Recent changes to Home

Home modified by Nathan Towne

Nathan Towne — Fri, 11 Feb 2022 17:03:49 -0000

--- v2
+++ v3
@@ -1,97 +0,0 @@
-sidmon for sudden ionospheric disturbance (SID) monitoring
-
-Introduction
-
-sidmon is a python program for receiving and recording submarine-transmitter signal intensities in the VLF frequency range using a computer sound card and the alsaaudio package.  The intensities of these signals reflect the ability of radio waves at those wavelengths to propagate in what is essentially a waveguide formed by the earth and the ionosphere above it.  Fluctuations in those signal intensities often reflect daytime perturbations of the ionosphere by solar processes, such as solar flares and coronal mass ejections, making VLF receivers useful tools for probing the sun and the earth's ionosphere.  For more information see the SID Monitors page and the SID data access page at the Stanford Solar Center.
-
-
-
-sidmon 3 is an enhanced sidmon 2 that can employ two loop antennas that are combined to form a simple phased array.  With a single loop, the signal intensity of a transmitter depends on the orientation of the loop relative to the great arc to the transmitter.  A loop is most sensitive if it is edge on (tangent) to the great arc, while an orthogonal loop intercepts no magnetic flux and hence has zero sensitivity to that transmitter.  Two loops, in contrast, can be combined with weights that 'point' the combined loops toward a transmitter, catching maximum flux into the data stream, while injecting equivalent noise of only one ADC.  This can be done digitally for each transmitter being monitored.  In this sense, the antenna/receiver system become isotropic - able to receive with equal sensitivity in all directions.
-
-This is an interesting technique for monitoring transmitter intensities, detecting SIDS, and isotropic observing in general.  There is also something interesting about the orthogonal beams mentioned earlier, i.e., the ones that intercept no flux from its transmitter, such as happens when the waves are traveling along the great arc.  But when the path deviates from the great arc, it catches some flux, which the receiver picks up.  So the more interesting thing is that the orthogonal beam can detect deviations of the path from the great arc.  In fact, there is remarkable sensitivity realized in sidmon 3 of < 0.1 degree on one-minute integrations, that allows another way to detect SIDs and how the ionosphere is impacted by x-rays from solar flares.  
-
-In the following figure, the uncalibrated intensity is the blue trace, while the calibrated direction relative to the great arc (more precisely, the beam pointing) is the red trace, to which the vertical scale applies.  Notice the very small range of that scale.  There is a SID detection after 1900 UT, evident in both the intensity trace and direction trace..
-
-
-
-The sidmon 2 usage document describes most of the setup of a sidmon 3 observatory.  The remainder of this document describes the setup of the loop antennae and beam pointing specific to sidmon 3.
-
-Antenna setup
-
-To measure source direction and transients, two loop antennae are required.  It is preferable to fabricate them identically, although antenna gains can be entered into the header file.  For example, imagine two antennae on one-meter spindles, one consisting of 30 turns, and the other 35 turns.  Their gain can be set to 30 and 35 m² T, where 'T' represents a turn on the spindle.  Their entries in the header files would be: 
# antenna ant0, 30
-# antenna ant1, 35
  The two loops are then mounted upright and at right angles to each other a short distance apart.  The antennae are wired to a stereo 3.5 mm audio connector.  In these connectors, the tip contact is channel 0, the center contact is channel 1, and the bottom sleeve contact is common.  Connect one wire from each antenna to the common contact, and the other wire of each to one or the other of the two remaing contacts.  It does not matter particularly which.
-
-At this point the user should set up single-antenna operation as outlined in the sidmon 2 usage document, and taking data.  It is not necessary to set up the veto feature.  At this point it time to determine a setting for the beam direction for each transmitter.  This value is entered in the header file on the transmitter's line.  To do this, there is a switch, --scan <point count>, that tells sidmon to scan beam rotation angles, taking intensity data and a cross correlation in the process.  
src/sidmon.py --device <device name> --scan 46 --channelcount 2
  The scan is over 180 degrees – not 360ˆ because the second 180 is redundant.  When done, it plots both of those quantities as shown in this figure.
-
-
-
-The first plot is of intensities of the transmitters being recorded.  The second is of the x/y cross correlation – more precisely they are of inverse tangents representing angles of the transmitter away from the primary beam, essentially a pointing error.  We are looking for the beam angle at which the error angle is zero, meaing that the primary beam is on the transmitter's bearing.  For example, the setting for the red trace is +44°, and this value is entered in the transmitter's line in the header file.
-
-Note that the slope of the error angle as a function of beam angle need not be negative.  It depends on which of the antennae is channel 0.  Also, because the loops can be flipped, which reverses the sign of the intercepted flux, this orientation of the loops affects the slope as well.  So one may set the slope as part of the setup by reversing the channel assignments, reversing the leads of one of the loop, or flipping one of the antennae.  This orientation also affects the sign of the angular error represented in the data.  
-
-One can fine tune the beam angle using from a supersid_plot.py graph, such as shown in the following figure of NML direction (relative to its primary beam) during day-time hours where the signal is relatively stable.  
src/supersid_plot.py -af <file path> -ps NML2 --dir

-
-
-
-During those hours, the transmitter direction is -0.1° from its primary beam.  Although already quite small in this example, this difference can be set to zero for later data taking by shifting the beam angle in the transmitter line in the header file by 0.1°, the sign of which is determined by the slope in the scan figure above.  Do not perform this step during night-time hours as the signal direction, like the intensity, varies erratically during those hours.
-
-The header file
-
-An example header file monitoring two transmitters in two goups and recording directions is this.
-
-# Site = A151
-# Contact = Nathan Towne towne56@ownmail.net
-# Longitude = -107.2391
-# Latitude = 34.1116
-# Elevation = 2020
-# LogInterval = 4.87
-#
-# Stations = NPM, NAA, NPMd, NAAd
-# Frequencies = 21400, 24000, 21400, 24000
-#
-# antenna = ant0, 0.89, 166.0
-# antenna = ant1, 1.0, 76.0
-#
-# samplerate = 64000
-# fourierframe = 16384
-# integrationtime = 4.87
-#
-# group = npm, 21100, 21700, 1
-# transmitter = NPM, 21400, lambda f: np.exp(-((f - 21400)/47)**2/2), -71.4, +21.420166, -158.151140, Pearl Harbour; Lualuahei; HI
-#
-# group = naa, 23600, 24400, 1
-# transmitter = NAA, 24000, lambda f: np.exp(-((f - 24000)/47)**2/2), 85.2, +44.644936, -067.281639, Cutler; ME
-
-Some of this is mentioned in the sidmon 2 usage document.  When running in the --channelcount 2 mode, there are additions in the Stations and Frequencies lines for the benefit of supersid_plot.py because sidmon outputs directions as well as intensities.  The additional names are arbitrary, but must be distinct.  There are also additional parameters in the transmitter lines.  To reiterate, this file may only be used with the sidmon --channelcount 2 switch because of the additional parameters.
-
-The antenna lines are there to provide the gain parameter.  In the example above, there is an additional parameter giving the antenna's orientation relative to geographic north, for reference.  But it is not used by sidmon. 
-
-The parameters samplerate, fourierframe, and integrationtime are present in the file and should not be given on the commandline.  The sample rate is in Hz; the fourier frame sample count should not be changed; and the integration time is in seconds.   The last is a duplicate of the LogInterval parameter.
-
-The transmitter lines have one additional required parameter beyond those required by sidmon 2, which is the beam direction in degrees as determined by the scan plot.  In the example above there are also latitude, longitude, and a description string placed there for reference.
-
-Other notes
-
-supersid_plot.py allows the --dir switch, which tells supersid_plot.py to show the vertical scale on the plot.  Use this switch when plotting directions where, unlike intensities, there is a definite unit to the quantities plottted.  The second figure above shows the scale and label with this switch.
-
-
-
-
-
-
-
-
-

Home modified by Nathan Towne

Nathan Towne — Fri, 11 Feb 2022 17:02:01 -0000

--- v1
+++ v2
@@ -1,8 +1,97 @@
-Welcome to your wiki!
+sidmon for sudden ionospheric disturbance (SID) monitoring

-This is the default page, edit it as you see fit. To add a new page simply reference it within brackets, e.g.: [SamplePage].
+Introduction

-The wiki uses [Markdown](/p/sidmon3/wiki/markdown_syntax/) syntax.
+sidmon is a python program for receiving and recording submarine-transmitter signal intensities in the VLF frequency range using a computer sound card and the alsaaudio package.  The intensities of these signals reflect the ability of radio waves at those wavelengths to propagate in what is essentially a waveguide formed by the earth and the ionosphere above it.  Fluctuations in those signal intensities often reflect daytime perturbations of the ionosphere by solar processes, such as solar flares and coronal mass ejections, making VLF receivers useful tools for probing the sun and the earth's ionosphere.  For more information see the SID Monitors page and the SID data access page at the Stanford Solar Center.

-[[members limit=20]]
-[[download_button]]
+
+
+sidmon 3 is an enhanced sidmon 2 that can employ two loop antennas that are combined to form a simple phased array.  With a single loop, the signal intensity of a transmitter depends on the orientation of the loop relative to the great arc to the transmitter.  A loop is most sensitive if it is edge on (tangent) to the great arc, while an orthogonal loop intercepts no magnetic flux and hence has zero sensitivity to that transmitter.  Two loops, in contrast, can be combined with weights that 'point' the combined loops toward a transmitter, catching maximum flux into the data stream, while injecting equivalent noise of only one ADC.  This can be done digitally for each transmitter being monitored.  In this sense, the antenna/receiver system become isotropic - able to receive with equal sensitivity in all directions.
+
+This is an interesting technique for monitoring transmitter intensities, detecting SIDS, and isotropic observing in general.  There is also something interesting about the orthogonal beams mentioned earlier, i.e., the ones that intercept no flux from its transmitter, such as happens when the waves are traveling along the great arc.  But when the path deviates from the great arc, it catches some flux, which the receiver picks up.  So the more interesting thing is that the orthogonal beam can detect deviations of the path from the great arc.  In fact, there is remarkable sensitivity realized in sidmon 3 of < 0.1 degree on one-minute integrations, that allows another way to detect SIDs and how the ionosphere is impacted by x-rays from solar flares.  
+
+In the following figure, the uncalibrated intensity is the blue trace, while the calibrated direction relative to the great arc (more precisely, the beam pointing) is the red trace, to which the vertical scale applies.  Notice the very small range of that scale.  There is a SID detection after 1900 UT, evident in both the intensity trace and direction trace..
+
+
+
+The sidmon 2 usage document describes most of the setup of a sidmon 3 observatory.  The remainder of this document describes the setup of the loop antennae and beam pointing specific to sidmon 3.
+
+Antenna setup
+
+To measure source direction and transients, two loop antennae are required.  It is preferable to fabricate them identically, although antenna gains can be entered into the header file.  For example, imagine two antennae on one-meter spindles, one consisting of 30 turns, and the other 35 turns.  Their gain can be set to 30 and 35 m² T, where 'T' represents a turn on the spindle.  Their entries in the header files would be: 
# antenna ant0, 30
+# antenna ant1, 35
  The two loops are then mounted upright and at right angles to each other a short distance apart.  The antennae are wired to a stereo 3.5 mm audio connector.  In these connectors, the tip contact is channel 0, the center contact is channel 1, and the bottom sleeve contact is common.  Connect one wire from each antenna to the common contact, and the other wire of each to one or the other of the two remaing contacts.  It does not matter particularly which.
+
+At this point the user should set up single-antenna operation as outlined in the sidmon 2 usage document, and taking data.  It is not necessary to set up the veto feature.  At this point it time to determine a setting for the beam direction for each transmitter.  This value is entered in the header file on the transmitter's line.  To do this, there is a switch, --scan <point count>, that tells sidmon to scan beam rotation angles, taking intensity data and a cross correlation in the process.  
src/sidmon.py --device <device name> --scan 46 --channelcount 2
  The scan is over 180 degrees – not 360ˆ because the second 180 is redundant.  When done, it plots both of those quantities as shown in this figure.
+
+
+
+The first plot is of intensities of the transmitters being recorded.  The second is of the x/y cross correlation – more precisely they are of inverse tangents representing angles of the transmitter away from the primary beam, essentially a pointing error.  We are looking for the beam angle at which the error angle is zero, meaing that the primary beam is on the transmitter's bearing.  For example, the setting for the red trace is +44°, and this value is entered in the transmitter's line in the header file.
+
+Note that the slope of the error angle as a function of beam angle need not be negative.  It depends on which of the antennae is channel 0.  Also, because the loops can be flipped, which reverses the sign of the intercepted flux, this orientation of the loops affects the slope as well.  So one may set the slope as part of the setup by reversing the channel assignments, reversing the leads of one of the loop, or flipping one of the antennae.  This orientation also affects the sign of the angular error represented in the data.  
+
+One can fine tune the beam angle using from a supersid_plot.py graph, such as shown in the following figure of NML direction (relative to its primary beam) during day-time hours where the signal is relatively stable.  
src/supersid_plot.py -af <file path> -ps NML2 --dir

+
+
+
+During those hours, the transmitter direction is -0.1° from its primary beam.  Although already quite small in this example, this difference can be set to zero for later data taking by shifting the beam angle in the transmitter line in the header file by 0.1°, the sign of which is determined by the slope in the scan figure above.  Do not perform this step during night-time hours as the signal direction, like the intensity, varies erratically during those hours.
+
+The header file
+
+An example header file monitoring two transmitters in two goups and recording directions is this.
+
+# Site = A151
+# Contact = Nathan Towne towne56@ownmail.net
+# Longitude = -107.2391
+# Latitude = 34.1116
+# Elevation = 2020
+# LogInterval = 4.87
+#
+# Stations = NPM, NAA, NPMd, NAAd
+# Frequencies = 21400, 24000, 21400, 24000
+#
+# antenna = ant0, 0.89, 166.0
+# antenna = ant1, 1.0, 76.0
+#
+# samplerate = 64000
+# fourierframe = 16384
+# integrationtime = 4.87
+#
+# group = npm, 21100, 21700, 1
+# transmitter = NPM, 21400, lambda f: np.exp(-((f - 21400)/47)**2/2), -71.4, +21.420166, -158.151140, Pearl Harbour; Lualuahei; HI
+#
+# group = naa, 23600, 24400, 1
+# transmitter = NAA, 24000, lambda f: np.exp(-((f - 24000)/47)**2/2), 85.2, +44.644936, -067.281639, Cutler; ME
+
+Some of this is mentioned in the sidmon 2 usage document.  When running in the --channelcount 2 mode, there are additions in the Stations and Frequencies lines for the benefit of supersid_plot.py because sidmon outputs directions as well as intensities.  The additional names are arbitrary, but must be distinct.  There are also additional parameters in the transmitter lines.  To reiterate, this file may only be used with the sidmon --channelcount 2 switch because of the additional parameters.
+
+The antenna lines are there to provide the gain parameter.  In the example above, there is an additional parameter giving the antenna's orientation relative to geographic north, for reference.  But it is not used by sidmon. 
+
+The parameters samplerate, fourierframe, and integrationtime are present in the file and should not be given on the commandline.  The sample rate is in Hz; the fourier frame sample count should not be changed; and the integration time is in seconds.   The last is a duplicate of the LogInterval parameter.
+
+The transmitter lines have one additional required parameter beyond those required by sidmon 2, which is the beam direction in degrees as determined by the scan plot.  In the example above there are also latitude, longitude, and a description string placed there for reference.
+
+Other notes
+
+supersid_plot.py allows the --dir switch, which tells supersid_plot.py to show the vertical scale on the plot.  Use this switch when plotting directions where, unlike intensities, there is a definite unit to the quantities plottted.  The second figure above shows the scale and label with this switch.
+
+
+
+
+
+
+
+
+

Home modified by Nathan Towne

Nathan Towne — Thu, 10 Feb 2022 16:39:53 -0000

Welcome to your wiki!

This is the default page, edit it as you see fit. To add a new page simply reference it within brackets, e.g.: [SamplePage].

The wiki uses Markdown syntax.

Project Members:

Nathan Towne (admin)

Recent changes to Home

Home modified by Nathan Towne

`sidmon` for sudden ionospheric disturbance (SID) monitoring

Introduction

Antenna setup

The header file

Other notes

Home modified by Nathan Towne

`sidmon` for sudden ionospheric disturbance (SID) monitoring

Introduction

Antenna setup

The header file

Other notes

Home modified by Nathan Towne

Project Members: