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receiver or repeater output frequency, simply find the the N number for the
offset and program it on the offset matrix.
Here's one more example. Let's say we want a + 1 MHz offset.
1 MHz = 1000 KHz. 1000 ÷ 5 = 200 = N
Converting to binary: (Obviously 200 is less than all values from 8K through
256, meaning that we need no diodes in those positions.)
Can we subtract 128 from 200? YES (Therefore diode at 128)
200 - 128 = 72
Can we subtract 64 from 72?
72 - 64 = 8
Can we subtract 32 from 8?
Can we subtract 16 from 8?
Can we subtract 8 from 8?
This +1 MHz TX offset is set up easily by diodes at 128, 64 and 8!
Programming of Minus offsets is covered in the Reference section of your
manual.
ADDITIONAL CIRCUIT NOTES:
The 19 100K resistors at the frequency programming matrix and the 14 100K
resistors at the offset matrix are called "pull down resistors" and are required
to ensure positive logic switching action of U6.
Transistor Q15 and its associated switching diodes ensure that the desired
offset is switched in during transmit, that offset programming does not
interfere when simplex is desired and that the offsets do not interfere with
receiver operation . . . and that receiver programming (21.4 MHz lower) does
not interfere with transmit operation. Obviously, these simple parts must be
installed correctly, or major PLL problems would result.
Note: The silkscreen on your PC board may contain diode placement
markings that differ from your calculated placement. Always follow your
calculated placement and ignore the silkscreen (which could contain errors).
Stage H: PROGRAMMING MATRIX ASSEMBLY
There are two diode matrix programming areas on your PC board. The
obviously larger area is for frequency channel programming. The second
space is for offset programming added in by U7-U10.
Correct assembly of the following section permits Q15 to switch off all three
transmit offset programming lines while receiving, allowing only the RECV
programming to be in effect. Be certain to orient the diodes correctly.
Install the following resistors:
YES (Therefore diode at 64)
NO
(Therefore NO diode at 32)
NO
(Therefore NO diode at 16)
YES (Therefore diode at 8)
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