FOUR Sawbuck Direct Conversion Receiver Instructions

: October 30, 2023
: FOUR

Table of Contents

FOUR Sawbuck Direct Conversion Receiver
Product Information
Product Usage
Introduction
Building Rules
Finishing The Breadboard
Building the Circuit Board
Parts List
Building the Kit
Alignment
Using The Sawbuck
Set-up
References
Read User Manual Online (PDF format)
Download This Manual (PDF format)

FOUR Sawbuck Direct Conversion Receiver

FOUR-Sawbuck-Direct-Conversion-Receiver-product

Product Information

The Sawbuck Direct Conversion Receiver is a DIY kit that allows you to build your own radio receiver. The kit includes a wooden breadboard, circuit board, and all necessary electronic components. The wooden breadboard can be finished any way you like, while the circuit board comes with a list of parts and instructions for assembly. The receiver requires a DC power supply of 9.0 to 14.0 volts and assumes that the operator has an understanding of antennas, DC power, and general receiver operation.

Building Rules:

Take your time
Get help if you don’t know how to solder parts on a circuit board
Use a magnifying glass for tiny parts
Build the kit step by step
Use protective eyewear
Be careful with ICs and transistors to avoid static damage
Mount parts flush and keep leads short

Finishing the Breadboard:

Use fine grit sandpaper to remove roughness from the wood
Apply paint, stain, or no finish at all
Apply three coats of finish with light sanding between coats and allow 24 hours of drying time
The decals that will be placed on the breadboard at the end of kit construction are black and red on yellow

Building the Circuit Board:
Tools and supplies needed:

Needle nose pliers
Diagonal cutters
Small flat blade and Phillips screwdrivers
Magnifying glass
20-40 watt soldering iron

Parts list:

1/8 watt resistors
R1 1000 ohm trim pot
R2 3.3K ohm
R3 100K ohm
Supplied insulated wire over the bottom of toroid

Product Usage

Assuming the operator has an understanding of antennas, DC power, and general receiver operation, the Sawbuck Direct Conversion Receiver can be used by following these instructions:

Ensure the power supply is DC 9.0 to 14.0 volts (battery or filtered supply)
Use the Woodchip transmitter to align the Sawbuck to the exact frequency, if available

Assembly instructions:

Mount and solder R1, 1000 ohm trim pot
Mount and solder R8, 10K ohm linear taper pot
Mount and solder R9, 10K ohm audio taper pot
Locate J5 a 1/8th inch phone jack and its mounting position on the right rear side of Diagram 1
Inspect the board for proper parts placement and good solder connections

Final Assembly:

Mount the circuit board to the wooden breadboard with black spacers and brass wood screws
Place the peel and stick-on decal on the front of the breadboard
Place the four rubber feet on the bottom of the breadboard (one in each corner)

Alignment:
If you have a Woodchip transmitter, the Sawbuck can be easily aligned by using the spot function of the Woodchip to put the Sawbuck on the exact frequency.

Introduction

The “Sawbuck” is a simple-to-build direct conversion receiver for 40 meters. The Sawbuck is designed to work with the Woodchip transmitter but also works well with other QRP transmitters. The Sawbuck is built on a double-sided circuit board and mounted to a small wooden breadboard. The Sawbuck is a direct conversion design with a bandpass ﬁlter, mixer/oscillator and audio ampliﬁer. A lowpass ﬁlter helps to attenuate high frequencies such as band noise and hiss. The audio output works well with earbuds or headphones. Speaker-level audio is best obtained by an external ampliﬁer like our Toothpick which also has a built-in CW ﬁlter. Provisions are made to accept Sidetone and receiver muting from the Woodchip transmitter. Antenna switching is available with our T/R switch kit.

Building Rules

Take your time. We recommend that you take at least three or four hours to complete your kit. If you take your time, in a few hours you can have a beautiful working project that you will be proud to own and operate.
If you don’t know how to solder parts on a circuit board, get help. Learning to solder is not hard, but please do not start this kit if you have never soldered before!
Most of the parts are tiny. Please use a magnifying glass.
Build the kit by the instructions, one step at a time.
Use protective eyewear.
Be careful with the ICs and transistors to avoid damage from static.
All parts should be mounted ﬂush or as close as possible to the circuit board keeping leads short. After soldering, clip all wires close to the board.

Finishing The Breadboard

The wooden breadboard furnished with your kit is your opportunity to express yourself. You get to ﬁnish it any way that you like…pick your color, pick your ﬁnish. MAY WE SUGGEST THE FOLLOWING?

Use ﬁne grit sand paper to remove any roughness from the wood. The four 1/4 inch sides will need some light sanding to remove some of the dark color left by the laser cut, especially if you are using a light color paint. Otherwise, several coats of paint may be used to cover well.
You can use brush on or spray paint or stain or no ﬁnish at all…it’s up to you.
You are in charge of getting the board ready. Three coats with light sanding between coats and about 24 hours of drying time will produce great results. NOTE: The decals that will be placed on your breadboard at the end of kit construction are black and red on yellow.
When the board is ﬁnished, locate the circuit board and place it on top of the breadboard. Center the circuit board and using a small nail, phillips screwdriver or another small pointed object, push a small starter hole into the breadboard at each corner mounting hole. The starter hole will help you to then drill a 1/16th inch hole at each starter hole. The drilled holes will be used to mount the assembled circuit board in the proper location at the end of the project. Place the breadboard aside for now.

Building the Circuit Board

Tools and supplies needed to build the circuit board:

needle nose pliers
diagonal cutters
small ﬂat blade and phillips screwdrivers
Magnifying glass
20-40 watt soldering iron

Parts List

1/8 watt resistors

R1 1000 ohm trim pot
R2 3.3K ohm
R3 100K ohm
R4 10k ohm
R5 1meg ohm
R6 470K ohm
R7 680 ohm
R8 50K ohm linear taper pot
R9 10K ohm audio taper pot

Capacitors

C1 60 pf. Trim pot
C2 82 pf ceramic disc npo
C3 .001 uf ceramic disc
C4 60 pf. Trim pot
C5 not used
C6 0.1 uf ceramic disc
C7 100 pf ceramic disc npo
C8 150 pf ceramic disc npo
C9 270 pf ceramic disc npo
C10 270 pf ceramic disc npo
C11 0.1 uf ceramic disc
C12. 0.1 uf ceramic disc
C13. 47 uf electrolytic
C14. 4.7uf electrolytic
C15 0.1 uf ceramic disc
C16 0.1 uf ceramic disc
C17 .01 uf ceramic disc

Other Parts

IC1 SA612AN
IC2 TL 431
IC3 L78L06
D1 1N4001
D2 1N4001
J1 RCA JACK
J2 2 pos. Terminal
J3 2 pos. Terminal
J4 2 pos. Terminal
J5 Phone Jack
SW1 SPDT slide switch
SW2 SPDT slide switch
Magnet Wire
Insulated wire (color varies)
L1 27uh choke (red/violet/gold/gold)(supplied) or (may use 25 turns #27 magnet wire
on T37-2)
T1 T-37-2 primary 1 turn solid insulated wire over bottom of secondary. Secondary 29
turns green magnet wire
Decal
4 wood screws
4 black spacers
4 rubber feet
wooden breadboard
circuit board
2 knobs

Building the Kit

Locate the parts bag. All of the parts required for circuit board construction are enclosed. You can work from the bag and ﬁnd each part as it is called for, but placing all of the parts from the bag into a bowl or small plastic tray may make it easier to sort and properly identify the parts. As each part is called for, be sure to identify it, then locate the proper mounting holes on the board. Insert the part and check it’s placement before soldering it in place. Cut all leads ﬂush with the board. Photos of this kit on our website can usually be viewed and enlarged on your computer.

Mount and solder SW1 (may require some force to seat)
Mount and solder SW2 (may require some force to seat)
Mount and solder J1 RCA jack
Mount and solder J2, J3 and J4 screw terminals
Mount and solder IC1, SA612AN
Mount and solder R2, 3.3k ohm (orange, orange, red)
Mount and solder R3, 100K ohm (brown, black, yellow)
Mount and solder R4, 10K ohm (brown, black, orange)
Mount and solder R5, 1meg ohm (brown, black, green)
Mount and solder R6, 470K ohm (yellow, purple, yellow)
Mount and solder R7, 680 ohm (blue, gray, brown)
Mount and solder C1, 60 pf. Trim cap
Mount and solder C2, 82 pf. (820) ceramic disc npo
Mount and solder C3, .001 uf. (102) ceramic disc
Mount and solder C4, 60 pf. Trim cap
C5 is not used in this version
Mount and solder C6, 0.1 uf. (104)ceramic disc
Mount and solder C7, 100 pf. (101)ceramic disc npo
Mount and solder C8, 150 pf. (104) ceramic disc npo
Mount and solder C9, 270f. (271) ceramic disc npo
Mount and solder C10, 270 pf. (271) ceramic disc npo
Mount and solder C11, 0.1 uf. (104) ceramic disc
Mount and solder C12, 0.1 uf. (104) ceramic disc
Mount and solder C13, 47uf. (391) electrolytic
Mount and solder C14, 4.7 uf. electrolytic
Mount and solder C15, 0.1 uf. (104) ceramic disc
Mount and solder C16, 0.1 uf. (104) ceramic disc
Mount and solder C17, .01 uf. (103) ceramic disc
Mount and solder IC2 TL431
Mount and solder IC3 L78L06
Mount and solder D1, 1N4001
Mount and solder L1, 27uh molded choke (red/violet/gold/gold)
Mount and solder T1, 29 turns magnet wire on T-37-2 toroid with one turn of supplied insulated wire over bottom of toroid $FOUR-Sawbuck-Direct-Conversion-Receiver-fig- $1$$
Mount and solder R1, 1000 ohm trim pot
Mount and solder R8, 10K ohm linear taper pot
Mount and solder R9, 10K ohm audio taper pot
Locate J5 a 1/8th inch phone jack and it’s mounting position on the right rear side of the circuit board. Refer to diagram 1 and modify the two lower soldering lugs to ﬁt in the two mounting holes closest to the right rear side of the board. Bend the lower back lug (lug B) 90 degrees so that it points down like the front lug. Using diagonal cutters, clip off the ends of lugs A and B as close as possible to the soldering hole. The remaining lugs should be as long as possible so that they will ﬁt through the mounting holes in the circuit board. Place J5 into position with lug A and B in the mounting holes and solder with J5 ﬂush against the board. The lugs may need slight trimming with the diagonal cutters to ﬁt the holes. Lug B may not come all the way through the hole, but a little extra solder to ﬁll the hole will sufﬁciently hold it in place. Use one of the wire leads saved from mounted resistors to complete mounting J5. Pass one end of the wire through lug C of J5 and into the circuit board mounting hole. Secure the top end of the wire to lug C of J5 and solder in place. Solder the other end of the wire on the bottom of the board and clip the excess wire.

Diagram 1.

This completes the construction of the circuit board. Inspect the board for proper parts placement. Make sure that solder connections are good and that there are no solder bridges.

Final Assembly

Mount the circuit board to the wooden breadboard with the black spacers and brass wood screws.
The peel-and-stick-on decal should be place on the front of the breadboard.
Place the four rubber feet on the bottom of the breadboard (one in each corner).

Alignment

Attach 9 to 13.8 volts at J2, an antenna at J1 and ear/headphones at J5. Turn on power with SW1. With the audio turned all the way up, you should be able to hear noise and perhaps signals. Set the tuning dial to mid-way. Turn the attenuator all the way toward the rear. Adjust trimmer C4 for the loudest volume (signals or noise). Using a signal generator set to 7040 KHz, adjust trimmerC1 until the 7040 KHz signal is heard. If no signal generator is available, you can use a signal from a transmitter or transceiver on 7040 KHz. It is also possible to use a receiver or transceivers receiver tuned to 7040 KHz with a wire running from it’s antenna jack to nearby the Sawbuck and listen for the Sawbuck’s signal as you tune C1. EASY WAY: Wait til early evening when there is plenty of activity on the band. Connect a good antenna to the Sawbuck and very slowly tune C1 until ham band signals are heard. Once you have signals approximately where you want, readjust C4 for maximum signal strength.

Note:
If you have a Woodchip transmitter, the Sawbuck can be easily aligned by using the spot function of the Woodchip to put the Sawbuck on the exact frequency.

Using The Sawbuck

It is assumed that the operator has an understanding of antennas, DC power and general receiver operation.

Antenna:
The antenna must be suitable for 40-meter operation. The antenna should be near resonance or attached to an antenna tuner. When using the Woodchip with this receiver, the easiest way to provide a signal to the receiver is to use a separate antenna to the receiver, which can be as simple as a 20-30 foot wire. A better option is our external T/R switch that can provide a means to switch the transmitter antenna as well as simultaneously mute the receiver via the ground short or open circuit. It will also allow the use of a foot switch for semi-break-in operation.

Power:
The power supply must be D.C. 9.0 to 14.0 volts. (battery or ﬁltered supply)

NOTE:
When using the Woodchip with the Sawbuck receiver, the same 12-14 volt d.c. the source may be used. You may run separate supply lines or use jumpers between the transmitter and receiver. A 9.0 volt battery works well with the Sawbuck and 12 to 14-volt supplies should be used with the Woodchip.

Sidetone from the Woodchip or other transmitter is applied at J3. When using the Woodchip, use the right side of the mute terminal connectors on both the Woodchip and Sawbuck. The left side of the mute terminal connectors on both the Woodchip and Sawbuck is not used if the negative power source is common to the Woodchip and Sawbuck. The receiver does not amplify the sidetone. Muting is accomplished when J4 is closed to the ground. This action causes the receiver audio to be shorted to the ground. The Woodchip transmitter supplies this action when it is switched from “receive” to “transmit”. By adding the Timber T/R switch, the transmit antenna will be automatically switched from the transmitter to the receiver as well as handling the receiver mute whenever the transmitter is switched to transmit. A foot switch, such as our “QLF” may be used with the T/R switch to provide a quick and easy alternative to using the slide switch on the Woodchip.

The LP—HP switch (SW2) will aid in blocking interfering high-frequency signals and band noises (especially hissing). It works best with strong signals since the lowpass also attenuates the desired signal (but not as much as high- frequency signals.) Try both positions for best results.

R1 functions as an R.F. attenuator. When signals on the band are loud (especially at night) the mixer can be overloaded and distort. Also strong shortwave broadcast stations can compete with desired amateur radio stations. This is effectively dealt with by adding attenuation. Turning the thumbwheel towards the front until signals are clearer and broadcast stations are gone or nearly gone will make desired amateur stations more readable. Unfortunately, many digital operators are using much more than the recommended 20 watts operating digital modes. These signals are strong and wide and create a challenge to simple QRP and QRPp receivers. Some signals can cause trouble up 10 or more KHz away. Use of the attenuator and low pass ﬁlter may help to tame the interference.

If you have any problems with your kit, please email us at:
w4fsv@breadboardradio.com You can also refer to our website at: www.breadboardradio.com.

Set-up

Sawbuck/Woodchip Set-up
The picture below shows how to interconnect the Sawbuck receiver with the Woodchip transmitter for mute, sidetone and power supply sharing. Use of colored wires is for clarity only, but is a good idea with any setup. In this example: Green is mute, White is sidetone, Black is ground and Red is Positive DC. Note: Black is also used for Negative DC and is electrically connected to Ground.

$FOUR-Sawbuck-Direct-Conversion-Receiver-fig- $3$$

Sawbuck/Woodchip Set-up
The picture below shows how to interconnect the Sawbuck receiver with the Woodchip transmitter and Timber T/R switch for mute, sidetone and power supply sharing. Use of colored wires is for clarity only, but is a good idea with any setup. In this example: Green is mute, White is sidetone, Black is ground and Red is Positive DC. Note: Black is also used for Negative DC and is electrically connected to Ground.

$FOUR-Sawbuck-Direct-Conversion-Receiver-fig- $4$$

Sawbuck / Woodchip Set-up WITH Foot Switch
The picture below shows how to interconnect the Sawbuck receiver with the Woodchip transmitter and Timber T/R switch for mute, sidetone and power supply sharing. Use of colored wires is for clarity only, but is a good idea with any setup. In this example: Green is mute, White is sidetone, Black is ground and Red is Positive DC. Note: Black is also used for Negative DC and is electrically connected to Ground.

$FOUR-Sawbuck-Direct-Conversion-Receiver-fig- $5$$

Foot Switch (like our QLF) can be connected as shown above. Coax must be connected for ground between Woodchip and Timber. Transmit/Receive is now controlled by foot switch.

$FOUR-Sawbuck-Direct-Conversion-Receiver-fig- $6$$

If you have any problems with your kit, please email us at:
w4fsv@breadboardradio.com You can also refer to our website at: www.breadboardradio.com.