AUTOMATIC UO-14 RX FREQUENCY CONTROL to use with KENWOOD TS 790 and G3RUH 9600 bps Modem

By IW3QUB, IW3QPC, IW3QWG
QTH: Cormons JN65RW - ITALY

Here is a simple but good AFC circuit for satellite FM operations. Its main features are:

very small stand-alone circuit: our mounted board measures only 40 x 26 millimeters. It easily fits inside the modem box.
The frequency control is activated only when UO-14 RX Audio is present.
Links and adjustment are very simple. No modifications are required for G3RUH 9600 bps modem. The small circuit is stand-alone: it doesn't use any part of G3RUH 1200 bps PSK modem.

SCHEMATIC DIAGRAM


 
                                 +-----|+5V     C1
                        +12 V *--+ IC1 +--------||---
                                 +-----|     |
                                             |            R1    ///
                                             |14      кФФ/\/\ФФФД>нФФД
                                         1-------| 3  Г         DL1
                         |-------- 4   кФ|  &    |----Д
                         |  &    |-------|  IC2a |    Г 13кФФФФФФП 11
                  +-------  IC2b |       2-------|    РФФФД &    ГoФФФФФФП
                  |      |-------|          ФСФ7      кФФФД IC2d Г       Г
                  Г                                   Г 12РФФФФФФй   TuneГ
                  РФФФФФФФФФФФФФФФФП                  Г                 /
                                   Г                  Г           Off /   On
                                   Г                  Г              *   *
                           +12 V   Г                  Г                  Г
                     C2     *      Г                  Г                  Г
                 УФФФДУФФФФФД      Г       8кФФФФФФП10Г   R2   ///       Г
                            Г      Г     кФФД &    ГoФСФФ/\/\ФФД>нФФД    Г
           C3               Г      Г    кСФФД IC2c Г           DL2       Г
       УФФФДУФФФФФП         Г      Г    Г  9РФФФФФФй                     Г
                  Г         Г      Г    Г                                Г
(Note 3)   R3     Г     3Г \Г7     Г    Г                         D1     Г
 AF IN *ФФ/\/\ФФФФСФФФФФФД+  \ 6   Г    РФФ* (Note 2)       3 *ФФФД>нФФФФй
                         ГIC3 >ФФФФй                   (Note 1)
 +12 V *ФФ/\/\ФФФФТФФФФФФД- /                               8 *ФФФФФФФФФФД
           R4     Г     2Г/ Г4                                          GND
                  Г        ФСФ       кФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФП
                  Г                  Г         The NAND Gate            Г
        кФФ\      Г                  Г                                  Г
     УФФСФ/\/\ФФФФй                  Г                      A B Г x     Г
         VR1 \                       Г  A кФФФФФФП  x      ФФФФФХФФФ    Г
                                     Г  ФФД &    ГoФФ       0 0 Г 1     Г
                                     Г  ФФД      Г          0 1 Г 1     Г
                                     Г  B РФФФФФФй          1 0 Г 1     Г
                                     Г                      1 1 Г 0     Г
                                     Г                                  Г
                                     РФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФФй

Note 1 connect these two points to the TS-790 Microphone Socket, at pin "3" (Frequency DOWN) and at pin "8" (GROUND).

Note 2 connect this point to G3RUH 9600 bps Modem, at U10 - pin "13" (See the "DCD" in the schematic diagram of the modem)

Note 3 connect to Audio Frequency coming directly from the TS-790 discri- minator (see the following scheme):

 
           +-----------+AF Out (discr.)       AF In+----------------+
           |  TS 790   |---------------------------| 9600 bps modem |
           |           |                        |  +----------------+
           +-----------+                        |  /-----------+
                                                --<  AFC board |
                                              AF In\-----------+

(We suggest to place the 820 KiloOhms resistor R3 lose by the "AF In" point of G3RUH 9600 bps modem.)

COMPONENTS LIST

Resistors: R1 = 470 Ohms Capacitors: C1 = 0.1 uF

R2 = 470 Ohms C2 = 0.1 uF

R3 = 820000 Ohms C3 = 0.015 uF

R4 = 8200 Ohms

VR1 = 10 KiloOhms Trimmer

Diodes: D1 = 1N 4148

DL1 = LED diode (Frequency DOWN)

DL2 = LED diode (DCD)

Integrated Circuits: IC1 = 78L005 {Voltage regulator}

IC2 = CD 4011 {NAND gates}

IC3 = TL081 {Operational amplifier}

ADJUSTMENT

No instruments are nedeed to adjust this circuit. When you have soldered all the components on a small board, you'll simply connect it to the TS-790 and to the G3RUH 9600 bps Modem. Then you'll turn on the transceiver and tune it on a frequency free from signals. At this point look at the LED diode DL1 (Frequency DOWN) and follow these two steps:

Step 1:

If the LED DL1 is switched off then switch it on rotating the trimmer VR1. If DL1 is already switched on, then skip to Step 2.

Step 2:

Slowly rotate the trimmer VR1 until the LED diode DL1 turns off; be careful to STOP ROTATING VR1 as soon as DL1 turns off. This ends the adjustment operations !

Good UO-14 operations from:

IW3QUB - Ferruccio
IW3QPC - Marco
IW3QWG - Marco

Click here to read more mods for the TS-790

Note 1	connect these two points to the TS-790 Microphone Socket, at pin "3" (Frequency DOWN) and at pin "8" (GROUND).
Note 2	connect this point to G3RUH 9600 bps Modem, at U10 - pin "13" (See the "DCD" in the schematic diagram of the modem)
Note 3	connect to Audio Frequency coming directly from the TS-790 discri- minator (see the following scheme):

Resistors:	R1 =	470 Ohms	Capacitors:	C1 =	0.1 uF
	R2 =	470 Ohms		C2 =	0.1 uF
	R3 =	820000 Ohms		C3 =	0.015 uF
	R4 =	8200 Ohms
	VR1 =	10 KiloOhms Trimmer

Diodes:	D1 =	1N 4148
	DL1 =	LED diode (Frequency DOWN)
	DL2 =	LED diode (DCD)

Integrated Circuits:	IC1 =	78L005	{Voltage regulator}
	IC2 =	CD 4011	{NAND gates}
	IC3 =	TL081	{Operational amplifier}