PA RX/TX Control Introduction

(go directly to build notes)

PA RX/TX Control Schematic

PA RX/TX Controlschematic

(go directly to build notes)

PA RX/TX Control Bill of Materials

Stage Bill of Materials

(resistor images and color codes courtesy of WIlfried, DL5SWB's R-Color Code program)

21 k 1/4W 1%br-blk-blk-br-br br-blk-blk-br-br1/4W
1100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W
52k2 1/4W 1% (2.2K)red-red-blk-brn-brn red-red-blk-brn-brn1/4W
22k7 1/4W 1% (2.7K)red-vio-blk-brn-brn red-vio-blk-brn-brn1/4W
147K 1/4W 1%yel-vio-blk-red-brn yel-vio-blk-red-brn1/4W
44K7 1/4W 1% (4.7K)yel-vio-blk-brn-brn yel-vio-blk-brn-brn1/4W
14K7 1/4W 1% (4.7K)yel-vio-blk-brn-brn yel-vio-blk-brn-brn1/4W
21N41481N4148 1N4148Axial
11N4734 5V6 Zener Diode1N4734 1N4734Axial
1Ferrite Bead Axial
610 nF (.01uF)103 103Ceramic
110 nF**103 103Ceramic
110 nF**103 103Ceramic
11100 nF104 104Ceramic
11000 uF/25Vdc Electrolytic
2misc hookup wireHookup
1misc hookup wireHookup
1db9 connector - PCB mount Jack
13.5mm stereo jack - PCB mount (rt-angle) Jack-RA
1BD139 NPN Transistor TO-126
1BD140 PNP Transistor TO-126
2BC546 NPN Transistor TO-92
1BC546 NPN Transistor TO-92
2BC556 PNP Transistor TO-92
1BC556 PNP Transistor TO-92
15K (Y502)Y502 Y502Trimpot

PA RX/TX Control Summary Build Notes

PA RX/TX Control Detailed Build Notes

Top of the Board

PA RX/TX Control Top View

Install Connectors, Trimmer, and Ferrite

Install Connectors, Trimmer, and Ferrite photo
P8-13.5mm stereo jack - PCB mount (rt-angle) Jack-RA 
P8-2db9 connector - PCB mount Jack 
L8-1Ferrite Bead Axial 
R8-165K (Y502)Y502 Y502Trimpot 
Needs to be initialized. Before installing this trimmer, adjust the resistance between the middle pin and either of the other pins to 2.5 K Ohm.

Install Transistors

Be careful to install the correct transistors (BC556s to the left and BC546s to the right) and orient them so their flat sides align with the flat side on the silkscreen.

The BD139 and BD140 have a metallic heatshield on one side of the vertical tab; align that metallic side with the black stripe shown on the graphic below.

Install Transistors photo
Q8-1BD140 PNP Transistor TO-126 
Q8-2BD139 NPN Transistor TO-126 
Q8-3BC546 NPN Transistor TO-92 
Q8-4BC546 NPN Transistor TO-92 
Q8-7BC546 NPN Transistor TO-92 
Q8-5BC556 PNP Transistor TO-92 
Q8-6BC556 PNP Transistor TO-92 
Q8-8BC556 PNP Transistor TO-92 

Install Diodes, Resistors, Capacitors

Be careful with some of the similar looking resistor values: 47k vs. 4k7; 2k7 vs 2k2

Also, please note that there are two regular signal diodes and one zener diode and mount them in their appropriate places.

Install Diodes, Resistors, Capacitors photo
D8-11N4734 5V6 Zener Diode1N4734 1N4734Axial 
D8-21N41481N4148 1N4148Axial 
D8-31N41481N4148 1N4148Axial 
R8-1100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W 
R8-21 k 1/4W 1%br-blk-blk-br-br br-blk-blk-br-br1/4W 
R8-31 k 1/4W 1%br-blk-blk-br-br br-blk-blk-br-br1/4W 
R8-42k2 1/4W 1% (2.2K)red-red-blk-brn-brn red-red-blk-brn-brn1/4W 
R8-52k2 1/4W 1% (2.2K)red-red-blk-brn-brn red-red-blk-brn-brn1/4W 
R8-62k2 1/4W 1% (2.2K)red-red-blk-brn-brn red-red-blk-brn-brn1/4W 
R8-72k2 1/4W 1% (2.2K)red-red-blk-brn-brn red-red-blk-brn-brn1/4W 
R8-82k2 1/4W 1% (2.2K)red-red-blk-brn-brn red-red-blk-brn-brn1/4W 
R8-102k7 1/4W 1% (2.7K)red-vio-blk-brn-brn red-vio-blk-brn-brn1/4W 
R8-92k7 1/4W 1% (2.7K)red-vio-blk-brn-brn red-vio-blk-brn-brn1/4W 
R8-114K7 1/4W 1% (4.7K)yel-vio-blk-brn-brn yel-vio-blk-brn-brn1/4W 
R8-124K7 1/4W 1% (4.7K)yel-vio-blk-brn-brn yel-vio-blk-brn-brn1/4W 
R8-134K7 1/4W 1% (4.7K)yel-vio-blk-brn-brn yel-vio-blk-brn-brn1/4W 
R8-144K7 1/4W 1% (4.7K)yel-vio-blk-brn-brn yel-vio-blk-brn-brn1/4W 
R8-174K7 1/4W 1% (4.7K)yel-vio-blk-brn-brn yel-vio-blk-brn-brn1/4W 
R8-1547K 1/4W 1%yel-vio-blk-red-brn yel-vio-blk-red-brn1/4W 
C8-110 nF (.01uF)103 103Ceramic 
C8-210 nF (.01uF)103 103Ceramic 
C8-310 nF (.01uF)103 103Ceramic 
C8-410 nF (.01uF)103 103Ceramic 
C8-510 nF (.01uF)103 103Ceramic 
C8-610 nF (.01uF)103 103Ceramic 
C8-710 nF**103 103Ceramic 
C8-7a10 nF**103 103Ceramic 
C8-10100 nF104 104Ceramic 
C8-11100 nF104 104Ceramic 
C8-12100 nF104 104Ceramic 
C8-13100 nF104 104Ceramic 
C8-14100 nF104 104Ceramic 
C8-15100 nF104 104Ceramic 
C8-16100 nF104 104Ceramic 
C8-17100 nF104 104Ceramic 
C8-18100 nF104 104Ceramic 
C8-8100 nF104 104Ceramic 
C8-9100 nF104 104Ceramic 
C8-201000 uF/25Vdc Electrolytic 

Install Vcc and Temporary Switch Connections

Install the 13.8 Vdc connection to its final place and temporarily wire in switches SX1 and SX2 to support testing

You may use any convenient technique to simulate switches sx2 and sx2 (e.g., alligator clips or clip leads)

Note: the diagram shows the "partial stack" of resistors where the leftmost lead (lead(1)) of SW1 connects. This is due to the subsequenc add-in of circuitry for controlling an external PA. The connection for SX1 must be made at the junction of the diode (on left) an the resistor (on right), as in this diagram:

Connection for left-hand lead of SX1

Install Vcc and Temporary Switch Connections photo
sx1_leadsmisc hookup wireHookup 
(temporary wires)
sx2_leadsmisc hookup wireHookup 
(temporary wires)
Vccmisc hookup wireHookup 
Power leads

PA RX/TX Control Testing

Test Step 1

Test Setup

Using a DMM, measure the voltages at +VTX and +VRX, as indicated below

Test Step 1

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
SX1 OFF: point +VTXVdc0_______
SX1 OFF: point +VRXVdc+12 to +13.8_______
SX1 ON: point +VTXVdc+12 to +13.8_______
SX1 ON: point +VRXVdc0_______

Test Step 2

Test Setup

  • Turn SX1 OFF. Connect Genesis G40 to the serial PC port directly or via USB/ Serial adapter. Settings in SDR software should be set according to theDB9 connector's Pins as shown below:
  • teststep2_table
  • Turn on SX2 (temporarily installed in Test Step 1) and +VTX should be +12-+13.8V.

More details on PC to G3020 connection and SDR settings

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
SX2 ON: +VTXVdc+12 to +13.8_______