174.5 MHz Radio
Inspired by a
of articles by John Rainey Smith in the Journal of
British Astronomical Association 1970
1970 October Vol.80 No.6; 1974 August Vol.84 No.5
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
by the pair of spaced
A vintage Hameg spectrum
served as an ideal receiver
due to its appropriate bandwidth of about 5 MHz.
Oscilloscope to monitor loading of the phase sensitive
Antennae phasing switch ( sq.wave driven ) / Gulton/Rustrak
2" chart-recorder /
L.F. amp; phase sensitive detector (sq.wave
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 /
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.
noise comparator inc noise head
Link to a diagram which
shows how two separated (and coupled aerials) provide a virtual grating
on the Sky.
link to Journal "Nature" Vol.161, No.4087, pp.312-313 (28 Feb 1948)
Astronomers J.G.Bolton & G.J.Stanley
Credit is due to (the late) "Electrovalue" component emporium of
Burnage for their
excellent component catalogue; store-keeping and counter
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
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