Eddystone Short Wave Manual page 24

22
EDDYSTONE SHORT WAVE MANUAL
THE FOUR BAND TRANSMITTER-continued
TUNING.
Example (1).
160 metres.
Tune V.1 anode current meter to bottom
of sharp dip by inserting the meter plug in jack
marked
" plate current
V.1."
Withdraw
plug and insert in jack marked " Plate current
To Cotoom.ome, Cu.,.
or TmAtomon-re 1.
To COUP1.1144 Coll.
OF TRANSMIT' ER.
B
To
AIC
4 EPPE.LIN
Fecoens
rCz
5416LE WIRE
rceoca.
V.3 " and tune to minimum anode current
here.
The Transmitter is now ready to be
connected to the aerial (two alternative ar-
rangements are shown in sketches "A" and
" B "). In each case the Aerial tuning con-
denser is swung until maximum anode current
is shown at V.3. No alteration to the final
amplifier (V.3) plate tuning condenser should
be necessary after tuning to minimum without
aerial load and to maximum with load, as
previously mentioned.
Example (2). 20 metres.
See that switch SW1 is switched to bring
in doubler stage (V.2). Tune V.1 to bottom
of sharp dip. A more accurate tuning point
of plate circuit V.1 can be found by inserting
the meter plug into grid current jack of V.2
(centre jack below meter)
and tuning to
maximum grid current. Insert meter plug
into plate current jack V.2 and tune very
carefully to bottom of sudden dip on the
meter.
Now insert plug into plate current
jack of V.3 and tune to minimum current ;
proceed as before for aerial load. The tuning
of 40 and 80 metres is precisely the same as
Example (1) and (2).
OPERATION FOR TELEGRAPHY.
By inserting plug attached
to morse
key into jack marked " Keying Jack " and
leave key open.
The plate' current to final
amplifier should be zero and maximum on
closing key (with aerial load). If the plate
current does not drop to zero, re -check entire
tuning operation.
TELEPHONY OPERATION.
The output from speech amplifier can
permanently be plugged into the jack on the
extreme end of back terminal panel. Telephony
is
obtained
by depressing switch SW2
adjoining jack mentioned above. This auto-
matically cuts out sending key and brings
speech amplifier into circuit. The amplifier
must, of course, be switched on separately.
AERIAL LOAD.
In view of the large number of different
types of Aerial and Feeder systems, the trans-
mitter utilises a 3 -turn aperiodic coil coupled
to the " dead " end of the plate coil of V.3.
This aperiodic coil is connected to the two
lead -out insulators on top of rack. From this
aperiodic coil an untuned transmission line
of twisted flex can be taken to whatever type
of Aerial and Feeder system it is desired to
use, provided that the untuned line terminates
with a further aperiodic coil coupled to centre
of Aerial Tuning Inductance. This is shown
in sketches "A" and " B."
Approximate total cost
of
parts
for
Transmitter portion only, including valves,
£16
Os.
Od.
Cost of Power Supply Unit and Speech
Amplifier is extra to above.
CONSTRUCTION.
This we leave
to the ability
of
the
individual -constructor, who will have- the
necessary technical knowledge which enables
him to follow the photographs, diagrams and
theoretical circuits.
A set of layout plans, with complete list
of parts, can be obtained at a cost of 1/6,
post free.
VALVES.
Crystal Oscillator
-
Mullard P.M.24M.
Frequency Doubler - Mullard P.M.24M.
Final Amplifier
-
R.F.P. 15.
COIL. DATA.
CON.
FORMER
WIRE
TURNS
TAparne
..-,
WiNctimilti
160 Metre X al. Plain. Cat. 955.
22ins"
634
5 Turns. Close.
5pocite
40 4 I thy )(Vol Tiveaketect936
.
)334
248
0
80 Mein 40ou6ke
.9
H
28'4
-
II
2 0 Metre Doublet! .i
u
H
6'1.
--
Ocakkgotiati
160 Mete Final. 3"dootrs.
macc.
52
--
Close.
ao Mese final
3"eltoon. /6 OCC.
28
--
..
40 Metre kinal.
31/6"CoyeeTubr.
See7ite
16
- -
2O Melee final.
346Caver7i4e.
..
.
7
--
-