Ramsey Electronics FZ-146 Specifications download pdf (Page 114)

FX 146 • 114

THE RX/TX OFFSET PROGRAMMING MATRIX

Diode placement in this matrix follows the same binary number principles as

used for frequency programming. This matrix is connected to the 16

programming inputs of U6 through the four binary adders (U7-U10).

Fewer programming positions are provided on the board simply because

there is no practical use for extremely large or very tiny frequency offsets.

The 1 to 8K range provides plenty of flexibility for non-standard channel

spacing.

U7 through U10 are called "4 bit" binary adders because they each can

handle four binary addition operations. For each bit, there are A and B inputs

and one S (sum) output. Examine the schematic diagram closely, and you

will see that all the frequency programming lines are connected to "A" inputs

and all offset lines go to "B" inputs. Notice further that the binary positions of

both matrixes correspond to each other exactly: the 8K offset position goes

to B1 of U7 and the 8K frequency programming position goes to A1. Their

sum appears at S1 (pin 1) and goes to U6. And so forth for all the other

binary positions of both matrix areas.

We made it very easy for you to set up the required receiver frequency and

standard 600 KHz transmit offsets. Simply insert diodes correctly in the

holes marked by circles, solder, and you're in business. Here's a

reproduced image of the PC Board's matrix area. See how the standard

offset positions are outlined with circles.

However, it's worthwhile to understand why the diodes are in those

positions. Let's work backwards, starting with the actual diode positions and

discover why they are put there.

Starting with the easiest, add up the values for the 2 diodes used in the

+RPT line:

8 + 16 +32 +64 = 120

120 X 5 KHz = 600 KHz, which is added by U10 and U9 to the frequency

programmed on the main matrix. To say it precisely: 120 is added in binary

form to the binary form of the N number.

1 2 ... 109 110 111 112 113 114 115 116 117 118 119 ... 144 145

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Ramsey Electronics FZ-146 Specifications Page 114