Amateur Radio Digital Modes Focus on Field Day Use Which bands? Why now? Amateur Radio Digital Modes Focus on Field Day Use N6MDV K6VHY November 14, 2017 How much power? When and who can I talk to …? What mode?

Field Day 2018 Digital Modes It has been suggested we do more digital modes in 2018 Why? Enables contacts on higher bands despite poor sunspot propagation Lower SNR required than phone contacts Develop additional skills for weak signal emergency communication Easier to learn than CW for weak signal use May be fun to learn and try new things Possibly attract additional operators who don’t do CW or Phone Why not? Takes effort to prepare for new radio connections, software, … Good use of operator time? Contact rate is slower than with a good CW or Phone operator Additional equipment needs: decoding computer, TNC Operators need to learn new skills Interference with other W6HA radio stations in FD ops RFI or scheduling of equipment

Sunspot Values Continue to Decline Reduce propagation at 20M and above Sunspots affection ionization Ionosphere refract radio waves Bends waves back to earth Responsible for long range propagation Declining propagation has reduced our contacts on higher frequencies CW and digital modes need less SNR than phone To maintain higher contacts need to Use modes that need less SNR CW would be best Use lower frequency bands 80 and 40 meters Smoothed Sunspot Numbers – Predict Propagation 2008 4.2 3.5 3.3 3.3 3.5 3.2 2.8 2.7 2.3 1.9 1.8 1.7 2009 1.8 1.9 2.0 2.2 2.3 2.7 3.6 4.8 6.1 7.1 7.6 8.3 2010 9.3 10.6 12.3 14.0 15.5 16.4 16.8 17.4 19.6 23.2 26.5 28.8 2011 30.9 33.4 36.9 41.8 47.6 53.2 57.2 59.0 59.5 59.9 61.1 63.4 2012 65.5 66.9 66.8 64.6 61.7 58.9 57.8 58.2 58.1 58.6 59.7 59.6 2013 58.7 58.4 57.6 57.9 59.9 62.6 65.5 68.9 73.0 74.9 75.3 75.9 2014 77.3 78.4 80.8 81.9 80.5 79.7 78.6 75.6 70.8 67.3 65.4 63.7 2015 61.9 60.5 59.7 59.1 57.8 55.5 53.1 51.2 49.7 48.6 47.4 46.1 2016 44.8 43.2 41.4 39.4 37.5 36.6 35.9 35.4 34.7 33.5 31.8 30.1 2017 29.2 28.6 27.9 27.3 26.7 25.8 24.5 23.0 21.8 20.9 20.2 19.6 2018 18.8 17.7 16.7 15.5 14.5 13.7 13.4 13.1 12.5 11.8 11.1 10.7 2019 10.1 9.6 9.3 9.0 8.9 8.9 8.9 8.9 9.2 9.5 9.8 10.2 2020 10.5 10.8 11.3 11.7 12.3 13.2 13.9 14.5 15.2 16.2 17.6 19.0 Next few years will be lower than last few years 2017

Digital is a Small Part of FD Traffic But still an opportunity for many contacts We have about 1200 contacts. If we add same ratio we will have another 100 contacts -> 400 points

Chart Suggests that PSK31 needs 20 dB less SNR than SSB Mode SNR Net data speed Needed Eb/N0 in 2500 Hz in bits/s SSB voice +10 20* +31 dB CW (ZRO-test, by ear) -18 0.54 +16 dB** CW (QRSS-3, waterfall ) -26 0.13 +14 dB** CW (RSCW, 12 wpm ) -12 4 +13 dB** OPERA-2 -23 0.23 +14 dB*** RTTY -5 32 +14 dB PSK31 -10 31 +9 dB WSPR -29 0.45 +5 dB**** WSPR-15 -38 0.056 +5 dB**** JT65 (for EME) -24 1.54 +5 dB**** Coherent BPSK on VLF -57 0.0058 -1 dB Theoretical limit -1.59 dB *very crude estimate ** based on peak average power; peak power 3 dB higher *** peak power is 3 dB higher; 2 dB lower if counting CRC-bits as information **** not counting energy in synchronization bits; otherwise 3 dB more Chart Suggests that PSK31 needs 20 dB less SNR than SSB

SNR relative to noise in a 2.5 kHz SSB bandwidth MODE BW(Hz) THRUPUT SNR(ave) SNR(pk) SNR(ave) Hz wpm dB dB dB at 1 char/sec SSB 2500 250 +6 +10 CCW 10 12 -15 -12 -15(12 wpm = 1 c/s) Hell 250 25 -13 -7 -17 WSJT 5 7 -22 -22 -20 PSK31 30 30 -12 -9 -17 RTTY 50 60 -9 -9 -17 Chart Suggests that PSK31 needs 20 dB less SNR than SSB However, other factors likely apply: Lower transmit power Congestion and overlap in the digital modes area of band General noise floor increase on field day May just need to try it to see if modeling projections are correct.

PSK31 Test Results Based on experiment of two HF rigs, noise generator, attenuator SNR 29.97 Perfect copy of 12 lines of text. 20.02 Perfect copy of 9 lines of text. 12.03 Perfect copy of 16 lines of text. 11.08 Near perfect copy of 13 lines of text message. 9.90 Much of the 11 lines of text are intelligible However, there are missing characters and a few missing words, 8.96 Much of the 12 lines of text are intelligible 7.70 Message text is readable but with considerable difficulty. 7.08 Message text is barely readable, occasional words distinguishable. 6.38 Message text is barely readable, occasional words distinguishable. However, much of the time Digipan was not able to demodulate and decode the message. 5.1 At this SNR the message text is not readable. Digipan was not able to demodulate and decode any of the message. But, I could still here the PSK31 signal. This experiment suggests that the previous charts are possibly 10dB too conservative Source: James A. Frazier, Jr., KC5RUO https://bpsk31.com/articles/psk31-vs-cw/

FD Propagation 7PM Phone Blue, Yellow, Brown, Red. Digital all colors Blue is at SNR 45 dB – recommended value for SSB and consistent with previous experience Gray is modeled at SNR 30 dB – likely area for PSK31. CW would be better yet. Based on PSK 31 needing 20dB less SNR and Transmit power set at 25W vs 100W for SSB i.e., 6dB (45-20+6 ~ 30 dB) VOAAREA modeling

20M Propagation FD 2018 Phone Blue, Yellow, Brown, Red 20M Propagation FD 2018 Phone Blue, Yellow, Brown, Red. Digital all colors Phone Phone 5PM 9AM Phone Phone Blue is at SNR 45 dB – recommended value for SSB and consistent with previous experience Gray is modeled at SNR 30 dB – likely area for PSK31. CW would be better yet. Based on PSK 31 needing 20dB less SNR and Transmit power set at 25W vs 100W for SSB i.e., 6dB (45-20+6 ~ 30 dB) VOAAREA modeling

Common Digital Modes – Potential for FD Use RTTY Radio TeleTYpe Two tones: 2295/2125 Hz Transmission speed: 45 baud, 5 bit characters => 60 WPM Bandwidth: 250Hz Typically at xx.080 – xx.099 part of the band PSK31 Phase shift Transmission speed 31 baud, varicode, => 50WPM Lower case characters are fewer bits Bandwidth: 60Hz Typically at xx.070 portion of band MFSK16 16 frequencies with Forward Error Correction (FEC) Transmission:15.625 baud 16-FSK, 15.625Hz spaced tones Bandwidth: 384Hz => 30WPM with FEC Known for contesting and faster Known for long rag chew – brag tapes Photos courtesy of http://hfradio.org.uk/html/digital_modes.html See that page for sounds also.

Another Option FT8 – New Mode July 2017 FT8 similar to JT65 but 4 times faster 15 second transmit and receive intervals Entire QSO in 1 minute Limited payload: call signs, signal report, minimal exchange E.g. grid squares, 73 Includes Forward Error Correction (FEC) May be in use this field day, as it is new and hams like new Reportedly even lower SNR needed than CW “SNRs from my receiver below –10 dB (measured in a 2,500-Hz bandwidth). Some of the 22 QSOs may have been difficult to complete on CW.” The new mode is named after its developers, Steven Franke, K9AN, and Joe Taylor, K1JT. The numeral designates the mode’s 8-frequency shift keying format. Tones are spaced at 6.25 Hz, FT8 signal occupies just 50 Hz. FT8 requires accurate time synchronization. An auto-sequencing feature offers the option to respond automatically to the first decoded reply to your CQ. Google ft8 for the software

How is Digital Done Computer connected to radio via TNC Computer connection to sound card Software on computer decodes sounds displays waterfall Operator clicks on open frequency space to call CQ or on a call Software auto loads other person’s call sign into macros Press appropriate Function key to transmit macro Four macros when running cq fd de w6ha k <call> 3A LAX 3A LAX de w6ha k <call> tu <call> agn? Agn? de w6ha k Three macros when search and pounce <call> de w6ha w6ha k <call> tu 3A LAX 3A LAX de w6ha TNC = Terminal Node Controller MPC = Multi Protocol Controller De = “this is” K = “over, go ahead” Agn = again abbreviation fd = field day tu = thank you

Computer Sound Card Connection & USB Control Connection Example Hook Up for PSK31 ICOM 7000 Radio RIGblaster TNC Computer sound card & USB connection CI-V and accessory connection on radio Strong PSK31 signal Decoding via Digipan software Macro buttons across the top Multiple signal decode on right Waterfall below ICOM 7000 multimode radio CI-V ACC Computer Sound Card Connection & USB Control Connection RIGblaster TNC Sound, control, CI-V link CW and digital modes

Concerns, Issues, Possible Solutions Inter-station interference with two transmitters on same band Band pass filters do a fine job keeping different bands separate But not for two stations on the same band Other groups make it work Radios with good internal filters / selectivity / low noise (e.g., KX-3 and K3) Careful placement of antennas Keep them far apart and oriented so nulls point toward each other Run rates will be slower than phone – likely true Data from 2015 shows the following results at non-optimal time of day, i.e, few stations on the air midnight or with poor antenna propagation on Sunday morning Digital log data Av time between QSO 2.6 minutes Min time between QSO 0 minutes – we might get our average time better Phone log data Av time 1.6 minutes per QSO (Sunday at 10 AM) Av time 1.06 minutes per QSO (Saturday 9 PM) AB6UI rate on FT8 was a QSO 4 minutes on average – new to mode Expect digital may be 2X slower than phone – with practice may do better

FD 2015 Details: Digital Contacts PSK31 ICOM 7000 nominally 20-30 Watts Rigblaster plug and play Lap top Windows 8.1 running digipan Total QSO: 45 10 at midnight Saturday, just to get some Great national antenna coverage, just few operators 35 Sunday AM starting at 7:30 AM Limited antenna coverage at that time of day Stats on QSO rate Saturday night Av minutes between QSO 4.5 minutes Max time 9 minutes Min time 2 minutes Sunday morning Av minutes between QSO 3.5 minutes Max time 10 minutes Min time 0 minutes If throw out the long times on Sunday AM, presuming equipment or people distractions Av time between QSO 2.6 minutes Compared to phone run rate 10 AM Sunday 1.6 minutes per QSO 9 PM Saturday 1.06 minutes per QSO With double points for digital, the points per minute are close with digital when number of stations has dwindled

FD 2015 Details: Run Rate Thoughts 20M station first 3 hours Saturday 1 minute each -- FAST 20M station 10AM Sunday 2.14 minutes each– Slowing 40M station first 3 hours Saturday 40M station Saturday 9PM 1.06 minutes each -- FAST 40M station 10 AM Sunday 1.36 minutes each Slowing Digital station better case 2.6 minutes per QSO Observations When there are plenty of stations And with good antenna Band Transceiver Operators A run rate on phone can be 1 QSO per minute for extended periods of time With digital PSK31, run rates appear to be close to the slower run rate on phone Possibly could be faster with more stations??? Or possibly just use to collect additional contacts

Next Steps for W6HA Field Day 2018 Decide if we want to do more digital Get interfaces and software for the rigs that will be used Train / practice using digital modes Decide how it will be used on field day As a separate CW / Digital station enabled for every band As an occasional mode on the different band stations e.g., 15, 20, 40 When should it be used? When phone run rate drops below a certain level? Which mode(s) Consider pushing ARRL publications to encourage: Digital use given low sunspots Mode based on portion of hour, i.e., psk on the hour, RTTY on the half – FT8 As a club set up a digital / SSB experiment day in the park Confirm that the mutual interference will be small Hands on practice and testing of the rigs / SW

Questions? Thoughts?