DRAKE L-4B - Low Pass Filter; Antenna Requirements; Ground Requirements

230 VOLT OPERATION
Amplifier Power Supply
F• LOW PASS FILTER
The L-48 has been designed in accordance with good engineering practices and
second harmonic content Is attenuated from the fundamental by at least 35 dB.
Because of the posSibiUty that you may be using a multiband antenna or have a
feed line that is resonant at a harmonic frequency, it is highly recommended that
a suitable low pass filter such as our Model TV-IOOO-LP be used with the L-4B.
G. ANTENNA REQUIREMENTS
The L-48 has been designed for use With antennas resonant at the operating fre-
quency and having approximate impedances Within the limits of 25 to 100 ohms.
The nominal output impedance of the L-4B is 50 ohms and the SWR of this load
should never exceed 2:1. Although there are many types of antennas which will
meet these requirements, the simplest is a one-half (1/2) wave dipole center fed
With S~ ohm coax. For a detailed discussion on antennas, we suggest referring
to an appropriate antenna book.
Most practical.antennas exhibit an SWR range over a complete amateur band that
exceeds 2:1. For this reason we recommend using an antenna matching network
such as our MN-2000 which will allow the L-48 to work into a 50 ohm load for
maximum
power transfer into the antenna.
CAUTION:
NEVER ATTEMPT TO OPERATE THE L--48 WITHOUT FIRST CON-
NEcTING IT TO AN ANTENNA OR 50 OHM DUMMY LOAD OF
SUFFICIENT POWER HANDLING CAPACITY OR SERIOUS DAMAGE
MAY RESULT.
H. GROUND REQUIREMENTS
The L-4B should be attached to a good earth ground through as short and as large
a ground strap as possible for best results. A binding post is provided on the
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