![]() ![]() It is faster than most of us can type, as you can see if you look at the log Contestia is all caps but fastest and with the lowest latency. NVIS paths are not long DX paths, and there is not too much skip in the daytime, so we have favoured speed over noise immunity. The NVIS signal path and using the 8/500 modes In practice additive white Gaussian noise is not the only signal path impairment, and interleaving the data stream with Olivia and Contestia gives better resistance against QSB and impulse interference, at the cost of extra latency. Some progress has been made across the intervening years. We will use Contestia 8/500 and Olivia 8/500 and Olivia 16/500 Noise immunityĬq souttwesinet cq southwestv net cqi outhwest netĬq southwest net cq southwest net cq southwest net However, when you compare the noise performance Modes we use It can be demanding to tune in a net.Ī weak signal mode that can be decoded even if you can’t hear the signalĪs you can see, I’ve had to fight quite hard to get back to the speed performance of WW2 mechanical teleprinters. It occupies a narrower bandwidth than many of the other modes on here. Popular in the 1990s, still heard occasionally. This is a mode from World War 2, which gets the job done in 20 seconds. Obviously less if you can do 30wpm, but roundabout 20 seems common enough. Your browser does not support the audio element. I don’t do Morse, so I have to believe FLDigi that this is Morse at 18wpm. ![]() Let’s take as a benchmark the grand-daddy of the lot, CW. Choosing a data mode is a balance between speed, consumed bandwidth, robustness in the presence of channel noise, fading and interference, how critical tuning is, and features.ĬQ SOUTHWEST NET CQ SOUTHWEST NET CQ SOUTHWEST NET DE MX0IOA MX0IOA MX0IOA We have been testing a few more common datamodes for the proposed SW net. There are too many datamodes around - there are legacy ones from the days of mechanical teleprinters, there are some for specialised purposes like sending weather charts, and there are some which have simply been overtaken by newer technology. When you launch FLDigi, you have to select a data mode from quite a bewildering array of modes. You can use either program for most of what we do.ĭMR780 from the Ham Radio Deluxe software suite ![]() FLDigi works very well on a Raspberry Pi 3.įLDigi supports forms and ARQ which makes it better for emcomms users. HRD is windows-only, FLDigi runs on Linux, Windows 4 and Mac. The two most popular programs for running interactive 3 datamodes nowadays are FLDigi (free) and the DM780 program in the popular software suite Ham Radio Deluxe. This is of value to operators in an emergency communications (emcomms) setup, and one popular software suite, FLDigi, is part of the NarrowBand Emergency Messaging Software NBEMS. Datamode software can be set up to transfer a bit-perfect copy of the original text, automatically requesting retransmissions (ARQ 2) if required. However, if you are going to use a computer than you can change the line code from on-off keying to something else, gaining robustness against noise or transient corruption. One datamode has been widely used in Amateur Radio - Morse Code, and indeed digimode software can be used to run a Morse net, with the proviso that everyone uses the same speed machine generated Morse 1 and conditions are reasonably good. We have been experimenting with datamode nets which are a way of getting signals out with much less power and bandwidth requirements than SSB voice. The NVIS signal path and using the 8/500 modes. ![]()
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