After my incredible journey underground with the FT-818 this past weekend, I'm planning another trip, this time with a dipole cut for 40m, and a matching unit that will almost certainly be needed, given the configuration underground.
A problem that I mentioned in my write-up was that of time-keeping, which I had fully allowed for in my first trip underground. Thanks to the good timekeeping of my mobile phone's internal (non-internet connected) clock, the Raspberry Pi could be kept within about 1.5-2 seconds of the correct time underground, and provided a time update for the Pi if it had to be rebooted (for every second that passes when it's not running, the Pi loses that much time).
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| 40m signals get deep underground, but GPS and mobile internet, and the time services they provide, don't, making FT8 etc difficult, but not impossible, to use. |
Whilst we have a lot of modes that don't need time synchronisation - PSK-31 and OLIVIA are obvious examples - it struck me that, under the domination of Joe Taylor's software and modes, we have as a hobby gone down a bit of a funnel towards a potentially problemtic dead end: that of needing accurate time synchronisation for all of them.
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| Receiving FT8, with a ~1.7s time error, deep underground. |
Undergrounding is, of course, so niche as not ever going to be a motivator to move away from time-dependant digital modes. GPS dongles allow us to maintain even better time in the absence of mobile internet signals, but are an added, if small complexity, and for Pi use, means we need more USB ports than are available in a portable radio set-up. GPS is not, of course, available underground, anyway.
UPDATE: Thanks to a heads-up from M5MAT, the solution to the time sync problem lies at this page by KK5JY. It works! Download both parts of the software, and follow instructions under the 'Build the software' heading.
John, 2 solutions. GPS via bluetooth (hope the Pi has bluetooth) as I use in my portable setup. JS8Call has a build in feature you can sync the time with received signals, something that Joe should consider in future WSJT versions. Very useful especially for portable operations (DXpdeitions) were GPS or a cellphone is not always at hand. 73, Bas
ReplyDeleteThank you, Bas. The JS8Call sync feature I didn't know about - very practical and well thought-out, necessary feature.
DeleteGPS is a non-starter, as there is no signal underground. Yes, the Pi has Bluetooth. The sync with the phone is only a connection between Pi and phone and the phone's internally-kept time, which is fairly accurate and allowed me to keep within ~2s, but it would drift over time, of course.