| Całkowite zaćmienie Słońca 20 marca 2015 |
| http://www.amsat.org/amsat/archive/amsat-bb/199908/msg00261.html Eclipse sun-noise report *** Bulletin-ID: 43239_IW8DPW *** From: I8CVS@IW8DPW.ICAM.ITA.EU To : ALL@WW A report on ECLIPSE SUN-NOISE from i8CVS QTH locator JN70ES Lat 40°.7694 North Long 14°.3861 East This report deal with measurement of sun-noise made during the sun-eclipse on day august 11 1999 The sun-noise S+N/N ratio has been measured at 2400 MHz,the 13 cm satellite band,and 10451 MHz,the 3 cm satellite band using equipments already made for the next amateur satellite PHASE-3D ECLIPSE FROM NAPLES IN UTC TIME BEGINNING MAXIMUM DARKENING (82%) END 09:23 10:43 12:12 Working conditions at 2400 MHz: 1,2 meters parabolic disc; G=27 dBi; F/D=0,45; feed RHCP polarized Overall equivalent noise temperature of the receiving system: Te=72 kelvin, i.e. NF=0,96 dB Equivalent antenna temperature when aimed at the cold-sky: Ta=20 kelvin Receiver bandwidth : BW=2400 Hz The solar flux in sfu released by the NOAA Space Environment Center station in San Vito (Italy) for 1415 and 2695 MHz at 11:00 UTC,day august 11/1999 has been interpolated at 2400 MHz by computer program and used for calculations in aid to radio measurements during the eclipse using the above mentioned equipments. 1415 MHz = 102 sfu 2695 MHz = 124 sfu Units: 1 sfu (Solar Flux Unit) = 10^-22 W/m^2/Hz ------------- 2400 MHz MEASURED DATA ------------- UTC NOISE LEVEL IN S+N/N RATIO COMMENT 08:50 5,8 / 6,0 dB Before beginning of the eclipse 09:32 4,4 / 5,0 dB 9 minuts after beginning 09:55 3,6 / 4,0 dB 10:13 3,6 dB at about 1/2 darkening 10:44 2,0 dB at max darkening 82% 13:00 5,0 / 5,5 dB 48 minuts after the eclipse end ----------------------------------------------------------------------------- Working conditions at 10451 MHz: 60 cm parabolic disc; G=33 dBi; F/D=0,38; feed RHCP polarized. Overall equivalent noise temperature of the receiving system:Te=101 kelvin, i.e. NF=1,3 dB Equivalent antenna temperature when aimed at the cold-sky Ta < 5 kelvin Receiver bandwidth:BW=2400 Hz Solar flux in sfu released by the NOAA Space Environment Center station in San Vito (Italy) at 11:00 UTC day august 11 1999 The values of sfu are for the following frequencies. 8800 MHz =261 sfu 15400 MHz =521 sfu ------------ 10451 MHz MEASURED DATA ------------ UTC NOISE LEVEL IN S+N/N RATIO COMMENT 08:55 3,8 / 4,0 dB Before beginning of the eclipse 09:35 3,1 / 3,2 dB 12 minuts after beginning 09:55 2,4 / 3,0 dB 10:18 2,3 / 2,8 dB at about 1/2 darkening 10:47 1:0 dB at max darkening 82 % 13:05 4,0 / 6,0 db 53 minuts after the end of the eclipse.Noise increases to 6 dB for few seconds during some fla res. ----------------------- FINAL REMARK: At 2400 MHz the sun-noise level falled out from 5,8/6 dB before the eclipse well down to 2 dB at maximum obstruction of 82 % At 10451 MHz the sun noise level falled out from 3,8/4 dB well down to 1 dB at maximum obstruction of 82 % The 1,2 meters disc at 2400 MHz has a lobe wide of 7,5° at -3 dB and the 60 cm disc at 10451 MHz has a lobe wide of 3,5° at -3 dB. Both lobes are wide enough to include the corona of the sun wich is kmow to be responsible for the most part of the noise energy radiated in to the electromagnetic radio window. The result of the above measurements of noise level radiated by the sun shows that apparently the noise level in to the 13 cm and 3 cm bands during the eclipse decreases much more than wath expected. The same effect on deep noise level riduction during the eclipse has been re ported at 432 MHz by many very well equipped EME stations in Italy. In antithesis to the above radio measurements showing a sun noise reduction, we note that the official NOAA station in San Vito Italy,well in to the eclip se at 1100 UT,reported sfu values for 1415 and 2695 MHz that are almost the same of that values reported by the station in Learmonth at 0400 UT or about 5 hours before the eclipse. The same happens with the 1415 and 2695 MHz sfu values reported by Sag Hill at 1600 UT about 4 hours after the eclipse.Please look on the sfu table at the end of the article. Please note that my 2400 MHz 5,8/6 dB noise level real measurements at 08:50 UTC,before the eclipse,match very well with the computer simulation using the sfu value released by Learmont at 0400 UT also before the eclipse. Interpolating 105 sfu at 1415 MHz with 125 sfu at 2695 MHz in to the Solar Noise Calculator program Ver.3,1 by WR0I i got in fact 5,8/6 dB noise level. This is exacly wath is to be expected using my Ta and Te and it is correct for my antenna and receiving system. In addition i wonder why i got only 2 dB of noise at 10:44 UTC at maximum obstruction,that is 4 dB fall in noise strength when San Vito reported two strong 102 sfu and 124 sfu for 1415 MHz and 2695 MHz respectively at 1100 UT wich is well in to the middle of the eclipse time. It seams that San Vito in Italy reported very small or no solar noise redu ction at all during the eclipse and that in contrast,my station as well in Italy reported a very strong noise reduction at 2400 MHz during the eclipse time. The situation of my measurement is completely reversed at 10451 MHz because my 3,8/4 dB noise level measured at 08:55 UTC before the beginning of the eclipse match wery well with PC computation interpoleting 259 sfu and 510 sfu at 8800 MHz and 15400 MHz respectively released from Learmonth at 0400 UT Please note that the above sfu data where released by Learmonth at 0400 UT also before the eclipse. I wonder why i got only 1 dB of noise at 10:47 UTC at maximum obstruction, that is 3 dB fall in noise strength when San Vito reported two even stronger 261 and 521 sfu for 8800 and 15400 MHz respectively at 1100 UT wich is well in to the middle of the eclipse time. The above 261 and 521 sfu from San Vito during the eclipse at 1100 UT are even stronger than Learmonth sfu before the eclipse for the same 8800 MHz and 15400 MHz respectively at 0400 UT very well far from the eclipse time. It seams that San Vito in Italy reported an increase of noise during the eclipse and that in contrast my station measured a very well fall of noise of 3 dB that is from 4 dB before the eclipse to 1 dB at maximum obstruction. In conclusion: The possibility of variations in solar flux during the eclipse test cannot be ruled completely but radio amateurs are in condition to use very well equip ped EME and satellite stations to deeply investigate and compare their measu rements with that released by the official sources and compare both results in order to made useful evaluations. The following Solar Radio Data related to the above discussion are those re leased by NOAA on Aug 11 1999 and they can be used for your evaluations. For daily Solar Radio Data information,please contact: gopher://proton.sel.noaa.gov:70/11/lists/radio ---------------------------  roduct: Solar Radio Data rad.txt:Issued: 0332 UT 12 Aug 1999 # # Prepared by the U.S. Dept. of Commerce, NOAA, Space Environment Center. # Please send comments and suggestions to sec@sec.noaa.gov # Units: 10^-22 W/m^2/Hz # Missing Data: -1 # # Daily local noon solar radio flux values - Updated once an hour # Freq Learmonth San Vito Sag Hill Penticton Penticton Palehua Penticton MHz 0400 UT 1100 UT 1600 UT 1700 UT 2000 UT 2200 UT 2300 UT 1999 Aug 11 245 50 18 16 -1 -1 19 -1 410 114 38 43 -1 -1 44 -1 610 75 109 62 -1 -1 65 -1 1415 105 102 102 -1 -1 111 -1 2695 125 124 124 -1 -1 133 -1 2800 -1 -1 -1 127 128 -1 130 4995 166 147 175 -1 -1 166 -1 8800 259 261 209 -1 -1 265 -1 15400 510 521 518 -1 -1 429 -1 --------------------------------- 73 de i8CVS Domenico |
PRZEJD NA FORUM