2-4. POWER REQUIREMENTS
The L 7 is furnished with its own separate Power
Supply which can be operated from either 120
VAC or 240 VAC
50-60 Hertz. Because of the large
variety of plug and socket configurations for 240
volt service, and because the L 7 can be operated
from either 120 Volts or240 Volts, a line plug is not
furnished with the L
7.
TheL 7is shippedfrom the
factory with jumpers connected to operate on 240
VAC. It is highly recommended that the L
7
be
operated from its own 240 Volts (15 Amps or
greater) circuit. If a 120 Volt circuit is all that is
available, it should be fused for 30 Amps and the
circuit conductors should not be less than No. 10.
No other equipment should be operated from this
circuit. DO NOT under any circumstances operate
the L 7 from a 120 Volt lighting circuit because the
circuit conductors are not large enough to carry
this load safely.
2-5. JUMPER CONNECTIONS
Figures 2-2 and 2-3 are diagrams of jumper con-
nections required for 120 and 240 Volt operation.
The jumpers in both the Amplifier and Power
Supply must be connected as shown or serious
damage to the
L
7
components may result.
2-6. ANTENNA REQUIREMENTS
The L 7 has been designed for use with antennas
resonant at the operating frequency and having
approximate impedances within the limits of 25 to
100 Ohms.
T)le nominal output impedance of the
amplifier is 50 Ohms and the SWR of this load
should never exceed
23. Although there are many
types of antennas which will meet these require-
ments, the simplest is a one-half wave dipole
center fed with 52 Ohm coax. For a detailed dis-
cussion on antennas, refer to an appropriate
antenna book.
2-7.
LOW PASS FILTER
The amplifier has been designed in accordance
with good engineering practices, and harmonic
attenuation meets or exceeds current FCC specifi-
cations. Because of the possibility that you may be
qsing a multiband antenna or have afeed line that
is resonant at a harmonic frequency, it is highly
recommended that a suitable low pass filter such
as the
R.
L. Drake Model TV-3300- be used with
the
L
7.
2-8. MATCHING NETWORK
Most practical antennas exhibit an SWR range
over a complete amateur band that exceeds
2:l.
For this reason we recommend using an antenna
matching network such as the R.
L.
Drake
MN-
2700 which will allow the L 7 to work into a 50
Ohm
load for maximum power transfer into the
antenna.
CAUTION
Never attempt to operate the
L
7
without first
connecting to an antenna or 50 Ohm Dummy
Load of sufficient power handling capacity
or serious damage may result.
2-9. GROUND REQUIREMENTS
For best results, the amplifier should be attached
to a good earth ground through as short and as
large a ground strap as possible. A binding post is
provided on the rear of the amplifier chassis for
the ground connection. It is always a good idea to
connect the chassis of all associated equipment
together
and
ground them at one point to avoid
ground loops. We recommend that all of the equip-
ment in your station be connected together and
grounded at the L
7
Amplifier chassis.
2-10. EXCITER REQUIREMENTS
To operate the amplifier at the maximum legal
input the exciter must provide 100 Watts PEP RF
power for
SSB operation and
75
Watts RF power
for CW,
AM,
RTTY and TUNE operation.
Locate the exciter as close to the amplifier as
practical
to
shorten the coaxial cable and ground
strap. Refer to figures 2-4 and 2-5 for recom-
mended connection arrangements.
2-11. TRANSMITTING AGC
The transmitting AGC voltage, which controls the
gain of the exciter, is presented at a connector
labeled XMTG AGC OUTPUT on the rear of the
L
7.
Any power level can be run up to 2000 Watts
PEP without peak
cliGping. A cable is furnished
with the amplifier which provides a connection
to the
R.
L.
DrakePS-7
or AC-4Power
Supply. This
connection
is
routed through the power supply to
the transmitter.
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