HELP INSTRUCTIONS for GH_NOISE - Proposed Recommendation ITU-R P.372-8 Combination of Radio Noise. This was previously known as CCIR Report 322-3 Atmospheric Radio Noise Data. TABLE OF CONTENTS 1.0 PROGRAM DESCRIPTION 2.0 HISTORY 3.0 PROPOSED UPDATES 3.1 MODIFIED SPAULDING 3.2 EQUATORIAL INTERPOLATION 3.3 REC533 4.0 OPERATING MODES 4.1 SINGLE LOCATION MODE 4.2 WORLDMAP MODE 5.0 MENU OPTIONS 5.1 NOISE SOURCE a.) ATMOSPHERIC b.) GALACTIC c.) MAN-MADE 5.2 EQUATOR a.) INTERPOLATE b.) NORMAL 5.3 POWER SUM a.) MODIFIED SPAULDING - Proposed modification b.) WEIGHTED POWER SUM - Original Spaulding c.) SIMPLE POWER SUM 6.0 INPUT PARAMETERS 7.0 OUTPUT PARAMETERS 7.1 N DBW 7.2 Fam 7.3 DL 7.4 DU 7.5 SigmaLW 7.6 SigmaN 7.7 SigmaUP 7.8 dFam 8.0 COMPARING WITH CCIR REPORT 322-3 9.0 REFERENCES 10.0 PROGRAM SUPPORT --------------------------------------------------------------------------------------------------------- 1.0 PROGRAM DESCRIPTION The GH_NOISE Software creates predictions of Atmospheric, Galactic, and Man-Made radio noise at specified locations. It is designed to operate on personal computers using the Microsoft Windows operating system. It contains proposed modification to the ITU distributed noise program NOIS2.EXE that was developed by Don Spaulding in about 1995, shortly before his retirement and untimely death. NOIS2.EXE executes in a DOS environment and is very awkard to use. But it does duplicate exactly the values of Report 322-3 Atmospheric Radio Noise Data [Ref. 4] for which Don was the ITU expert. While developing HF radio noise software for a customer, it was determined that NOIS2.EXE could produce "disturbing" results under specific combinations of Season, Time Block, Frequency, Man-Made Noise, and Location (Latitude/Longitude). Most notably, the calculated results for the statistical values of the noise (SigmaLW, SigmaN, SigmaUP) could reach values that are obviously bad. To see the full text of the ITU submission being presented to the ITU in April 2007, look in the sub-directory "reports" for the Word document named "itu_submission.doc". 2.0 HISTORY Before Don Spaulding retired, he developed "An Updated Noise Model for Use in IONCAP" (NTIA Report 87-212) [Ref. 1]. He described how the three noise sources (Atmospheric, Galactic, Man-Made) should be properly combined. The problem previous to the report was: (from page 28 of the report) All three noise processes are represented by log-normal distributions. The median value of the total is obtained by summing the three individual medians, after converting to watts. ..., this procedure is not strictly correct, since only the mean values add, and for log-normal distributions, the median value and the mean value are different. The rest of the report then develops a methodology to combine the three noise sources using the split log-normal distributions. For almost every situation, the results are good. But it was found that whenever DU or DL exceed 12dB, the calculated results for the statistical values of SigmaLW, SigmaN, and SigmaUP reach exceeding large values. Values that are larger than any of the combined sigmas. The program NOIS2.EXE, available from the ITU, was written by Don Spaulding and will produce calculated values of Radio Noise. It does not produce the graphical maps that exist in Report 322-3. The software supplied here can produce the exact same results as NOIS2.EXE for single point calculation, and can also replicate the maps in Report 322-3. Fortunately, since I was the one who produced the maps in Report 322-3, the maps produced here use the same graphical software and are thus easy to compare. One thing to remember about Report 322-3 is that a plot for a specified season and time block is discontinuous at the equator. This is because the page is for the same season in each hemisphere. The maps produced by this program, are for the season defined in the Northern Hemisphere. Why Report 322-3 was done that way is a mystery to me. All it does is add confusion. 3.0 PROPOSED UPDATES 3.1 MODIFIED SPAULDING After Don Spaulding and Frank Stewart(the other author to the report) retired, I obtained possession of their reports and notes. While researching the sigma calculation problem described under HISTORY above, I discovered two hand written lines of code that limited the atmospheric noise statistics of DU and DL to 12dB. When this was inserted into the code, all problems were resolved. But after studying the problem with John Caruana of Australia, we decided to use the Spaulding method if DU and DL are less that 12dB, and a slight adjustment to the Spaulding method when DU or DL are greater than 12dB. *** This modification requires 8 lines of code to be added to subroutine GENOIS.for. 3.2 EQUATORIAL INTERPOLATION If you observe the plots of noise variability (DU, DL, Sigmas) for Atmospheric noise in Report 322-3, they are valid independent of latitude and longitude. Thus, for example, values of DU 10 feet north of the equator can be quite different from those 10 feet south of the equator, because they are from different seasons. I am therefore proposing to interpolate these values whenever calculations are performed in the equatorial region. I have used the latitudes of the Tropic of Cancer and the Tropic of Capricorn (approximately +/-23.5 degrees). Thus, the value of atmospheric DU at 10 degrees North latitude at a given time block and season, will be an interpolation of the values of DU in the specified time block and season, and the DU of the specified time block of the OPPOSITE season. *** This modification requires 5 lines of code to be added to subroutine GENFAM.for. 3.3 REC533 I would also propose that the ITU Recommendation 533 should be changed to combine the noise sources this same way. It currently performs the very simple power sum calculation of the medians. Which is statistically incorrect. 4.0 OPERATING MODES GH_NOISE may be operated in the following modes: 4.1 SINGLE LOCATION MODE The user interface permits the specification of several input parameters as discussed in section 6. For single-location predictions, the user first specifies latitude and longitude as well as the system inputs of choice and clicks on SINGLE. Predictions for that location are shown in lower panel of the form. A new prediction is added to the panel when SINGLE is clicked again. If you wish to save the predictions, click on SAVE instead of SINGLE. The predictions will again appear in the lower panel and will also be saved to a file called gh_noise.txt. The file may be viewed under the NOTEPAD program by clicking VIEW. NOTEPAD may then be used to save the file under a unique filename. 4.2 WORLDMAP MODE Worldwide noise predictions may be produced by clicking on the user interface WORLDMAP menu item. Worldwide predictions will then be shown as contour intervals on a world map using the input specifications entered on the user interface. Previously entered latitude and longitude values will be disregarded, and predictions will be created at grid intervals of three degrees in latitude and six degrees in longitude. When the user interface is employed, results are presented as contour lines on the world map, and you may use the PARAMETER menu item to select the noise parameter to be plotted. The CONTOURS menu item may be used to select various contour-line intervals. Worldwide grid data is automatically saved to a file called noise_grid.txt, which may be viewed using the NOTEPAD menu item. The file is overwritten each time WORLDMAP is called. Files may be saved under unique names using NOTEPAD controls. The screen image may be sent to the clipboard or printed using the menu controls. When using the PRINT option, it is best to select LANDSCAPE orientation in your printer setup. The default parameter plotted is Fam and the default method of plotting is black/white 5dB contours. This allows very easy comparison to Report 322-3. Realize that plotting the parameters of DL, DU, SigmaLW, SigmaN, SigmaUP will not be very interesting. This is because they are constant over longitude in local time and only vary between Northern and Southern hemisphere. Data values of the current plotted parameter may be viewed from the map by positioning the cursor over the desired location and clicking the mouse. Data values will then appear in the information row under the top-row menu. A left click will produce the interpolated data value at the cursor location. Right clicking will jump to the nearest grid location and read the value there. The grid-location values are the same as those found in the noise_grid.txt data file. 5.0 MENU OPTIONS Described below are the features of the remaining menu options. 5.1 NOISE SOURCE Selections of the Noise Source menu items permit the analyst to make predictions for atmospheric, galactic or man-made noise individually, or from the combination of all three noise sources (the default configuration). The default combination of all three sources yields values of N DBW and its associated statistical parameters that correspond to those in HF prediction software such as REC533, VOACAP, or ICEPAC. By selecting ONLY Atmospheric and a Frequency of 1 MHz, you will produce the maps of Report 322-3 (these are also found in Recommendation ITU-R P.372-8). The noise sources combined will be the ones that are checked. A group code on the output will indicate which noise sources were combined. For example, a code group of "AGM" means that all three noise sources were combined. a.) ATMOSPHERIC Predicted data and contour maps include the contribution of Atmospheric noise (ANOS) only, as depicted in the CCIR 322-3 report [Ref. 4]. This noise selection is useful when man-made noise levels and/or galactic noise levels are significantly high and thus mask those of atmospheric noise alone. Prediction of atmospheric noise alone is also useful when results are compared with CCIR 322-3. b.) GALACTIC Data and maps include galactic noise (GNOS) only. Galactic noise values vary only with frequency, in accordance with: GNOS in dB above kTob = 52 - 23log(freq in MHz). GNOS statistical factors are fixed values, where: DUG = 2.0dB, DLG = 2.0dB, SigmaG = 0.5dB, SigmaDUG = 0.2dB and SigmaDLG = 0.2dB. Note that if you are trying to compare calculations with the noise produced by VOACAP or ICEPAC that at HF frequencies, Galactic noise is quite often masked. That is because it is blocked from entering the ionosphere. Thus, you may wish to ignore Galactic noise. c.) MAN-MADE Data and maps include man-made noise only. Man-Made noise levels are fixed at all locations but vary with frequency. A user input level (MAN) is first entered at 3 MHz in -dBW/Hz, and is converted by the program in accordance with: MMN in dB above kTob = 204 - MAN + 13.22 - 27.7log(freq in MHz). MMN statistical factors are fixed values, where: DUM = 9.7dB, DLM = 6.0dB [Ref. 2], SigmaM = 5.4dB, SigmaDUM = 1.5dB & SigmaDLM = 1.5dB. 5.2 EQUATOR a.) INTERPOLATE The CCIR 322-3 charts of atmospheric noise Fam values show a smooth transition across the equator. However, when the statistical factors are graphed on a world map the contour lines are revealed to have equatorial discontinuities. This is due to the coarseness of the measured data, where only a few measurement locations were available in the Southern Hemisphere and none at the equator itself. The result is an unrealistic shifting of the DU, DL and sigma contours at the equator. Selecting INTERPOLATE (default) is the proposed modification to the software. It will interpolate Atmospheric noise statistics (DUA, DLA, sigmas) within +/-23.5 degrees of the equator. This represents the area between the Tropic of Cancer and Tropic of Capricorn. The result is to produce statistical data that is more likely to be encountered in the real world. When "Interpolate" is selected, the letter "i" is added to the prediction line code group. For example, when equatorial interpolation is performed for all three noise sources, the code group would be "AGMi". b.) NORMAL NORMAL will produce results the same as NOIS2.EXE and current HF prediction software. When "Normal" is selected, the letter "n" is added to the prediction line code group. 5.3 POWER SUM a.) MODIFIED SPAULDING When "Modified Spaulding" is selected, the letter "m" is added to the prediction line code group. This is the default and proposed modification. b.) WEIGHTED POWER SUM - Spaulding NTIA Report 87-212 This is what is currently used in NOIS2.EXE and current HF prediction software. When "Weighted Power Sum" is selected, the letter "w" is added to the prediction line code group. c.) SIMPLE POWER SUM This is used by the ITU REC533 HF prediction software and is statistically incorrect. It is also the current method of ITU Rec 372-8 (as of Jan 2007). When "Simple Power Sum" is selected, the letter "s" is added to the prediction line code group. 6.0 INPUT PARAMETERS Input parameters required are: Season Local Time Block Frequency Man-Made Noise level Latitude Longitude Input values for each prediction may be entered in the six edit boxes of the user interface. Place the mouse cursor over an edit box to view the permitted ranges and suggested values. Frequency entries are limited to the .01 to 30 MHz range which are the limits of the Report 322-3. Note that the maps in CCIR Report 322-3 are normalized at 1 MHz. Red values of Galactic and Man-made Noise are shown on the Frequency Line, and the values change when a new computation is made with SINGLE or SAVE after the frequency is changed. (You may click UPDATE to see new values before making a run.) These values are in dB above kTob. 7.0 OUTPUT PARAMETERS The following output parameters are computed in all operating modes. 7.1 N DBW Median hourly noise power in dBW for a noise power bandwidth of 1 Hertz at the receiver input terminals, assuming a short lossless vertical antenna. Predicted noise power is derived from the CCIR 322-3 charts and are for conditions when there are no local thunderstorms [Ref. 3, p. 3-3]. In the default selection of all three sources, this parameter and its associated statistical parameters includes the power sum of atmospheric, man-made and galactic noise sources. Default N DBW and associated statistical parameters are computed in accordance with Reference 1 except that the value of the Man-Made Noise lower decile, DLM, was later changed from 7 to 6 dB by Dr. Spaulding [Ref. 2]. When other Noise Source combinations are used, N DBW records the noise values of those sources. For example, if atmospheric noise alone has been selected, N DBW corresponds to the CCIR 322-3 report values except that the noise power is in dBW. 7.2 Fam Median atmospheric noise power in dB above kTob. In GH_NOISE, the computed value of Fam = N DBW + 204. Fam is only equal to the Fam of CCIR Report 322-3 [Ref. 4] when atmospheric noise alone has been selected for the computations and the Frequency is 1 MHz. For other noise source combinations, the Fam column is used to record noise values in dB above kTob, regardless of the basis for the N DBW parameter. 7.3 DL dB below median noise power exceeded 90% of the days of a month, for the noise sources selected. 7.4 DU dB above median noise power exceeded 10% of the days of a month, for the noise sources selected. 7.5 SigmaLW Standard deviation of DL, for the noise sources selected. 7.6 SigmaN Standard deviation of N DBW, for the noise sources selected. 7.7 SigmaUP Standard deviation of DU, for the noise sources selected. 7.8 dFam This is Fam - Fam0, where Fam0 is Fam using the Simple Power Sum method. This is done for comparision purposes. 8.0 COMPARING WITH CCIR REPORT 322-3 Users may compare GH_NOISE results with the charts of CCIR 322-3 [Ref. 4]. Select only "Atmospheric" under NOISE SOURCE. Make sure you use Frequency of 1 MHz and compare the output parameter Fam. Fam is not affected by EQUATOR or POWER SUM selections. The maps of GH_NOISE are for the season defined in the Northern hemisphere. The maps of Report 322-3 are for the same season in the Northern and Southern hemisphere. Thus, the map of GH_NOISE requires you to look at two different pages in Report 322-3. 9.0 REFERENCES: [1] Spaulding, A. D. and Stewart, F. G. [1987], "An Updated Noise Model for use in IONCAP", NTIA Report 87-212m pp30-34, January 1987. [2] Lane, George, VOACAP Help, General, Documents, "Correction to Man-Made Noise". [3] Lane, George, "Signal-to-Noise Predictions Using VOACAP, A User’s Guide", published by Rockwell Collins, Cedar Rapids, Iowa 52498, 2000, 2001. [4] CCIR Report 322-3, "Characteristics and Applications of Atmospheric Radio Noise Data", International Telecommunication Union, Geneva, 1988. [5] Spaulding, A. D. and Washburn, J. S., "Atmospheric Radio Noise: Worldwide Levels and Other Characteristics", NTIA Report 85-173, April 1985. 10.0 PROGRAM SUPPORT GH_NOISE is a software program developed by Gregory R. Hand and is free to use. Questions about the program’s operation and any suggestions for improvements are welcome and may be addressed to: e-mail: gregory.hand@gmail.com The program is freely available from the website: www.greg-hand.com/noise/gh_noise.zip