Digital Transition

So it turns out we're going fully-digital in March (the Midhurst transmitter). This, apparently, explains why we've got absolutely shonky Freeview reception at the moment. Channels disappearing, then re-appearing, appallingly broken-up pictures and sound etc. Ahh, digital. Degrades so much more finally than Analogue...


My parents went this time last year. My dearly sainted mother described the process as "the picture was horrible or unwatchable for a couple of months. Then your father retuned and it got better".  Well, we've got the same.

Since about Jan 10th , the BBC multiplex (Mux-1) has been fine. But availability of everything else has been spotty: poor to nonexistent during the day, occasionally fine in the evening, rarely good late at night.

Nerd that I am, I've managed to track this behaviour on my Myth box using "tzap". 

Here's a working channel:

 tzap -a 0 -f 0 -d 0 -c scan_localfreq_channels.conf 'BBC ONE'
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
reading channels from file 'scan_localfreq_channels.conf'
tuning to 754000000 Hz
video pid 0x0258, audio pid 0x0259
status 1e | signal 0000 | snr 0000 | ber 001fffff | unc 0000303d | FE_HAS_LOCK
status 1e | signal 0000 | snr 0000 | ber 000000d0 | unc 00000000 | FE_HAS_LOCK
status 1e | signal 0000 | snr 0000 | ber 00000080 | unc 00000000 | FE_HAS_LOCK
status 1e | signal 0000 | snr 0000 | ber 000001c0 | unc 00000000 | FE_HAS_LOCK

And here's one that's probably not right now:

tzap -a 0 -f 0 -d 0 -c scan_localfreq_channels.conf 'Channel 4'
using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0'
reading channels from file 'scan_localfreq_channels.conf'
tuning to 826166670 Hz
video pid 0x0230, audio pid 0x0231
status 1a | signal 0000 | snr 0000 | ber 001fffff | unc 00000000 | FE_HAS_LOCK
status 1a | signal 0000 | snr 0000 | ber 001fffff | unc 00000000 | FE_HAS_LOCK
status 1a | signal 0000 | snr 0000 | ber 001fffff | unc 00000015 | FE_HAS_LOCK
status 1a | signal 0000 | snr 0000 | ber 001fffff | unc 00000000 | FE_HAS_LOCK
status 1a | signal 0000 | snr 0000 | ber 001fffff | unc 00000000 | FE_HAS_LOCK

Spot the differences? Status = 1e on BBC1, 1a on Channel 4. Constant high Bit Error Rate on C4, variable but much lower on BBC1.

Later in the evening I might get to see actual values for "signal" and "snr" (Signal-to-Noise) on both channels, which is an indication all is working well at the minute.

Now the experience of my parents above means basically that I should just sit back, wait until the switchover is complete in mid-March, and then start worrying if I can't get it to work again. And I'm mostly resigned to this. But I have a nagging feeling I'm actually looking at a local problem, not a switchover artefact: Up in the roof we've got a signal booster, tucked away where we can't see it. And I'm wondering whether it's gone "phut" recently....

Back Garden Astronomy - 2012-01-13

Very cold out tonight (Google says currently -2C) which combined with poor optical conditions meant only a short go with the 'scope tonight of about an hour.

Poor conditions were a disappointment; I think it's mostly dew / fogging on the scope (I was taking care to keep my frosty breath away as much as possible). Couldn't get good focus on stars and a massive halo around Jupiter.

Nonetheless, got some seeing in of:

• Jupiter - Closer to vertical than on previous views (well; it's just past South at peak altitude, what did I expect?). Nice to see an out-of-plane moon although I've had to verify in Stellarium that it wasn't anything else (Callisto; Io's on closest-to-Jupiter in-plane duty tonight).
• Betelgeuse - Much redder than I was expecting, although some of that might be exaggerated due to diffraction and the focussing problems I was having. Very distinctive though.
• Aldebaran - Again, much more colour than I was expecting
• Pleiades - Would be a fascinating object to study with the right equipment; I was getting too cold to do it justice
• Procyon - Again, quite distinctive but couldn't get steadied down enough to have a good gander.

As ever, though, it's the surprises that make it. As I was eyes-out looking around for a good target, at about 2045ish, a very large very bright orange fireball went over from about Jupiter (South-South-West) pretty much due-north. It's the first time I've seen one leave a big trail, with visible "sparks" breaking off. It got right overhead and disappeared (burnt out?) about 45 degrees above North. The whole thing only lasted about 10 seconds from appearing, growing a tail, particles streaming off, to disappearing. Very impressive. If I lived elsewhere and it'd been East-West I'd have guessed it might have been Phobos-Grunt re-entering.