All stations - Freienbach - Landschlacht

Solar Radio Flux by Christian Monstein

The solar radio noise is measured daily with amateur instrumentation, theat means I use an old communication receiver AR3000 modified
for radio astronomy purposes. The detector is composed of an analoge multiplier S042P (Siemens). The Yagi-antenna is a standard TV antennae (BIV/V)  for channel 37.
The antennae is fixed in meridian, but the elevation is  tilted once or twice per month according to the actual elevation of the suns orbit (Transit Meridian Instrument).
The receiver is programmable via RS232 with a Windows compatible PC running under XP and Borland Builder 6. This PC is also part of
the internal network, thus the data can be captured very easily. Every month a graph and a listing will be produced and stored in the archive below.

During 2019, after 23 years of observation local radio interference (due to DVB-T and mobile phone activity) went terribly strong and wide-band, such that solar observations went impossible.

Actual measurements

Single frequency light curve AR3000.
The graph above shows the actual received signal presented in degree
Kelvin absolut aequivalent antenna noise temperature.
Every measurement-point is individually calibrated under software control
with a semiconductor noise source in
the frontend box (focal plane unit). Calibration takes place automatically
twice per minute, for equations see tables below.
The plott is updated automatically every couple of minute.
Callisto light curves S-band
Multi frequency light curves produced by Callisto
Non calibrated data during transit of the sun.
Dynamic solar spectra are stored in FIT-files
Access to documents and data here.


Top: LCD-screen showing sun passage in Math-CAD

Mid left: Power supply 12V
Mid mid: DCF77-receiver supplying 1MHz clock, Computer mouse
Mid right: e-Callisto Radiospectrometer 45MHz...870MHz


Receiver AR3000, Quadratic detector (S042P) and attenuator -10dB
Integrator 6.8msec is also in the blue box

Personal Computer Windows XP
Top left: Preamplifier KUHNE +20dB, 5MHz....1500MHz
Top right: SPDT Daico (selection between calibration or antenna)

Centre: Noise source and 2 attenuators 23dB in total
Right: Calibration SPDT (selection between noise source or T0)

Bottom: cables from antenna and to receiver as well as some control cables

Yagi antenna for channel 36 (WIPIC) pointing to the transit position of the sun

Kalibration Tant = antenna temperature [Kelvin]
Tcold = reference temperature = 273.15Kelvin + measured ambient temperature [°C]
Thot = noise source temperature = 701Kelvin
Ihot = measured digits when the noise source is applied
Icold = measured digits when the termination resistor having ambient temperature is applied
Iant = measured digits when the antenna is switched on while pointing to the sky or to the sun
S = solar flux expressed in sfu where 1sfu = 10^(-22) W/m^2/Hz = 10'000FU = 10'000Jansky
Tant = antenna temperature, see above
pi = 3.1416,  k = Boltzman constant = 1.38E-23 J/K
G = antenna gain in the order of 14dB +/- 0.6dB
lambda = wavelength = 49.18cm at 610MHz
r/R = correction factor of sun distance to the earth (one number per month)

Analysis of temperature
Shown left the home brewed analysis software tool.

Every data set of each day is read into the plot window
(white dots)  and then Fourier-transformed. All higher
frequencies are set to zero and the residual spectrum
is then Fourier-transformed back into the time-domain,
see yellow plot.
By this way we get a kind of filter function. The plot
between the two green vertical lines are analyzed by
reading minimum and maximum values. This difference
is presented as DeltaT (Antenna temperature of the sun).
This temperature difference (sun-background) is then
multiplied by some system parameters to get the solar
radio flux, see equations above.