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.
FX-146
•
33
Sample BASIC Program Listing
50 PRINT “Enter Receiver Frequency as 6 digits with NO decimal!”
52 INPUT “For example: 146520. Enter here: “; F
55 N = F/5
60 PRINT “The FX146 or FX220 N number for binary conversion is “; N
101 AA = 0
102 BB = 0
103 CC = 0
104 DD = 0
105 EE = 0
106 FF = 0
107 GG = 0
108 HH = 0
109 II = 0
110 JJ = 0
111 KK = 0
112 LL = 0
113 MM = 0
114 NN = 0
115 OO = 0
116 PP = 0
200 IF N => 32768! THEN AA = 1
205 IF N > 32768! THEN NA = N - 32768!
206 IF N < 32768! THEN NA = N
210 IF NA => 16384 THEN BB = 1
215 IF NA > 16384 THEN NB = NA - 16384
216 IF NA < 16384 THEN NB = NA
220 IF NB => 8192 THEN CC = 1
225 IF NB > 8192 THEN NC = NB - 8192
226 IF NB < 8192 THEN NC = NB
230 IF NC => 4096 THEN DD = 1
235 IF NC > 4096 THEN ND = NC - 4096
236 IF NC < 4096 THEN ND = NC
240 IF ND => 2048 THEN EE = 1
245 IF ND > 2048 THEN NE = ND - 2048
246 IF ND < 2048 THEN NE = ND
250 IF NE => 1024 THEN FF = 1
255 IF NE > 1024 THEN NF = NE - 1024
256 IF NE < 1024 THEN NF = NE
260 IF NF => 512 THEN GG = 1
265 IF NF > 512 THEN NG = NF - 512
266 IF NF < 512 THEN NG = NF
270 IF NG => 256 THEN HH = 1
275 IF NG > 256 THEN NH = NG - 256
276 IF NG < 256 THEN NH = NG
280 IF NH => 128 THEN II = 1
285 IF NH > 128 THEN NI = NH - 128
286 IF NH < 128 THEN NI = NH
290 IF NI => 64 THEN JJ = 1
295 IF NI > 64 THEN NJ = NI - 64
296 IF NI < 64 THEN NJ = NI
300 IF NJ => 32 THEN KK = 1
305 IF NJ > 32 THEN NK = NJ - 32
306 IF NJ < 32 THEN NK = NJ
310 IF NK => 16 THEN LL =1
315 IF NK > 16 THEN NL = NK - 16
