Receiver Operating Parameters; Detection Mode; If Bandwidth; Gain Mode - Watkins-Johnson Company WJ-8718A/MFP Instruction Supplement

WJ-8718A/MFP INSTALLATION AND OPERATION
frequency range is
+/-
8.00 kHz and is displayed in kHz to a 10 Hz r.esolution. If the re-c.eiver is
not equipped with the 10 Hz BFO Option, the LSD of the displayed BFO fr-equency is not
connected to the synthesizer.
The LSD of the BFO OFS/THRS LVL display is also used to display dwell time and
threshold levels, as described in paragraphs 2.4.4.7.4 and 2.4.4.7.5.
2.4.4.6 Receiver Operating Parameters
Receiver operating parameters are enter-ed on the Microprocessor Front Panel
switches and transferred to the receiver automatically. Parameters ,can be stored in a memory
using the STORE switch, and transferred to the receiver from memory using the RECALL
switch. See paragraph 2.4.4.7 for a discussion of the memory channels.
Selectable parameters are detection mode, IF bandwidth, RF gain (MGC only), and
gain mode. The parameters are discussed in paragraphs 2.4.4.6.1 to 2.4.4.6.4.
2.4.4.6.1
Detection Mode
Detection modes are selected by the AM, FM, USB, LSB, ISB, CWV (variable), and
CWF (fixed) pushbuttons. The CWV switch is associated with the BFO switch and must be
engaged to establish a new BFO frequency in the addressed receiv·er (see paragraph 2.4.4.5).
In the AM, FM, and CW modes; the line audio and phones audio are taken from the
receiver's AM, FM, and CW detectors, respectively. One of the five available bandwidths can
be selected for AM, FM, and CW modes. The CWV switch enables the variable BFO. The CWF
switch enables the fixed BFO (455 kHz). In the ISB mode, USB and LSB audios are available and
can be monitored with stereo headphones.
2.4.4.6.2
IF Bandwidth
The IF BANDWIDTH/kHz switch block allows selection of .3,
1,
3.2, 6, and
H)
kHz
IF bandwidths. In the AM, FM, and CW detection modes, anyone of the five bandwidths should
be selected. Bandwidth selection is ineffective in the USB, LSB, and ISB det.ection modes, when
a sideband filter bandwidth of approximately 3 kHz is assumed. To indi-cate this, the LED on
the 3.2 kHz IF bandwidth switch will glow.
2.4.4.6.3
Gain Mode
The GAIN MODE switches are MGC (Manual Gain Control), SLOW (AGC), and
FAST (AGC). The differences in decay times of fast AGC and slow AGC make them useful for
different kinds of signals. In the fast AGC mode, the .gain of the receiver adjusts about as
quickly for a rise in signal strength (attack time) as it does for a fall in signal str·ength (decay
time). Fast AGC attack and decay time is approximately 15 milliseconds for each. In the slow
AGC mode, attack time is also fast, but decay time is approximately 2 seconds slower. For AM
and FM signals, the t9tal power in the carrier and sidebands does not vary much with time at
the transmitter. The main purpose for AGC is to compensate for atmospheric losses; therefore,
fast AGC is best for AM and FM signals. For pulsed signals, such as telegraphy and single
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