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. -- o...@nerdnetworks.org (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:Elecraft@mailman.qth.net >> >> 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
