One Valve Short Wave High Frequency Amplifier Or Short Wave - Eddystone Short Wave Manual

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EDDYSTONE SHORT WAVE MANUAL
ONE VALVE SHORT WAVE
HIGH FREQUENCY AMPLIFIER
OR SHORT WAVE CONVERTER.
BATTERY MODEL
Showing panel and chassis views of this neat assembly.
Models for either battery or A.C. mains use ate described.
This simple and inexpensive unit can be
used in two important ways. With an existing
broadcast receiver it can be employed
as a
short wave converter for obtaining reception
of short wave signals ; secondly, with an all -
wave set or a specially designed short wave
receiver it can be used in front of either as an
additional high frequency amplifier with
con-
siderable gain in performance and selectivity.
The unit is simple to build and no change
of construction is necessary for use in either
form.
If, therefore, it
is used at first as a
converter it need not be scrapped if an all wave
set is later purchased, but can be used in
front of this as a high frequency amplifier.
The unit is built on a die-cast chassis
with metal panel which makes up into
an
attractive assembly. A smart metal container
cabinet is also available, if required.
The
circuit includes a screened grid high frequency
pentode valve with associated coil and tuning
condenser.
The wave length of 13.75-99
metres is covered by three interchangeable
coils as follows :
Range
1, 13.75-17-26.5 ;
Range 2, 25.0-51.8
;
Range 3, 49.0-99.0.
This method is highly efficient since there
are
no switch losses and the tuning capacity is
small.
The circuit, when the unit is used as a
converter, becomes an electron coupled os-
cillator, and since a battery valve has no
independent cathode as
in
the
A.C.
type,
the special iron cored filament choke,
Cat.
No. 1062, must be used. Oscillation is con-
trolled by a 50,000 ohm potentiometer. When
using the set as an H.F. amplifier, naturally
the valve
is
never used
in an
oscillating
condition, and this control is used to obtain
regeneration with greatly improved results.
Another feature of the unit is the Eddystone
patented Bandspread Tuning device, which
greatly facilitates the ease of tuning and general
operation of the set.
BATTERY SUPPLY AND
CQNNECTIONS.
A separate set of batteries or the existing
batteries of the broadcast set may be utilised.
In this latter case, however, it will not be
necessary to connect leads L.T. neg. or H.T.
neg. to the batteries as these connections will
be made automatically by the earth connection
to the receiver. Therefore, join L.T. + and
H.T. + only.
If common batteries are used
the switch on the unit will be inoperative.