I decided to measure the Astra 2E and 2F signal again after replacing the Inverto Quad LNB for an Invacom Quad. The signal strength has improved but it's difficult to give all the credit to the Invacom LNB since other factors may play a significant role as well, like colder weather, less obstacles without leafs on surrounding trees and also possibly better dish alignment. But the signal strength itself is not the main point of this article. It's the variations in the strength during the day.
During a regular daily observations, the pattern of signal variations became clear and quite consistent. While Astra 2F is much less prone to signal drops, watching 2E makes it a roller coaster ride experience in Prague, Czech Republic. Despite being in the out-of-footprint area, it's quite easy to lock onto any 2F transponder, at any time of day, with a 180 cm PF one-piece dish. The LNB can be tweaked to improve signal on either V or H polarization by approximately 1 dB but I never managed to make get most of the signal on both polarizations at the same time.
With Astra 2E, the situation gets much more complicated at 00:30 AM CET. Every day at this time, the signal on all 2E transponders drops rapidly below receivable levels. Although the Dreambox 500/820 HD tuner shows 7.0 dB, the DVB-S2 transponders drop out and a satfinder shows 6.5 dB only. Perhaps the receiver tuner (BCM4505) is not capable of dealing with such low signal, even though 6.6 dB should be enough to get a stable picture. The Satfinder is perhaps more reliable. On the other hand, the DVB-S transponders hold more steady - the picture does not start breaking up till 6.1 dB, which is below the official minumum.
About 75 minutes later, at 2 AM, the signal is back to lockable levels on some of the 2E transponders but doesn't get to standard values for several more hours. By 10 AM, all 2E transponders are locked again. The most signal comes in during primetime, at 20:00 - 23:00 CET, almost 3 dB more on some transponders. The signal bump is not that significant, yet still present, on Astra 2F transponders. 2F remains receivable around the clock with a slight weather proof safety margin.
Another critical moment comes around noon, when couple of 2E transponders get to the very edge of being lockable and some of those even fade out. This also lasts about 2 hours.
It's going to be interesting to see what Astra 2G brings. It's impossible to estimate much before the satellite is in orbit. The UK spotbeam will most likely have different characteristics, given the fact 2G is manufactured by Airbus, while 2E and 2F are EADS Astrium products... and even then 2E and 2F behave differently in fringe reception areas.
The following table shows signal levels measured with Dreambox 500 HD in December 2014. The SNR values will vary with different satellite receivers. For example the Vu+ Solo 2 different SNR values than a Dreambox. The minimum SNR needed for stable reception on DM500HD as well as DM820 HD differes depending on the broadcast standard. For DVB-S at 5/6 FEC, the minimum SNR needed is 6.2 dB, while 7.2 dB is necessary for DVB-S2/8PSK at 2/3 FEC