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Observational Results
with a Ku-band Interferometer
Evgeny Ulanov
Horst Thum, Noah Schneiders
Astropeiler Stockert e.V.
Setup of Interferometer
parabolic antenna
low-noise block downconverter
LNB
LNB
A.1
A.2
Outdoor
Indoor
Powersplitter
Lowpass filter
(950 MHz)
Lowpass filter
(950 MHz)
What do we use for phase measurement?
Bandpass filter
(656 MHz)
Bandpass filter
(656 MHz)
25 MHz
Quarz
Oscillator
Powersplitter 1:4
Powersplitter 1:4
A
B.1
C.1
B
B.2
C.2
AD8302
Summing mixer
Logarithmic rectifier
+
Log.
D
Log.
Logarithmic rectifier
Phase
Log.
F.1
E
A/D - Converter
G
dB-Difference
East / West
F.2
It is an Analog Device AD8302, which is
an industry standard IC for VSWR,
impedance diagnostics and other
measurements.
Solar transit first light
• Angular error of the antenna
• No big fringes in East+West
direction
Small baseline interferometer
Large baseline
interferometer
Sun
At 10 GHz, the baseline
has be below 2 m to see fringes down
to zero for a sun measurement.
This is due to the large object size.
Phase measurements are possible
with any object size.
• Opening angle of dish antenna
• Half power width for setup used
• Half power width for fringes
• Number of fringes at 50% Power
• Earth rotation
• Finges period minimal at Dec. = 0°
• Fringes measured (at target Dec)
Orion A
Detecting weak signals by Fourier transformation
Orion A Transit
Transit 500 Sec
Periode 40 Sec
Sample 1/Sec
Time 8 * 256 Sec
Objekt
Frequency 13
13 * 0,0019 Hz
East +
West
Phase
Observation over multiple days
Orion A observation over 10 days
Sidereal day
Sun in side lobe
Day 10
Day 9
Day 8
Day 7
Day 6
Day 5
Day 4
Day 3
Day 2
Day 1
Solar time of first day
Other sources:
Omega Nebula M17
345 Jansky
2.4.2014
31.3.2014
1.4.2014
Other sources:
Cygnus A
RA 21:00
3C405
130 Jansky
Dec 40:44
RA 20:00
RA 19:00
Fringe-Frequency:
10.3.2014
0.025 Hz = FFT-Line
13
11.3.2014
Cyg A
12.3.2014
Dec = 40.75
13 *Cos 40.75 = 10
Fringe Frequency =
0.019 Hz
13.3.2014
14.3.2014
15.3.2014
16.3.2014
Observation at the Limit
Is Jupiter really
70 Jansky strong?
Virgo A (M87)
38 Jansky ?
Integrating over
4 days
Strong M1 Signal
Summary of results
As reference points, the details
of Franz, F5SE were taken
Conclusion
• We have built a transit interferometer from commercial CATV / SAT-TV
components
• We have designed a simple phase measurement system
• We have demonstrated, that the phase information provides more
detection sensitivity than evaluating the amplitude
• Using the Fourier transformation of the recorded time serious of the
phase signal allows to detect relatively weak sources otherwise buried
in noise
• With this technique, it was possible to observe a number of galactic
and extragalactic sources
• Published values for flux density may be erroneous for the Ku-Band
range