work with a commercial rig, when it is noisy I turn off the FT1000 and go with the K2. It far outperforms all of the competition. Therefore, I think that if you are not seeing a difference and your K2 has been built correctly, then either (1) you have no noise or (2) it is not pulse noise. In your case I would worry about a construction error or a bad or incorrect part as I noted no increase in noise after I installed the KNB2, and have not heard of this happening from anyone else. Hearing that the K2 Noise Blanker 'doesn't work' or 'adds noise' is to me about the same as hearing 'my Lamborghini doesn't have any pickup'; something is wrong in your particular case; either a construction error or a bad or incorrect part. These are NOT expected problems with the KNB2, which has stellar and frankly unequaled performance. I hope that helps. 73, Roger Rehr W3SZ FN20ah 2 Merrymount Road Reading, PA 19609-1718 http://www.qsl.net/w3sz ++++++++++++++++ From: "Gary Surrency" To: "'Mike McCoy'" , "'Elecraft Reflector'" , "'Elecraft Support'" Cc: "CSinfo (E-mail)" Date: Tue, 5 Nov 2002 11:03:23 -0700 Subject: [Elecraft] K5PU: RE: KNB2 current requirements 13mA when on. 2mA turned off. It's on the front page of the KNB2 manual. -- 73, Gary AB7MY ========= gary at elecraft.com Elecraft Technical Support +++++++++++++++++ Reply-To: From: "Sverre Holm - LA3ZA" To: , Subject: RE: [Elecraft] Noise Blanker Date: Mon, 23 Dec 2002 02:38:37 +0100 There is a test that originates with Elecraft that consists of touching and scratching the transistor with a metallic screwdriver. It is the transistor right in front of the noise blanker, I believe it is the post-mixer amplifier. I had exactly the same problem as you and discovered eventually that it actually did supress the noise generated in this way. There should be more info on this in the archives of the Elecraft reflector under 'Noise blanker' 73 Sverre LA3ZA www.qsl.net/la3za > -----Original Message----- > From: elecraft-admin at mailman.qth.net > [mailto:elecraft-admin at mailman.qth.net] On Behalf Of Rick Wheeler > Sent: 18. desember 2002 03:02 > To: elecraft at mailman.qth.net > Subject: [Elecraft] Noise Blanker > > > How can one tell if the Noise Blanker is working OK? I live > in a relatively quiet (RF that is) area with an occasional > electric fence or household generated noise. But no matter > what I do (Lo Thr, Hi Thr, nb1, nb2, or off) I can not detect > an inkling of difference or attenuation of man made noise. I > can generate noise with a hand-held drill or garbage disposal > and no difference is detected with the noise blanker on or off. > > I am familiar with the types of noise (at least the types > listed in the Noise Blanker manual) the Noise Blanker is > supposed to suppress. Is there any other common device I can > use to "test" my Noise Blanker? > > Rick > K4LX +++++++++++++++++ From: "Brian Machesney" To: "'elecraft'" Date: Mon, 30 Dec 2002 23:33:11 -0500 Subject: [Elecraft] KNB2 effectiveness Some time ago I promised to comment on my experience with the KNB2, since one user was unable to discern any reduction of "household" noise sources. I have problems with intermittent, but severe noise from power lines and electric fences. Having just installed it, I find the KNB2 to be quite effective against these offenders, though not as effective as the noise blankers in either my FT1000MP or IC706mkIIg. Conversely, I also find less intermodulation effects with the KNB2 than the Yaesu and ICOM blankers. In short - I like it. Brian K1LI K2 # 3070 - K2, KNB2, KSB2, K160RX, KPA100 ++++++++++++++++++ Date: Sat, 01 Feb 2003 07:34:32 -0600 To: "David Walker" , From: Tom Hammond Subject: Re: [Elecraft] Noise Blanker Option Dave: >Can anyone tell me how effective the NB option is? Is it a vital option >for most people? For an audio (.WAV file) demonstration of the noise blanker doing its job, download the sample file on my web site: http://home.earthlink.net/~n0ss Once at the home page, click on the link to the DOWNLOAD page (at the bottom of the home page). At the download page, drop down to the FIRST offering below the heading "K2-Related Files". This is an 841kB WAV file of a recording I made a while back to demonstrate the effectiveness of the KNB2. PLEASE NOTE that the KNB2 is effective only on short-duration noise spikes, such as that which might come from power lines, spark plugs, some kitchen appliances, electric fencers, etc. It is NOT effective on atmospheric static from lightning, etc. Additionally, the noise must be of a signal level sufficient to be able to trigger the NB to operate. The K2 is so darn quiet (with regard to background noise) that some noises (even though of the required type) cannot be blanked because they are still much too low to allow the NB to trigger on them. The Elecraft KNB2 is probably one of the MOST effective NBs I've ever used, BUT it's not infallible. Now, is the NB 'vital'? Good question. Probably not for most of us. BUT there will be times when just about all of us will either use, or wish we had, the NB. There will be times when it can, and will, save a QSO. And, there will be times when NOTHING will save the QSO. 73, Tom Hammond N0SS +++++++++++++++++++ From: WA9GQT at aol.com Date: Sun, 16 Mar 2003 15:04:14 EST To: rol at zeelandnet.nl, elecraft at mailman.qth.net Subject: [Elecraft] Re:KNB2 Low threshold distorted sound Hi Roland! Look on the KNB2 manual near the end of the manual. It gives the mod to prevent some of this distortion. Something about a 33 pF capacitor between pins 7 & 8 on the MC1350 IC. I have done this mod & it definitely helps. Take care. 73, Rod WA9GQT K2 # 1900 Rev B with KPA100 +++++++++++++++++++ To: benko at aztek-eng.com, elecraft at mailman.qth.net Date: Sat, 29 Mar 2003 10:28:35 -0500 Subject: Re: [Elecraft] What value for R88 with the KN2B From: Daniel L Brinneman Hi Larry, If you have the new REV. B boards, 3000 or more, then follow REV. E of the K2 schematic dated Feb. 16, 2003. If you have REV. A boards, 2999 or less, then follow REV. D of the Noise Blanker documentation dated Aug. 20, 2002. Daniel kg4dni ============================== On Sat, 29 Mar 2003 08:01:22 -0700 Larry Benko writes: > I posted a question yesterday and have received a couple of > comments and questions but no definitive reply. I don't think > that I made the original question clear enough so I will try > again. +++++++++++++++++++ From: "Bob - AG5Q" To: "Larry Benko" , Subject: Re: [Elecraft] What value for R88 with the KN2B Date: Sat, 29 Mar 2003 09:59:44 -0600 Hi Larry, You do need the 2.7K resistor for R88 to provide a DC path to ground for the leakage current of varactor diode D29 in the crystal filter. Without this resistor, D29 will not perform it's desired tuning function. Since R88 is across a tuned circuit, there may be some other useful effect, such as broadening the response of the circuit. In general, you can't connect a diode to a capacitor without having a DC path to some voltage source (or ground). Otherwise, the diode leakage current charges the capacitor. This current is highly variable so it's better to just eliminate its effect with a resistor. The resistor can usually be very large compared to other impedances in the circuit because the leakage current is very small; for example, it's less than 50na for D29. 73/ Bob - AG5Q ----- Original Message ----- From: "Larry Benko" To: Sent: Saturday, March 29, 2003 9:01 AM Subject: [Elecraft] What value for R88 with the KN2B > I posted a question yesterday and have received a couple of > comments and questions but no definitive reply. I don't think > that I made the original question clear enough so I will try > again. > > Specifically, Rev. E of the K2 schematic, dated Feb. 16, 2003, > says on sheet 2 of 4 in the upper right corner that if the KNB2 > Noise Blanker is installed to remove R88 on the K2 RF board and > makes no mention of putting any component back in its place. > > Rev. D of the Noise Blanker documentation, dated Aug. 20, 2002, > says to remove R88 on the K2 RF board and to then install a > 2.7k resistor in the R88 location. The KNB2 kit does provide > this 2.7k resistor. > > Which is correct? Do I follow the instructions for the KNB2 or > the NEWER schematic for the K2? > > Apparently the original components R88, R89, R90 make up a 5dB > pad which also provides some impedance stabilization to drive the > crystal filter. The KNB2 has a bandpass filter which appears to > do the same function perhaps at the same level or not. The > presence of R88 would change the level to the crystal filter > slightly. > > Thanks again and 73, > Larry Benko, W0QE ++++++++++++++++++ Reply-To: dock0evz at earthlink.net From: "Doc K0EVZ" To: "Elecraft " Cc: "doc k0evz earthlink" Date: Wed, 2 Apr 2003 22:38:34 -0600 Subject: [Elecraft] Effect of "Level" Control Gang: I just accidentally switched the "Level" Control from "LO THR" to "HI THR".....and WOW what a *huge* difference in background noise. All of a sudden the desired signals are just there, with almost no band noise. When I switch back to "Lo Thr" the noise level comes up dramatically and the signals seem to be about the same as with the other setting. Wow, all of a sudden the band is very much quieter. This effect is there--the quieter background--whether the NB is on or off, as far as I can tell. This is not a subtle difference, IMHO. What has happened here? I have read the manual on page 87, but am still confused. Gotta tell ya, sure wish I had stumbled on this setting change before. Have apparently been listening to loads of band noise for years [g]. Anyway, can anyone enlighten me on this? Thanks in advance. 73, --Doc/K0EVz ++++++++++++++++++++ From: "Bob - AG5Q" To: "Bruce D. McLaughlin" , "'Larry Benko'" , Subject: Re: [Elecraft] What value for R88 with the KN2B Date: Fri, 4 Apr 2003 21:58:20 -0600 Hi Bruce, You need the resistor so the xtal filter will work properly. It provides a path to ground for the leakage current through D29. 73/ Bob - AG5Q ----- Original Message ----- From: "Bruce D. McLaughlin" To: "'Bob - AG5Q'" ; "'Larry Benko'" ; Sent: Friday, April 04, 2003 7:48 PM Subject: RE: [Elecraft] What value for R88 with the KN2B > OK. I am now very confused. (It doesn't take a lot to confuse me I'm > sorry to say). I have K2 #3209. I finished the radio a couple of days > ago and now I'm also about done with the noise blanker. So, do I > install the 2.K resistor or not? Although the schematic with my rig is > Rev C, it appears to have the same instructions as Rev E. That is R88 > and R90 removed and R89 replaced with a jumper. There is no mention of > installing any replacement resistor at R88 and yet, the earlier > instructions that came with the NB say to install the 2.7K. One reply > to the earlier questioner said no and one said yes. So . . . what > should I do , i.e., is there a consensus? > > Bruce - W8FU +++++++++++++++++ From: Kevin Rock To: elecraft at mailman.qth.net, ARDUJENSKI at aol.com Date: Mon, 05 May 2003 10:15:41 -0700 Reply-To: kevinrock at earthlink.net Subject: Re: [Elecraft] KNB1/B2?? I find the noise blanker helpful when an electric fence fires up in the area. I have also used it to lessen the noise of mixers when my YL starts making something in the kitchen while I'm trying to copy CW. I haven't been able to defeat the blender with it though :) Kevin. KD5ONS ++++++++++++++++++ Reply-To: From: "Ron D'Eau Claire" To: Subject: RE: [Elecraft] Does AGC level change effectiveness of KNB2? Date: Mon, 12 May 2003 06:55:24 -0700 The effectiveness of the noise blanker is affected by signal level.=20 In some cases on 80 meters, for example, I have gone from no action to = full blanking by switching the preamplifier ON! Using a preamp on 80 is not something one would normally do, so it was a surprise to listen to a lot = of impulse noise on that band that the Noise Blanker didn't touch - even in "low threshold" position - and then hear the noise disappear and the = signals pop out nice and clear when I turned the preamp on.=20 So I suppose the AGC level could have a similar effect.=20 Ron AC7AC K2 # 1289 -----Original Message----- Does the AGC level change the effectiveness of the noise blanker? 73 de NA8M John ++++++++++++++++++++ Reply-To: From: "Sverre Holm - LA3ZA" To: "'John Huffman'" , Subject: RE: [Elecraft] Does AGC level change effectiveness of KNB2? Date: Mon, 12 May 2003 16:22:47 +0200 The AGC setting of the K2 does not affect the KNB2 action. The AGC voltage is derived at the output of the IF chain and feeds back to the MC1350 IF amplifier. The noise blanker is before the MC1350, so AGC action should not change the performance or effectiveness of the KNB2. A simple test of the noise blanker is to scratch Q22, the post-mixer amplfier, with a screw driver. This noise is the right kind of noise for the noise blanker. 73, Sverre ------------------ Sverre Holm, LA3ZA www.qsl.net/la3za ++++++++++++++++++++ Reply-To: pjhend at ameritech.net From: "pjhend at ameritech.net" To: n5qq at arrl.net, elecraft at mailman.qth.net Subject: RE: [Elecraft] KNB2? questionable operation Date: Mon, 12 May 2003 12:04:48 -0400 Ron, I had a similar situation=2E Until last December I never encountered any s= uch noise in my home QTH where the KNB2 was needed=2E I played around will all= sorts of power tools, motors, etc trying to generate some man made noise s= o I could test the NB unit=2E No luck creating any noise whatsoever - guess that's a good thng! :-) I had no idea if the darn thing worked or not=2E However, when I took my K2 to my folks home in PA over Christams, I encountered lots of intermittent noise, which as it turned out, was my mother's sewing machine=2E I hit the KNB2 and it worked like MAGIC! 100% o= f the S7 noise dissapeared=2E I finally got to hear for myself what everybod= y was raving about! So=2E=2E=2E=2Egot a sewing machine handy??? good luck! Paul W8BBR =20 Any quick suggestions to check for problems in the KNB2? 73 Ron N5QQ ++++++++++++++++++ From: "pfb" To: Cc: Date: Thu, 5 Jun 2003 13:00:11 -0400 Subject: [Elecraft] Solved Problem Noise Blanker - K2 Ser# 3479 To All, Problem solved. Receiver is as hot as ever.!! And the NB works fine!!! Here is the description of the problem: On the solder side of the RF board.... I bent over capacitor C161 to keep it low on the board as instructions indicate and I bent it in a direction that "hide two leads of the female section of P1" that is attached to the main board. I never soldered the two leads hidden under the capacitor C161. I should have bent it the other direction. Thanks to all that helped solve this. Everyone that responed helped and contributed in isolating this problem that took it a step at a time and I appreciate it. Paul K8QT +++++++++++++