Will the K2 noise blanker help with this QRM?
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Now that I've had my K2 working for a few weeks, I've begun to get a
sense of what the local RF conditions at my location are like. I live in a dense urban environment, in an apartment building, so I know that I'm going to have to live with a fair amount of QRM. That said, I'm seeing some noise on 80m that is always present at night, on 3580 khz and other places. It looks like strong, steady carriers every 10-20 hz. The noise level is a constant S9 or more. I'm just wondering if the K2 noise blanker would help with this. You can see a waterfall screenshot and listen to a wav file example here: http://nerdnetworks.org/stuff/80m_waterfall.png http://nerdnetworks.org/stuff/80m_qrm.wav Thanks in advance for any suggestions! -- [hidden email] (Owen B. Mehegan) 'Thank you in advance for having my back.' --Chas ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Will the K2 noise blanker help with this QRM?
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no the noise blanker is not going to help with that sort of noise, it's
designed for impulse type noise (ignition noise, electric fences etc ) The DSP audio filter has an auto notch feature that can remove a carrier and this may help somewhat On Thu, 2010-12-23 at 18:29 -0800, Owen B. Mehegan wrote: > Now that I've had my K2 working for a few weeks, I've begun to get a > sense of what the local RF conditions at my location are like. I live > in a dense urban environment, in an apartment building, so I know that > I'm going to have to live with a fair amount of QRM. That said, I'm > seeing some noise on 80m that is always present at night, on 3580 khz > and other places. It looks like strong, steady carriers every 10-20 > hz. The noise level is a constant S9 or more. I'm just wondering if > the K2 noise blanker would help with this. You can see a waterfall > screenshot and listen to a wav file example here: > > http://nerdnetworks.org/stuff/80m_waterfall.png > http://nerdnetworks.org/stuff/80m_qrm.wav > > Thanks in advance for any suggestions! > > -- > [hidden email] (Owen B. Mehegan) > 'Thank you in advance for having my back.' > --Chas > > > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html -- 73 Brendan EI6IZ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Will the K2 noise blanker help with this QRM?
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In reply to this post by omehegan
Chas,
The K2 noise blanker works well on impulse type noise (like gasoline engine impulse noise or lightning static), but it is not effective on noise that has a slower rise time such as general atmospheric noise. I would suggest the KDSP2 noise reduction algorithms as a potential better solution for the noise you are encountering. 73, Don W3FPR On 12/23/2010 9:29 PM, Owen B. Mehegan wrote: > Now that I've had my K2 working for a few weeks, I've begun to get a > sense of what the local RF conditions at my location are like. I live > in a dense urban environment, in an apartment building, so I know that > I'm going to have to live with a fair amount of QRM. That said, I'm > seeing some noise on 80m that is always present at night, on 3580 khz > and other places. It looks like strong, steady carriers every 10-20 > hz. The noise level is a constant S9 or more. I'm just wondering if > the K2 noise blanker would help with this. You can see a waterfall > screenshot and listen to a wav file example here: > > http://nerdnetworks.org/stuff/80m_waterfall.png > http://nerdnetworks.org/stuff/80m_qrm.wav > > Thanks in advance for any suggestions! > > -- > [hidden email] (Owen B. Mehegan) > 'Thank you in advance for having my back.' > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by omehegan
3580 is a magic frequency, actually 3979.xx is the vertical (horizontal?) oscillator frequency in OLD tube TV sets. I've been listening to that buzz for decades. Best Holiday Wishes to all - Monty K2DLJ O That said, I'm > seeing some noise on 80m that is always present at night, on 3580 khz > and other places. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Will the K2 noise blanker help with this QRM?
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Oh good grief. 3.579 (approx) MHz is the color burst frequency, and pretty much any standard NTSC color TV set (vacuum tube or solid state) has a crystal oscillator that runs on that frequency. The _horizontal_ sweep oscillator is on about 15 kHz, and the _vertical_ sweep oscillator runs at slightly less than 60 Hz. This same 3.579 MHz oscillator is the reason for the persistent weak signal on 14.312 or 14.313 (the 4th harmonic of 3.579) that plagues many of us. Also, many devices use this same 3.579 (more or less) frequency to control some internal function or process - crystal controlled clocks, fax machines, microwave oven timers, and video games being only few examples. TV sets are locked to a particular frequency by the transmission they receive, whereas other devices are not. This is the reason you can often hear many many individual signals around these frequencies - particularly on 20 meters. I am not too sure about more modern HDTV receivers. Hopefully they use a different mechanism,. so perhaps we will see a gradual lessening of this problem as time passes. Or not. - Jim, KL7CC Monty Shultes wrote: > 3580 is a magic frequency, actually 3979.xx is the vertical (horizontal?) oscillator frequency in OLD tube TV sets. I've been listening to that buzz for decades. > Best Holiday Wishes to all - Monty K2DLJ > > O That said, I'm > >> seeing some noise on 80m that is always present at night, on 3580 khz >> and other places. >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Will the K2 noise blanker help with this QRM?
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In reply to this post by MontyS
On 12/24/2010 3:34 AM, Monty Shultes wrote:
> 3580 is a magic frequency, actually 3979.xx is the vertical > (horizontal?) oscillator frequency in OLD tube TV sets. I've > been listening to that buzz for decades. 3579.545...kHz is the color subcarrier frequency in the NTSC (analog) color television system which was used in the US and many other countries for both tube-type and solid-state receivers. It is not used in current digital TV systems. See http://en.wikipedia.org/wiki/NTSC for more than you ever wanted to know about NTSC. -- 73 de K2ASP - Phil Kane Elecraft K2/100 s/n 5402 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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----- Original Message -----
> On 12/24/2010 3:34 AM, Monty Shultes wrote: > >> 3580 is a magic frequency, actually 3979.xx is the vertical >> (horizontal?) oscillator frequency in OLD tube TV sets. I've >> been listening to that buzz for decades. incorrect .... the above is the colorburst frequency and you list the correct freq as 3.579545. the vertical rate is 60 Hz, the horizontal rate is 15,734 Hz. The above does not matter if the set is solid state or (old tubes). It is usually the "flyback" (HV transformer that helps generate HV and horizontal scan rates among other things) the radio hears. And some people with sensitive hearing can also hear it (really). 72 Ron, wb1hga ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Jim Wiley-2
That's what I was afraid of. I spent some time the other night looking
into DSP filtering that I could do on my PC, but I realized after awhile that once the S9+20 signal has gone through the K2 and deafened it, filtering it out of the audio is a bit pointless - I'm still going to be missing all the weaker signals. If anyone wants to look at and comment on the intermittent horrible 40m QRM I get, here are some visual and audio samples: http://nerdnetworks.org/stuff/40m_waterfall.png http://nerdnetworks.org/stuff/40m_qrm.png http://nerdnetworks.org/stuff/40m_qrm.mp3 This stuff manifests as an S9 or greater buzz/hash that slowly creeps up and down in frequency. 40 will be nicely usable and relatively quiet, and then this stuff starts up and I might as well just shut off the radio (or try 80, which is at least sometimes usable even with the previous QRM I asked about). I suspect that if a constant-frequency QRM like the stuff on 80 can't be filtered easily, this varying stuff can't be either. I have heard about the MFJ and Timewave noise canceling gizmos, I can imagine one of those working OK on the TV noise, but I would assume that this stuff that moves around wouldn't be so easy to deal with. My friend told me that I need to use a "move to a cabin in the woods" filter. -- [hidden email] (Owen B. Mehegan) 'Something is rotten in the state of Denmark.' --William Shakespeare On Dec 24, 2010, at 4:01 AM, Jim Wiley wrote: > > > Oh good grief. 3.579 (approx) MHz is the color burst frequency, and > pretty much any standard NTSC color TV set (vacuum tube or solid > state) has a crystal oscillator that runs on that frequency. The > horizontal sweep oscillator is on about 15 kHz, and the vertical > sweep oscillator runs at slightly less than 60 Hz. This same 3.579 > MHz oscillator is the reason for the persistent weak signal on > 14.312 or 14.313 (the 4th harmonic of 3.579) that plagues many of us. > > > Also, many devices use this same 3.579 (more or less) frequency to > control some internal function or process - crystal controlled > clocks, fax machines, microwave oven timers, and video games > being only few examples. TV sets are locked to a particular > frequency by the transmission they receive, whereas other devices > are not. This is the reason you can often hear many many individual > signals around these frequencies - particularly on 20 meters. > > > I am not too sure about more modern HDTV receivers. Hopefully they > use a different mechanism,. so perhaps we will see a gradual > lessening of this problem as time passes. Or not. > > > - Jim, KL7CC > > > > Monty Shultes wrote: >> >> 3580 is a magic frequency, actually 3979.xx is the vertical >> (horizontal?) oscillator frequency in OLD tube TV sets. I've been >> listening to that buzz for decades. >> Best Holiday Wishes to all - Monty K2DLJ >> >> O That said, I'm >> >>> seeing some noise on 80m that is always present at night, on 3580 >>> khz >>> and other places. >>> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[hidden email] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> >> ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by omehegan
Owen,
Unless I'm reading the waterfall spectrum frequency scale incorrectly, the line spacing you see on 80M is suspiciously close to 60 Hz. Do you observe this same interference line spacing across the 80M band, or only in the vicinity of 3580 kHz? The audio file sounds like the noise I experience here in the northeast U.S. during much of the year, except immediately after a strong rainstorm, which suggests an arc source on the nearby utility distribution system in my own situation -- your source(s) may be different. While there are many possible methods of 60 Hz power line interference coupling into your setup, most involve some form of common-mode coupling. A good tutorial on this issue is Jim, K9YC's article, which has been frequently cited in this forum: http://www.audiosystemsgroup.com/RFI-Ham.pdf . Another widely cited article is that by Chuck, W1HIS: http://www.yccc.org/Articles/W1HIS/CommonModeChokesW1HIS2006Apr06.pdf . Others have weighed in on the feasibility of attenuating the interference with DSP, but I would start by trying to eliminate possible sources of 60 Hz noise within your own household. Try running your K2 from a battery source while turning off individual power circuits at your breaker panel (if accessible to you), and see if the noise disappears. Of course it's essential to enlist the support of other members of the household before you begin turning off their favorite gadgets! The interference sources may well be outside your own apartment, yet within your building, in which case greater diplomatic skill is required. Your 40M noise source sounds qualitatively different to me from that on 80M, and the waterfall spectrum display is obviously different from that you observed on 80M. It would appear that you may be dealing with at least two different sources of interference. 73, and good luck! Mike, K8CN |
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