rjr@mgweed.UUCP (Bob Roehrig) (05/02/85)
Someone asked about mods for the Icom 22S. I have been well pleased
with mine, except for one minor problem, which I will mention later.
I don't know where this document came from that I will quote from
and I assume that the mods in mine were made from this dope.
(I got mine 2nd hand and it already worked below 146).
"to operate below 146 mhz:
1. locate IC1 on synthesizer board. remove diodes connected to
pins 7 and 8 going to pin 13, and the 10k resistor from pin
13 going to ground.
2. Connect pin 13 to pin 16 of IC-1.
3. locate IC-10 on the PLL board. Cut pin 2 close to the
board and bend upwards. Cut the path between pins 2 and 5.
Connect a 10k resistor from pin 5 to ground. Connect cathode
of a silicon switching diode to pin 2. Connect its anode to
pin 5 of IC-8. Connect a jumper between IC-10 pin 2 and 5.
4. Connect another diode on IC-10: cathode to pin 5, anode
to pin 6.
These mods still have the radio operating on 15 kHz channels.
The ./. N factor for the channel you want is figured
as F-144.39 / .015
For example, 144.990 is divide by 40, and 145.005 is divide
by 41.
I found that the RF stages in both the rcvr and xmtr needed
repeaking to use below 146 MHz. There is no way the 22S will
cover 144 to 148, RF-wise. You can get 3 out of the 4 MHz
and that is about it.
My 22S block diagram shows that a reference frequency of 7.5
kHz is used, derived from a 7.68 MHz osc. I would assume that
to get a 20 kHz spacing between channels, one would need to
use a crystal that would derive a 10 kHz reference - I have
not explored this.
The problem I mentioned was intermittent locking of the PLL.
The problem was caused by corroded connections in the plug
on the matrix board. Cleaning did no good, so I removed the
pins and the board connector and "hard wired" the matrix board
using ribbon cable.
/-/-/-/-/-/-/-/ additional changes /-/-/-/-/-/-/-/-/-/-/
I tripled the number of channels the 22S will operate on
by adding one switch on the rear of the unit. This switch
is now wired as the power switch. The original front panel
power switch is now labeled C, E (center), and D. The original
duplex switch is left alone - A, S (simplex) and B.
All diodes were removed from the matrix board and new ones were
installed as shown below, except to rows 0, 6, and 7.
The C-E-D switch is now wired as follows:
1. ground the common contact.
2. connect the C contact of the switch to the D7 wire of the
matrix board.
3. connect the D contact to the D6 wire of the matrix board.
4. Connect two 2.7k resistors from +9 volts to the C and D lines.
5. Install diodes in positions D1 thru D5 as follows:
CHAN D5 D4 D3 D2 D1 FREQ CHAN D5 D4 D3 D2 D1 FREQ
1 x x x 146.01 11 x 146.34
2 x x x x 146.04 12 x 146.37
3 x x 146.07 13 x x 146.40
4 x x x 146.10 14 x 146.43
5 x x x 146.13 15 x x 146.46
6 x x x x 146.16 16 x x 146.49
7 x x x 146.19 17 x x x 146.52
8 x x x x 146.22 18 x 146.55
9 x x x x 146.25 19 x x 146.58
10 x x x x x 146.28
NOTE: I have put no diodes in row D0. This row is only
needed for frequencies ending in "5".
Position 24 on the selector is blank and is used to
obtain 146.31, which requires no diodes.
With the modifications as outlined, the following channels
are available:
SIMPLEX CHANNELS
________________
CHAN FREQ CHAN FREQ CHAN FREQ
____________ ____________ ____________
14D 146.43
15C 145.50 15D 146.46 15E 147.42
16C 145.53 16D 146.49 16E 147.45
17C 145.56 17D 146.52 17E 147.48
18C 145.59 18D 146.55 18E 147.51
19C 145.62 19D 146.58 19E 147.54
REPEATER CHANNELS
(outputs shown)
_________________
CHAN FREQ CHAN FREQ
____________ ____________
(Dup A) (Dup B)
1C 146.61
2C 146.64 2D 147.00
3C 146.67 3D 147.03
4C 146.70 4D 147.06
5C 146.73 5D 147.09
6C 146.76 6D 147.12
7C 146.79 7D 147.15
8C 146.82 8D 147.18
9C 146.85 9D 147.21
10C 146.88 10D 147.24
11D 146.94 11E 147.30
12D 146.97 12E 147.33
13D 147.00 13E 147.36
14E 147.39
24D 146.91 24E 147.27
I wired the following other channels as follows for local
use:
CHAN FREQ DIODES Sw pos.
20 145.635 0-1-4 C
21 145.575 0-1-2-3 C
22 145.800 1-2-3-4 C
23 147.375 0-1-2 Ebrian@sdcsvax.UUCP (Brian Kantor) (05/03/85)
Since the synthesizer in an IC22S uses 8 bits to set the frequency, it is quite easy to drive it with a microprocessor. I use exactly this scheme in a remote base, where the touch-tone commands are converted by the Z80 system controller into the synthesizer input to put the radio on any frequency in the band. But a more practical idea: since the endings of all frequencies at .015 spacings are unique in the top two MHZ of two meters, you can easily use something like a 2716 to translate 9 bits (two BCD thumbwheels and a 0/5 toggle) into the synthesizer input. That way you can dial up any frequency the radio will do directly. There are 11 address bits on a 2716, so you can even use the other 3 512 word partitions for special effects - or (this is nifty), switch one of the address lines with the transmit line, which gives you the ability to have custom offsets for repeaters and such - since the transmit and receive frequencies are separately stored and separately loaded into the synthesizer from the prom. At about $6 for the switches, and $3 for the chips, its a cheap mod! Brian Kantor, WB6CYT UC San Diego decvax\ brian@ucsd.arpa akgua >--- sdcsvax --- brian ucbvax/ Kantor@Nosc