WEBVTT NOTE Digital Operating on HF 1 00:00:00.000 --> 00:00:09.040 Sideband, by mode. Two rules, and they are different, which is exactly why the pool asks both. 2 00:00:09.040 --> 00:00:20.000 Question. Which mode is normally used when sending RTTY signals via AFSK with an SSB transmitter? 3 00:00:20.900 --> 00:00:24.180 Answer. LSB. 4 00:00:24.780 --> 00:00:38.180 Question. What is the standard sideband for JT65, JT9, FT4, or FT8 digital signal when using AFSK? 5 00:00:39.080 --> 00:00:41.648 Answer. USB. 6 00:00:42.248 --> 00:01:05.829 RTTY uses LSB. The WSJT-X family uses USB. There is no unifying principle; they are separate conventions from separate eras. Get it wrong and your signal appears mirrored in frequency and nobody decodes it. 7 00:01:05.829 --> 00:01:30.785 Where the modes live. Mode, Digital generally, 20 m; Location, 14.070 to 14.100 MHz. Mode, FT8, 20 m; Location, approximately 14.074 to 14.077 MHz. Mode, RTTY shift; Location, 170 Hz, the most common amateur HF figure. 8 00:01:30.785 --> 00:01:48.528 The FT8 slice is tiny, 3 kHz carrying dozens of simultaneous signals at 50 Hz each, which is the whole point of the mode's design. FT8's clock requirement. 9 00:01:48.528 --> 00:01:54.208 Question. Which of the following is required when using FT8? 10 00:01:55.108 --> 00:02:01.254 Answer. Computer time accurate to within approximately 1 second. 11 00:02:01.854 --> 00:02:19.529 FT8 transmits in synchronised 15-second slots and the decoder relies on knowing when each began. More than about a second out and nothing decodes, in either direction, so you appear to be transmitting into a void. 12 00:02:19.529 --> 00:02:32.226 Run NTP. This is the first thing to check when FT8 stops working, and it is routinely the answer. And the etiquette that follows from the slot structure: 13 00:02:32.226 --> 00:02:44.586 Question. Which of the following is good practice when choosing a transmitting frequency to answer a station calling CQ using FT8? 14 00:02:45.486 --> 00:02:52.090 Answer. Find a clear frequency during the alternate time slot to the calling station. 15 00:02:52.690 --> 00:03:10.341 Because transmissions alternate, the frequency the caller uses is free while they are receiving. Answering in a clear spot during the opposite slot avoids two stations landing on each other. Winlink and its protocols. 16 00:03:10.341 --> 00:03:27.271 Question. Which of the following describes Winlink? A. An amateur radio wireless network to send and receive email on the internet. B. A form of Packet Radio. C. 17 00:03:27.271 --> 00:03:37.261 A wireless network capable of both VHF and HF band operation. D. All these choices are correct. 18 00:03:38.161 --> 00:03:41.681 Answer. All these choices are correct. 19 00:03:42.281 --> 00:03:48.001 Question. What is another name for a Winlink Remote Message Server? 20 00:03:48.901 --> 00:03:51.381 Answer. Gateway. 21 00:03:51.981 --> 00:03:55.741 Question. What is VARA? 22 00:03:56.641 --> 00:04:08.233 Answer. A digital protocol used with Winlink. 23 00:04:08.833 --> 00:04:21.953 VARA and PACTOR are the two ARQ protocols that carry Winlink traffic on HF. Both are connected, point-to-point, error-corrected links. 24 00:04:21.953 --> 00:04:29.803 Question. How do you join a contact between two stations using the PACTOR protocol? 25 00:04:30.703 --> 00:04:40.023 Answer. Joining an existing contact is not possible, PACTOR connections are limited to two stations. 26 00:04:40.623 --> 00:04:54.463 Unlike a CW or SSB contact, there is nothing to break into. A PACTOR or VARA link is a negotiated connection between exactly two stations. 27 00:04:54.463 --> 00:05:04.243 Question. Which of the following is a way to establish contact with a digital messaging system gateway station? 28 00:05:05.143 --> 00:05:10.983 Answer. Transmit a connect message on the station's published frequency. 29 00:05:11.583 --> 00:05:14.903 Interference on an ARQ link. 30 00:05:14.903 --> 00:05:31.838 Question. What symptoms may result from other signals interfering with a PACTOR or VARA transmission? A. Frequent retries or timeouts. B. Long pauses in message transmission. C. 31 00:05:31.838 --> 00:05:39.970 Failure to establish a connection between stations. D. All these choices are correct. 32 00:05:40.870 --> 00:05:44.390 Answer. All these choices are correct. 33 00:05:44.990 --> 00:06:05.145 All three are the same underlying event: ARQ detecting errors and asking again. Interference does not corrupt the message, the protocol will not deliver corrupt data, it slows the link down and eventually drops it. 34 00:06:05.145 --> 00:06:05.710 AREDN. 35 00:06:05.710 --> 00:06:15.516 Question. What is the primary purpose of an Amateur Radio Emergency Data Network (AREDN) mesh network? 36 00:06:16.416 --> 00:06:23.616 Answer. To provide high-speed data services during an emergency or community event. 37 00:06:24.216 --> 00:06:42.641 The mesh networking from the Technician track, organised as a deployable network: repurposed Wi-Fi hardware on amateur frequencies, self-healing, carrying video, file transfer, and messaging at speeds no HF mode approaches. 38 00:06:42.641 --> 00:06:44.376 When nothing decodes. 39 00:06:44.376 --> 00:07:01.247 Question. What could be wrong if you cannot decode an RTTY or other FSK signal even though it is apparently tuned in properly? A. The mark and space frequencies may be reversed. B. 40 00:07:01.247 --> 00:07:12.776 You may have selected the wrong baud rate. C. You may be listening on the wrong sideband. D. All these choices are correct. 41 00:07:13.676 --> 00:07:17.196 Answer. All these choices are correct. 42 00:07:17.796 --> 00:07:37.551 Three failures with one symptom, and the diagnostic order that resolves them: Sideband. LSB for RTTY, USB for the WSJT-X family. Try the other one, it is one click and it fixes this more often than anything else. 43 00:07:37.551 --> 00:07:54.510 Mark/space reversed. Most software has a "reverse" switch, which is the same fix from the other direction. Baud rate and shift. 45.45 baud with 170 Hz shift is standard amateur RTTY. 44 00:07:54.510 --> 00:08:09.699 For FT8 specifically, add a fourth: check the clock. Check yourself. You are set up for RTTY on 14.080 MHz and hear signals but decode nothing. First thing to try? 45 00:08:09.699 --> 00:08:24.236 FT8 shows plenty of signals on the waterfall and decodes none of them. Likely cause? Two stations are exchanging a Winlink message via PACTOR. Can you join? 46 00:08:30.236 --> 00:08:49.640 The other sideband. RTTY is LSB by convention; if it was left on USB, mark and space are reversed. Computer clock more than about a second out. FT8 needs accurate time to locate the 15-second slots. No. 47 00:08:49.640 --> 00:08:56.076 PACTOR connections are point-to-point; there is no contact to join.