VAS images are transmitted continuously 24 hours per day every half hour. Not for VHF reception of the polar orbiters in the 137 MHZ VHF band. Excellent pictures can be received on the VHF frequencies under a heavy canopy of trees. A chain saw is needed for Geo-stationary reception. Trees in the way mean you don't get a picture, at least in the summer time.
Trees have a tendancy to block the microwave signals.
Usually you can find SOME place to put the dish to see the satellites. Mounting on a pole or your roof may help the situation. This is the only magazine in the US devoted to environmental satellites. It contains many articles and construction projects by RIG members. A unique feature is high quality centerfolds of satellite imagery.