QCX-20 Build

• 2018-11-14 Ordered second QCX-20 after burning the signal generator (Si5351A) of the first one (#2543) which was purchased December 2017.
• 2018-11-20 Kit arrived while I was in Annapolis removing some gear from Constance in preparation to take her to Smith's Marina on Tuesday.
• 2018-11-21 Wound and installed T1 (3.55), installed IC2 socket (3.2), installed DIP integrated circuits IC3 and IC5-10 (3.3), and installed sixteen 100nF capacitors C2, C3, C6, C12, C29, C32, C34, C35, C36, C39, C40, C41, C48, C49, C50, and C52 (3.4). After installation, verified connectivity of each solder joint using a DVM from each pin of the installed component to a pad or component elsewhere on the board per the artwork on page 11 of the manual. Measured each capacitor. Values ranged from 83nF to 87nF for all but three of the 18 capacitors in the kit; these were installed. The other three were from 90nF to 100nF. About 3.5 hours.
• 2018-11-22 Installed five 474nF capacitors C11 (470nF), C43 (434nF), C44 (437nF), C45 (464nF) and C46 (464nF). Installed five 1nF capacitors C14 (1.02nF), C16 (947pF), C18 (947pF), C23 (949pF) and C33 (933pF). Installed four 10nF capacitors C4 (9.8nF), C7 (10nF), C10 (10nF) and C42 (9.7nF). Installed two 47nF capacitors C9 (45nF) and C13 (45nF). Installed a single 39nF capacitor C17 (40nF). Installed two 2.2nF capacitors C19 (2.3nF) and C20 (2.4nF). Installed one 33nF and one 3.3nF capacitors C15 (3.2nF) and C53 (31.5nF). Had to remove a 1nF capacitor mistakenly installed in C53's place, should have been installed at C23. It was destroyed in the removal process. Installed two 390pF capacitors C25 (376pF) and C26 (374pF). Installed two 180pF capacitors C27 (181pF) and C28 (181pF). Installed on 30pF capacitor C30 (27pf). Steps 3.4 through 3.15. About 2 hours.
• Need a replacement for "102" C23. See 2018-11-29.
• 2018-11-23 Installed three 1µF capacitors C21 (1.04µF, blue), C22 (1.07F, blue), and C31 (1.35µF). Installed four 1N4148 diodes D1, D2, D4, and D5 (4nA, 710mV 0pF). Installed one 1N5819 D3 (0.72A, 257mV, 0pF). Installed 20MHz crystal XTAL1. Installed 27MHz crystal XTAL2. Installed sixteen 10k resistors R1, R7, R14, R34, R40, R46, R49, R52, R64 resistors (9.968k to 10.46k ohms). Steps 3.17 through 3.21. About 2 hours.
• 2018-11-25 Installed ten 1K resistors R3, R4, R19, R26, R37, R42, R45, R53, R54, R55, R62, and R63a (994 to 1005 ohms). Installed twelve 3.3K resisitors R12, R13, R15, R16, R20, R22, R23, R25, R44, R56, R59, and R65 ( 3289 to 3334 ohms). Installed four 100 resistors R5, R6, R8, and R9 ( 99.1 to 100.1 ohms). Installed three 120k resistors R38, R43, and R60 ( 119k to 120k ohms). Installed two 33k resistors R28 and R29 (33.08k and 33.15k ohms). Installed two 47k resistors R30 and R31 (46.75k and 47.33k ohms). Installed two 36k resistors R32 and R33 (36.16k and 36.31k ohms). Installed one 270 resistor R48. Installed one 470ohm resistor R41 (470.5 ohms). Installed one 3.9k resistor R61 (3905 ohms). Installed one 4.3k resistor R18 (4291 ohms). Installed one 5.1k resistor R11 (5108 ohms). Installed one 7.5k resistor R21 (7591 ohms). Installed one 750k resistor R35 (756.8k ohms). Steps 3.22 through 3.35. About two and half hours.
• 2018-11-26 Installed 22k trimmer R47. Installed 500 ohm trimmer R27. Installed two 50k trimmers R14 and R24. Installed two 47µH inductors L5 and L6 (0.04mH, 1.5ohm). Installed four 10µF electrolytic capacitors C24, C37, C38, and C51 (9.728µF, 6.1ohm; 10.01µF 4.1ohm; 10.18µF 4.1ohm; 9.664µF 3.5ohm). Installed one 470µF electrolytic capacitor R47 (458.8µF, 0.25ohm). Installed 30pF trimmer C1. Installed one MPS751 transistor Q6 (hFE=311, Vf=615mV). Installed six BS170 transistors Q1, Q2, Q3, Q4, Q5, and Q7 ( C=64pF, Vt=2.6; C=64pF, Vt=2.6; C=64pF, Vt=2.6; C=64pF, Vt=2.6; C=65pF, Vt=2.6; C=65pF, Vt=2.6). Installed the 2x3 header. Installed the four pin GPS header. Installed the three pin DVM/RF header. Skipped the single pin test points. Installed the power connector. Installed the 8705 power regulator IC11. Installed the seven pin headers for the LCD. Installed toroid L4 (meter fails, resistance only 0.29ohms). Installed toroid L2 (meter fails, resistance only 0.27ohms). Steps 3.36 through 3.53. About two and one-half hours.
• 2018-11-29 Installed toroids L1 and L3. LCR meter's range is 0.01mH-20H, therefore, did not measure the toroids. Installed RF output BNC connector. Installed 3.5mm stereo connectors. Installed buttons S2 and S3. Installed rotary encoder. Installed gain control potentiometer R36. Took a 1nF capacitor from the broken QCX and installed it as C23 (1.015nF). Installed the eight 12mm hex spacers, four for the LCD, and four to support the PCB. Installed the 16-pin female connector on LCD module. Installed IC2, the programmed ATmega328P microcontroller. Installed the LCD and the remaining 4 screws. About one and one-half hours.
  • First power with dummy load connected with 13.8VDC.
  • Alignment 8.7 Peak BPF 45x(2^05); Volume set to mid-point. I-Q Balance 25*(2^09), insensitive to adjustment; Phase Lo 24*(2^07), insensitive to adjustment; Phase Hi 27*(2^08), insensitive to adjustment;
  • Only first thirty degrees of volume control effective. Very sharp peak on BPF.
  • Inspection: electrolytic capacitors oriented correctly. Transistors oriented correctly. Diodes oriented correctly. IC oriented correctly. Found solder blob on bottom of board joining to op amp? pins, dropped away when touched.
  • Factory Reset of processor.
  • 8.7 Peak BPF: 40*(2^06) about half meshed, 24*(2^05) at fully opened, 30 jumping to 36*(2^03) at fully closed, single peak.
  • 8.8 I-Q Balance: min volume 25*(2^05), max volume 40*(2^13). Volume set to produce 30*(2^08), varies to 34*(2^08).
  • 8.9 Phase Lo: 20*(2^06) minimum at full counter clockwise end of travel.
  • 8.10 Phase Hi: 29*(2^07) full clockwise end of travel. 20*(2^06) minimum at full counter clockwise end of travel.
  • 8.7 Peak BPF: 46*(2^06) about half meshed, 28*(2^05) at fully opened, 42*(2^03) at fully closed, single peak.
  • 8.8 I-Q Balance: 32^07 near full clockwise, minimum at 22*(2^06)
  • 8.9 Phase Lo: set to 22*(2^03). 23*(2^04) minimum at full counter clockwise end of travel. 36*(2^07) near full clockwise.
  • 8.10 Phase Hi: set to 20*(2^04). 20*(2^04) at full counter clockwise end of travel. 37*(2^07) minimum at full clockwise end of travel.
  • Somewhat more than 400mW output per voltage of 5W at the QRP Labs dummy load showing 5.5V. RadioShack SWR/Power meter show ... into the QRP Labs dummy load. Should be 4.5W @ 13.8VDC input based upon the power curves shown on page 132 of the QCX manual.
• 2018-12-01 Began transmitting WSPR on 14.096.500 dial frequency which is being received as 14.097.0[789]x per the WSPRnet reporter
• 2018-12-03 Transmitting proceeded with spots till 2018-12-02 04:32, about five hours after starting. On 2018-12-03 01:33, the QCX clock had gained forty seconds in 37.5 hours. Seems that the 20MHZ system clock is beating fast by about 4,678 beats per second. Changed the 8.6 System frq setting from 20,000,000 to 20,004,678. Reset the clock to 01:41, one second slow ;( and the 6.5 Start to 04. The transmitting frequency is set to 14,096,500 and WSPRnet show reception at 14,097,090. Changed 8.5 Ref freq from 27,004,000 to 27,004,510, the transmitting frequency to 14,097,100, and reset the clock to 17:20.
• 2018-12-04 Most recent spot is 2018-12-03 23:24 which is about fourteen and a half hours ago after getting spotted for nine and a half hours (2018-12-03 13:44 to 2018-12-03 23:24), nearly twice as long as last time. QCX clock is currently two seconds fast or 2 * 20,004,678 beats in twenty-four hours which is 463 beats per second. Reset 8.6 System frq setting to 20,005,141. Reset clock to 14:18, less than a second slow. Need that GPS clock kit to arrive, be assembled, and connected. ... No spots. Changed 8.5 Ref freq back to 27,004,000 and dial freq back to 14,096,500 and got spotted by nineteen locations on the next cycle.
• 2018-01-07 03:25z Clock has drifted again. Now 4 to 5 seconds fast due to drifting since 2018-12-04 14:18z, which is 61 hours. Which is about 409 Hz fast, which would set the system frq to 20,004,732, nearly back to where we were before resetting the system frq on 2018-12-04. So lets' split the difference to 20,004,936.
• Measurement below taken before 2019-02-01
• 2019-02-01 Reflowed solder on all 8 connections of T1 and all three of C1. New readings are 8.7 Peak BPF: 40*(2^06). No change.

Location 		Voltage 		Comment
+ supply terminal 	11.98 	14.27		As I already mentioned: a 12V supply
Clk0 test pin 		~1.70 	~1.70		The Clk0 pin in normal operation has a 3.3V peak-peak squarewave with 50% duty cycle. The DVM is measuring the average of that. Measuring here makes a lot of nasty noise in the audio.
Clk1 test pin 		~1.70 	~1.70		The Clk1 pin in normal operation has a 3.3V peak-peak squarewave with 50% duty cycle. The DVM is measuring the average of that. Measuring here makes a lot of nasty noise in the audio.

Left side of C2 	3.40 	3.42		This is the voltage of the Si5351A supply, pins 1 & 7
Right side of D2 	4.96 	4.98		This is the +5V regulated supply

T1 pins 1, 2, 3 & 4 	0.00	0.00	Not able to reach pin 2	-- Primary (from RX/TX Switch Q5) and Secondary 3 (feeds band pass filter)
T1 pins 5, 6, 7 & 8 	2.36	1.79	XXX Not able to reach pin 7 -- Secondary 1 and Secondary 2 both inputs to Quadrature Sampling Detector feed from 5VDC to GND voltage divider of R2/R1 (5.86k/5.84k) with 100nF RF noise bypass(??) capacitor C6. R52/R51(5.86k/5.86k) also form a 5VDC to GND voltage divider as do R50/R49 (5.87k/5.84k).

C43-46 are the QSD integrating capacitors. The voltage across each one differs slightly. The following measurements show these small differences. 
Top side of C43 	2.28 	1.59	XXX Feed from QSD output (QSD X0, Y3) for IC5 pin 3
Top side of C44 	2.44	2.38  	XXX Feed from QSD output (QSD X3, Y0) for IC5 pin 2
Top side of C45 	2.42	2.24	XXX Feed from QSD output (QSD X1, Y2) for IC5 pin 6
Top side of C46 	2.30	1.57	XXX Feed from QSD output (QSD X2, Y1) for IC5 pin 5

IC5 pin 1 		2.64 	2.74		IC5a output, the pre-amp Image output
IC5 pin 2 		2.46	2.66	Preamps feed from QSD output and integrating capacitor C44 (QSD X3, Y0)
IC5 pin 3 		2.26	1.59	XXX Preamps feed from QSD output and integrating capacitor C43 (QSD X0, Y3)
IC5 pin 4 		0.00	0.00
IC5 pin 5 		2.28	1.57	XXX Preamps feed from QSD output and integrating capacitor C46 (QSD X2, Y1)
IC5 pin 6 		2.46	2.66	Preamps feed from QSD output and integrating capacitor C45 (QSD X1, Y2)
IC5 pin 7 		2.44 	2.97		IC5b output, the pre-amp Quadrature output
IC5 pin 8 		11.67 	13.91		This is the supply voltage minus the voltage drop caused by the reverse polarity protection diode D3 

IC6 pin 1 		2.44 	2.68		IC6a output
IC6 pin 2 		2.44	2.62~2.74
IC6 pin 3 		1.63	1.91
IC6 pin 4 		0.00	0.00
IC6 pin 5 		1.55	1.63
IC6 pin 6 		2.44	2.66~2.72 
IC6 pin 7 		2.44 	2.68		IC6b output
IC6 pin 8 		11.67	13.91

IC7 pin 1 		2.64 	2.77		IC7a output
IC7 pin 2 		2.64	2.75~2.82
IC7 pin 3 		1.99	2.11
IC7 pin 4 		0.00	0.00
IC7 pin 5 		1.89	2.01
IC7 pin 6 		2.64	2.77~2.85
IC7 pin 7 		2.64 	2.77		IC7b output
IC7 pin 8 		11.67	13.91

IC8 pin 1 		2.46 	2.72		IC8a output
IC8 pin 2 		2.46	2.72
IC8 pin 3 		0.65	0.65
IC8 pin 4 		0.00	0.00
IC8 pin 5 		0.67	0.65~0.67
IC8 pin 6 		2.48	2.72
IC8 pin 7 		2.48 	2.72		IC8b output
IC8 pin 8 		11.67	13.91

IC9 pin 1 		4.84 	4.82		IC9a output
IC9 pin 2 		4.84	4.82
IC9 pin 3 		0.65	0.65
IC9 pin 4 		0.00	0.00
IC9 pin 5 		0.67	0.67
IC9 pin 6 		2.44	2.70
IC9 pin 7 		2.44 	2.70		IC9b output
IC9 pin 8 		11.67	13.91~13.93

IC10 pin 1 		5.83 	6.93		IC10a output
IC10 pin 2 		5.83	6.93
IC10 pin 3 		5.83	6.93
IC10 pin 4 		0.00	0.00
IC10 pin 5 		4.21	5.02
IC10 pin 6 		3.94	4.80
IC10 pin 7 		5.83 	6.93		IC10b output
IC10 pin 8 		11.67	13.91

Q1, Q2, Q3		5.20W
L3 output		4.0W rising to 4.9W (L3 should be 0.77µH)
L2 output		2.5W rising to 4.4W (L2 should be 0.90µH)
L1 output		1.0W rising to 1.5W (L1 should be 0.77µH)

RF Power			1.47W	Per 9.2 RF Power
				~1.0W	Per RadioShack SWR/Power Meter Cat No. 21-534	(twitchy calibration)