Nighthawk CW Transceiver Kit V3

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"Nighthawk"

CW Transceiver Kit V3.1

Brief Introduction

The "Nighthawk" CW transceiver is based on a well-known US design by Dave Benson,

K1SWL at Small Wonder Labs. Its classic design includes a standard heterodyne

receiver, to give high sensitivity and low noise, originally published in QST

magazine (Nov 1994). A proven ham transceiver design using standard technology.

The “Nighthawk" is a modified version offering the following improvements:

1. An 12F629 microcontroller (MCU) has been added to provide an automatic keyer with call

sign memory and operator sidetone.

2. Potentiometer variable front-end diode attenuator. Attenuation reduces interference

resulting from the use of long wire antennas, and this method avoids potentiometer

adjustment noise.

3. The transmitter uses a 2SC1970 driver and RD15HVF1 final to give 10W single tone

output to give more output power (The original design only delivered 3-5W).

4. The transceiver rx-tx switching uses a relay to provide better isolation, and a

transmitter delay control circuit has been added to avoid excessive relay switching.

5. The original low-pass filter has been changed to a better-performing band-pass filter

(Two coupled parallel resonant circuits gives better selectivity)

6.The original 3MHz VFO has been changed to an 11.0592MHz VXO, greatly improving the

stability of the oscillator while retaining the original superheterodyne architecture.

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The development of the current version of the kit was based on experience gained from

actual use and debugging. This document covers the V3.0 hardware version. This is

identified by the name“YEYING_3”which can be found on the PCB.

Specifications

Frequency: Covers from 7.000-7.040MHz (approx.)

Mode: CW

Receiver sensitivity: Not stated

Transmit output: 10W

Power: 12V (recommended linear regulated power supply)

Typical receive current: About 100-120mA

Typical transmit current: About 1.8A

Antenna: 50 ohm, unbalanced

Technical Description

Please refer to the schematic shown on last page of this document.

The signal from the antenna first passes through a band-pass filter (T7, T8) which helps

to reject unwanted signals. This filtered signal then goes through an attenuator

consisting of D8 and D9 which allows user adjustment of the signal amplitude before being

passed to the first mixer (U4).

The circuit comprising Q3 and associated components forms the local oscillator. This

generates a frequency of about 11.000-11.040MHz. This is 4MHz above the received signal

frequency. The local oscillator is used for both reception and transmission.

After U4 mixes the received signal with the local oscillator, the 4MHz intermediate

frequency (IF) output signal passes to a crystal filter composed of Y2, Y3 and Y4. This

crystal filter passband is narrow, providing excellent performance. The filtered IF

signal is then fed to the second mixer U3. In this mixer, the local oscillator signal is

generated internally by the NE602 with crystal Y1. The frequency set by Y1 and CX1 is

about 800Hz higher than the frequency of the IF signal. After mixing, the resulting

(demodulated audio) signal is about 800Hz. This (audio) is subsequently passed to the

audio amplifier and filter stages, and finally to the headset (SPK).

The transmitter is controlled by the MCU which turns on (“keys”) the transmitter using

the “TX” pin (pin 7 of U6) via Q2. Q7 and Q9 then activate the tx-rx relay (K1), and Q8

applies power to the transmitter power amplifier driver.

The transmit signal is generated by the VXO oscillator (Q3 etc), and after mixing this

signal in U5 with its internal 4MHz oscillator (using Y5 and CX2), the resulting RF

signal is at the correct output frequency, between 7.000-7.040MHz. The mixer output is

bandpass filtered by T2 and T3, and then amplified through Q6, driver Q4 and power

amplifier Q5. The RF output then passes through the low-pass filter network (L3, L2),

through the relay contacts of K1, and out to the antenna.



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During transmit, Q1 mutes the receiver to prevent the transmitted signal from being

heard. The internal timer in the PIC 12F629 MCU is configured as an audio oscillator to

generate a sidetone output in the headset. This allows the distinctive "dit dit dah" CW

keyer signal to be heard in the headset.

Component Selection

This kit contains two types of toroid rings: NXO-100 and T50-2. The NXO-100 exterior is

colored black, while the T50-2 toroids are red. Pay careful attention to this when

winding these.

T5 and T6 are 1: 4 transmission line transformers. These are wound using 0.5

mm wire on the NXO-100 (black) ferrite toroids. Fold the wire in half, twist

the wires together, and wind 5 turns on each of these toroids (Refer to the

diagram). Tin the ends, and connect the primary and secondary turns as

shown.

T4 is a high-frequency transformer.

It is wound using 0.5 mm wire wound

on a NXO-100 (black) ferrite ring.

Wind 12 turns for the primary coil

and 10 turns for the secondary.

Connect the primary and secondary

coils as shown (adjacent) and on

the PCB. PRI is the primary, SEC is

secondary.

L2 and L3 are powdered iron toroids. Wind 14 turns of 0.5 mm enameled wire onto each of

these T50-2 (red) toroids.

All the high-frequency capacitors less than 1000pF are disk ceramic, and those larger

than 1uF are electrolytic capacitors. All resistors are ¼W 5%.

Note: If you need better performance, use appropriate equipment to test each 4.000MHz

crystal. Select three crystals which are as close as possible to the same frequency for

use in the crystal filter.

Component Testing and Construction

Before installing all the components, first test all transistors, resistors and

capacitors with a multimeter. Then, using the schematic and the PCB board overlay

diagram, install all the components. It is usually best to mount the components in order

of lowest to highest height. After soldering is completed, you must check your soldering

for any short circuits. Because there are static sensitive CMOS and MOSFET components, in

order to prevent electrostatic breakdown, your soldering iron should be properly grounded

or disconnect it from the power when soldering the final power amplifier MOSFET. The kit

includes integrated circuit sockets which can effectively prevent bad soldering of the



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integrated circuits. Once everything is in order, check the power supply is connected

with the correct polarity. This must not be wrong.

Note: All of the adjustable inductors are the same

7x7mm size, but L6 DOES NOT have the internally fitted

capacitor in its base. Please check the inductors

carefully to ensure you do not incorrectly solder one

in the wrong place! See the picture in the parts list

below.

Note: Q4 must be installed using the insulating gasket

and insulating spacer! When debugging, you MUST

install the heatsink!

Typical insulating gaskets and grommets for

TO-220 devices can be seen in this diagram:

The power plug requirements for this transceiver are

as follows:

Alignment and Testing

1. After the PCB has been assembled, connect the power. You

should hear the relay pull in with a "click" sound for just

a few seconds and then it will release. This indicates that

the keying delay circuit is operating correctly.

2. Adjust W3 to set the correct power amplifier (Q5) bias. This

should be adjusted so the quiescent current on transmit is about

100mA-130mA. It should not be set too high, to avoid excessive

idle current during transmit, nor set too low which will cause

reduced output power.

3. Rotate W2 fully counterclockwise, then use a non-metallic screwdriver to adjust L6

while using a frequency counter to

measure the frequency of the local

oscillator circuit at TP1 (See

below).

Note: The “superVXO” circuit used

here is not stable if the

inductance of L6 is too high. To

check this, monitor the receiver

with headphones during adjustment.

If the receiver breaks into self-



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oscillation (“motor-boating”), then the inductance of L6 is too high. In this

case, wind out the core of L6 to reduce the inductance. This also increases the low-

end VXO frequency.

Based on numerous tests, the transceiver oscillator can be tuned down to around

11.000 MHz. When using a frequency meter to test the local oscillator, make sure you

use a small 10pF series capacitor to couple the signal to the input of the frequency

counter, the lower the better, to avoid shifting the local oscillator frequency.

After the lower limit frequency is determined, then adjust W2 fully clockwise.

Measure the local oscillator frequency. It should be about 11.040MHz. Fine-tune L6

to ensure that tuning with W2 gives a local oscillator range of 11.000-11.040MHz.

4. After adjusting the local oscillator, connect the receiver to an antenna or a

signal source. Adjust W2 so the signal is audible in the headset, and then

repeatedly adjust T1, T7 and T8 to peak the received signal. Then adjust CX1 to give

the best sound quality (With an audio output of 800Hz, a frequency meter can also be

used to test U3 pin 7 to ensure that the crystal frequency is set to 4.000800MHz).

Because T1, T7 and T8 need to be adjusted to give a reasonably flat passband

response, it may be necessary to fine-tune these a number of times with typical

amateur test equipment, so do not rush to complete these adjustments.

5. Transmitter alignment requires a connection to a dummy load, an oscilloscope

and/or a power meter. Key the transmitter, and adjust CX2 to ensure that the

frequency of U5 on pin 7 is exactly 4.000000MHz.

6. Then adjust T2 and T3 for maximum output power while monitoring the power (or

voltage) on the dummy load. Check the output power across the tuning range by

adjusting W2. Fine-tune the adjustment of T2 and T3 to ensure that the output power

is reasonably similar across the frequency range.

At this point, the Nighthawk alignment is basically complete. When using the

transceiver, ensure a suitable dummy load is used during alignment or a suitable

antenna when transmitting! If this is not

done, the power amplifier transistor will be

damaged!

Installation in a Chassis

The circuit board can be easily installed

into a standard aluminum chassis measuring

97 x 40 x 120mm. (Note: This kit does not

include this housing. It is necessary to

purchase your own enclosure)

Operation

Because this transceiver is a superheterodyne design, its selectivity and

interference rejection performance is outstanding. With a full-length half-wave

dipole antenna, typical conditions should permit communication over distances of

around 1,000 km, or even greater distances depending on propagation conditions and

the operating skills of the operator.



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Automatic / Manual Keying Selection

The MCU will automatically recognise and select the correct automatic or manual

keying mode if the key is connected to a mono plug (Manual) or a stereo plug

(Automatic)

If the middle ring is connected to ground on the stereo plug, the PIC 12F629 MCU

will automatically detect the inserted manual key when the power is turned on. Note:

The manual mode does not support the callsign key input, automatic calling or

sidetone configuration.

The key plug wiring diagram is shown below:

Automatic Call

If the SET button is briefly pressed and released, the transceiver will

automatically call "CQ CQ CQ DE callsign callsign callsign PSE K". (If the callsign

has not been programmed, the auto call’s three callsigns will be replaced by eight

sets of seven ‘dahs’)

Transceiver Configuration

Code Sending Speed Adjustment

Press and hold the SET button for about 3 seconds until you hear the "Da da da"

function tone in the headphones, then release the SET button. You will then hear a

"dit dit" tone.

Within 3 seconds, press the "dah" paddle to increase code speed, or press the "dit"

paddle to reduce code speed. (Without any input within 3 seconds, the MCU will

automatically exit the setup mode and retain the original speed)

After the "dit dit" tone is heard, you can continue to adjust the speed using the

paddles. After the desired speed is set, wait for about 3 seconds. A "Dit dit dit"

will be heard confirming the setting and the exit from the (speed) setup mode.

Sidetone Adjustment

Press and hold the SET button for about 3 seconds until you hear the "Da da da"

function tone, but do not release the SET key. Wait another 3 seconds until the

second "Da da da" tone is heard, and then release the SET button.

Within 3 seconds, press the "dah" paddle to increase the sidetone frequency, or

press the "dit" paddle to reduce the frequency. (Without any input within 3 seconds,

the MCU will automatically exit the setup mode and retain the original tone

frequency)

Automatic key "dit" paddle

or manual key contact

Automatic key "dah" paddle

or manual key ground

Automatic key common ground

or manual key ground



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You can continue to adjust the tone using the paddles. After the desired tone is

set, wait for about 3 seconds, and the "Dit dit dit" sequence will be heard to

confirm the setting and exit from the (tone) setup mode.

Callsign Configuration

Press the SET button and hold for about 3 seconds. Continue to hold (3 seconds)

until the first "Da da da" feature sound, and then the second "Da da da", and

finally the third "Da da da" sound is heard. Then release the button to enter the

callsign configuration mode.

The callsign entered this way: When you hear the tone "Di di", enter the first

character of the callsign in Morse code using the dit or dah paddles. When you hear

a second "Di di" after the beep, then enter the second character, or, if you made a

mistake with entry of the first character, you will continue to hear a "ticking"

sound, but do not enter anything at this time. After 3 seconds, you will hear

"ticking" sound, you can enter the first symbol of the second character.

So, the idea is, between the first and second characters, you must wait to hear a

"Di di" tone. Until then, do not press the key! Once all of the callsign characters

have been entered, do nothing after you hear the last beep. After 3 seconds, the

"beep beep" sound will be heard as the MCU exits the configuration menu.

The callsign is then written into internal EEPROM by the MCU. For that reason, do

not enter the configuration menu process (or turn the power off) to allow time for

the write operation to be completed correctly. At the same time, do not panic if a

configuration error occurs. Just re-enter the configuration menu again and repeat

the process again.

Parts List

1/4W Resistors

R1,R29,R35,R37 4.7K

R2,R5,R12,R41 1M

R3,R6,R24,R25,

R30,R39,R42

10K

R4,R14,R18 22K

R7 470

R8,R9,R11 510K

R10,R13,R26,R27,R36 10

R15 51

R16,R19 220

R17,R21 330 /1W

R20,R31,R32,R33,R34,R38

, R40

1K

R22 1.5K

R23 100K

R28 120



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Variable Resistors

W1,W2 10K（103）

W3 10K（103）

Chokes, Inductors, Transformers

T1,T2,T3,T7,T8 7x7-7MHz Note capacitor in base

T4,T5,T6 NXO-100 toroid

L1,L5 22uH Choke

L2,L3 T50-2

L4 100uH Choke

L6 7x7 NO BASE CAPACITOR!

Z1,Z2,Z3 Ferrite bead



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Ceramic Capacitors

C1 820p(821)

C2,C20,C36,C42,C47,C49,

C54,C55,C56

0.01uF(103)

C3,C9,C12,C15,C16,C17,

C21,C23,C24,C25,C26,C29

,C30,C32,C33,C34,C35,C3

7,C40,C43,C46,C48,C57,C

58, C59,C60

0.1uF(104)

C4 2200pF(222)

C5 0.033uF(333)

C6,C7,C10,C13,C18,C19,

C53

150p

C8,C11,C14,C22,C28,C31,

C45

47p

C27 220p

C38,C44 1000pF(102)

C39,C41 470p

C50,C52 27p

C51 2p

Electrolytic Capacitors

CP1,CP6,CP10,CP11,CP12,

CP13

100uF /25V

CP2,CP7 10uF /25V

CP3,CP4,CP5,CP8,CP9 470uF /25V

CP14,CP15 1uF /50V

Trimmer Capacitors

CX1,CX2 5/20p

Semiconductors

D1,D2,D4,D5,D6,D8,D9,D

10,D11

1N4148

D3 1SV149

Please insert in accordance

with the PCB markings

D7 1N4001

LED1 3mm two-color LEDs



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Q1,Q7 2SK30A

Q2 8050

Q3 9018

Q4 2SC1970

Q5 RD15HVF1

Q6 2SC3355

Q8 B772

Q9 8550

Switch

SW1 Pushbutton

Integrated Circuits

U1 4558（DIP8） With IC socket

U2 7808（TO220）

U3,U4,U5 NE602（DIP8） With IC socket

U6 PIC12F629（DIP8） With IC socket

U7 78L05（TO92）

Crystals

Y1,Y2,Y3,Y4,Y5 4.000MHz

Y6,Y7 11.0592MHz

Other Components

J2 BNC（Q9）socket

J4 DC connector

J1 3.5mm stereo jack SPK (For headphones)

J3 3.5mm stereo jack KEY（Insert key）

K1 HK4100F-9V relay

PCB ×1

0.51mm diameter wire

Heat sink, four nuts and bolts, insulating gaskets and spacers, one each

After receiving the kit, please check for any missing parts. If you have any

questions, please contact the shop.



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PCB Component Layout Diagram



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Understanding Resistor Color Codes and Capacitor Values

Resistor values are printed using colored rings, the most common types being 5% and

1% tolerance parts. 5% parts have four colored rings, 1% have five colored rings.

The value is read as follows:

Ceramic capacitors are generally marked in pF (10-12F), some using the exact value,

(i.e. 1000p, 220p, etc), while others use exponential notation (i.e.102, 221, etc)

where the first two digits gives a numerical value, then a single digit is added to

show the number of zeros added after these first two digits. For example, “102”

represents a value of 10, while the following 2 adds two zeros i.e. 10 and 00 or

1000pF. “221” represents a value of 22, while the 1 adds one zero, i.e. 220pF.

Here 62 means 62pF Here 102 means 1000pF

Polarized Electrolytic Capacitors

Electrolytic capacitors are polarized so make sure the polarity is correct when

inserting then into the PCB. Do not install them the wrong way around。

Inductors

The important feature is the number of turns on the coil which can be a guide to its

inductance:



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This toroid has 12 turns which should be evenly distributed around the core.

IC Identification

8 pin DIP package 20 pin DIP package

Transistor Identification

TO92 package and pins 1N4148 The＋－polarity 1N4001 The＋－polarity


Nighthawk CW Transceiver Kit V3

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