"Nighthawk" CW Transceiver Kit V3.1

"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. 1

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. 2

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 3

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- 4

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 lowend 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. 5

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 key "dit" paddle or manual key contact Automatic key "dah" paddle or manual key ground Automatic key common ground or manual key ground 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) 6

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, 10K R30,R39,R42 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 1K, R40 R22 1.5K R23 100K R28 120 7

W1,W2 Variable Resistors 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 8

C1 C2,C20,C36,C42,C47,C49, C54,C55,C56 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 C4 C5 C6,C7,C10,C13,C18,C19, C53 C8,C11,C14,C22,C28,C31, C45 C27 C38,C44 C39,C41 C50,C52 C51 CP1,CP6,CP10,CP11,CP12, CP13 Ceramic Capacitors 820p(821) 0.01uF(103) 0.1uF(104) 2200pF(222) 0.033uF(333) 150p 47p 220p 1000pF(102) 470p 27p 2p Electrolytic Capacitors 100uF /25V CP2,CP7 10uF /25V CP3,CP4,CP5,CP8,CP9 470uF /25V CP14,CP15 1uF /50V Trimmer Capacitors CX1,CX2 5/20p D1,D2,D4,D5,D6,D8,D9,D 10,D11 D3 Semiconductors 1N4148 1SV149 D7 LED1 1N4001 3mm two-color LEDs Please insert in accordance with the PCB markings 9

Q1,Q7 2SK30A Q2 8050 Q3 9018 Q4 2SC1970 Q5 RD15HVF1 PCB 1 Q6 Q8 2SC3355 B772 Q9 8550 SW1 Switch 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 Y1,Y2,Y3,Y4,Y5 Y6,Y7 J2 J4 78L05(TO92) Crystals 4.000MHz 11.0592MHz Other Components BNC(Q9)socket DC connector J1 3.5mm stereo jack SPK (For headphones) J3 3.5mm stereo jack KEY(Insert key) K1 HK4100F-9V relay 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. 10

PCB Component Layout Diagram 11

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 (10-12 F), 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: 12

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 13

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