Taron and Gene,
I haven't had DirecTV in a long time, but when I had it, I would routinely lose my picture during rain storms. Not all the time, but probably a few dozen times over five years. For HDTV, DirecTV now uses a 20" dish and Dish uses a 21" dish, so that may get them a bit more head room for rain fade.
VOOM is probably a bit more susceptible to rain fade because they use 8PSK with a lower FEC rate. 8PSK, which Dish Network is also now using for its HDTV, and what DirecTV will likely use in the future, is more susceptible to rain fade at comparable levels of error correction.
VOOM has capacity for 39 HD channels specifically because they use a 5/6 FEC rate with turbo coding, which gives them ~50Mbps per transponder. This lets them fit three HD channels per each of their 13 transponders with stat mux. Dish Network uses a 2/3 FEC rate with turbo coding, which gives them 39Mbps and change, or space for two HD channels per transponder with a little left over, but with somewhat greater resistance to rain fade, even when accounting for the lower radiated power of their satellite.
VOOM's Rainbow1 satellite may deliver higher power levels on the ground, but this still may not be sufficient to compensate for the low level of error correction during bad weather. It's also possible that the satellite's footprint delivers a slightly better signal--with more resistance to rainfade--to some regions and a lower signal in others. The problem of rainfade is obviously exacerbated when many customers have installs that were not optimally peaked (i.e. at least 50-55 on old scale).
Yeah, I used to have an 18" dish with Directv for years,and never experienced any break ups during heavy rain, and I can remember signals getting down in the mid 60's sometimes, with no signs of trouble. VOOM needs to do something about this. I haven't installed the larger dish, as I'm still on the fence about it. Besides, we really shouldn't have to spend the extra money just to enjoy VOOM thru light rain. VOOM should be taking care of this problem!
There's really nothing VOOM can do about it, because increasing the FEC rate to provide more resistance to rainfade would force them to drop anywhere from 1/4 to 1/3 of their HDTV channels. The only solution that doesn't involve elimination of HD channels is a larger dish.
If enough people complain, VOOM will do one of two things. Either they'll develop and deploy a slightly larger dish for new customers, say 20-22", or they'll increase the bandwidth dedicated to error correction and begin dropping a lot of HD channels, or they'll drop a few HD channels and significantly increase the compression (and degrade the picture) on the rest.
For prospective VOOM customers that are worried about rainfade, I would recommend you buy your own compatible 24" or 30" in advance (cost is about $30 + shipping), and have the installer use it instead. VOOM may deploy a slightly larger dish at some point, but until then, customers are on their own.