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Modulation Inputs
DESCRIPTION
The external FM, pulse or amplitude modulation signals are applied to the HP 8340B/41B at these
three connectors.
PANEL LAYOUT
MODULATION INPUT
FUNCTIONS
PULSE MODULATION INPUT is TTL compatible; a TTL high input (>+2 volts) causes maximum
selected RF power output, while a TTL low input causes minimum RF output (>80 dB RF on/off ratio).
The pulse repetition frequency is dc to 20 MHz in non-leveled applications, 100 Hz to 5MHz when
internally leveled. The specifications given in Section I detail the electrical requirements of the PULSE
modulation input, and explain the subsequent effects on the RF output. The damage levels for this
input are >+12 volts or <-20 volts. This input is also used for the [SHIFT] [PULSE] operation.
AM MODULATION INPUT accepts a —1 volt to +1 volt signal, at a frequency of dc to 100 Khz (3 dB
bandwidth). With an AM input of 0 volts, the RF output level (the reference level) is unaffected; at — 1
volts input the RF is shut off, and at +1 volts input the RF output is 100% (6 dB) higher than the
reference level (hence there must be >6 dB of headroom between the reference power level and the
maximum power level available at that frequency). The on (0 volt input) to off (-1 volt input) ratio is a
function of power level and frequency, but is always greater than 20 dB. The amplitude of the RF
output changes linearly as the AM input changes from —1 to +1 volts. The specifications given in
Section I list all electrical requirements of the AM input, and explain the subsequent effects on the RF
output. Damage level for this input is >+12 volts or <-12 volts.
FM MODULATION INPUT accepts a —8 volt to +8 volt signal when on the 1 MHz/Volt sensitivity, or a
—1 volt to +1 volt signal when on the 10 MHz/Volt sensitivity. Any signal greater than these limits will
cause distortion. The deviation changes linearly as the FM input changes from 0 to its upper or lower
voltage limit. The rate is determined by the frequency of the FM input signal. Table 1-1 lists relevant
specifications. Damage level for this input is >9 volts or <—9 volts.
Figure 3-15.
Modulation Inputs
3-36
Operating Information
HP 8340B/41B
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