Fun on the Waterfall A Operating PSK-31 Presented

Fun on the Waterfall A Operating PSK-31 Presented to the QRP Forum 2001 ARRL South Western Division Convention Barry L. Geipel – AD 6 HR Lake Perris QRP Society September, 2001

Overview • Invented by Peter Martinez, G 3 PLX • PSK 31 is a new digital mode which utilizes the processing power of computers and sound cards. • Software on the computer converts inputted text to audio level wave forms which can be fed into most standard SSB radios. • The same software listens to the output of the radio and decodes the audio signals back into text.

Overview • PSK 31 is designed for conversational QSO’s. • There is no error correction built into the mode, so you can never count on the message being received error free. • Therefore it is not good for automated mail boxes and the like.

Technology • PSK 31 uses phase shift keying to produce logical zeros and ones. • The bandwidth and baud rate are both 31 Hz (therefore the name, PSK 31) • Characters are formed using combinations of zeros and ones in a coding scheme called Varicode.

Varicode • The end of a character is signaled by two or more consecutive zeros. • Varicode is much like the Morse code in that the most common characters have the least number of bits.

Varicode • However, Varicode supports a much larger set of characters than Morse, including upper and lower case alpha characters. • The shortest characters are all lower case alpha characters so in casual contacts, do not use upper case characters since they take much longer to transmit.

Varicode NUL 101011 SOH 1011011011 STX 101101 ETX 110111 EOT 1011101011 ENQ 1101011111 ACK 101111 BEL 1011111101 BS 101111 HT 11101111 LF 11101 VT 1101101111 FF 101101 CR 11111 SO 110101 SI 1110101011 DLE 10111 DC 1 1011110101 DC 2 1110101101 DC 3 1110101111 DC 4 1101011011 NAK 1101101011 SYN 1101101101 ETB 1101010111 CAN 11011 EM 1101111101 SUB 1110110111 ESC 110101 FS 1101011101 GS 111011 RS 1011111011 US 1101111111 SP 1 ! 11111 " 101011111 # 111110101 $ 111011011 % 1011010101 & 101011 ' 101111111 ( 11111011 ) 11110111 * 101101111 + 111011111 , 1110101 - 110101 . 1010111 / 110101111 0 10110111 1 10111101 2 11101101 3 1111 4 10111 5 101011011 6 101101011 7 110101101 8 110101011 9 110110111 : 11110101 ; 110111101 < 111101101 = 1010101 > 111010111 ? 1010101111 @ 1010111101 A 1111101 B 11101011 C 10101101 D 10110101 E 1110111 F 11011011 G 11111101 H 10101 I 1111111 J 111111101 K 101111101 L 11010111 M 1011 N 1101 O 10101011 P 11010101 Q 11101 R 10101111 S 1101111 T 1101101 U 101010111 V 110110101 X 101011101 Y 101110101 Z 101111011 [ 1010101101 111110111 ] 111101111 ^ 111111011 _ 1010111111 . 101101101 / 1011011111 a 1011 b 1011111 c 101111 d 101101 e 11 f 111101 g 1011011 h 101011 i 1101 j 111101011 k 10111111 l 11011 m 111011 n 1111 o 111 p 111111 q 110111111 r 10101 s 10111 t 101 u 110111 v 1111011 w 1101011 x 11011111 y 1011101 z 111010101 { 1010110111 | 11011 } 10101 ~ 1011010111 DEL 1110110101

Waveforms • PSK 31 waveform sending a series of logical zeros.

Waveforms • PSK 31 waveform sending a series of logical ones.

Getting Started • Getting started in PSK 31 can be quite easy if you have a few basic components. • Most hams have everything they need to get going right away. • The minimalist system may not be the most fun, so you will eventually want to build up a few extra components.

Hardware – minimalist system • A stable SSB radio capable of tuning the PSK 31 frequencies. • A computer with a 16 bit sound card in the 133 Mhz or higher class. • Audio patch cords. • Plug the patch cord from your rigs headphone jack to your computer sound cards mic jack. • Hold your rigs mike up to your computers speaker and key the mike when want to transmit.

Hardware – a bit better • A stable SSB radio capable of tuning the PSK 31 frequencies. • A computer with a 16 bit sound card in the 133 Mhz or higher class. • A audio patch for wired up as before. • Another audio patch cord with a 100: 1 voltage divider hooked into your rigs mic input. • Set the VOX level and go!

Hardware – a bit better • A simple interface cable • This circuit can often be built into a standard mic housing.

Hardware – the best • A stable SSB radio capable of tuning the PSK 31 frequencies. • A computer with a 16 bit sound card in the 133 Mhz or higher class. • An interface cable appropriate for your other hardware. • Depending on the interface cable, you may also need a free serial port.

Hardware – the best • Interface cable can be easily built or purchased. • Uses the serial line to key the rig. • Isolates the computer side from the radio preventing RF feedback. • The Inland Valley Alliance of Amateur Radio Clubs did a club project to build one of these: • http: //www. geipelnet. com/barry/PSK 31. pdf

Software • Most of the work in PSK 31 is done in software, therefore you will need a PSK 31 software package. • Most of them are FREE!! • Available on the Web. • Digi. Pan (http: //members. home. net/hteller/digipan/download. htm) • Win. PSK (http: //www. qsl. net/ae 4 jy/winpsk. htm)

Operating • Each software package had different interfaces. You will need to become familiar with the package you choose. • Your radio should be tuned to one of the listed operating frequencies. Your software will show you a representation of all signals in your radios bandpass. • The hardest part of PSK is adjusting the audio drives for maximum performance.

Operating - receive • On receive you can adjust the volume control on the radio until you see the best quality signal. Your software operating guide will explain how this is done. • Some packages allow you to view multiple signals that are within your rigs bandpass.

Operating - transmit • Transmitting can be a bit tricky, and for the most part you will rely on signal reports to set your output audio correctly. • In general, you will use your operating system audio control to adjust the output volume. A good rule of thumb is that you want your radio’s ALC meter to just barely deflect.

Operating - transmit • When adjusting the output volume, be sure that you are adjusting the correct port. Many computers have both a headphone out and a line out. Both can be used for PSK 31, but each will have separate controls.

Operating – signal reports • In PSK 31, the most useful signal report is your IMD (inter modulation distortion) measured in d. B. • IMD’s are measures using dead air. Most software will give you an IMD report. You should strive for an IMD of less than – 20 d. B. • The most common cause for a bad IMD is to much audio drive into the mic. • The solution is to turn back the audio drive using your computers audio configuration.

Operating - QRP • PSK 31 has an incredible ability to pull signals out, therefore we should all strive to use as little power as possible. • The experts are saying use 30 watts • Barry says, “Use 5 watts or less!”

Frequencies • Here is list of suggested operating frequencies. 1838. 15 k. Hz 3580. 15 k. Hz 7070. 15 k. Hz 14070. 15 k. Hz 21080. 15 k. Hz 28070. 15 k. Hz 28120. 15 k. Hz 10137. 15 k. Hz 18100. 15 k. Hz 24925 k. Hz

Web Resources • Web Resources: – General Info: • http: //www. packetradio. com/bbbb. htm • www. aintel. bi. ehu. es/psk 31. html • psk 31. org – Interface Cables • http: //www. geipelnet. com/barry/PSK 31. pdf • www. packetradio. com/psk 31. htm • www. westmountainradio. com