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Re: Hum noise filter help...

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  • Christopher Gross
    Another possibility (besides filtering) would be the two-antenna approach, which is something I keep meaning to try but haven t gotten around to yet. Basically
    Message 1 of 21 , Mar 1 8:35 AM
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      Another possibility (besides filtering) would be the two-antenna approach, which is
      something I keep meaning to try but haven't gotten around to yet. Basically you use a second
      antenna solely for picking up AC noise (placing it near some noisy wiring or an appliance in
      the house) and combine the signal with the one from the real antenna-- but out of phase, so
      that the hum is cancelled out. I think the only tricky part would be in getting the two signals
      balanced.

      I found a Web page by an amateur radio operator who had a similar problem, except that he
      was listening on shortwave rather than VLF:

      http://www.qsl.net/k9gdt/radio/k9klt/k9klt.htm

      Chris
    • Walter
      Hi Chris, ... That s something I didn t think of. In order to get a feeling: how far away are the transmitters, what power, what frequency ? Walter
      Message 2 of 21 , Mar 3 12:02 AM
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        Hi Chris,

        a little late:

        > Actually AC hum is less of a problem for me now than BCI; as I've
        > mentioned before, there are a lot of high-powered commercial
        > transmitters in the area, and they produce images down in the LW and
        > VLF range. There is also quite a bit of rectification going on in the
        > house and nearby structures, which means that I'm picking up audio
        > signals by induction!

        That's something I didn't think of. In order to get a feeling: how far
        away are the transmitters, what power, what frequency ?

        Walter
      • Walter
        ... Hi Bear, vertical? Horizontal frequency is 15625 Hz here in Germany. (line repetition rate) picture repetition is 25 Hz or 50 Hz for a Halbbild . What I
        Message 3 of 21 , Mar 3 12:08 AM
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          > Try configuring one of the Delay or Echo
          > filters with the delay time as 1/Horizontal frequency,

          Hi Bear,

          vertical? Horizontal frequency is 15625 Hz here in Germany. (line
          repetition rate) picture repetition is 25 Hz or 50 Hz for a 'Halbbild'.

          What I observe: lots of weak lines without delay line. Much less but
          very strong lines with delay line active.

          Walter
        • mike l dormann
          any one of you guys using an inspire DAN type filter? mike w7dra, inventer of the DAN On Sat, 03 Mar 2007 08:08:02 -0000 Walter
          Message 4 of 21 , Mar 3 1:17 AM
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            any one of you guys using an inspire "DAN" type filter?

            mike w7dra, inventer of the DAN
            On Sat, 03 Mar 2007 08:08:02 -0000 "Walter" <fedderwi@...>
            writes:
            > Try configuring one of the Delay or Echo
            > filters with the delay time as 1/Horizontal frequency,

            Hi Bear,

            vertical? Horizontal frequency is 15625 Hz here in Germany. (line
            repetition rate) picture repetition is 25 Hz or 50 Hz for a 'Halbbild'.

            What I observe: lots of weak lines without delay line. Much less but
            very strong lines with delay line active.

            Walter




            [Non-text portions of this message have been removed]
          • Christopher Gross
            ... Hi Walter, I m about 10-15 miles from the NJ Meadowlands, where there are a lot of 50 kW AM transmitters (WABC is the strongest signal-- I once picked it
            Message 5 of 21 , Mar 3 6:18 AM
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              >
              > That's something I didn't think of. In order to get a feeling: how far
              > away are the transmitters, what power, what frequency ?
              >
              > Walter
              >

              Hi Walter,

              I'm about 10-15 miles from the NJ Meadowlands, where there are a lot
              of 50 kW AM transmitters (WABC is the strongest signal-- I once picked
              it up on my kitchen sink with a telephone induction coil!), and there
              is a 10 kW AM transmitter within walking distance (WMCA97: 970 kHz).
              Since 9/11, some of the stations that used to transmit from the WTC
              have been transmitting from the Alpine Tower, which is a few miles
              north of here, and my home town (Oradell, NJ) has recently started a
              public-service radio station at the high end of the AM band.

              Here is a list of some of the stations transmitting in the area:

              WABC (770 kHz, 50 kW)
              WMCA57 (570 kHz, 50 kW)
              WMCA97 (970 kHz, 10 kW)
              WINS (1010 kHz, 50 kW)
              WBBR (1130 kHz, 50 kW)
              WOR (710 kHz, 50 kW)
              WCBS (880 kHz, 50 kW)

              And so on, and so on... There are also a lot of TV and FM transmitters
              in the area, but I've never noticed any RFI from them.

              Chris
            • Walter
              ... Thats most interesting. I have transmitters 10-15 miles away but ten times the power. So I should think about these effects. Maybe it s the explanation to
              Message 6 of 21 , Mar 3 7:08 AM
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                > WABC (770 kHz, 50 kW)
                > WMCA57 (570 kHz, 50 kW)
                > WMCA97 (970 kHz, 10 kW)
                > WINS (1010 kHz, 50 kW)
                > WBBR (1130 kHz, 50 kW)
                > WOR (710 kHz, 50 kW)
                > WCBS (880 kHz, 50 kW)

                Thats most interesting. I have transmitters 10-15 miles away but
                ten times the power. So I should think about these effects. Maybe
                it's the explanation to some signals I can't pin down.

                Thanks!
                Walter
              • Christopher Gross
                ... Maybe ... I think it s why I have so much trouble picking up WWVB clearly-- the signal comes through, but it s buried under a lot of noise (TV picture-tube
                Message 7 of 21 , Mar 3 7:35 AM
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                  --- In VLF_Group@yahoogroups.com, "Walter" <fedderwi@...> wrote:

                  Maybe
                  > it's the explanation to some signals I can't pin down.
                  >

                  I think it's why I have so much trouble picking up WWVB clearly-- the
                  signal comes through, but it's buried under a lot of noise (TV
                  picture-tube harmonics may be involved as well), and one of the mixing
                  products of WOR and WABC is 60 kHz. I've also found "noise zones" at
                  120 and 200 kHz, which correspond to the mixing products of other AM
                  stations...


                  Chris
                • Dale Reed
                  Sorry if my comment is off thread but the low end of the AM broadcast band(570kHz for example) is noisy at our home because of what I assume is a defective
                  Message 8 of 21 , Mar 3 7:47 AM
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                    Sorry if my comment is off thread but the low end of the AM broadcast
                    band(570kHz for example) is noisy at our home because of what I assume is a
                    defective power transformer(or the connections to it) on the street. I
                    e-mailed Seattle City Light a few months ago but apparently they have more
                    important fish to fry. Dale
                    ---
                    $ dale-reed@... Seattle, Washington $
                  • John Popelish
                    ... You should be able to get a much better idea where this noise is coming from, if you have a small, battery powered AM receiver to use as a signal sniffer.
                    Message 9 of 21 , Mar 3 8:30 AM
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                      Dale Reed wrote:
                      > Sorry if my comment is off thread but the low end of the AM broadcast
                      > band(570kHz for example) is noisy at our home because of what I assume is a
                      > defective power transformer(or the connections to it) on the street. I
                      > e-mailed Seattle City Light a few months ago but apparently they have more
                      > important fish to fry. Dale

                      You should be able to get a much better idea where this
                      noise is coming from, if you have a small, battery powered
                      AM receiver to use as a signal sniffer. Tune it to the low
                      end of the band, between stations, so you just hear noise.
                      Then place the radio near the power lines entering or
                      exiting the power meter base or other accessible parts of
                      the distribution system, and listen for an increase in the
                      noise level. You can also check out at the pole, near the
                      ground wire that runs down under the bottom of the pole. It
                      may be louder at some other near by pole than yours, so you
                      can help the power company locate the bad connection. Such
                      bad connections are a fire hazard, so the power company
                      should be interested in fixing this.
                    • Dale Reed
                      ... Already did this. Also did it inside the house with the main circuit breaker on and off which changes the noise in the receiver and I guess it shows that
                      Message 10 of 21 , Mar 3 8:49 AM
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                        > You should be able to get a much better idea where this noise is coming
                        > from, if you have a small, battery powered AM receiver to use as a signal
                        > sniffer.

                        Already did this. Also did it inside the house with the main circuit
                        breaker on and off which changes the noise in the receiver and I guess it
                        shows that the source is *not* in the house. Kinda hard to tell because the
                        noise changes direction as determined by rotating the simple magnetic loop
                        antenna of the AM radio.

                        Reminds me a couple decades ago when I served on a Seattle Light voluntary
                        committee concerned with the old(and I hope now put to bed) concern about
                        possible dangers to humans from the EM fields caused by overhead powerlines.
                        As I remember measurements made by the power companies, and others, that the
                        largest magnetic fields in most homes were caused by currents flowing in
                        water pipes and electrical wiring rather than the fields from power lines
                        either on the street or high voltage lines near some homes.

                        Aha, I got it back on the 60Hz thread! Dale
                        ---
                        $ dale-reed@... Seattle, Washington $
                      • Shawn Korgan
                        Hi Mike, It s too bad the DAN filter is not available in kit format... I know when I used one for a short time it worked fairly well. It would be nice to own
                        Message 11 of 21 , Mar 3 7:52 PM
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                          Hi Mike,

                          It's too bad the DAN filter is not available in kit format... I know
                          when I used one for a short time it worked fairly well. It would be
                          nice to own a DAN filter for experimental use. Do any of the chips
                          in the circuit need programmed or can a person simply purchase all
                          the parts and solder everything together?

                          <http://image.gsfc.nasa.gov/poetry/inspire/DAN/index.html>

                          I believe the INSPIRE project has all the running DAN filters. Bill
                          Taylor had an extra unit which we were considering using for an on-
                          line audio stream from Alaska however I'm not certain what happened
                          with this project/unit?

                          Shawn
                        • mike l dormann
                          i have bill taylors unit and the one given to me by len yee. i do not know if he has any left. i have the original 8 bit at 122 KHZ, a 12 bit stereo unit at
                          Message 12 of 21 , Mar 3 11:52 PM
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                            i have bill taylors unit and the one given to me by len yee. i do not
                            know if he has any left.

                            i have the original 8 bit at 122 KHZ, a 12 bit stereo unit at 122 KHZ,
                            the 8 bit built for bill and his arctic "dew line" set up that never got
                            going.

                            my units all MSI/SSI - 74121/74160/7408 et al, plus a 6116 8x1024 memory
                            some nice maxim A/Ds and D/As

                            ancient history..............

                            mike w7dra
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