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Cygnus-A remark
G4FAS
173.2 MHz Radio
Telescope
(
Phase-switched
interferometer )
Inspired by a
series
of articles by John Rainey Smith in the Journal of
the
British Astronomical Association
1970
August
Vol.80 No.5;
1970 October Vol.80 No.6; 1974 August Vol.84 No.5
Illustrative view
Two ten element Yagi aerials looking skywards on an
east / west base line and spaced about 22 metres apart.
If observed from a point on the terrestial equator the virtual lobes would seem to be
4.5 degrees apart, equivalent to a diurnal period of 18 minutes per lobe.
My observations at 53 deg N are somewhat different i.e. showing a timebase distortion
of about 1.66x and therefore an apparent diurnal period of 30 minutes per lobe.
Penned as Cygnus-A whispered through the virtual lobes presented
by the pair of 10 element Yagis spaced 22metres apart.
Modules
A vintage Hameg spectrum analyser served as an ideal receiver
due to its appropriate bandwidth of about 5 MHz.
------------------------
Oscilloscope to monitor loading of the phase sensitive detector.
------------------------
Antennae phasing switch ( sq.wave driven ) / Gulton/Rustrak 2" chart-recorder /
L.F. amp; phase sensitive detector (sq.wave driven); D.C. amp & 1000Hz square wave switch
------------------------
The lowest unit is an experimental 30 MHz intermediate frequency amplifier.
------------------------
Not shown are E<->W (20dB/CF439) aerial pre-amplifiers / and other test-instruments /
a stabilised 12 Volt P.S.U. for all solid state modules, including the aerial pre-amplifiers
which receive their D.C. power via the aerial cables.
G4COM noise comparator inc noise head
Go
to charts of other objects
Credit is due to (the late) "Electrovalue" component emporium of
Burnage for their
excellent component catalogue; store-keeping and counter service.
Sadly as with many other similar establishments they are long gone.
( How are today's science teachers coping ? )
Most of the hardware including antennae and copies of the relevant BAA journals are offered (for approx. material cost)
to anyone who can convince me they will go to good home.
But first consider the following quotation from an old B.A.A. "Nature, Aims and Methods" handbook : --
" - - - anyone capable of building a television set without detailed instructions should (be able to) manage a radio telescope. "
COPYRIGHT © 2008 GEOFF ROYLE G4FAS
Two ten element Yagi aerials looking skywards on an
east / west base line and spaced about 22 metres apart.
If observed from a point on the terrestial equator the virtual lobes would seem to be
4.5 degrees apart, equivalent to a diurnal period of 18 minutes per lobe.
My observations at 53 deg N are somewhat different i.e. showing a timebase distortion
of about 1.66x and therefore an apparent diurnal period of 30 minutes per lobe.
Penned as Cygnus-A whispered through the virtual lobes presented
by the pair of 10 element Yagis spaced 22metres apart.
Modules
A vintage Hameg spectrum analyser served as an ideal receiver
due to its appropriate bandwidth of about 5 MHz.
------------------------
Oscilloscope to monitor loading of the phase sensitive detector.
------------------------
Antennae phasing switch ( sq.wave driven ) / Gulton/Rustrak 2" chart-recorder /
L.F. amp; phase sensitive detector (sq.wave driven); D.C. amp & 1000Hz square wave switch
------------------------
The lowest unit is an experimental 30 MHz intermediate frequency amplifier.
------------------------
Not shown are E<->W (20dB/CF439) aerial pre-amplifiers / and other test-instruments /
a stabilised 12 Volt P.S.U. for all solid state modules, including the aerial pre-amplifiers
which receive their D.C. power via the aerial cables.
G4COM noise comparator inc noise head
Link to a diagram which
shows how two separated (and coupled aerials) provide a virtual grating
on the Sky.
External
link to Journal "Nature" Vol.161, No.4087, pp.312-313 (28 Feb 1948)
Astronomers J.G.Bolton & G.J.Stanley
Go
to charts of other objects
Credit is due to (the late) "Electrovalue" component emporium of
Burnage for their
excellent component catalogue; store-keeping and counter service.
Sadly as with many other similar establishments they are long gone.
( How are today's science teachers coping ? )
Most of the hardware including antennae and copies of the relevant BAA journals are offered (for approx. material cost)
to anyone who can convince me they will go to good home.
But first consider the following quotation from an old B.A.A. "Nature, Aims and Methods" handbook : --
" - - - anyone capable of building a television set without detailed instructions should (be able to) manage a radio telescope. "
COPYRIGHT © 2008 GEOFF ROYLE G4FAS