Ensemble II VHF RX Builders' Notes

RF Front End Introduction

General

This stage begins at the VHF antenna. The incoming VHF RF signal is preamplified and filtered and presented as the "RF" signal to the ADE + Double Balanced Mixer (DBM). That mixer also accepts the Local Oscillator's output (BEFORE the Quadrature Clock Generator) as the "LO" input. The two signals, "RF" and "LO" are then mixed to result in the "IF" output of the DBM. This output contains the sum and difference products of mixing the two inputs. The sum component is filtered out, sending the difference component into the Quadrature Sampling Detector (QSD) stage.

For example, assume that the VHF signal of interest is at a frequency of 145.200 MHz. Thanks to the firmware in the on-board microcontroller in the LO stage, the LO will produce an output of 116.16 MHz. The DBM accepts the preamplified and filtered incoming RF signal at 145.200 MHz along with the LO signal of 116.16 MHz, to produce a signal with sum and difference components:

261.36 MHz (Σ)
29.04 MHz (Δ)

The sum (Σ) is discarded and the difference (Δ = 29.04 MHz) is sent to the QSD stage. If the SDR software was configured to set the center frequency at 145.200 MHz, then it would manifest itself in the QSD as 29.04 MHz.

In the above example, then, an incoming RF VHF signal of 145.210 MHz would mix down to a QSD input of 29.05 MHz, 10 kHz above the center frequency.

(go directly to build notes)

RF Front End Schematic

(Resistor testpoints (hairpin, top, or left-hand lead), as physically installed on the board, are marked in the schematic with red dots)

(above schematic has clickable areas that can be used for navigation)

(go directly to build notes)

RF Front End Bill of Materials

Stage Bill of Materials

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

Check	Designation	Component	Marking	Category	Circuit
❏	C07	band-specific		misc	RF Front End
❏	C11	band-specific		misc	RF Front End
❏	C13	band-specific		misc	RF Front End
❏	C14	unused capacitor		Unused	RF Front End
❏	C15	band-specific		misc	RF Front End
❏	C16	band-specific		misc	RF Front End
❏	D04	1N5227B	1N5227B	Axial	RF Front End
❏	J04	BNC Connector Male - PCB mount		Jack	RF Front End
❏	L01	band-specific		misc	RF Front End
❏	L01_core	band-specific		misc	RF Front End
❏	L02	band-specific		misc	RF Front End
❏	L02_core	band-specific		misc	RF Front End
❏	L03	band-specific		misc	RF Front End
❏	L03_core	band-specific		misc	RF Front End
❏	L04	band-specific		misc	RF Front End
❏	L04_core	band-specific		misc	RF Front End
❏	L05	unused inductor		Coil	RF Front End
❏	L05_core	unused inductor		Coil	RF Front End
❏	Magwire26_31in	Magnetic Wire, enameled #26		Magnetic	RF Front End
❏	magwire30_40in	Magnetic Wire, enameled #30		Magnetic	RF Front End
❏	T02	band-specific		misc	RF Front End
❏	T02-core	band-specific		misc	RF Front End
❏	C08	trimmer capacitor 30 pF	green	Trimmer	RF Front End
❏	C10	trimmer capacitor 30 pF	green	Trimmer	RF Front End
❏	C12	trimmer capacitor 30 pF	green	Trimmer	RF Front End
❏	C09	4.7 uF 10% 16V X7R RAD	475	Ceramic	RF Front End
❏	R13	33 1/6W 5%	ora-ora-blk-gld	1/6W	RF Front End
❏	R27	47 1/6W 5%	yel-vio-blk-gld	1/6W	RF Front End
❏	R14	120 1/6W 5%	brn-red-brn-gld	1/6W	RF Front End
❏	R15	2.2k 1/6W 5%	red-red-red-gld	1/6W	RF Front End
❏	R18	2.2k 1/6W 5%	red-red-red-gld	1/6W	RF Front End
❏	R19	2.2k 1/6W 5%	red-red-red-gld	1/6W	RF Front End
❏	R12	10 k 1/6W 5%	brn-blk-ora-gld	1/6W	RF Front End
❏	Q01	BF991 SMT Dual-Gate MOSFET		SOT-143	RF Front End
❏	U07	ADM +DB Double-balanced Mixer	ADE	SMT Mixer	RF Front End
❏	C37	0.1 uF	(smt) black stripe	SMT 1206	RF Front End
❏	C39	0.1 uF	(smt) black stripe	SMT 1206	RF Front End
❏	C41	0.1 uF	(smt) black stripe	SMT 1206	RF Front End
❏	C42	0.1 uF	(smt) black stripe	SMT 1206	RF Front End
❏	C38	0.01 uF	(smt)	SMT 1206	RF Front End
❏	C40	0.01 uF	(smt)	SMT 1206	RF Front End

Band Specific Items for 6m Band

Check	Designation	Component	Marking	Category	Notes	Circuit
❏	C07	trimmer capacitor 30 pF	green	Trimmer		RF Front End
❏	C11	2.7 pF	2.7J	Ceramic		RF Front End
❏	C13	150 pF 5%	151 (may be blue or tan)	Ceramic	(may be blue colored)	RF Front End
❏	C15	180 pF 5%	181	Ceramic		RF Front End
❏	C16	220 pF 5%	221	Ceramic		RF Front End
❏	L01	0.35uH 11T #26 on T25-6(yellow) (7")	yellow	Coil		RF Front End
❏	L01_core	T25-6 toroid core	yellow	Toroid		RF Front End
❏	L02	0.35uH 11T #26 on T25-6(yellow) (7")	yellow	Coil		RF Front End
❏	L02_core	T25-6 toroid core	yellow	Toroid		RF Front End
❏	L03	0.35uH 11T #26 on T25-6(yellow) (7")	yellow	Coil		RF Front End
❏	L03_core	T25-6 toroid core	yellow	Toroid		RF Front End
❏	L04	0.78 uH 17T #30 on T25-6 (yellow) (8")	yellow	Coil		RF Front End
❏	L04_core	T25-6 toroid core	yellow	Toroid		RF Front End
❏	T02	0.53 uH 14T/2x7 bifilar #30 on T25-6(yellow) (8")	yellow	Xfrmr		RF Front End
❏	T02-core	T25-6 toroid core	yellow	Toroid		RF Front End

Band Specific Items for 4m Band

Check	Designation	Component	Marking	Category	Circuit
❏	C07	trimmer capacitor 30 pF	green	Trimmer	RF Front End
❏	C11	2.2 pF	2.2	Ceramic	RF Front End
❏	C13	120 pF 5%	121	Ceramic	RF Front End
❏	C15	82 pF	82J	Ceramic	RF Front End
❏	C16	270 pF 5%	271	Ceramic	RF Front End
❏	L01	0.25 uH 9T #26 on T30-6 (yellow) (6")	yellow	Coil	RF Front End
❏	L01_core	T25-6 toroid core	yellow	Toroid	RF Front End
❏	L02	0.25 uH 9T #26 on T30-6 (yellow) (6")	yellow	Coil	RF Front End
❏	L02_core	T25-6 toroid core	yellow	Toroid	RF Front End
❏	L03	0.25 uH 9T #26 on T30-6 (yellow) (6")	yellow	Coil	RF Front End
❏	L03_core	T25-6 toroid core	yellow	Toroid	RF Front End
❏	L04	0.53 uH 14T #30 on T25-6 (10")	yellow	Coil	RF Front End
❏	L04_core	T25-6 toroid core	yellow	Toroid	RF Front End
❏	T02	0.13uH 7T/2x4 bifilar #30 on T25-6(yellow) (6")	yellow	Xfrmr	RF Front End
❏	T02-core	T25-6 toroid core	yellow	Toroid	RF Front End

Band Specific Items for 2m Band

Check	Designation	Component	Marking	Category	Circuit
❏	C07	trimmer capacitor 10 pF	white	Trimmer	RF Front End
❏	C11	1.2 pF	1A	Ceramic	RF Front End
❏	C13	100 pF 5%	101	Ceramic	RF Front End
❏	C15	82 pF	82J	Ceramic	RF Front End
❏	C16	270 pF 5%	271	Ceramic	RF Front End
❏	L01	0.08uH 6T #26 on T25-12(green) (5")	green	Coil	RF Front End
❏	L01_core	T25-12 toroid core	green	Toroid	RF Front End
❏	L02	0.06 5T #26 on T25-12(green) (4")	green	Coil	RF Front End
❏	L02_core	T25-12 toroid core	green	Toroid	RF Front End
❏	L03	0.06 5T #26 on T25-12(green) (4")	green	Coil	RF Front End
❏	L03_core	T25-12 toroid core	green	Toroid	RF Front End
❏	L04	0.53 uH 14T #30 on T25-6 (10")	yellow	Coil	RF Front End
❏	L04_core	T25-6 toroid core	yellow	Toroid	RF Front End
❏	T02	0.13uH 7T/2x4 bifilar #30 on T25-6(yellow) (6")	yellow	Xfrmr	RF Front End
❏	T02-core	T25-6 toroid core	yellow	Toroid	RF Front End

RF Front End Summary Build Notes

Install FET PreAmp Transistor (Q1)
Install SMT Capacitors
Install the Double-Balanced Mixer (U7)
Wind and Install the Coils (L1-L4)
Wind and Install T2
Continuity Test the Inductors
Install Ceramic Capacitors
Install Trimmer Capacitors
Install Diode and Resistors
Install Antenna Jack (J4)
Test the Stage

RF Front End Detailed Build Notes

Bottom of the Board

Install FET PreAmp Transistor (Q1)

Check	Designation	Component	Marking	Category	Orientation	Notes
❏	Q01	BF991 SMT Dual-Gate MOSFET		SOT-143

Install SMT Capacitors

Watch out! There are two types of SMT caps required for this step. The 0.01 µF caps are in the clear strips and shown as yellow in the graphic; the 0.1 µF caps are in the strips with the black strips and are shown using white markings on the graphic.

Check	Designation	Component	Marking	Category
❏	C37	0.1 uF	(smt) black stripe	SMT 1206
❏	C39	0.1 uF	(smt) black stripe	SMT 1206
❏	C41	0.1 uF	(smt) black stripe	SMT 1206
❏	C42	0.1 uF	(smt) black stripe	SMT 1206
❏	C38	0.01 uF	(smt)	SMT 1206
❏	C40	0.01 uF	(smt)	SMT 1206

Install the Double-Balanced Mixer (U7)

Check	Designation	Component	Marking	Category	Orientation	Notes
❏	U07	ADM +DB Double-balanced Mixer	ADE	SMT Mixer		Take ESD precautions

Top of the Board

Wind and Install the Coils (L1-L4)

If you are unfamiliar with winding and installing inductors, you may want to refer to the WB5RVZ construction hints for coils (toroidal) and transformers ( toroidal and binocular). Click here for details on identifying toroid cores.

Decoding the trqansformer specifications:

Transformers' windings are specified using the pattern "nnT/wXmmT" or "wXmmT/nnT", where:

"nn" is the number of turns in the single winding
"mm" is the number of turns in the multiple windings
"w" = the number of multiple windings (e.g., 2 = bifilar; 3 = trifilar, etc.)

Thus, e.g., "18T/2x9T bifilar #30" means, using #30 wire, produce a single 18 turn primary winding and two 9-turn secondary windings; "2x9T bifilar/ 18T #30" means, using #30 wire, produce two 9-turn primary windings and a single 18 turn secondary winding.

Wind and Install the Coils (L1-L4) photo

Check

Designation

Component

Marking

Category

Orientation

Notes

❏

L01

band-specific

Band	Component	Marking
6m	0.35uH 11T #26 on T25-6(yellow) (7") (Coil)	yellow
4m	0.25 uH 9T #26 on T30-6 (yellow) (6") (Coil)	yellow
2m	0.08uH 6T #26 on T25-12(green) (5") (Coil)	green

misc

❏

L01_core

band-specific

misc

❏

L02

band-specific

Band	Component	Marking
6m	0.35uH 11T #26 on T25-6(yellow) (7") (Coil)	yellow
4m	0.25 uH 9T #26 on T30-6 (yellow) (6") (Coil)	yellow
2m	0.06 5T #26 on T25-12(green) (4") (Coil)	green

misc

❏

L02_core

band-specific

misc

❏

L03

band-specific

Band	Component	Marking
6m	0.35uH 11T #26 on T25-6(yellow) (7") (Coil)	yellow
4m	0.25 uH 9T #26 on T30-6 (yellow) (6") (Coil)	yellow
2m	0.06 5T #26 on T25-12(green) (4") (Coil)	green

misc

❏

L03_core

band-specific

misc

❏

L04

band-specific

Band	Component	Marking
6m	0.78 uH 17T #30 on T25-6 (yellow) (8") (Coil)	yellow
4m	0.53 uH 14T #30 on T25-6 (10") (Coil)	yellow
2m	0.53 uH 14T #30 on T25-6 (10") (Coil)	yellow

misc

❏

L04_core

band-specific

misc

❏

L05

unused inductor

Coil

❏

L05_core

unused inductor

Coil

❏

Magwire26_31in

Magnetic Wire, enameled #26

Magnetic

❏

magwire30_40in

Magnetic Wire, enameled #30

Magnetic

Wind and Install T2

Decoding the trqansformer specifications:

Transformers' windings are specified using the pattern "nnT/wXmmT" or "wXmmT/nnT", where:

"nn" is the number of turns in the single winding
"mm" is the number of turns in the multiple windings
"w" = the number of multiple windings (e.g., 2 = bifilar; 3 = trifilar, etc.)

Check

Designation

Component

Marking

Category

Orientation

Notes

❏

T02

band-specific

Band	Component	Marking
6m	0.53 uH 14T/2x7 bifilar #30 on T25-6(yellow) (8") (Xfrmr)	yellow
4m	0.13uH 7T/2x4 bifilar #30 on T25-6(yellow) (6") (Xfrmr)	yellow
2m	0.13uH 7T/2x4 bifilar #30 on T25-6(yellow) (6") (Xfrmr)	yellow

misc

❏

T02-core

band-specific

misc

Continuity Test the Inductors

Using your ohmmeter, test the installed coil and transformer windings by probing the test points with the matching letters:

Test Points	UOM	Nominal Result	Your Result
"A" - "A" (L1)	Continuity	YES	_______
"B" - "B" (L2)	Continuity	YES	_______
"C" - "C" (L3)	Continuity	YES	_______
"D" - "D" (L4)	Continuity	YES	_______
"E" - "E" (T2 - primary)	Continuity	YES	_______
"F" - "F" (T2 Secondaries)	Continuity	YES	_______

Install Ceramic Capacitors

Check

Designation

Component

Marking

Category

Orientation

Notes

❏

C11

band-specific

Band	Component	Marking
6m	2.7 pF (Ceramic)	2.7J
4m	2.2 pF (Ceramic)	2.2
2m	1.2 pF (Ceramic)	1A

misc

❏

C13

band-specific

Band	Component	Marking
6m	150 pF 5% (Ceramic)	151 (may be blue or tan)
4m	120 pF 5% (Ceramic)	121
2m	100 pF 5% (Ceramic)	101

misc

❏

C14

unused capacitor

Unused

❏

C15

band-specific

Band	Component	Marking
6m	180 pF 5% (Ceramic)	181
4m	82 pF (Ceramic)	82J
2m	82 pF (Ceramic)	82J

misc

❏

C16

band-specific

Band	Component	Marking
6m	220 pF 5% (Ceramic)	221
4m	270 pF 5% (Ceramic)	271
2m	270 pF 5% (Ceramic)	271

misc

❏

C09

4.7 uF 10% 16V X7R RAD

475

Ceramic

Install Trimmer Capacitors

Pay careful attention to the orientation of the trimmer capacitors. Align the squared-off side with the corresponding straight line on the silk-screen.

Check

Designation

Component

Marking

Category

Orientation

Notes

❏

C07

band-specific

Band	Component	Marking
6m	trimmer capacitor 30 pF (Trimmer)	green
4m	trimmer capacitor 30 pF (Trimmer)	green
2m	trimmer capacitor 10 pF (Trimmer)	white

misc

❏

C08

trimmer capacitor 30 pF

green

Trimmer

❏

C10

trimmer capacitor 30 pF

green

Trimmer

❏

C12

trimmer capacitor 30 pF

green

Trimmer

Install Diode and Resistors

Mount D4 hairpin style. The lead at the cathode (banded) end of D4 should be a hairpin lead.

Note: on some earlier boards, R27 was marked as R14 (R27 is next to C14 on the board). The real R14 is between R15 and T2. R27 is up toward the top of the board, underneath the date.

Check	Designation	Component	Marking	Category
❏	D04	1N5227B	1N5227B	Axial
❏	R13	33 1/6W 5%	ora-ora-blk-gld	1/6W
❏	R27	47 1/6W 5%	yel-vio-blk-gld	1/6W
❏	R14	120 1/6W 5%	brn-red-brn-gld	1/6W
❏	R15	2.2k 1/6W 5%	red-red-red-gld	1/6W
❏	R18	2.2k 1/6W 5%	red-red-red-gld	1/6W
❏	R19	2.2k 1/6W 5%	red-red-red-gld	1/6W
❏	R12	10 k 1/6W 5%	brn-blk-ora-gld	1/6W

Install Antenna Jack (J4)

Check	Designation	Component	Marking	Category	Orientation	Notes
❏	J04	BNC Connector Male - PCB mount		Jack

RF Front End Completed Stage

Top of the Board

Bottom of the Board

RF Front End Testing

Current Draw

Test Setup

Power up the board and connect the board to the PC's USB port

Measure the current draw

Test Measurements

Testpoint	Units	Nominal Value	Author's	Yours
Current Draw	mA	< tbd	tbd	_______

Voltage Tests

Test Setup

Power up the board and connect the board to the PC's USB port

Measure the voltages at the testpoints below (all WRT regular ground (use the "/QSD EN" shunt wire for Gnd))

If the voltage at R19 is not around half the 5V rail, the next stage (QSD) will not work. Look at the R18/R19 voltage divider as the likely culprit.

Test Measurements

Testpoint	Units	Nominal Value	Yours
R14 hairpin	V dc	12	_______
R18 hairpin	V dc	5	_______
R19 hairpin	V dc	2.5	_______
R12 left-hand lead	V dc	3.3	_______

Ensemble II VHF RX 05_RF Front End

RF Front End Introduction

General

RF Front End Schematic

RF Front End Bill of Materials

Stage Bill of Materials

Band Specific Items for 6m Band

Band Specific Items for 4m Band

Band Specific Items for 2m Band

RF Front End Summary Build Notes

RF Front End Detailed Build Notes

Bottom of the Board

Install FET PreAmp Transistor (Q1)

Install SMT Capacitors

Install the Double-Balanced Mixer (U7)

Top of the Board

Wind and Install the Coils (L1-L4)

Decoding the trqansformer specifications:

Wind and Install T2

Decoding the trqansformer specifications:

Continuity Test the Inductors

Install Ceramic Capacitors

Install Trimmer Capacitors

Install Diode and Resistors

Install Antenna Jack (J4)

RF Front End Completed Stage

Top of the Board

Bottom of the Board

RF Front End Testing

Current Draw

Test Setup

Test Measurements

Voltage Tests

Test Setup

Test Measurements