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Eclipse sun-noise report from I8CVS



ALL @WW          de:I8CVS  18.08.99 08:34  14  10229 Bytes
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

---------------------------
:Product: 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

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