HP 8648 A/B/C/D - Changpuak.ch

Overview The HP 8648A/B/C/D signal generator covers the frequency ranges
shown in the following table.
The frequency bands are:
0.1 to< 249MHz
249 to < 501 MHz
501 to < 1001 MHz
1001 to < 2001 MHz
2001 to 4000 MHz
Frequency Ranges
1 Model 1 Frequency Range
HP 8648A 100 kHz to 1000 MHz
HP 8648B 9 kHz to 2000 MHz
HP 8648C 9 kHz to 3200 MHz
HP 8648D 9 kHz to 4000 MHz
The output amplitude range is from + 10 to -136 dBm except for
frequencies 5 2500 MHz on the HP 8648B/C/D where the higher end
of the range is + 13 dBm.
The HP 8648A/B/C/D supports AM, FM, and phase modulation. The
possible modulation sources are:
Internal 400 Hz or 1 kHz source.
External ac- or dc-coupled source.
w Internal 1 kHz plus external dc-coupled source.
Internal variable frequency/waveform source (Option lE2 only).
Al Front Panel The front panel contains two RPGs (rotary pulse generators), the
keyboard, and the display.
The two RPGs, one for frequency and one for amplitude, are
connected directly to the controller on the A3 board. Each RPG
receives power and ground from the controller. Each RPG returns two
out-of-phase pulsed lines when the knob is turned.
The keyboard is a matrix of keys as shown in Table 5a-1. The
keyboard is scanned by the controller. Scanning pulses are sent
alternately to the keyboard rows and are read back on the columns
when a key is pressed. The controller determines which key was
pressed based on the row that was pulsed and the column that the
signal was returned on. The column lines are pulled-up through
resistors and are pulsed low when a key is pressed. The row output
latches are open-collector, therefore, pulses can not be seen until the
circuit is completed by pressing a key. The keyboard connects directly
to the controller at A3J3.
The display is driven by the controller through data latches on the
A3 assembly. The display control lines are eight bi-directional data
Theory of Operation 5a-3