TX Driver and PA Introduction


Here is a Youtube Video of Dragan 4O4A's QSO with his completed G3020. Plough through this last stage and you can be there, too!

NB: If you Plan to Use the Transceiver for Digital Modes

From the Preston Smith's (WJ2V) FAQ on the GenesisRadio web site:

Q: My final PA gets hot/blew out while transmitting in digital mode. What happened?

A: The Genesis is suppled with a 1" heat sink for the final. This is adequate for casual SSB or CW operating, but not for digital (e.g. PSK31, SSTV, WSPR) modes, which are much more demanding. Linear key-down modes require a larger heat sink, and a fan to protect the final PA, an IRF 510.

If you blow one, you can buy a replacement for about two dollars at Radio Shack. You can find a direct fit, only taller, replacement heat sink at Digikey: 2" and a 2.5" heatsinks have Digikey part numbers: HS287-ND and HS133-P-ND, respectively.

Either should work, but also consider a small fan on top for long key down or contest modes.

(go directly to build notes)

TX Driver and PA Schematic

TX Driver and PAschematic

(go directly to build notes)

TX Driver and PA Bill of Materials

Stage Bill of Materials

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

11 k 1/4W 1%br-blk-blk-br-br br-blk-blk-br-br1/4W
310 ohm 1/4W 1%br-blk-blk-gld-br br-blk-blk-gld-br1/4W
1100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W
11R 1/4W 1% (1R)brn-blk-blk-silver-brn brn-blk-blk-silver-brn1/4W
3330 1/4W 1%ora-ora-blk-blk-brn ora-ora-blk-blk-brn1/4W
1390 1/4W 1%ora-whi-blk-blk-brn ora-whi-blk-blk-brn1/4W
1470 1/4W 1%yel-vio-blk-blk-brn yel-vio-blk-blk-brn1/4W
168.0 1/4W 1%blu-gry-blk-gld-brn blu-gry-blk-gld-brn1/4W
2BN43-202 Binocular core
110 nF (.01uF)103 103Ceramic
1100 nF104 104Ceramic
3100 nF104 104Ceramic
4100 nF104 104Ceramic
147 uH molded inductor 10%yel-vio-blk-slv yel-vio-blk-slvChoke
2shunt wire (cut-off lead)Cutoff
1M3 screw and nut setHDW
1Magnet wire, enameled #20Magnetic
1TO-220 1" Heatsink Misc
1TO-39 heatsink Misc
1SPDT 2 positionSPDT
1SPDT 2 positionSPDT
1SPDT 2 positionSPDT
1Power MOSFET IRF510IRF510 IRF510TO-220
12N3866 NPN Transistor TO-39

TX Driver and PA Summary Build Notes

TX Driver and PA Detailed Build Notes

Top of the Board

TX Driver and PA Top View

Install Driver Transistor and Heat Sink

Install the 2N3866 transistor and its heatsink. Refer to the instructions in Phase 6 for details on mounting and installing the 2N3866.

misc10-2TO-39 heatsink Misc 
Q10-22N3866 NPN Transistor TO-39 

Wind and Install the Dual Binocular Transformer

Glue together the two binary cores as indicated in the graphic, below:

Binary cores

Take care when gluing the two cores together to carefully set and align them so they are aligned with one another, as in the image. There is a tendency, especially when using "Super Glue" to let them slide out of aligment just as the glue sets, making recovery and realignment quite difficult.

Twisted Wire

Prepare a 40 cm (~16") long piece of enameled copper wire and fold it over so that it is two 20 cm wires joined at the one end

Twist the wires together so that you get approximately three twists per 10 mm (3 twists per every 0.4 inches) of length

Wind the Wire through the Core

Click Picture to Enlarge

Phase 10 - TX driver and power FET assembly

Thread the twisted wires (folded end first) through the glued cores, starting in hole 1, coming out the other end and looping back through the top core to exit at hole 3. Continue from hole 3 into hole 2, coming out the other end and looping back into the upper core so as to exit at hole 4.

When finished winding, cut the folded end of the twisted wire off, such that you noe have four wire ends.

The pair at hole 1 represents the primary leads; the pair at hole 4 represents the secondary leads of the wound transformer.

Using an ohm meter, identify the ends of each wire as indicated on the graphic above. You may want to use a small piece of colored hookup wire insulation to identify the "a-a1" pair (or, if you prefer, the "b-b1 pair") wire's ends.

Mount the Transformer

You do not need to worry how to figure out the phasing; if you match the designated leads (a1, b1, a, b) with the holes as marked in the graphic below, you will have correct phasing.

Wound cores

Wound cores

Transformer mounting

Insert transformer's leads into the PCB holes, as indicated above. Form the leads and pull them tight. Then cut off the excess (on the underside of the board) so that approximately 5mm (1/8") of wire is protruding out on the underside of the board.

Remove the transformer from the PCB, scrape the enamel coating from the 4 leads but DO NOT TIN them as yet (tinning the leads could cause them to be too "fat" to go back into the holes).

Insert the 4 transformer leads back into the PCB and solder them.

misc10-1Magnet wire, enameled #20Magnetic 

Install Passive Components

Install resistors, capacitors, chokes

Some PCBs for the G3020 have a silkscreen image suggesting that the component to be installed just above the 1 ohm ("1R") resistor is a 470 nH inductor. The silkscreen is incorrect. It should be a 330 ohm resistor, NOT an inductor. See the top of the board graphic - it is correct.
Beware - there is NO 470uH inductor here

C10-810 nF (.01uF)103 103Ceramic 
R10-11R 1/4W 1% (1R)brn-blk-blk-silver-brn brn-blk-blk-silver-brn1/4W 
R10-210 ohm 1/4W 1%br-blk-blk-gld-br br-blk-blk-gld-br1/4W 
R10-310 ohm 1/4W 1%br-blk-blk-gld-br br-blk-blk-gld-br1/4W 
R10-410 ohm 1/4W 1%br-blk-blk-gld-br br-blk-blk-gld-br1/4W 
R10-568.0 1/4W 1%blu-gry-blk-gld-brn blu-gry-blk-gld-brn1/4W 
R10-6100 1/4W 1%br-blk-blk-blk-br br-blk-blk-blk-br1/4W 
R10-7330 1/4W 1%ora-ora-blk-blk-brn ora-ora-blk-blk-brn1/4W 
R10-8330 1/4W 1%ora-ora-blk-blk-brn ora-ora-blk-blk-brn1/4W 
R10-9330 1/4W 1%ora-ora-blk-blk-brn ora-ora-blk-blk-brn1/4W 
R10-10390 1/4W 1%ora-whi-blk-blk-brn ora-whi-blk-blk-brn1/4W 
R10-11470 1/4W 1%yel-vio-blk-blk-brn yel-vio-blk-blk-brn1/4W 
Note: This is a 470R, NOT a 4k7 or 47k.
R10-121 k 1/4W 1%br-blk-blk-br-br br-blk-blk-br-br1/4W 
C10-1100 nF104 104Ceramic 
C10-2100 nF104 104Ceramic 
C10-3100 nF104 104Ceramic 
C10-4100 nF104 104Ceramic 
C10-5100 nF104 104Ceramic 
C10-6100 nF104 104Ceramic 
C10-7100 nF104 104Ceramic 
R10-12100 nF104 104Ceramic 
L10-347 uH molded inductor 10%yel-vio-blk-slv yel-vio-blk-slvChoke 

Install the 2 Jump Wires

Install the 2 Jump Wires photo
JMP10-1shunt wire (cut-off lead)Cutoff 
JMP10-2shunt wire (cut-off lead)Cutoff 

Install PA FET and Heat Sink

Be sure the transistor is oriented with its flat "Drain Flange" (see BOM for the final transistor) facing the bottom of the board.

orientation of the final transistor

Install PA FET and Heat Sink photo
Q10-1Power MOSFET IRF510IRF510 IRF510TO-220 
hdw10-1M3 screw and nut setHDW 
misc10-1TO-220 1" Heatsink Misc 

Install Remaining Wires

Install the remaining permanent wires to the board. Some have been already installed in previous phases. At this point, if you have not removed any temporary wires/switches, you should do so now. For your help in this effort, all permanent (non-switch associated) wires are itemized in the following table:

Wires A-A and B-BMisc Hookup WireFinal Permanent Wires Vcc Connection (Phase 8)
Wire C-CMisc Hookup WireFinal Permanent Wires W9 (Phase 9)
Wire D-DMisc Hookup WireFinal Permanent Wires This Phase
Wire E-EMisc Hookup WireFinal Permanent Wires This Phase
Wire F-FMisc Hookup WireFinal Permanent Wires This Phase
Wire G-GMisc Hookup WireFinal Permanent Wires W8 (Phase 9)
Wire H-HMisc Hookup WireFinal Permanent Wires W4 (Phase 7)
Wire I-IMisc Hookup WireFinal Permanent Wires This Phase
Wire J-JMisc Hookup WireFinal Permanent Wires This Phase
Wire K-KMisc Hookup WireFinal Permanent Wires W3 (Phase 6)

Click to see a high resolution picture of the wires.

Install Remaining Wires photo

Install Remaining Switches

If, at this point, you have not removed any temporary switches, you should do so and then ensure you have all of the permanent switches.

Some builders may have postponed the actual wiring and installation of switches in earlier stages, in order to make handling of the board less complicated. If this is the case, those switches must be installed at this point and it would be a good idea to review any tests associated with the switches with a view toware repeating the tests.

Note that there were two options to handling the band-switching of the oscillator's crystals: the original design, using the panel, LEDs, and DPDT switches; and the use of the Rotary Switch with no LEDs. It is your decision.

Refer to the Final Diagram for the final positioning and wiring of all of the Switches

Watch out for the pre-amp and attenuator switches in the Final Diagram. In the lower right hand corner there are they are labeled PREAMP and ATTN. According to the wiring of these two switches in the diagram, the names on the two switches have been reversed. The upper switch should be labeled ATTN and the lower switch should be labeled PREAMP.

The table below provides information on the switches, their function, and the stage withn which they were described/defined/installed:

CheckSwitchFunctionStage in Which Defined
BandSwitchSwitches one of 4 crystals into LOBand Switch
AF Gain Switch
Selects 23dB or 46dB gain on RX I and Q to PCRX Mixers/OpAmps
RF Preamp
Switches +15 dB PreAmp into or out of RF pathLP Filters and PreAmp
RF Attenuator
Switches -17dB RF Attenuator into RF pathLP Filters and PreAmp
Monitor SwitchCW/SSB Digital CW Monitor On/OffCW Monitor

SW10-1SPDT 2 positionSPDT 
AF Gain 23dB/46dB
SW10-2SPDT 2 positionSPDT 
RF Pre-Amp
SW10-3SPDT 2 positionSPDT 
RF Attenuator

TX Driver and PA Testing

Finals Resistance Tests

Test Setup

with power off, measure:

  • Resistance from source to gate of the IRF10 MOSFET Final Amplifier. Should be greater than 1.2k ohms (in the range of 1.3k-1.6k)
  • Resistance from source to drain (in the same range, but rising to eventually over 7k ohms)
Finals Resistance Tests

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
IRF10 PA source-to-gate resistancek ohm1.3 - 1.6tbd_______
IRF10 PA source-to-drain resistancek ohm1.3 rise to > 7tbd_______

Driver Voltage Test

Test Setup

While transmitting, measure the voltage at the emitter of the 2N3866 driver transistor. It should be +/- 2.5vdc.

Driver Voltage Test

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
Emitter of driver transistorVdc2.5tbd_______