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for S/N 304 thru 320
Latest version of the 1W-10 (S/N greater than 500) Join the 1Watters QRPp email list See who is QRV on the QRV webpage Last Updated Tue, 13 Jul 2021 17:11:21 -0400 Always check the Addendum Section for updates | |
Build this 10 Meter QRPp Transceiver for $46
Designed for 1 Watt output on 10 Meters using 12 VDC
VXO Frequency Range is approximately 28,052.2 to 28,061.6 kHz
Full QSK, Dual Conversion Design
Includes built in keyer IC
The purpose of this transceiver is to provide a high quality
inexpensive transceiver for achieving DXCC and WAS via QRPp
This transceiver was designed for home and portable operation.
The name of this radio is "The One Watter" or "1Watter".
The Xcvr has low noise and is very sensitive and selective.
The VXO covers both sides of the standard QRP CW calling frequencies.
The PCB size is only 2.5" (63,5 mm) by 3.8" (96,5 mm)
I would like to thank Chuck Adams, K7QO for suggesting the new kit
and appreciate his help testing it to remove all the bugs and bad smoke.
He has some great pictures on his website at http://www.k7qo.net/onewatters.html
and a 10 part youtube video series 1Watter Transceiver Build, Phase 1 by K7QO
My personal operating experiences including QRPp WAS, QRPp DXCC and
Pictures, Data and Links is at http://1watters.com
Full Size Schematic
Building Instructions:
DO NOT REMOVE ANY PARTS FROM THE PLASTIC BAGS UNTIL INSTRUCTED TO DO SO
1. Be careful if you inventory the parts; they are small and easy to lose. Parts List
Do not mix up the toroids between the plastic bags.
Keep all toroids in their plastic bags until called for installation.
Do not mix up the blue 1N5711 signal diodes with the blue NPC-127 zener diodes.
The 1N5711 signal diodes are taped together and the zeners are loose.
If you are missing any parts, contact me immediately. I will ship the parts the same day.
If you find extra parts in the kit, check the Addendum else throw them in your junk box.
This kit includes all parts to create a functioning transceiver EXCEPT the tune pot.
Included parts are: 2 phone jacks, a bnc jack, a push-button, volume control pot, magnet wire and heat sink.
This kit uses several all black ferrite toroids. One (1) FT37-43 and multiple FT37-61 toroids; they look the same.
The FT37-43 is included in the bag with the SMT capacitors.
Mark the bag with the SMT caps as "-43" and the bag with the resistors as "-61"
This will help with identification later on when installing inductors and transformers.
Install the parts in the order per this document to prevent mechanical installation problems later.
Each 1Watter is provided with a Serial Number, which is attached to the bag holding the PCB and magnet wire
Attach the label to the rear of your 1Watter enclosure or wherever suitable
The Serial Number may later be used for tracking 1Watter QSO contests.
This kit requires the following items to complete the kit:
hook-up wire/coax to connect the PCB to the chasis and an optional power on/off switch and optional case.
Any Addendums will be listed by date at the end of this document
2. Install all SMT capacitors
These capacitors are easy to install, especially if you have some kind of part holding/positioning tool.
I find a plain wooden toothpick will hold the 1206 size caps while soldering but
my favorite tool is a pair of diagonal headed tweezers
There are 20 pieces 100n SMT capacitors on the PCB (plus 1 extra in the bag)
Do not install C36 at this time
____C6,7,8,9,10,11,12,13,14,19,27,33,37,38,41,44,46,47,48
3. Install all 1/8 Watt Resistors.
You will need a magnifying device to verify the resistor color codes.
Bend the resistor leads a sharp 90 degrees from the body of the resistors.
R20, the volume control will be connected later.
Save 5 cut resistor leads to ground the crystal cases later.
____R1,2: 51 Green-Brown-Black-Gold
____R3,9: 470 Yellow-Violet-Brown-Gold
____R4: 2K2 Red-Red-Red-Gold
____R5: 500 Horizontal mounted pot (in hardware bag)
____R6,7,8,17,18,19: 4K7 Yellow-Violet-Red-Gold
____R10: 1K Brown-Black-Red-Gold
____R11: 1K5 Brown-Green-Red-Gold
____R12: 1K2 Brown-Red-Red-Gold
____R13: 1M Brown-Black-Green-Gold
____R14: 4R7 Yellow-Violet-Gold-Gold
____R15: 2M2 Red-Red-Green-Gold
____R16: 10K Brown-Black-Orange-Gold
4. Install all Diodes - observe polarity.
____D1,2: 1N5711 blue glass diodes
____D3: 1N5256B silver 30 V Zener
____D4,6,7: 1N4148 red glass diodes
____D5: MV209 varactor - leave 1/8 inch (3 mm) space between the PCB and diode body
____D8: 1N5817 black diode
____D9,10: NPC-127 blue 5.6 V Zener
5. Install all IC sockets - observe polarity.
____U2,4,5,6,9: Match the notch on the IC socket with the pattern on the PCB
6. Install all remaining capacitors in the order shown.
____C5: 40p yellow trimmer cap - flat side into square hole
____C23,24,26: 60p brown trimmer caps - flat side into square hole
____C1,2,3,4: 120p labeled 121J NPO disc cap
____C15: 47p labeled 470 small yellow cap
____C16: 56p labeled 56J NPO disc cap
____C17,39: 47n labeled 473 small yellow axial cap
____C18: 1p0 labeled 1 dark tan disc cap
____C20,25: 43p labeled 43J NPO tan disc cap
____C21,22: 220p small yellow cap labeled 221
____C28: 3p labeled 3 small brown NPO disc cap
____C29,30,31,32: 680p labeled 681 small yellow cap
____C34: 120p labeled 121J NPO disc cap
____C35: 68p labeled 68J NPO disc cap
____C36: 100n yellow axial replacement for the 100n SMT cap - see Addendum
____C40,52: 10uF black electrolytic - observe polarity
____C42,49: 47uF blue electrolytic - observe polarity
____C43: 33uF black electrolytic - observe polarity
____C45: 33p labeled 33J NPO dark tan disk cap
____C50: empty
____C51: empty
____Cs: empty - see Mods section
____Cx: empty - see Mods section
7. Install all Voltage Regulators and Transistors
Do not install Q1 at this time.
____U1: 78L10 voltage regulator; note orientation on the PCB
____U3,7: 78L08 voltage regulator; note orientation on the PCB
____U8: 78L05 voltage regulator; note orientation on the PCB
Temporarily connect a +12V source in series with a 100-200 ohm current
limiting resistor to J3-2 pad and power supply ground to J3-3 pad (ground)
Measure the output voltages of U1 (10V), U-7 (8V) and U-8(5V) to make sure they are correct.
Temporarily put a clipped resistor lead from emitter to collector of transistor Q10
Measure the output voltage of U3 (8V) to make sure it is are correct.
Remove the clipped resistor lead and remove the power source and continue with parts installation.
____Q2: PN2222
____Q3,6,7: 2N3904
____Q4: MPSH10
____Q5: J310
____Q8,9: J113
____Q10: 2N3906
____Q11: 2N7000 - CAUTION...static sensitive
8. Install all five 8-pin DIP ICs.
____U2: NE602A balanced mixer; the dot positioned towards C18
____U4: NE602A balanced mixer; the dot positioned towards C26
____U5: NE602A balanced mixer; the dot positioned towards C28
____U6: LM386N-4 audio amplifier; the dot positioned towards C37
____U9: ATtiny45 Keyer with Sidetone; the dot positioned towards C46
9. Wind and install all Toroid Inductors. Wind all wires on the toroids clockwise.
9.1 Install inductors L1 & L2
Cut two 9" pieces of #26 red wire.
____L1,2: Wind 10 turns of #26 red wire on the T37-10 black powered iron toroid, tightly spaced.
Trim the wires of L1 and L2 to a half inch each.
Tin & Strip the insulation to the base of the toroid using a hot solder pencil.
Spread the turns over most of the toroid
Install L1 & L2 into the PCB, pull the leads tight using needle nose pliers, solder and trim
You should be able to straighten the toroid to match the outline on the PCB
9.2 Install transformer T4
Cut 15" of #30 red wire and 6 inches of #27 green wire.
____T4: Wind 21 turns of #30 red wire on an T37-10 black powered iron toroid, tightly spaced.
Trim the #30 wires of T4 to one inch.
Wind 3 turns of #27 green wire on the T37-10 black powered iron toroid, tightly spaced.
Trim the #27 wires of T4 to a half inch each.
Tin & Strip the insulation to the base of the toroid using a hot solder pencil.
Install T4 with the #30 wires into the outside (upper and lower) holes on the PCB
and the 3 turn #27 wire thru the center holes of the PCB for T4
pull the leads tight using needle nose pliers, solder and trim
You should be able to straighten the toroid to match the outline on the PCB
9.3 Install transformer T2
Cut 11" of #26 red wire and 4 inches of #26 red wire.
____T2: Wind 14 turns of #26 red wire on an T37-10 black powered iron toroid, tightly spaced.
Trim the #26 wires of T2 to one inch.
Tin & Strip the insulation to the base of the toroid using a hot solder pencil.
Tin the middle inch of the 4 inch red #26 wire or optionally tin the whole wire
Wind 1 turn of the #26 tinned wire on the T37-10 black powered iron toroid.
Install T2 with the 15 turns #26 wires into the outside (upper and lower) holes on the PCB
and the single turn #26 wire thru the center holes of the PCB for T2
pull the leads tight using needle nose pliers, solder and trim
You should be able to straighten the toroid to match the outline on the PCB
9.4 Install transformer T3
Cut 11" of #26 red wire and 4 inches of #26 red wire.
____T3: Wind 14 turns of #26 red wire on an T37-10 black powered iron toroid, tightly spaced.
Trim the #26 wires of T3 to one inch.
Tin & Strip the insulation to the base of the toroid using a hot solder pencil.
Tin the middle inch of the 4 inch red #26 wire or optionally tin the whole wire
Wind 1 turn of the #26 tinned wire on the T37-10 black powered iron toroid.
Install T3 with the 15 turns #26 wires into the outside (upper and lower) holes on the PCB
and the single turn #26 wire thru the center holes of the PCB for T3
pull the leads tight using needle nose pliers, solder and trim
You should be able to straighten the toroid to match the outline on the PCB
9.5 Install inductor L4
Cut 9" of #27 green wire.
____L4: Wind 10 turns of #27 green wire on an FT37-43 black ferrite toroid, tightly spaced.
The FT37-43 black ferrite toroid is packed in the bag with the SMT caps
Trim the wires of L4 to a half inch each.
Tin & Strip the insulation to the base of the toroid using a hot solder pencil.
Spread the turns over most of the toroid
Install L4 into the PCB, pull the leads tight using needle nose pliers, solder and trim
You should be able to straighten the toroid to match the outline on the PCB
9.6 Install transformer T1
Cut 9" of #26 red wire and 4 inches of #27 green wire.
____T1: Wind 10 turns of #26 red wire on an FT37-61 black ferrite toroid, tightly spaced.
The FT37-61 black ferrite toroids are packed in the bag with the resistors
Trim the #26 red wires of T1 to one inch.
Wind 2 turns of #27 green wire on the FT37-61 black toroid, tightly spaced.
Trim the #27 green wires of T1 to a half inch.
Tin & Strip the insulation to the base of the toroid using a hot solder pencil.
Install T1 with the #26 wires into the outside (upper and lower) holes on the PCB
and the dual turn #27 wire thru the center holes of the PCB for T1
Pull the leads tight using needle nose pliers, solder and trim
You should be able to straighten the toroid to match the outline on the PCB
9.7 Install inductor L3
Cut 16" of #30 red wire.
____L3: Wind 24 turns of #30 red wire on an T37-2 red toroid, tightly spaced.
Trim the wires of L3 to a half inch each.
Tin & Strip the insulation to the base of the toroid using a hot solder pencil.
Spread the turns over most of the toroid
Install L3 into the PCB, pull the leads tight using needle nose pliers, solder and trim
You should be able to straighten the toroid to match the outline on the PCB
9.8 Install inductor L6
Cut 13" of #26 red wire.
____L6: Wind 18 turns of #26 red wire on an T37-2 red toroid, tightly spaced.
Trim the wires of L6 to a half inch each.
Tin & Strip the insulation to the base of the toroid using a hot solder pencil.
Spread the turns over most of the toroid
Install L6 into the PCB, pull the leads tight using needle nose pliers, solder and trim
You should be able to straighten the toroid to match the outline on the PCB
9.9 Install inductor L5. This inductor determines the upper and lower frequencies of the 1Watter.
Cut 17" of #30 red wire.
____L5: Wind 25 turns of #30 red wire on an T37-2 red toroid, tightly spaced.
Trim the wires of L5 to a half inch each.
Tin & Strip the insulation to the base of the toroid using a hot solder pencil.
Install L5 into the PCB, pull the leads tight using needle nose pliers, solder and trim
You should be able to straighten the toroid to match the outline on the PCB
9.10 Install transformer T5
Cut 10" of #34 red wire and 4" of #30 red wire.
____T5: Wind 8 turns of #34 red wire on an BN-43-2402 black ferrite binocular.
The BN-43-2402 black ferrite binocular is packed in the bag with the SMT caps
Trim the red wires of T5 to one inch each.
Wind 2 turns of #30 red wire on the BN-43-2402 black ferrite binocular.
Trim the #30 wires of T5 to one half inch each.
Tin & Strip the insulation on all 4 wires to the base of the binocular.
The #34 wire leads for the 8 Turn winding go to the two pads closest to the IC, Pins 1 and 2.
The #30 wire leads go to the two pads farthest away from the IC or toward the bottom of the PCB.
Install T5 into the PCB, pull the leads tight using needle nose pliers, solder and trim.
10. Install all Crystals.
There are 5 pieces of 8.064 mHz crystals included in the kit.
These crystals are graded for frequency and resistance.
If you find a crystal with a black dot, install it in X6.
If you find 2 crystals with black dots, install in X2 & X6.
The Filter Crystals X3,4,5 should not have a black dot.
When installing the crystals, tilt the crystals about 20 degrees while soldering
This will raise the crystal a small bit above the PCB after straightening
and will prevent trace shorts to the case of the crystal
Do not overheat the crystals.
____X1: 20.000 mHz crystal
____X2,3,4,5,6: 8.064 mHz crystals
When soldering the crystal cases to ground, do not overheat the crystals
____Solder one resistor lead across the top of crystals X3,4,5
____Solder one resistor lead from the top of X4 to the ground below (top center)
____Solder one resistor lead from the top of X2 to the ground below (upper right)
____Solder one resistor lead from the top of X6 to the ground below (upper right)
11. Connections.
Recommend chassis/enclosure for the 1Watter from mouser.com Part # 537-CR-442
Connect the 500 ohm volume pot (R20) using any insulated wire.
Connect the volume control high side to the center of J6 on the PCB.
Connect the volume control cold side to a ground on J6.
Connect the volume control center wiper to a 3.5 mm phono jack
Connect the 3.5 mm phono jack ground to the cold side of the volume control pot.
Connect a user supplied pot (5K or 10K or 100K or 1 Meg) to the "Tune" connector J1.
Connect the tune control wiper to the center hole on J1.
Connect the provided BNC connector to the "Ant" connection next to L1 on the PCB.
Connect paddles or a straight key to J5 via the other 3.5 mm phono connector
Connect the Push Button, one wire to the center of J4, the other wire to one of the ground connections
Before you apply power to the 1Watter, make sure your power polarity is correct
The 1Watter was designed to operate from a 12 volt Sealed Lead Acid Battery
Connect +12.6V volts (+/- 1 volt) to the holes in the upper right corner of the PCB.
12. Receiver Alignment.
Connect any antenna to the 1Watter. Anything from a 2 foot wire up a large antenna.
Apply power to the 1Watter and set the volume control to maximum.
Adjust C5 and C26, back and forth for maximum noise coming from the speaker/headphones.
If you connected an antenna, you may hear CW signals by tuning the Tune Pot.
13. Transmit Alignment using an Oscilloscope or a Calibrated Accurate Receiver
The band pass filter (X3,4,5) center frequency is 8,061.7 kHz +/- 100 Hz
The transmit oscillator part of U2, X2 and L6 should match that frequency +/- 100 Hz.
Find a signal in the tune range of the transceiver. As you tune across the signal,
the loudest audio frequencies should be about 600 Hz +/- 100 Hz
Next we will adjust for maximum carrier output. You will need a 10 meter receiver or an oscilloscope.
If you do not have either, we will align the transmitter after we install the final transistor.
The Tune Control Oscillator operates from 19,990.5 to 19,999.9 kHz
The Transmit Carrier Oscillator operates at 8,061.7 kHz
These two signals are mixed to produce the 28,052.2 to 28,061 kHz transceiver frequency, but
the mixer also produces other frequencies that must be rejected.
Preset the power control R5 to half way
Preset C23 for 25 percent of maximum capacitance
Preset C24 for 25 percent of maximum capacitance
C23 has broad tuning while C24 has very sharp tuning.
Preset the Tune Pot to half way or in the middle.
Place the Keyer into straight key mode
While listening to a receiver near 28,060 kHz or watching a scope at the junction of R1/D4,
adjust C24 to max signal on the scope or receiver.
If using a receiver, you will need to hunt for the actual signal.
After finding the signal, readjust both C23 and C24 for maximum signal.
After alignment, C23 should be near 25 percent capacitance
and C24 should be near 25 percent capacitance.
Make sure that you have aligned the filter to the correct frequency and not an alternate
frequency generated by the transmit mixer. Measure the frequency using a scope of freq counter.
14. Install the RF Final Transistor Q1
____Q1: 2N5109 - leave 1/8 inch (3 mm) space between the PCB and transistor case
____Q1 heat sink: - push the heat sink over the case of Q1; align heat sink to match PCB pattern.
15. Sidetone volume setting.
The sidetone volume is fixed/set by R15,2M2 & C45,33p.
To lower sidetone volume, decrease the value of C45 or increase the value of R15
To raise sidetone volume, increase the value of C45 or decrease the value of R15
Replacements for R15 and C45 are not included in the kit
16. Transmit Final Alignment using milliamp meter
Connect a 50 ohm dummy load to the output of the transceiver and power up with 12V.
Place the keyer into straight key mode (see instructions below)
Connect xcvr to power supply through an amp meter, 250 mA or greater.
Key the transmitter and adjust R5 for exactly 250 milliamps.
If C23 & C24 were not aligned in a prior step then preset C23 to 25 pct and C24 to 25 pct capacitance
Ajusting C24 for maximum milliamps current. Adjust R5 to keep the current at 250 Ma.
repeat several times until you know that C23 & C24 are peaked and R5 is set for 250 Ma.
After alignment, C23 should be near 25 percent of maximum capacitance
and C24 should be near 25 percent of maximum capacitance
If you have a wattmeter, insert it between the dummy load and the tranceiver.
It should measure very near 1 watt output.
You may also adjust R5 for 20 volts P-P on a scope.
It is recommended that you do not adjust R5 for more than 1 watt to prevent instability.
This completes the 1Watter Tranceiver alignment.
The 1Watter Service Manual
17. Optional modifications to and experiments with the 1Watter
17.1 NE602A gain increase for U4 and U5
You may increase the gain by placing a 27K (not included) or higher value resistor (Rx on the PCB) across pins 1 and 8 of U5
17.2 Frequency Range Mods
You may change the frequency span of the 1Watter by changing the number of turns on L5
Too many turns and the oscillator stops working or becomes unstable.
Add capacitance at Cx, between the crystal X1 and L5 and ground. Try 3-10 pF for starters.
18. The 1Watter Keyer Instructions
This is a very basic Iambic-Mode-B Keyer using an ATmel AVR Microprocessor
On power-Up, the keyer defaults to 15 WPM and a sidetone of 625 Hz and annunciates "1W" [ .---- .-- ] via Int'L Morse Code.
Connecting a straight key with a Mono Plug automatically places the keyer into straight key mode.
Moving the "Speed Pot" changes the speed from 5 WPM up to 36 WPM (version 3 and higher only)
The internal timing oscillator in the Keyer Chip is an RC oscillator that runs at 9.6 MHz +/- 10 pct Factory Calibration.
Typical accuracy is +/- 5 percent; The accuracy can be impoved to +/- 2 percent if one takes the time to calibrate
the oscillator and reprogram the keyer chip. This procedure is too time consuming for 200 chips but may be OK for you.
The accuracy is typically +/- 5 pct so your sidetone may be off by +/- 5 pct and your keying WPM may also be off.
That means if you set the WPM speed to 20 WPM, you may actually have it set at 19 or 21 WPM; should not be a problem.
The keyer is placed into the "Command" mode by pressing and releasing the Cmd Button.
The keyer has the following commands available after pressing the Cmd Button:
"A" (.-) Toggles transmit sidetone audio
The sidetone mode setting is saved on power-down.
If transmit sidetone flag was set, then clear flag and announce "Y"; Y=yes, we turn on transmit sidetone audio
If transmit sidetone flag was clear, then set flag and announce "N"; N=no, we turn off transmit sidetone audio
Sidetone audio is always active when a CMD is issued.
"B" (-...) Enter Beacon Mode (version 2 and higher only)
Hit CMD button and enter "B" to start Beacon Mode
Listen for a DIT to acknowledge ready to select message number
Enter message number...1, 2 or 3
Message repeats over and over
Hit paddles, dit or dah or straight key to turn off beacon mode
"E" (.) or "T" (-) Toggles between normal keyer and straight key mode, acknowleged by annunciating
"S" (for Straight Key Mode) in code. The keyer mode is NOT saved on power-down.
Connecting a straight key with a Mono Plug automatically places the keyer into straight key mode.
"M" (--) Enter Beacon Message(s) (version 2 and higher only)
Hit CMD button and enter "M" to enter message
Listen for a DIT to acknowledge ready to select message number
Enter message number...1, 2 or 3
Listen for a DIT to acknowledge ready to enter a character
Enter one character at a time, then wait for another "dit"
To enter a word space, do not enter anything in between annunciated "dits"
At the end of the message, do not forget to add empty character time.
This allows you to pause and listen between CQ calls. Recommend between 10 and 20 word spaces.
Terminate message entry mode by send "AR" or ".-.-."
"R" (.-.) Toggles between normal and reverse paddles keys, acknowleged by annunciating "P" (for normal paddles)
or "X" (for reversed paddles) in code. The paddles (normal or reverse) are saved on power-down.
"S" (...) Set keyer speed in WPM. Speed is entered as two numerical digits.
After sending the "S" command, the keyer sends a DIT (e) as a prompt for the first speed character (0-4)
After sending the first speed number, wait for another DIT (e) prompt and send the 2nd number (0-9)
Depending upon what you enter, you will hear a "?" for ERROR or an "R" for a "Roger" acknowlegement.
Valid keyer speeds are 1 to 45 WPM (good luck trying to send/use 1 WPM)
The keyer speed setting is saved on power-down.
"F" (..-.) Sets the sidetone frequency.
After sending the "F" command, the keyer sends a DIT (e) as a prompt for the tone character (0-9)
Depending upon what you enter, you will hear a "?" for ERROR or an "R" for a "Roger" acknowlegement.
The sidetone frequency setting is saved on power-down.
The following table equates the sidetone number with the sidetone frequency:
0 = 1000 Hz
1 = 833 Hz
2 = 714 Hz
3 = 625 Hz
4 = 555 Hz
5 = 500 Hz
6 = 455 Hz
7 = 417 Hz
8 = 385 Hz
9 = 357 hz
"V" (...-) Announces the keyer version number (version 0 and higher only)
Sends a 0 or 1 or 2 or 3 ...
"X" (-..-) Puts the keyer into transmit or tune mode
Hit paddles dit or dah or straight key to turn off tune mode
The keyer has Deadman Insurance. In the event that the keyer issues 64 successive DITs or
64 successive DAHs, the keyer will shut down and cease to operate.
You must power down the keyer chip to restart normal operation.
To Reset the Keyer to the Default mode, hold the Cmd button active until you hear "1W"
Then immediately release the Command Button, else you will send another Command request.
Source code and hex files for the keyer are available at http://kitsandparts.com/keyer
Addendum Section:
Sep 07 2015 1330 - C51 is not shown on the PCB; it is used for 160 meters only.
Sep 07 2015 1905 - C44 is shown twice on the PCB; the C44 capacitor connected to D7 should be designated C52.
Sep 17 2015 1128 - C36 a SMT part, is incorrectly connected on the PCB; do not install C36 SMT cap; instead,
connect a 100n axial yellow cap from C36/Q9 to ground as shown in the picture.
Sep 28 2015 2359 - U3, the NE602 IC in the lower left corner should be labeled U4 on the PCB
Oct 19 2015 1339 - C16 was listed as 100 pF in the instructions; should be 56 pF NPO; corrected instructions.
Oct 31 2015 1247 - On the PCB, the power control pot labeled R6 should be labeled R5
Nov 16 2015 1259 - The Natural Sidetone Mod improves the audio quality and accuracy of the transmit sidetone frequency.
Perform this Mod after the 1Watter is built and tested.
Replace R15 with a 1M resistor.
Install a 4M7 ohm resistor on the bottom of the PCB across the Drain and Source of Q8
Install a 4M7 ohm resistor on the bottom of the PCB across the Drain and Source of Q9
Variable capacitor settings:
| Maximum Capacitance | Midway Capacitance | Minimum Capacitance | |||
|---|---|---|---|---|---|
 |  |  |
If you need an alignment tool for the trimmers, look up "GC 8608" - available at newark.com and onlinecomponents.com
End of Addendum Section: top