"An Effective 2040m CW Transceiver - DOC - DOC"
A Homebrew 20/40m Binaural CW Transceiver Hannes Coetzee, B. Eng (Electron), ZS6BZP and Christo Pelster, M.Eng (Electron), ZS6AHQ A binaural CW transceiver covering the 20 and 40m amateur bands is presented. (40m is ideal for country wide contacts and 20m offers the opportunity for DX contacts.) Power levels of 10W on 40m and 5W on 20m ensure reliable contacts with reasonable power drain if battery operation is required. The design has been optimised for reproducibility by relatively inexperienced persons having only access to the minimum amount of test instruments (if they are comfortable working with SMD components). The result is ideally suited as a club project or for hams wishing to construct their own gear for “Summits-on-the-Air” (SOTA) activities. Introduction When the achievable performance of the various receiver architectures is compared to the complexity, cost and availability of components and reproducibility, few can beat the Direct Receiver (DC) configuration. But unfortunately the basic DC receiver is not without its drawbacks and shortcomings. The major drawback of a DC receiver is the lack of image suppression. It is very apparent in a busy band with closely spaced CW signals. Despite this the DC receiver is very popular for homebrewing and low power, portable equipment. This may be an indication that the image problem is not as serious as what may be thought at first and that it may be possible to enjoy amateur radio to the fullest despite this inherent drawback. It was decided to make use of a Binaural DC  receiver design to help overcome some of the drawbacks. The design can also form the basis for a full featured, phasing method Single-Side band transceiver. Basic DC Receiver A local oscillator (LO) signal, operating very close to the received frequency, is mixed with the received signal. The result of this mixing process is two frequencies, the sum component at double the operating frequency, and the difference component at audio or base-band. The difference (audio) component is filtered out (selected) and amplified to a suitable level. Direct Conversion Receiver Antenna NE/SA602 TL071 LM386 Mixer/ Pre- Audio Oscillator Amplifier Amplifier Figure 1. Basic Direct Conversion Receiver Binaural I-Q DC Receiver In the Binaural I-Q DC receiver the process is taken one step further: The incoming signal is first divided into two paths, each feeding a mixer. A local oscillator (LO) signal, operating very close to the received frequency, is also divided into two paths, but with a 90º-phase difference between the two LO signals. The two LO signals are mixed with the two received signals. Once again the difference (audio) components are filtered out (selected) and amplified to suitable levels. The outputs are fed to a stereo headphone or two loudspeakers. Pre- Audio Antenna Mixer Amplifier Amplifier 0 Oscillator Power 90 Splitter Mixer Pre- Audio Amplifier Amplifier Figure 2. Basic Binaural I-Q DC Receiver The 90º-phase difference between the two signals allows the human mind to create a virtual stage of signals. The mind now not only classifies signals in terms of frequency, but also in terms of position. It is now much easier to focus on individual CW signals, especially in a crowded band. This helps to overcome the inherent drawback of the basic DC receiver. Implementation The basic Binaural DC RX design is now extended to provide solid performance on the sometimes-challenging 20 and 40m amateur bands. SOTA 20/40m CW Binaural Transceiver NE602 by ZS6BZP and ZS6AHQ 7/14MHz TL072 Audio Amp Pre- LM386 Amp NE602 Vol 20m 20m Rx HPF Side OR TL072 Tone HPF 13.6 MHz Pre- LPF LM386 HPF Amp Vol 6.8MHz HPF 14.5MHz LPF 40m Tx Audio 40m LPF Amp Push-Pull 0º 90º 7.5 MHz MOSFET LPF Side Tone Power 4 CW key Amplifier (NE555) (74AHC04) 180º Encoder LCD_LOAD 74AHC251 PIC16F84 AY-0438 4½ Digit 20m/40m LCD Driver 20m 32 segment LCD_DATA 40m LCD_CLK LCD A STEP 32 28- DDS_CLOC DDS_DAT Tx/R DS_FSYN Rx Tx 28.7MHz x 20m BAN 2 40m D (74AHC04) +T A K C x CW X-Tal • x3 x3 +R Tx/Rx Key Ref Osc AD983 LPF x Control (74AHC04) (74AHC04) 56- 50MHz 5 57.4MHz DDS 6.222- 6.8MHz 6.377MHz Figure 3. SOTA 20/40m CW Binaural Transceiver Block diagram Input/Output Filter A selectable band pass filter is required at the input of the receiver to ensure that the receiver only responds to the signals of interest. But band pass filters normally require alignment, which implies that some additional test equipment may be required. This is in contrast to the design goals of simplicity and reproducibility. The solution is to use separate high pass and low pass filters. A 6.8 MHz, fifth order Chebyshev high pass filter with 0.5 dB ripple and a 14.5 MHz, fifth order low pass filter are permanently in the signal path. When operation on 40m is required, an additional 7.5 MHz low pass filter is switched in the signal path. For operation on 20m, a 13.6 MHz, fifth order Chebyshev high pass filter with 0.5 dB ripple is switched in the signal path. The wider-than-absolutely required filter bandwidths ensure reproduce-ability while still protecting the receiver from strong, out-of-band signals. The same filter combinations are used in the transmit path. Very high voltages exist on a band pass filter with the planned 10-Watt power level. Once again this will require special components, but the separate high-low pass filter combination ensures a clean output signal. Use is made of IM-5 moulded inductors. The Q values of moulded or bought-out inductors are adequate for the required power level and the requirements of low or high pass filter arrangements. Capacitors are low cost ceramic units with a zero temperature coefficient (NP0). 100V ratings are once again adequate for the required power levels. A 100 kΩ, 1-Watt resistor at the antenna terminal bleeds any static build-up to ground. This helps to protect the transceiver against electro-static-discharge (ESD) damage without influencing the functioning of the TRX. Mixers Deciding on the specific mixer to implement was a difficult decision as so many options were available. Suitable candidates include a selection of passive, double balanced mixers from Mini-Circuits, active mixers from Analog Devices and a balanced mixer using CMOS IC‟s developed by one the authors [2,3]. The ease of implementation, low noise figure and medium gain eventually swung the decision in favour of the NE602 family, an old favourite among radio amateurs. Balanced inputs and outputs are required to get the „602 to perform at its best. On the input side this is easily implemented with a RF transformer wound on a balun core. Impedance matching from the filter‟s 50 Ω to the high impedance of the „602 is also implemented on the same RF transformer. Power dividing of the received signal are accomplished by paralleling the inputs of the two „602‟s, no need for exotic power dividers here. Audio Buffers The balanced outputs of the „602 are converted to a single ended audio signal with the aid of a low cost, low noise op-amp implemented in a differential amplifier configuration. The 1.5 kΩ impedance of each of the „602‟s outputs defines the gain of the audio stage in conjunction with the 22 kΩ feedback resistors. A simple audio high pass filter with a corner frequency of 300 Hz is implemented with the aid of the 330 nF DC blocking capacitors. 4.7 nF capacitors across the feedback resistors help to limit the audio bandwidth. Higher value capacitors can reduce the bandwidth even more, but the audio quality may suffer when monitoring SSB signals. A 100 nF capacitor across the inputs of the differential amplifier prevents brake through of very strong commercial AM broadcasts. Audio Amplifiers A stereo 10 kΩ potentiometer does duty as a volume control. The audio signals are fed to another two Old Faithfuls: LM386 audio power amplifiers. There is nothing special about the implementation. The 10 Ω, 10 nF combination at the output ensures that the amplifier is properly terminated at high frequencies and prevent RF from braking through on the audio. An R-C feedback network between the output (pin5) and pin 8 reduces the bandwidth of the LM386 and saves the ears from the notorious high frequency hiss generated by the LM386. The side tone signals are fed via another 10 kΩ potentiometer to the normally grounded input. The output level of the „386 is adequate to drive a small 8 Ω loudspeaker to comfortable levels or earphones to ear-splitting levels. The outputs of the two „386‟s drive two small loudspeakers mounted on either side of the enclosure to give the binaural advantage even when earphones are not used. VFO Generating a clean, stable, adjustable local oscillator and displaying the operating frequency can be much more complex than the transmitter and receiver circuitry. Once again many options were investigated, ranging from free-running VFO‟s with variable capacitors to exotic Phase-Locked-Loops under microprocessor control. The simplest solution seemed to be a dedicated voltage controlled oscillator, the LTC1799. On paper it seemed a viable option, but measurements done on a sample highlighted the shortcomings of this device very clearly. The stability, phase noise and “purity of note” are simply not good enough for communications purposes. Generating the two LO signals with the required 90º-phase difference at the operating frequencies of 7 and 14 MHz are done with the aid of dual flip-flop logic gates (SN74AHC74) clocked at four times the operating frequency. The quadrature outputs of the flip-flops are terminated in two resistor divider networks that ensure a modest load current of 5 mA / gate and the correct drive levels for the mixers . The LO frequency required for operation at 14.350 MHz is thus 57.4 MHz. Free-running oscillators operating at such a high frequency tends to be very unstable, or other techniques require lots of complicated circuitry. It was decided to use a low frequency LO operating at between 6.2 and 6.4 MHz followed by two frequency triplers (x9) to generate the required clock signal to feed the quadrature generator (dual flip-flops). Operation on 7 MHz requires an additional divider, implemented with a flip-flop, ensuring easing band selection with the aid of a 74AHC251 multiplexer. The two, frequency triplers are implemented with a single CMOS hex buffer (SN74AHC04). The output of the VFO is squared before driving the first tripler. A square wave can be considered as the fundamental (sine wave) and a large amount of odd harmonics added together. The fundamental is suppressed by a tuned circuit formed by a capacitor and inductor. The third harmonic is selected by the tuned circuit formed by the same inductor and the other capacitor. The output signal is once again squared by one of the CMOS inverters and the process repeated for the next tripling action.  A low cost Direct Digital Synthesiser (DDS) controlled by a PIC processor is probably the simplest way to generate a very clean and stable LO signal. The PIC can then also display the frequency on a low cost, 4½-digit Liquid Crystal Display. The readability of these displays is better than the 2 x 16 types. A low cost rotary encoder is used for frequency adjustment purposes. TM An Analog Devices AD9835 complete DDS is well suited for the requirements. Most modern DDS‟s generates a very clean output if the clock frequency is at least eight times higher than the output frequency. 50 MHz clock oscillators are common and relatively low cost. An Elliptical low pass filter using standard, off-the-shelf components follows the output of the DDS. This ensures a spectrally clean signal to drive the frequency tripler chain. The output frequency of the VFO is shifted (lowered) by eight hundred Hertz during transmission to ensure that the transmitted signal is on the same frequency as the received signal. DDS TM TM A PICMicro 16F84A manufactured by Microchip is used to calculate and send the programming commands to the DDS. This microprocessor is also used to display the frequency and handle other functions such as frequency adjustments from the rotary encoder, band select, tuning step changes and transmitter-receiver offsets. The internal RC oscillator is used reduce component count. TM The 32-segment display driver (AY-0438) is also manufactured by Microchip The DDS uses a 50 or a 40 MHz crystal oscillator as a reference. The output of the DDS is calculated based on this reference frequency and the programming word in the following relationship: Fout = (Fclk x Freg)/2^32  The DDS frequency for 20m must therefore be 4/9 of the displayed frequency and 8/9 of the displayed frequency for 40m. The PIC has a few tasks that it needs to perform, almost at the same time, but independent of each other (not strictly multi-tasking): 1. Check Band Selection switch 2. Check Tx/Rx mode 3. Check Step Change input 4. Check for changes in the Shaft Encoder (increment or decrement) 5. Check frequency limits 6. Calculate the Digits to be displayed and send them to the display 7. Calculate the DDS word and send them to the DDS chip The DDS word is only calculated and sent to the DDS chip when the frequency has changed (including band change) and when the Tx/Rx mode changed. When no user input is active, the DDS retains the previous generated frequency. This avoids additional output spurious signals. The frequency limits for the 20m and 40m band are set in the PIC code to ensure no out-of- band transmissions are possible. The display flashes to indicate when the lower or higher limit was reached. Side tone Oscillator Another Old Faithful is called up for duty as the side tone oscillator. The 555 is probably the world‟s most versatile IC. A low power, CMOS version (7555) is preferred for this application, but any version will function in the circuit. The output is fed via a simple, low-pass filter to the audio amplifiers. The levels are adjustable via the pre-set potentiometers. A side tone is generated whenever the key is pressed, independent of the radio been in transmit mode or not. The side tone generator serves double duty as a test oscillator for debugging the audio stages and as a CW practise aid. RF Power Amplifier Two square wave signals with a 180º phase difference are available from the flip-flops. The frequency of these signals is either at 7 or 14 MHz, depending on the selected band. Hex inverting gates (SN74AHC04) are used to buffer these signals. The remaining inverting gates are paralleled to drive a pair of power FETs normally used in switched mode power supply applications. The push-pull output signal is transformer coupled via a balun core to the applicable output band pass filter. Power to the FETs is supplied via a centre tap on the transformer. The balanced configuration prevents DC saturation of the transformer core. The driver inverting gates are only powered during the transmit cycle. The 74AHC04‟s are run from a 6V supply to ensure that the power FET‟s are properly switched on. This voltage is slightly higher than normal, but still with-in the manufacturers absolute maximum rating of 7V. Gate resistors ensure that the power FETs are totally switched off during reception. The diodes that are built into the FETs provide reverse polarity protection in case the supply to the Transceiver is accidentally connected the wrong way round. Availability of Components It may be difficult to obtain some of the components in low quantities. Agents for all the components can be found on the Internet and they will be more than willing to supply larger quantities for example for a club project. Construction This transceiver is definitely not a beginner‟s project. This is not due to the complexity, but rather because many of the components used are only available as surface mounted devices (SMD). A double sided, through plated PC board considerably eases the construction of the transceiver. The PC board is a standard Euro card (100 x 160 mm) size. The microprocessor and DDS portion is cut off to enable it to be mounted on the front panel of a suitable enclosure. It is recommended that the output audio stages are built and tested first. After this is done connect loudspeakers and a suitable power supply. Touching the inputs of the amplifiers will result in a loud hum or noise, indicating that there is a good chance that the output stage is functioning correctly. Next step is the completion of the sidetone oscillator. Shorting of the “key” connections must result in an approximately 800 Hz tone on the loudspeakers. It is now the time to get brave and take on the mixed technology (leaded and SMD) microprocessor and DDS board. This board can easily be tested on its own once completed. The rest of the transceiver can now be completed with the experience gained working with SMD. Operation Operation is very simple with the lack of bells-and-whistles. The transmitting frequency is 800 Hz lower than the received frequency. It is easiest to start at the low frequency side and tune through a signal until it becomes audible in the left ear. This ensures that the correct side band is selected and that the transmitted frequency is nearly zero-beat with the station that you want to contact. The binaural effect is also very apparent as the CW signal “moves” from in front of you in an elliptical fashion to the right, again in front of you and then slightly to the left as the received frequency is increased. It is a very unique and enlightening experience on a crowded CW band. The step size is changed by pressing the STEP button. The default step size is 10 Hz, which is useful for CW tuning, while the coarsest step size is 1 kHz. The step size cycles through 10 100 1000 1 Hz. It is easiest to search for activity with the bigger step increments and then use the small increments for fine-tuning. The receiver unfortunately suffers from a few spurious responses. These are probably caused by the clock signals of the DDS and the PIC as well as the multiplication and divider circuits. The receiver was found to be more than useful despite this. Summary An effective, dual band, binaural CW transceiver was described. One of the main drawbacks of a direct conversion receiver (lack of image suppression) is turned into an operator aid with the implementation of the binaural I-Q principle. To reduce the component count and enhance repeatability, “luxuries” such as an AGC and an S-meter is omitted. The design focussed on solid RF performance with readily available components. The transceiver is ideally suited as a club project or for personal construction, as long as the constructor has experience with surface mounted components. References 1. A Binaural I-Q Receiver. Rick Campbell, KK7B. The ARRL Handbook for Radio Amateurs 2002. pp 17.70 – 17.75 2. A Low-Cost, High Performance Mixer for HF Applications. P J Coetzee, Engineer‟s Notebook, RF-Design, June 1995 3. Multi-band, direct conversion receiver. Hannes Coetzee, ZS6BZP. Electronics World, February 1998. pp138-143 4. Circuits, Systems & Standards. Edited by Ian Hickman. Electronics World + Wireless World. November 1991. pp 939 – 943 5. CMOS Frequency Multiplier. Gert Baars. Elektor Electronics. 7-8/2004. pp 34 – 35 20m COM 40m RV1 7.5 MHz LPF 10K +5VRx +12V C1 1 1 2 3 SW1A L1 L2 1 2 +12V 6 5 4 3 2 1 6.8MHz HPF 14.5MHz LPF 1 2 1 2 C2 C91 2 1 1u5H 1u5H 100nF 2 1 100nF 1 1 1 Antenna C3 R1 1 2 2 C8 C9 C10 C4 C5 C6 4n7F 22K C7 10uF C11 P1 270pF 180pF 270pF L3 L4 470pF 820pF 470pF C12 C13 100nF 16V 10uF 1 8 1 2 1 2 1 2 1 2 1 2 10nF 330nF 1 2 R5 2 2 2 2 1 680nH 680nH 1 2 IC2 1 2 3 IC1A 1 10K + 1 1 1 1 1 2 6 1 2 1 4 1 16V C19 2 1 R2 C14 C15 C17 IN1 OUTA 2 3 IC3 220uF 2 100K L5 L6 270pF 470pF 270pF C20 2 C18 - TL072 7 + 5 1 2 1uH 1uH C21 C22 C23 1 2 IN2 C24 100nF 2 2 Speakers 2 2 1 4 - 1 150pF 100pF 150pF 330nF LM386N LS1 2 1 1 2 1 2 1 2 10nF 5 2 1 R4 RV2 R3 6 5 4 3 2 1 2 2 4 8 SW1B 6 OUTB 1 2 10K 10R 1 1 1 OSCA 8 2 +5VRx 3 +6VTx 1 7 VCC 3 22K RX 1 2 1 2 OSCB GND 20m COM 40m 13.6 MHz L7 L8 C26 IC4A 3 470nH 470nH NE612 C25 1 2 LS2 14 1 74AHC04 4 HPF C27 5 100nF 1 C28 1 2 4n7F 100nF TX 2 2 2 10nF 6 2 2 SW2A RV3 2 7 10K Q1 T1 +5VRx 2 1 IC4B IRF510 2 3 1 1 2 3 74AHC04 +12V P2 3 4 1 N=2 N=7 R41 C29 C92 2 1 IC4D 1K5 2 1 100nF 5 3 2 74AHC04 IC4C 1 4 4 2 1 2 1 2 9 8 74AHC04 C30 R8 C31 10uF C32 1 5 6 R9 N30 C34 C35 4n7F 22K 100nF 16V 10uF 3 8 10K R10 C33 10nF 330nF 1 2 R6 1 2 IC4E 2 1 1 2 1 2 IC5 1 2 5 IC1B 10K 1 + 6 1 74AHC04 T2 1 4 7 16V C37 Earphone 2 1 2 1 11 10 6 1 1K 10nF IN1 OUTA 6 3 IC6 220uF 2 C38 2 C36 - TL072 7 + 5 1 2 0° IC4F +12V N=1 R11 1 2 IN2 C39 100nF 2 2 4 - 1 74AHC04 5 68R 330nF LM386N 1 13 12 4 N=3 10nF 5 2 1 R13 RV4 R12 2 4 8 1 1 N=1 6 OUTB 1 2 10K 10R C40 R14 C42 OSCA 8 0° 90° +5VRx 3 100nF C41 3 2 1 2 1 2 7 VCC 3 22K 1 2 1 10nF N30 IC7A OSCB GND C44 C93 Buffer / Driver To Control 2 2 1 +5V 74AHC74 +5V 1K 10nF NE612 C43 1 2 2 1 4 14 100nF C45 +12V P3 1 2 PRE VCC 5 R15 4n7F 330nF 100nF 2 D Q 68R 1 2 +6VTx 3 R7 2 2 CLK 1K IC8A +5V 6 C94 14 2 1 74AHC04 1 Q 7 2 1 C48 1 2 CLR GND 2 10nF +ST 330nF C47 C46 2 7 2 1 100nF Q2 IC9 1 2 IC8B IRF510 100nF 8 3 R16 74AHC04 ÷4 VCC OUT 10K +ST 3 4 1 2 4 2 1 IC8D +5V TR RES 3 1 1 74AHC04 IC8C Side tone 5 7 R17 +ST 9 8 74AHC04 R19 IC7B CV DIS 1 2 PSU 1 5 6 10K +5V 74AHC74 generator 1 6 1 C52 10 GND THR 10K 2 IC8E 10nF 12 PRE 9 R18 LM555 2 74AHC04 D Q 8K2 IC11 2 11 10 11 C49 +12V 78L05 +5V 180° CLK 100nF 3 1 2 IC8F +5V 8 VI VO GND 1 1 74AHC04 13 Q 13 12 CLR C53 C54 100nF 10uF 2 16V 2 2 SW3 +12V 1 SW2B +ST ON/OFF 1 1 1 2 IC12 18.667 - 19.133MHz 56 - 57.4MHz RX 1 6.222 - 6.377778MHz C55 C56 R20 78L06 +6VTx R22 +5V R21 220uF 100nF 10K 2 3 1 10K C57 1 2 R23 IC13A BATT1 TX 3 VI VO GND 2 2 1 1 1 1 2 1 2 10K +5V 74AHC74 +5V +12V 2 10K 1 2 4 14 1 2 Q3 C58 C59 10nF 2 PRE VCC 5 BATTERY 2 2N2905 100nF 10uF From DDS 2 1 C60 IC14D D Q +12V 16V 14 3 2 2 P4 10nF C61 IC14C C62 3 R24 +ST SW2C 1 2 13 12 1 2 2 1 3 4 5 6 1 2 11 10 9 8 CLK 1K 1 IC15 +5V 6 RX 1 1 2 2 2 IC14F 68pF IC14B 74AHC04 18pF IC14E 74AHC04 4 6 1 Q 7 SW4 2 TX 7 2 R25 74AHC04 74AHC04 74AHC04 3 D0 W CLR GND 3 IC16 330R C63 C64 +5V 2 D1 5 1 78L05 +5VRx IC14A 560pF 150pF 1 D2 Y KEY 2 3 1 ÷2 1 1 1 1 1 74AHC04 15 D3 VI VO GND 2 1 1 14 D4 L9 R26 13 D5 IC13B C65 C66 1u2H L10 10K 12 D6 74AHC74 +5V 100nF 10uF 2 470nH D7 +5V 10 16V Multiplier 2 2 2 11 12 PRE 9 1 10 A 16 D Q 2 2 9 B VCC 11 C67 1 7 C 8 CLK 10nF SW1C G GND C68 8 2 10nF 13 Q Title 40m 74AC251 1 CLR 40/20m CW Tranceiver - TX & RX 2 2 20m 3 Size Document Number Rev A3 20/40m TRX 02 Date: Wednesday, November 16, 2005 Sheet 1 of 2 R2 7 1 2 DISPLAY IC17 DSPL1 1 1 10K 39 35 R2 8 C6 9 2 SEG1 38 34 SEG1 SW5 10K 100nF LOAD SEG2 37 7 SEG2 A 40 SEG3 33 6 SEG3 2 1 B CL K SEG4 32 5 SEG4 Rotary Encoder 2 2 C +5VD1 34 SEG5 29 36 SEG5 3 DATA IN SEG6 28 37 SEG6 4 +5VD1 35 SEG7 27 30 SEG7 R2 9 DATA OUT SEG8 26 29 SEG8 1 2 SEG9 25 11 SEG9 SEG10 24 10 SEG10 1 1 10K SEG11 23 9 SEG11 C7 0 SEG12 22 31 SEG12 R3 0 100nF SEG13 21 32 SEG13 10K SEG14 20 25 SEG14 2 SEG15 19 24 SEG15 2 SEG16 18 15 SEG16 R3 1 31 SEG17 17 14 SEG17 +5VD1 10K +5VD1 LCD SEG18 16 13 SEG18 1 1 2 IC18 SEG19 15 26 SEG19 17 C7 1 SEG20 14 27 SEG20 1 16 RA0 18 SEG21 13 21 SEG21 OSC1/CLKIN RA1 47pF SEG22 SEG22 C7 2 1 12 20 2 22pF RA2 2 SEG23 11 19 SEG23 RA3 3 SEG24 10 18 SEG24 2 RA4/CLK1 SEG25 9 17 SEG25 SEG26 8 22 SEG26 15 6 R3 3 +5VD1 SEG27 7 23 SEG27 R3 2 OSC2/CLKOUT RB0/INT 7 1K 1 SEG28 6 4 SEG28 1 2 4 RB1 8 1 2 VDD SEG29 5 8 SEG29 1 MCLR RB2 9 SEG30 4 38 SEG30 1 +5VD1 10K RB3 10 C7 3 36 SEG31 3 3 SEG31 14 RB4 11 C7 4 100nF VSS SEG32 30 40 SEG32 VDD RB5 12 47pF BP 1 BP 2 1 5 RB6 13 AY0438 BP 2 C7 5 VSS RB7 DISPLAY1 100nF PIC16F84 R3 4 C7 6 C7 7 2 1K 8p2F 8p2F 2 1 2 R4 2 1 2 1 2 SW6 +5VD1 330R DDS OUT 1 R3 5 C9 5 1 1 2 C7 8 IC19 10nF L11 L12 P5 Band Change 1 2 47pF 7 14 1 2 1 2 1 2 1 3 10K 8 SCLK IOUT 8u2H 8u2H 1 2 1 1 1 C7 9 9 SDATA C8 0 +5VD1 2 100nF R3 6 FSYNC 16 1 2 C8 1 C8 2 C8 3 1K COMP 82pF 150pF 82pF X1 2 1 2 +5VD1 50MHz 12 10nF 2 2 2 SW7 +5VD1 4 3 11 PSEL0 2 1 R3 7 V OUT 10 PSEL1 REF IN C8 4 1 1 1 2 C8 5 FSEL 3 1 2 TX/RX G G 2 47pF REF OUT 1 3 +5VD1 10K C8 6 10nF 2 1 2 C8 7 10nF 6 1 2 1 100nF MCLK FS ADJ 1 R3 8 +5VD1 2 10K 15 13 R3 9 +5VD1 AVDD AGND 3K9 1 SW8 R4 0 4 5 2 1 2 C8 8 DVDD DGND 2 1 1 100nF AD9835BRU Step 1 2 10K C8 9 2 C9 0 100nF 100nF 2 2 IC10 P6 7805 +5VD1 +12V 1 3 1 VI VO POWER GND 1 1 2 Title C5 0 C5 1 40/20m CW Tranceiver - DDS & Control 10uF 10uF 2 16V 16V Size Do cument Number Re v 2 2 A4 20/40m TRX 01 Da te: Wednesday, November 16, 2005 Sheet 2 of 2