Thursday, 10 May 2018

More Pi?

I was waiting for the postman to arrive with excitement this morning.  He was bringing me a new Raspberry Pi - my latest ham radio fascination!

A wonderful aspect of the Pi - apart from its tiny physical size and low cost - is the fact that it boots up from an SD card, where all the software and data is held.

The Pi 3B+.  Much faster but still fits in Model 2 cases (if you use one).

This meant that, having only just downloaded the latest NOOBS package a couple of days ago, getting the Pi 3B+ going was simply a matter of removing the SD card from the Model 2 and sticking it in the card slot of the new unit.

I was glad, at this point, to see that the Model 2 SD socket, which had a relatively high failure rate in its spring-loaded card capture mechanism, has been abandoned in favour of a friction-only unit.  Very much better!  The Model 3B+ also comes with in-built WiFi connectivity, so there is no need for a USB dongle any more, at least if you have strong signal coverage around the house.  That's one USB port freed up, too!

Booting is, of course, pretty quick, and the WSJT-X software already downloaded earlier this week was sitting there on the SD card, needing only a click to start it up.  If only a Windows OS and files could be transferred across so easily!

Since posting about WSPR reception with the Model 2, I have progressed to using my ZLP data interface on the Pi, allowing transmission.  The Model 2 handled all this with no need for driver installation or complexities like that.  It was just slightly slow, in that the Pi took a second or so to activate the rig.  But not so slow as to cause problems.

Where the Model 2 couldn't work very well was with the very fast turnaround mode, FT8.  It took several seconds to decode everything, which made having a QSO impossible.

With the Model 3B+, and the 'Decode' menu item selected on 'Fast', FT8 works very well indeed.  If it's set to 'Deep' decoding, it's then too slow for QSOs.  There is a similar delay on deep decoding even when using my recent HP laptop.

Usefully, the Model 3B+ is fast enough to both handle digimodes and internet browsing at the same time, something the Model 2 couldn't really do at all.  It also looks like it is fairly good at keeping accurate time; most signals were within a small fraction of a second.  I think that, with an internet connection, the Pi keeps itself regularly time-updated, though I need to look into this a bit more.

Overall, I feel the latest Pi is equal in performance to my 1-year old HP laptop - at a tenth of the price!  It can also be easily deployed in my field shack, where there is only a 12V DC supply - much better than stepping up to 19V for a laptop.  All I need now is a 7" LCD screen for it, although even my spare LG monitor will work off 12V DC, sparing some cash for this month!

To give you a flavour, here's a 1.5 minute video of how it looks in practice (at 28MHz!).  CPU use with FT8 running is only about 13%, and the CPU runs at only a warm, not hot temperature:

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