RX RF In Introduction


In this phase, we complete the permanent path for the RF between the S/H detectors/modulators, removing the temporary wire path installed in the preceding phase. The permanent path includes the low-pass and band-pass filters, and the relay (K1) that switches the RF path from its default RX configuration to the TX configuration.

Relay K1 is powered from the Vtx bus. activated via the PTT control signals. The Vtx will be provided in the finished board via a wire, connecting the K1 coil to the Vtx bus via. This wire is designated the "C-C" wire in the final wiring diagram.

We also add switch-selectable RF attenuation (17dB) and switch-selectable RF pre-amplification (15dB) circuitry, with the relays (K2 and K3) that switch these circuits in and out of the path. The relays K2 and K3 are powered from the Vrx bus, when it is switched to the relays via switches S2 and S3 (the schematic designates them as S1 and S2).

RX RF In Schematic

RX RF Inschematic

RX RF In Bill of Materials

Stage Bill of Materials

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

1Magnet wire, enameled #20 28" (70 cm) for the pair of coilsRX RF In
11K5 (1.5k) 1/4W 1%brn-grn-blk-brn-brn brn-grn-blk-brn-brn1/4W RX RF In
2220 1/4W 1%red-red-blk-blk-brn red-red-blk-blk-brn1/4W RX RF In
233 1/4W 1%ora-ora-blk-gld-brn ora-ora-blk-gld-brn1/4W RX RF In
1330 1/4W 1%ora-ora-blk-blk-brn ora-ora-blk-blk-brn1/4W RX RF In
1390 1/4W 1%ora-whi-blk-blk-brn ora-whi-blk-blk-brn1/4W  RX RF In
1560 1/4W 1%grn-blu-blk-blk-brn grn-blu-blk-blk-brn1/4W RX RF In
268 1/4W 1%blu-gry-blk-gld-brn blu-gry-blk-gld-brn1/4W RX RF In
16R8 1/4W 1% (6.8)blu-gry-blk-silver-brn blu-gry-blk-silver-brn1/4W RX RF In
3JRC27F/012 relayJRC27F/01212V relayRelay JRC27F/012 12V RX RF In
11.5 uH molded inductor axial"L1A" on pcb RX RF In
11.5 uH molded inductor axial"L3A" on pcb RX RF In
11.8 uH molded inductor axial"L2A" on pcb RX RF In
9100 nF104 104ceramic RX RF In
1330 pF331Ceramic"C2" on pcb RX RF In
1330 pF331Ceramic"C6" on pcb RX RF In
1330 pF331Ceramic"CL1" on pcb RX RF In
1330 pF331Ceramic"CL9" on pcb RX RF In
1680 pF681Ceramic"C3" on pcb RX RF In
1680 pF681Ceramic"C5" on pcb RX RF In
1680 pF681Ceramic"CL7*" on pcb RX RF In
147 uH molded inductoryel-vio-blk-gld yel-vio-blk-gldchoke RX RF In
1DPDT SwitchDPDTS2 RX Attenuator Off/OnRX RF In
1DPDT SwitchDPDTS3 RX Pre-Amp On/Off switchRX RF In
10 pFjumperjumper wire - "C1" on pcb RX RF In
10 pFjumperjumper wire - "C7" on pcb RX RF In
10 pFjumperjumper wire - "CL10" on pcb RX RF In
10 pFjumperjumper wire between top holes of CL6 and CL5 - "CL6" on pcb RX RF In
1misc hookup wiremisc  RX RF In
1TO-39 heatsink misc RX RF In
12N3866 NPN Transistor TO-39 RX RF In
1T50-2redtoroidL1 toroidal coil (17T (14") #20) RX RF In
1T50-2redtoroidL2 toroidal coil (17T (14") #20) RX RF In

RX RF In Summary Build Notes

RX RF In Detailed Build Notes

Bottom of the Board

RX RF In Bottom View

Top of the Board

RX RF In Top View

Remove Temporary Wire

Remove the temporary wire installed in phase 5

Install Passive Components

Install resistors, capacitors, chokes, and jumpers

When installing the jumpers, allow the jumper to clear the board by a quarter of an inch (~6mm) to allow for testing

Install Passive Components photo
R586R8 1/4W 1% (6.8)blu-gry-blk-silver-brn blu-gry-blk-silver-brn1/4W
R5933 1/4W 1%ora-ora-blk-gld-brn ora-ora-blk-gld-brn1/4W
R9933 1/4W 1%ora-ora-blk-gld-brn ora-ora-blk-gld-brn1/4W
R3768 1/4W 1%blu-gry-blk-gld-brn blu-gry-blk-gld-brn1/4W
R7568 1/4W 1%blu-gry-blk-gld-brn blu-gry-blk-gld-brn1/4W
R61220 1/4W 1%red-red-blk-blk-brn red-red-blk-blk-brn1/4W
R98220 1/4W 1%red-red-blk-blk-brn red-red-blk-blk-brn1/4W
R60330 1/4W 1%ora-ora-blk-blk-brn ora-ora-blk-blk-brn1/4W
R62560 1/4W 1%grn-blu-blk-blk-brn grn-blu-blk-blk-brn1/4W
R63390 1/4W 1%ora-whi-blk-blk-brn ora-whi-blk-blk-brn1/4W 
R701K5 (1.5k) 1/4W 1%brn-grn-blk-brn-brn brn-grn-blk-brn-brn1/4W
E1300 pFjumper
jumper wire - "C1" on pcb
E1930 pFjumper
jumper wire - "CL10" on pcb
E3200 pFjumper
jumper wire between top holes of CL6 and CL5 - "CL6" on pcb
E3300 pFjumper
jumper wire - "C7" on pcb
E189100 nF104 104ceramic
E192100 nF104 104ceramic
E202100 nF104 104ceramic
E205100 nF104 104ceramic
E223100 nF104 104ceramic
E224100 nF104 104ceramic
E227100 nF104 104ceramic
E79100 nF104 104ceramic
E91100 nF104 104ceramic
E220330 pF331Ceramic
"C2" on pcb
E284330 pF331Ceramic
"CL9" on pcb
E323330 pF331Ceramic
"CL1" on pcb
E329330 pF331Ceramic
"C6" on pcb
E211680 pF681Ceramic
"C5" on pcb
E318680 pF681Ceramic
"CL7*" on pcb
E326680 pF681Ceramic
"C3" on pcb
L21.5 uH molded inductor axial
"L1A" on pcb
L51.5 uH molded inductor axial
"L3A" on pcb
E3281.8 uH molded inductor axial
"L2A" on pcb
R5747 uH molded inductoryel-vio-blk-gld yel-vio-blk-gldchoke

Install Antenna Switching Relays

Install Antenna Switching Relays photo
E187JRC27F/012 relayJRC27F/01212V relay
Relay JRC27F/012 12V
E191JRC27F/012 relayJRC27F/01212V relay
Relay JRC27F/012 12V
E217JRC27F/012 relayJRC27F/01212V relay
Relay JRC27F/012 12V

Install PreAmp Transistor

NOTE: the heat sink is factory supplied so tight that it would not be possible to place it over the 2N3866 after the transistor is soldered to the PCB. Therefore it is important to insert the 2N3866 into the heat sink first.

Prepare the heat sink by gently spreading its collar.

Place the transistor over the heat sink with the marking lip in the middle of the gap, push it down with the flat side of metal tweezers. The grip should be firm and tight (if it is too tight or loose, remove the transistor and adjust the collar)

The transistor and its heatsink will resemble this when ready for mounting

Place the 2N3866 into PCB (marking lip alignment as per photo). Solder it approx 4-5 mm (about 3/16") above PCB, just enough to clear any surrounding components.

TIP: Initially, solder one lead only. Then adjust for height and level, as needed, and then solder the other two leads.

E87TO-39 heatsink misc
E2222N3866 NPN Transistor TO-39

Wind and Install LPF Toroids

This transceiver requires exactly two wound toroids! L1 and L2 (each 1.45 uH) are each wound on a T50-2 core with 17 turns of 0.8 mm (#20 AWG) wire, exactly as per photo. Make sure to remove enamel coating and tin the leads before mounting. The length of wire required for each coil is about 13-14" (about 35 cm).

Wind and Install LPF Toroids photo
L1 toroidal coil (17T (14") #20)
L2 toroidal coil (17T (14") #20)
wire2Magnet wire, enameled #20 
28" (70 cm) for the pair of coils

Install Underside Jumper Wire

Refer to the "W3" on the topside diagram below.

W3 top view

Insert a "marker" wire lead or a short length of ssolder into the holes at each end of W3 (to identify the holes. Then, turn over the board and install the length of wire that will become W3 on the underside (removing the temporary hole identifying wires as you install each end of W3).

Take care to use a very short end of the wire when inserting into the hole. Do not let the end protrude more than a mm or so on the top side of the board, as it will be extremely difficult to cut off the excess end in the cramped quarters topside.

Install Underside Jumper Wire photo
w3misc hookup wiremisc 

Temporarily Install SW2 and SW3

S2 is the Attenuator on/off switch; S3 is the Pre-Amp on/off switch.

Connect the two switches using temporary wires w1 and w2 and a temporary connection to the 12V bus.

If possible, use IC clip leads to avoid soldering and then removing the temporary wires.

These switches will be permanently installed in the PC RX/TX Control Phase (Phase 8)

Temporarily Install SW2 and SW3 photo
S2 RX Attenuator Off/On
S3 RX Pre-Amp On/Off switch

RX RF In Testing

Coils Continuity Test

Test Setup

Refer to the graphic showing the three continuity test points "A" and "B1, B2". Using the Ohmmeter, test for continuity between A and B.

If you do not get continuity, then refer to the graphic at the beginning of this phase (depicting an underside view of the rx path from the bnc connector to the mixers). Trace continuity through each point until the break is discovered.

Coils Continuity Test

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
A (jumper wire) and B1 (bottom lead of 100 nF coupling capacitor)Ohms01_______
A (jumper wire) and B2 (bottom lead of 100 nF coupling capacitor)Ohms01_______

Attenuator Test

Test Setup

Test Attenuator and Pre-Amp Operation Attenuator

To test attenuator preamplifier:

  • Power on the board and connect I/Q out to PC's stereo Line-In (or "mic") jack
  • Tune the SDR PC program to a 40m signal (or connect a signal generator)
  • Observe signal strength
  • Turn S2 (attenuator) switch on
  • Observe signal strength - signal will decrease for approximately 17dB

Pre-Amplifier Test

Test Setup

With power still on and signal present:

  • Turn S2 (attenuator switch OFF
  • Observe signal strength
  • Turn S3 (pre-amp switch) ON
  • Observe signal strength - you should see an improvement of 15dB

Voltage Test

Test Setup

With power on and S3 (Pre-Amp switch) ON:

Measure the voltage at the testpoint shown below - should read 2.2V dc (with respect to ground). The testpoint is the junction of the 33 Ohm and 6.8 Ohm resistors at the emitter end of the 2N3866 Pre-Amp transistor.

Voltage Test

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
TestpointV dc~2.22.01_______

RX Complete

Test Setup

At this point, the receiver has been completed. Now, remove the temporary switches (S2 and S3) and their associated wires, and move on to the transmitter!