ate: Mon, 05 Feb 2001 21:37:12 -0800 From: Wayne Burdick Subject: [Elecraft] K2 noise blanker mod - theory discussion A couple of builders are wondering whether to do the KNB2 mod or not. One wrote: > > In the spirit of making something excellent even more excellent > > and having the need to build something (just finished the K1) I thought I > > would do the mod. There's also the very first line in the alert: "We have > > discovered that the original KNB2 noise blanker impacts K2 receive > > performance somewhat, even when turned OFF". That's good enough for me. > > > > I have noticed that the new circuit has no band pass adjustment as the > > original had and as the current K1 NB has. The tweaking part of my brain > > wonders why this is so, even though I think it is slick no adjustment is > > necessary. The design part of my brain (almost non-existent) can't figure > > out the non-need for it. Is it just that it is so well matched now by > > design? The long answer: The modified noise blanker circuit better terminates the post-mixer I.F. amplifier. This eliminates some intermod noted by our European customers who lived near high-power broadcast stations, and in general improves the receiver's IMD performance with the blanker installed. Specifically, the new filter uses a resistive input divider rather than a capacitive divider, providing increased return loss (i.e., lower SWR) in the vicinity of the I.F. (about 4.8-5.1 MHz). The original circuit had good return loss too, but over a narrower band, due to the very high Q of its filter. The lower Q of the new filter is the reason why it need not be tuned. The lower Q also provides a reduced delay, which may slightly alter the NB performance on certain noise types, but overall the performance is about the same. Some builders have taken the "ain't broke, don't fix it" approach and have not made the mods. But anyone concerned with maximizing the K2's receive performance should definitely do it, especially if they live in a high-QRM area. And of course all KNB2s shipped since the mods were first made have been supplied with the new parts. 73, Wayne N6KR +++++++++++++++++++++++++++++++++++++++++++++ Date: Sat, 19 Aug 2000 14:07:35 -0400 From: "David A. Belsley" Subject: Re: [Elecraft] Searching Elecraft archives Bob: Build a small in-line plug (8 pin, but 6 will do) to replace P1 that has 100 ohms between pins 1 and 6 470 ohms between pins 1 and 5 560 ohms between pins 2 and 6 Plug and play. best, dave belsley, w1euy - --On Saturday, August 19, 2000 10:36 AM -0700 Bob Tellefsen wrote: > We are supposed to be able to search the archives on a keyword basis, but > so far I can't seem to figure it out. > Can anyone clue me in? > > I'm looking for info on the modification of the early Noise Blanker to the > current version. +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > I want to do some testing with the NB removed from the K2. I vaguely > remember a mention of how to add some resistors to replace temporarily the > pad that now resides on the NB and that goes away when the NB is removed. > > Can anyone direct me? > Thanks and 73, > Bob N6WG ++++++++++++++++++++ Reply-To: "Ron D'Eau Claire" From: "Ron D'Eau Claire" To: Subject: Re: [Elecraft] NB option K2 Date: Tue, 4 Jun 2002 09:01:18 -0700 > What is the Noise Blanker supposed to block? Besides automobile > noises... > Daniel It's excellent for killing the racket from cheap lamp dimmers! Ron AC7AC K2 # 1289 +++++++++++++++++++++ Date: Tue, 04 Jun 2002 11:03:09 -0500 To: ham_tech at juno.com, elecraft at mailman.qth.net From: Tom Hammond =?iso-8859-1?Q?N=D8SS?= Subject: Re: [Elecraft] NB option K2 Daniel: >Tuning up in the frequency I find some harmonic noises. Then I zero beat >this tone. > >What is the Noise Blanker supposed to block? Besides automobile >noises... The noise blanker pretty much works ONLY on short-duration spike-type noises, such as spark plug noise, most power line noises (due to loose hardware or broken insulators), electric fencers, vacuum cleaners, electric mixers. It will (sometimes) help (only) to reduce the popping from precipitation static as well, but it's not specifically designed to address this type of noise. What it won't address such things as (certainly NOT an exhaustive list): atmospheric noise (static from storms) key clicks (or splatter) from nearby stations real 'signals' received (e.g. spurs from your PC, internal CPU, mixing products) spurs from the TV >Besides what is written in the manual about the theorectical process of >the circuit, does anyone have a different explaination?? I'm afraid I can't help you there... but I'll bet there is someone out there who can. 73, Tom Hammond N0SS +++++++++++++++++ Date: Tue, 04 Jun 2002 09:09:03 -0700 From: Phil Wheeler Organization: Outstanding To: ham_tech at juno.com Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] NB option K2 Daniel, The NB (any NB) is not effective on atmospheric noises you receive on the antenna. It will deal with ignition noise and also local noise at a fixed station which is generated by various sources. For example, if yoiu have a Dremel tool or an electric drill, run it near the rig and you will find the NB does a good job on that. I occassionally hear that type of noise (dunno where from) when operating in the shack and the NB does a good job on it. There are devices which deal with the noised attibuted to atmospherics (for want of a better word). The basically use a dedicated noise antenna and amplify and phase shift that noise to cancel the noise received on your main antenna. I have one (JPS ANC-4) and find it fussy to adjust and seldom use it. I think MFJ sells one. And there was an article or two re this (wiht a design) in QST in the early to mid 90s. 73, Phil ham_tech at juno.com wrote: >Hi, > >Tuning up in the frequency I find some harmonic noises. Then I zero beat >this tone. > >What is the Noise Blanker supposed to block? Besides automobile >noises... +++++++++++++++++++ From: "ZOOM" To: , Subject: Re: [Elecraft] NB option K2 Date: Tue, 4 Jun 2002 12:11:37 -0400 The noise blanker is used to block/attenuate pulsed noise. Robert VE3RPF ++++++++++++++++++++ Date: Tue, 04 Jun 2002 09:16:02 -0700 From: Phil Wheeler Organization: Outstanding To: ham_tech at juno.com Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] NB option K2 Daniel, Following up on my last msg, here are some links re antenna noise cancellers. http://www.hard-core-dx.com/nordicdx/antenna/special/mfj1026_7.html http://www.timewave.com/a_doc.html (ANC-4 manuals) http://www.eham.net/forums/Elmers/19524 As is indicated, they can be made to work. But it takes a well-selected noise antenna and a bit of tweaking. 73, Phil ++++++++++++++++++++