Unfortunately the demonstrations are not accurate representations of real world conditions. The EXTFSK64 tests were done on a six core, 3 GHz CPU with less than 40% CPU load. The "low end" laptop with ETFSK was not faced with anywhere near the CPU load exhibited in most RTTY contest situations. Neither demo stressed the USB bandwidth (polling two rigs, and running a sound card based panadapter) or stressed the memory capability (processing a cluster feed at > 100 spots per minute, polling two rigs with multiple commands every 10 to 50 msec, logging and duping QSOs from other stations on a multi- station LAN).
A significant number of amateurs run "hand me down" processors that barely meet the N1MM+ minimum standard (1.6 GHz processor, 512MB/1GB RAM) which are then "loaded to the gills" with CPU and memory intensive processes. Measurements at microHAM in 2010 showed +/- 2ms jitter with EXTFSK and an FTDI USB to Serial UART. 4 ms p-p jitter already represents nearly 20% of a bit period - equivalent to changing the path length by more than 700 miles within each bit - and will result in a noticeable loss in decoder signal to noise ratio even with "strong" signals. 73, ... Joe, W4TV On 3/24/2018 1:43 PM, M. George wrote:
This is a bit of a cross post related to Elecraft K3/K3S internal FSK timings generated with a USB FDTI chipset com port. I wanted to get some hard measured numbers in a video so I took the time to make the following two videos. Sorry if you are subscribed to multiple lists and get a duplicate or two on the video links. I do think it's interesting... if you can make it through my verbose videos! They don't lack for details on making sure I'm transparent with the setup. If anything, it will give something to reference as the discussion/debate continues. Video #1 <https://www.youtube.com/watch?v=FN0SlOHcMQw> Showing Higher End PC's Generating FSK Diddle Timings: https://www.youtube.com/watch?v=FN0SlOHcMQw Video #2 <https://www.youtube.com/watch?v=L48mebqLigs> (new as of this morning) Showing a 13 year old single core, 1.1ghz Pentium Laptop Generating FSK Diddle Times (32 bit Win 7 with MMTTY): https://www.youtube.com/watch?v=L48mebqLigs Max NG7M
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