Operation Of The - Heathkit THE TWOER Assembly Manual

Page 4
8 MC
El]
OSCILLATOR
TRIPLER V5A
CIRCUIT DESCRIPTION
24 MC
TRIPLER V5B
72 MC
DOUBLER V4A
144 MC
O
TO POWER SUPPLY
FINAL RF
AMPLIFIER V4B
AUDIO DRIVER VIA 4
SPEECH
AMPLIFIER V1B
AND MODULATOR
AUDIO OUTPUT
V2
RECEIVER V3 0
TO POWER
SUPPLY
4 -SWITCHES ON THE BASIC BLOCK DIAGRAM
HAVE BEEN SIMPLIFIED FOR EASE IN FOL-
LONING THE CIRCUIT ALL SNITCHES ARE
GANGED AND OPERATED SIMULTANEOUSLY
SHOWN IN TRANSMIT POSITION,
TRANSMITTER SECTION
TO
TRANS-
MITTER
POWER SUPPLY
The basic signal from which the final trans-
mitter output is obtained (8 mc) is generated
at 1/18 of the final output frequency in tube
section V5A. This circuit is crystal controlled
providing excellent frequency stability and is
known as an "electron coupled" Pierce oscil-
lator. "Three times" frequency multiplication
is obtained in the plate circuit by tuning the
output to 24 mc. This signal is coupled to the
following stage through C6.
Tube section V5B multiplies the 24 mc signal
again by three, providing a 72 mc signal which
is coupled to the following stage through C8.
Stage V4A is a frequency doubler which provides
an output at 144 mc to drive the final amplifier
grid.
V4B is the final amplifier and operates "straight
through;" i.e., the input and output circuits are
tuned to the same frequency. RF output is
coupled to the antenna, through C17 and the
transmit -receive switch contact, from a tap
TO
MODULATOR AND
AUDIO DRIVER
ANTENNA
/
144 M
TRANSMIT -
RECEIVE
0
approximately 1/2 turn from the "cold" end of
the final tank coil L4. The actual tap point is not
critical and can be adjusted for optimum coupling
if deemed necessary. Since most antenna feed
lines will be in the vicinity of 50-75 ohms, the
suggested tap point will provide near optimum
coupling for most typical situations.
At the rear antenna terminal, there is
pro-
vided a rather unique power output detector
circuit consisting
of diode D1, resistor R8
and capacitor C18 and C19. This system, used
in conjunction with an external voltmeter, sup-
plies a convenient means of tuning the final
tank circuit for maximum power into the anten=
na transmission line. As the power consumed
by this device is negligible, the meter may be
left in the circuit at all times to indicate proper
operation of the transmitter. The meter jack
for this purpose is a three circuit standard
phone jack and the reading is made with the
plug inserted approximately halfway into the
jack, such that the tip of the meter plug con-
tacts only the first terminal in the jack.