HP 8340A Operating Manual page 210

ment data-taking machine would need to sample
the RF signal at a very fast rate to maintain accurate
frequency information. Stepped CW Sweeps also
offer the advantage of maintaining the synthesized
frequency features of the 8340A at each frequen­
cy. A stepped CW Sweep can be accomplished in
several ways.
1. Program sequential CW test frequencies.
2. Program the frequency sweep range then enable
the manual sweep mode. Perform a stepped
manual sweep by repetitively programming the
step up/increment function.
3. Program the CW frequency to the start frequen­
cy, the Step Size to an appropriate value, then
repetitively program
function.
Considering the speed of programming the above
approaches, methods 2 and 3 are most efficient
time wise. This program illustrates a stepped
sweep using these approaches.
PROGRAM 2
10
!STEPPED CW
20
60=?19
30
PRINT CHR$(12)
40 OUTPUT 80i"IPPM1"
DISP "ENTER START FREQUENCY
50
60 IMPUT A
DISP "ENTER STOP
70
E:O rnPUT B
90 IF A>B THEN GOTO 50
100 DISP "ENTER STEP SIZE
110 INPUT S
120 IF SIB-A THEN 90
130 D=<B-A)/S
140
INTEGER D
150 PRINT "THE 8340A IS STEPPED SWEEPING"
160 PRINT " ... TO STOP THE SWEE P•PRESS
170 OUTPUT S0; 1 1 SF11181''GZCW1';A11'GZ' 1
180
FOR I=l TO D
190
OUTPUT SOi"UP"
200
NEXT I
210
GOTO 170
220 E ND
PROGRAM 2 EXPLANATION:
Lines
10-40:
The 8340A address is entered in SO and
the 9826A CRT display is cleared. Then
the 8340A is put in a predefined state
via instrument Preset and pulse modula­
tion is turned on to enable the 27. 8 kHz
Square Wave
from the 8755C.
50-90:
Start frequency is entered in variable A
and stop frequency in variable B. If A>B
other values must be entered.
the step up/increment
GH z "!
in
FREQUENCY GHz"i
in
in GHz"i
PAUSE"
Amplitude modulation
Scans by HB9HCA and HB9FSX
100-120:
Frequency step size is entered in vari­
able S and compared to the full sweep. If
S>B-A, another
entered.
130-140:
The number of steps is calculated and
assigned to D
integer.
150-170:
Programs frequency step size and the
CW frequency is set to the start value.
Then information for the user is dis­
played on the CRT.
180-210:
The 8340A frequency is incremented
from start to stop frequency. When the
stop frequency is reached, the 8340A is
programmed back to the start frequency
and the cycle begins again.
Set up the equipment as shown in figure 2 by add­
ing the 8755C, the 180TR or 182T, the 11664B,
and a test device like a 4 to
It is important that the two rear panel connections
from the 8340A to the 8755C/182T and modula­
tion drive connections are made for a proper CRT
display. For the example measurement set the
following front panel controls:
On the 8755C:
Channel 1:
Display ............................... OFF
(press all the display push buttons so that
they are all out)
Channel 2:
Display .................................. B
dB/DIV ............................. 10 dB
Reference Level ................ . ... -10 dB
Ref. Level Vernier ..................... OFF
On the 182T or 180TR:
Magnifier ............................... X1
Display . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I NT
Reset the 9826A, scratch the 9826A memory and
type in the above program. Then perform the
following:
The 8340A is now being stepped in frequency bet­
ween the start and stop frequencies.
The sweep may not cover the full screen; however,
this is normal. In CW mode, the 8340A delivers on
the sweep output connector a voltage proportional
to the frequency value. Thus, if the frequency is 10
6
step value must be
and made to be an
6
GHz Bandpass Filter.