Self Modulating Oscillator - Eddystone Short Wave Manual

20
EDDYSTONE SHORT WAVE MANUAL
SELF MODULATING OSCILLATOR
FOR LINING UP I.F. STAGES
The photograph shows the simplicity
of this useful Home Oscillator.
This Oscillator will prove a useful piece
of equipment for the experimenter's workshop.
It is really a miniature transmitting station
using very low power. The principal object
of the Oscillator is to simplify the lining
up
of intermediate frequency stages.
For the
conventional 450 kc. and 465 kc. intermediate
frequencies, an Eddystone 4 -pin BR coil is
necessary, the dial reading being 47° and 43°
respectively.
By using
suitable
coils
the
Oscillator can be worked on any wave length
from 12 to 2,000 metres.
With the many reliable
stations now
transmitting on advertised frequencies, there
will be no difficulty in making an accurate
calibration.
CONSTRUCTION.
The photograph, together with
circuit
diagram, provides a clear insight to the
as-
sembly and wiring.
It should be noted that
the valveholders
are
mounted with
grid
terminals pointing towards the panel.
The
2 volt valve is an HL2 type and 60 volts
high-tension will be sufficient.
CALIBRATING.
Calibration is done by connecting valves,
batteries, etc., and
placing the oscillator
alongside a receiver. Tune receiver to
a known
station, and by using in the oscillator a coil
which is known to cover the wavelength of
the station being received, carefully rotate
oscillator control knob until a high-pitched
note
is
heard superimposed on the
trans-
mission being received. This indicates the
oscillator
and transmitter
to be in step.
Should the note from the oscillator be too
loud it can be reduced by moving unit slightly
away from the receiver. This also sharpens
tuning and ensures more accurate calibration.
If a stronger signal is required, it
is recom-
mended that the aerial from the receiver be
closely coupled to the oscillator coil.
LIST OF PARTS.
EDDYSTONE.
Price
1 Microdenser, Cat. No. 900/100 ..
5/-
1
Pointer Knob and Dial, Cat. No. 1027 ..
1/3
2 Frequentite Valveholders, Cat.
No.
949,
4 -pin, at 1/5 each
..
..
2/10
2 Frequentite Terminal Saddles,
Cat.
No.
1046, at 1/- each ..
2/-
1
4 -pin BR Coil, Cat. No. 932
5/ -
Total, 16s. ld., plus coils extra if required.
MISCELLANEOUS.
1 T.C.C. Condenser, M type, .0005 mfd.
I
Dubilier Condenser, 670 Mica type, .006 mfd.
1 Erie 1 watt Resistance, 2 megohrn
1 Panel, 4" x 6" x lif", Ebonite or Bakelite
..
1 Baseboard, 6" x 6", 1" Plywood
. .
Screws, 8 R.H.,
x 4
..
Screws, 5 R.H., i" x 4 ..
Connecting Wire, Washers, Soldering Tags, etc.
Approx. price, 5s. 6d.
VALVE.
1 Mazda HL2 Metallised
4/9
HL2 M eT.
CIRCUIT DIAGRAM.
LT*"
0
0