KNB2 Performance
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I too have found the KNB2 lacking in most real world noise situations. I
even built a second one. Yes, when you scratch Q22 it works. However, that is irrelevant. Most impulse noise on the air in my area slips right through. Compared to the FT1000 and FT736R it is a poor third. Time to redesign it. Make it plug compatible and you'll sell many. My order for KNB2-2 stands. Joe K4AA Joe Squarzini, Jr. 688 Rossmore Ct. Great Falls, VA 22066 Home (703) 759-4943 Fax (703) 759-0656 _______________________________________________ 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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Joe,
I do agree with you for the full 100%! I do have here a Ten-Tec Paragon. The same waste of money (the NB of course). I'm also the luck owner of a Drake TR7/R7. The noise blanker is FABULOUS. It would be of great help to may of us to redesign it or at least make an other version with different specs available. Evert, PA2KW K2, #4836 -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Joe Squarzini Sent: 17 July 2005 18:30 To: [hidden email] Subject: [Elecraft] KNB2 Performance I too have found the KNB2 lacking in most real world noise situations. I even built a second one. Yes, when you scratch Q22 it works. However, that is irrelevant. Most impulse noise on the air in my area slips right through. Compared to the FT1000 and FT736R it is a poor third. Time to redesign it. Make it plug compatible and you'll sell many. My order for KNB2-2 stands. Joe K4AA Joe Squarzini, Jr. 688 Rossmore Ct. Great Falls, VA 22066 Home (703) 759-4943 Fax (703) 759-0656 _______________________________________________ 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 _______________________________________________ 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 Joe Squarzini
Perhaps one of the design wizards that reads this list could come up with
something like this http://www.ussc.com/~turner/syn_blank.html adapted for HF and the K2. My guess is that noise blanker effectiveness is directly related to the characteristics of the noise. One blanker's design specs are effective on noise with certain pulse widths and levels, whereas another noise blanker works well on eliminating noise with a different pulse width and level. This is why one rig's noise blanker works well at one QTH, but the same rig is ineffective on the noise at another QTH. Also some locations are plagued with more than one noise source, each source having quite different characteristics. Now a truly variable multistage noise blanker would be wonderful, but I suspect hard to design and costly to build. I know that this is way beyond my capabilities. But I would build one if someone could design and publish the details. A kit would be even better. :-) Darrell On July 17, 2005 09:29 am, Joe Squarzini wrote: > I too have found the KNB2 lacking in most real world noise situations. I > even built a second one. Yes, when you scratch Q22 it works. However, that > is irrelevant. Most impulse noise on the air in my area slips right > through. Compared to the FT1000 and FT736R it is a poor third. Time to > redesign it. Make it plug compatible and you'll sell many. My order for > KNB2-2 stands. Joe K4AA -- 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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With technology available today I wonder if it would be possible to design a
2-stage tracking NB! Just in the same manner as auto beat canceling. I'm a better builder than designer , but can't help myself throwing out some thoughts on this. Stage 1 when turned on search and lock on the noice pattern and stay locked. Stage 2 workes same way as stage 1 , but can be turned on after stage 1 to lock on a second pattern. Each reactivation starts a new search for patterns. Do some of you designers think this is possible? I would gladly throw an extra $30,40,50 for a high performance NB. Tom LA1PHA K2/100 3829 , K1 1491 ----- Original Message ----- From: "Darrell Bellerive" <[hidden email]> To: <[hidden email]> Sent: Monday, July 18, 2005 7:06 AM Subject: Re: [Elecraft] KNB2 Performance > Perhaps one of the design wizards that reads this list could come up with > something like this http://www.ussc.com/~turner/syn_blank.html adapted for > HF > and the K2. > > My guess is that noise blanker effectiveness is directly related to the > characteristics of the noise. One blanker's design specs are effective on > noise with certain pulse widths and levels, whereas another noise blanker > _______________________________________________ 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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Tom,
I believe you are speaking of functions that can be (and should be) implemented in DSP (if it is to 'search', some intelligence is required). The KDSP2 de-noiser does provide a lot of noise reduction similar to what you are describing - unfortunately, it is a bit more than $30,40,50. The KNB2 deos a good job with impulse noise above the set threshold. The blanking width can be modified by changing a capacitor if a different width is needed for a particular noise situation. Beyond that, the addition of the KDSP2 adds the intellegence and levels of control to deal with other types of noise. 73, Don W3FPR > -----Original Message----- > > With technology available today I wonder if it would be possible > to design a > 2-stage tracking NB! > Just in the same manner as auto beat canceling. > I'm a better builder than designer , but can't help myself > throwing out some > thoughts on this. > Stage 1 when turned on search and lock on the noice pattern and > stay locked. > Stage 2 workes same way as stage 1 , but can be turned on after > stage 1 to > lock on a second pattern. > Each reactivation starts a new search for patterns. > Do some of you designers think this is possible? > I would gladly throw an extra $30,40,50 for a high performance NB. > > Tom LA1PHA K2/100 3829 , K1 1491 > > ----- Original Message ----- > From: "Darrell Bellerive" <[hidden email]> > To: <[hidden email]> > Sent: Monday, July 18, 2005 7:06 AM > Subject: Re: [Elecraft] KNB2 Performance > > > > Perhaps one of the design wizards that reads this list could > come up with > > something like this http://www.ussc.com/~turner/syn_blank.html > adapted for > > HF > > and the K2. > > > > My guess is that noise blanker effectiveness is directly related to the > > characteristics of the noise. One blanker's design specs are > effective on > > noise with certain pulse widths and levels, whereas another > noise blanker > > > > No virus found in this outgoing message. Checked by AVG Anti-Virus. Version: 7.0.323 / Virus Database: 267.9.0/50 - Release Date: 7/16/2005 _______________________________________________ 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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Unfortunately, the KDSP2 is in the wrong part of the receiver chain for
impulse noise reduction. Effective impulse noise reduction needs to be done at the RF/IF level before filtering. The crystal filter in the IF will distort and elongate the noise pulse making it much more difficult to eliminate. A DSP at RF frequencies would probably be a good choice, but much more costly to produce. Dynamic range may also be a problem. The cost of a good noise blanker would be a secondary consideration for those in high noise areas, where the $1000+ radios are seriously impaired. What is a $100 or more to eliminate the noise and be able to fully use the radio. Those with intermittant noise may be less inclined to spend big bucks. Darrell VA7TO On July 18, 2005 05:03 am, W3FPR - Don Wilhelm wrote: > Tom, > > I believe you are speaking of functions that can be (and should be) > implemented in DSP (if it is to 'search', some intelligence is required). > The KDSP2 de-noiser does provide a lot of noise reduction similar to what > you are describing - unfortunately, it is a bit more than $30,40,50. > > The KNB2 deos a good job with impulse noise above the set threshold. The > blanking width can be modified by changing a capacitor if a different width > is needed for a particular noise situation. Beyond that, the addition of > the KDSP2 adds the intellegence and levels of control to deal with other > types of noise. > > 73, > Don W3FPR -- 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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On Mon, 18 Jul 2005, Darrell Bellerive wrote:
> > The cost of a good noise blanker would be a secondary consideration for those > in high noise areas, where the $1000+ radios are seriously impaired. What is > a $100 or more to eliminate the noise and be able to fully use the radio. > Those with intermittant noise may be less inclined to spend big bucks. Well Said! My k2 sits on the shelf, as I live in an old industrial area of the city.....sometime I can operate between 2 AM and 6 AM. I have a LOT of money tied up...but it does have a nice retro look. Thom www.baltimorehon.com/ Home of the Baltimore Lexicon www.tlchost.net/hosting/ Web Hosting as low as 3.49/month _______________________________________________ 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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Thanks, everyone, for all the input on noise blankers.
A more sophisticated noise blanker is certainly possible. It would need about twice as many parts, and to fit in the available space would require nearly all SMDs, including 0603 size passives and TSSOP ICs. This implies a completely pre-assembled module, which is one of the things we tried to avoid in the K2 :) Still, this is definitely on the wish-list. When we do get to it, we'll be looking for testers who have all sorts of horrible noise to throw at it. 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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In reply to this post by Darrell Bellerive
Hi all,
I had a slight problem with my KPA100, but fixed it. I had neglected to solder pin 1 of U1. Its just something about seeing a round land instead of the rectangular ones and skipping over it when soldering thinking it was another part. Got that fixed pretty quickly but have one more problem. I first installed the KPA100 in the K2 and it works perfectly as much as I can tell. I then hooked up the KAT100 in the EC2 enclosure with the cable it it seems to work fine. I then installed the KPA100 in the EC2 enclosure along with the KAT100 and I am getting weird things happening. I am now mostly getting the info 080 when turning on the K2 after turning on the kat100 first. I am doing this with the kat2 installed in the k2 and using ant1 to feed the aux rf on the kat100 faceplate. I think I am doing everything per the manuals, but you know me, I could have missed a few important items in the instructions. If anyone has a suggestion I would appreciate it. I will doing some more testing soon. Steve, W2MY _______________________________________________ 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 wayne burdick
wayne burdick wrote:
> A more sophisticated noise blanker is certainly possible. <snip> > Still, this is definitely on the wish-list. When we do get to it, we'll > be looking for testers who have all sorts of horrible noise to throw at it. My experience over the past 49 years as a ham tells me YES! I want this. Noise of various types is the biggest problem I face in my day-to-day hamming, and it is getting worse and worse. A solution to longer rise-time manmade electrical noise would be welcome. Who knows, the new device might be flexible enough to deal with some types of BPL. -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco _______________________________________________ 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 ALSO WOULD GO FOR A BETTER BLANKER,,,
keeping things in perspective,,,, MY K2,, with MY powerline noise,,, is superior to my Icom 756P2, and my TT omni6+... the tentec has a very good one and the icom does NOT.... to me that is the weakest part of the Icom series bill _______________________________________________ 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 wayne burdick
On Mon, 18 Jul 2005, wayne burdick wrote:
> A more sophisticated noise blanker is certainly possible. > Still, this is definitely on the wish-list. When we do get to it, we'll be > looking for testers who have all sorts of horrible noise to throw at it. Hand raised, Baltimore's worst electrical noises await. Thanks.. 73,Thom-k3hrn www.zerobeat.net Home of QRP Web Ring, Drakelist home page, Free Classified Ads for amateur radio, QRP IRC channel Elecraft Owners Database www.tlchost.net/ Web Hosting as low as 3.49/month _______________________________________________ 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 wayne burdick
While an internal blanker would be consistant with the design goals of the K2,
an external blanker would also be acceptable. Most severe noise problems are at a home QTH, and not at locations where portable operations are conducted. Less noise at the campsite than at home. A fully assembled internal SMD noise blanker module is still preferable to not being able to fully use the K2. Even if we couldn't assemble it, at least we could still plug it in to the headers. :-) Darrell VA7TO On July 18, 2005 09:47 am, wayne burdick wrote: > Thanks, everyone, for all the input on noise blankers. > > A more sophisticated noise blanker is certainly possible. It would need > about twice as many parts, and to fit in the available space would > require nearly all SMDs, including 0603 size passives and TSSOP ICs. > This implies a completely pre-assembled module, which is one of the > things we tried to avoid in the K2 :) > > Still, this is definitely on the wish-list. When we do get to it, we'll > be looking for testers who have all sorts of horrible noise to throw at > it. > > 73, > Wayne > N6KR -- 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 Vic K2VCO
There is an easier way to take care of the noise/NB... Go to your next door
neighbor with a rep. from the utility company. Ask them to turn off their power and then one by one turn the circuits back on to see where the noise is coming from! And then with the power company solve it. This we did here. I can take a S8 noise level and with the 250 cw filter on the KX1, filter the noise out completely. Paul Gates K1 #0231 KX1 #1186 XG1 [hidden email] ----- Original Message ----- From: "Vic Rosenthal" <[hidden email]> To: "Elecraft Reflector" <[hidden email]> Sent: Monday, July 18, 2005 1:09 PM Subject: Re: [Elecraft] Re: KNB2 > wayne burdick wrote: > > > A more sophisticated noise blanker is certainly possible. > > <snip> > > > Still, this is definitely on the wish-list. When we do get to it, we'll > > be looking for testers who have all sorts of horrible noise to throw at > > it. > > My experience over the past 49 years as a ham tells me YES! I want > this. Noise of various types is the biggest problem I face in my > day-to-day hamming, and it is getting worse and worse. A solution to > longer rise-time manmade electrical noise would be welcome. Who knows, > the new device might be flexible enough to deal with some types of BPL. > > -- > 73, > Vic, K2VCO > Fresno CA > http://www.qsl.net/k2vco > _______________________________________________ > 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 > 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 Bill Steffey NY9H
I would think that be-moaning the fact of a better noise blanker would be to
find the source of the noise which is pretty easy to do usually and with the help of the FCC things change. Paul Gates K1 #0231 KX1 #1186 XG1 [hidden email] ----- Original Message ----- From: "Bill NY9H" <[hidden email]> To: "Elecraft Reflector" <[hidden email]> Sent: Monday, July 18, 2005 1:21 PM Subject: Re: [Elecraft] Re: KNB2 > I ALSO WOULD GO FOR A BETTER BLANKER,,, > > keeping things in perspective,,,, > MY K2,, with MY powerline noise,,, > is superior to my Icom 756P2, and my TT omni6+... > > the tentec has a very good one and the icom does NOT.... > to me that is the weakest part of the Icom series > > > > bill > > _______________________________________________ > 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 > 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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On Mon, 18 Jul 2005, Paul Gates wrote:
> I would think that be-moaning the fact of a better noise blanker would be to > find the source of the noise which is pretty easy to do usually and with the > help of the FCC things change. Let's see, using that logic, I can get rid of all the locks on my doors as soon as I know I've found all the crooks and the state has them all in jail. Somehow, like having an effective noise blanker, I'll count on the locks. 73,Thom-k3hrn www.zerobeat.net Home of QRP Web Ring, Drakelist home page, Free Classified Ads for amateur radio, QRP IRC channel Elecraft Owners Database www.tlchost.net/ Web Hosting as low as 3.49/month _______________________________________________ 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 Vic K2VCO
Hi Vic,
Have you met an Evasive Noise Blanker? It won't send 'QRZ test' at you either! 73, Geoff GM4ESD Vic Rosenthal wrote: > My experience over the past 49 years as a ham tells me YES! I want this. > Noise of various types is the biggest problem I face in my day-to-day > hamming, and it is getting worse and worse. A solution to longer > rise-time manmade electrical noise would be welcome. Who knows, the new > device might be flexible enough to deal with some types of BPL. _______________________________________________ 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 wayne burdick
Wayne,
sign me up; I got lots of bad noise from a variety of sources; I would only love my K2 all the more... 73, Dave W5SV wayne burdick wrote: > Thanks, everyone, for all the input on noise blankers. > > A more sophisticated noise blanker is certainly possible. It would > need about twice as many parts, and to fit in the available space > would require nearly all SMDs, including 0603 size passives and TSSOP > ICs. This implies a completely pre-assembled module, which is one of > the things we tried to avoid in the K2 :) > > Still, this is definitely on the wish-list. When we do get to it, > we'll be looking for testers who have all sorts of horrible noise to > throw at it. > > 73, > Wayne > N6KR _______________________________________________ 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 Vic K2VCO
I agree Vic. My location is pretty noise during the day, esp. in the summer.
Frequently it is S5-S7 during the afternoon. The KNB2 does the best job of any noise blanker I have ever had, but it is not up to everything I experience. An effective noise blanker would be high on my list. Eric KE6US -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Vic Rosenthal Sent: Monday, July 18, 2005 10:10 AM To: Elecraft Reflector Subject: Re: [Elecraft] Re: KNB2 wayne burdick wrote: > A more sophisticated noise blanker is certainly possible. <snip> > Still, this is definitely on the wish-list. When we do get to it, > we'll be looking for testers who have all sorts of horrible noise to throw at it. My experience over the past 49 years as a ham tells me YES! I want this. Noise of various types is the biggest problem I face in my day-to-day hamming, and it is getting worse and worse. A solution to longer rise-time manmade electrical noise would be welcome. Who knows, the new device might be flexible enough to deal with some types of BPL. -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco _______________________________________________ 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 _______________________________________________ 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 Vic K2VCO
Joe et al: I experienced the same thing with my KNB2. A "sort of" fix, for me, was to increase the size of both timing capacitors so as to lengthen the blanking pulse. I increased C11 from .001 uF to .0047 uF, and C12 from .0068 uF to 0.033 uF. In each case, this represented an approximately 5X increase. This seemed to help quite a bit, particularly on power line buzz, but I am sure there are further improvements that could be made. I believe that the basic design of the KNB2 needs to be changed, but I haven't the time to play with it now. What got me started was when I had just completed the KNB2, and I set about to test it's operation. I found that the blanker did not respond to my traditional "noise source" (more about that in a minute) but did seem to work when scratching the top of Q22. So, the KNB2 works, in it's own way, but it seems to be effective for only a limited range of noise types. Immediately after completing the KNB2, I tried my "traditional" tests (below) and found that the KNB2 was totally ineffective. I thought it was broken. However, after communicating with Gary Surrency, he put me onto the "scratch Q22" method, and of course, it was just fine. So, what was the difference? Why had my traditional noise blanker test failed? Some background follows: Several years ago (before I owned a K2) I was searching for a controllable noise source to use for testing and aligning noise blanker systems. I thought about what a noise pulse was, and decided that the most important characteristics of noise were (1) very short duration, high amplitude signals, and (2) very wide bandwidth. After a few tries involving use of Model-T ignition coils, door buzzers, some other ways to create "artificial noise", I hit upon the idea of using a sweep generator. If you think about how a sweeper works, it sends out a signal that covers a very wide band, and the dwell time on any particular frequency is very short. If the sweeper is set so that it's output signal covers the entire range of the receiver being tested, then depending on the sweep rate, the time that the swept signal is present in the receiver's IF passband is very small - it appears basically as a noise pulse. At the same time, because some blankers work on the idea of "out of band" noise, the swept signal also meets that requirement. For example, for a HF receiver, I might set the sweeper to start at 100KHz and sweep up to maybe 50 MHz. For a VHF or UHF set, I might set the sweeper to run from 20 MHz below the receiver tuning range to 20 MHz above. In any case, you can see that when using rapid sweep rates the signal is on any particular frequency for only a very short time (microseconds to milliseconds, depending on sweep rate). As a bonus, the output level controls of the sweep generator allowed me to adjust the "noise" pulses from very weak (less than 1 microvolt) to extremely strong (+10 dBm) at the receiver antenna jack. I was using a old HP 8601 that I found on eBay for less than $50, but most any sweeper covering the range will do, and home-made units are not that hard to make, particularly if all you want is "swept noise" and precise control over frequency and output level are not required. By this I mean you don't need "frequency counter" type readouts, and the output level need not be precisely calibrated. What I was actually trying to do was simulate 160 meter LORAN pulses and "Woodpecker" over the horizon radar signals, which a few years ago were among the most egregious "QRN" ever heard. By adjusting the sweep rate, I could simulate signals "ticking over" once or twice a second (an idling engine type noise), to "power line buzz" which occurs at 120 Hz. This worked like a charm, and was great for adjusting noise blankers, such as the ones in my Drake "C" line. As years passed, I found the setup worked with pretty much any rig having a noise blanker, such as the Kenwood, ICOM and Yaesu sets, as well as most everything else. In fact, this setup has worked on anything I have tried so far, except for the KNB2! To really give a "real world" test, I could also mix in signals from conventional signal generators to see how much the blankers "hashed up" the wanted signal while doing their thing. I used a scope to look at either / or the receiver IF signal or the audio output. It was all very interesting and informative, and I learned quite a bit about blankers in the process. So, what's with the KNB2? Possibly one reason the Elecraft KNB2 fails this test is because it was designed after the LORAN A stations and the "Woodpecker" were history. I don't know this for a fact, it is just supposition. However, I maintain that a good noise blanker should be able to handle this type of interference, because who knows when some administration or military group somewhere will decide to use the HF bands for pulse (LORAN) or swept signal (Woodpecker) type transmissions again. To me, a good blanker should be able to handle ignition noise, power line leaks, electric appliances, lightning, static discharges from raindrops or snowflakes hitting the antenna, the "Woodpecker" and more. No blanker can completely clean up all noise, and some will distort the intended signal to a greater or lesser degree while operating, but all should produce a significant reduction in noise. Natural lightning is perhaps the most difficult, because the pulse duration can be quite long, but I believe putting up with a "hole" in the desired signal for several milliseconds (or tens of milliseconds?) is preferable to having to listen to those very loud crashes. My present rig, other than the K2, is a Yaesu FT-1000 Mark 5. It has 2 blanker settings, each of which is adjustable over a wide range of levels. It is interesting to hear even raucous power line noise or TV set horizontal oscillator signals disappear as adjustments are made. However, I will also say that at the more aggressive settings, the Yaesu blanker can "hash up" a signal pretty badly. It becomes a balancing act to use enough blanker to get rid of the noise while at the same time maintaining enough intelligibility to copy. Just some idle ramblings. I will go home now. I hope some of you find this interesting. - Jim, KL7CC _______________________________________________ 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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