AOR SDU5500 Manual page 22

Section 4-4
Reprogramming the 10.7 MHz IF
It is possible to use a companion radio with an IF not of 10.7 MHz but within the range of 5.7 to 15.7
MHz by reprogramming the IF frequency employed by the SDU5500 to a resolution of tens of Hz.
Sweep direction is selectable depending on the heterodyne configuration of the radio, however the
maximum sweep span may be narrower than 10 MHz due to the IF characteristics and centre frequency
of the companion radio.
Usefulness
In order to provide a useful bandwidth of at least 1 MHz (± 500kHz), as a rule of thumb, the limits of IF
should be considered as 6.7 to 14.7 MHz.
Limitations in respect of maximum span
A span of 10 MHz (± 5 MHz) is only possible when the IF is set to 10.7 MHz. When a different IF is
reprogrammed, the maximum span width is reduced by twice the difference between 10.7 MHz and the
new IF.
1) For example, if a new IF of 13 MHz is employed, the maximum span can be calculated as follows:
13 - 10.7 = 2.3
2.3 x 2 = 4.6
10 - 4.6 = 5.4 MHz
2) For example, if a new IF of 7.3 MHz is employed, the maximum span can be calculated as follows:
10.7 - 7.3 = 3.4
3.4 x 2 = 6.8
10 - 6.8 = 3.2 MHz
Important note: When reprogramming the centre frequency, first set SPAN width to 1 kHz prior to
reprogramming to ensure that the selected span band width is always valid or reprogramming will not be
possible, as span width defaults to 10000 kHz (10 MHz).
Set the span width to 1 kHz by selecting menu 4. Press SPAN then press
The LCD will confirm selection as "SPAN : 1kHz" on the LCD.
Staying with menu 4, select the centre frequency menu by pressing CF Key in the IF of the
companion radio, for example, if using a Kenwood TS870S, an IF of 8.83 MHz is required.
Key
The LCD confirms selection of the new IF frequency "CF : 8.83000MHz"
The maximum span width will be:
Try it out, you may select a span of 6260kHz maximum, an error beep is emitted if you attempt to enter a
figure greater than this ! The Kenwood TS870S offers unity gain between aerial input and I.F. output
resulting in good dBm accuracy of a few dB in the range of -90 to -40dB with MDS around -100dBm
(2uV).
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So the maximum span width would be 5.4 MHz (± 2.7 MHz)
So the maximum span width would be 3.2 MHz (± 1.6 MHz)
then press
10.7 - 8.83 = 1.87
1.87 x 2 = 3.74
10 - 3.74 = 6.26 MHz
So the maximum span width will be a
respectable and useful 6.26 MHz (± 3.13 MHz)
then press .