Ian,
They probably are adequate for 'just listening'. In a lot of cases,
not using a ground works just fine too. Just depends on the
circumstances. Receivers just don't seem to be very 'picky' like
transmitters are. Since the 'ground' can sort of affect where you
hear things from, that's one of those 'things' to consider too.
There are very few 'perfect' antennas or installations, almost all of
them are a compromise in some way. The idea is to make the best of
what you got (Ooooo, is that a can of worms!). And the mostest
important thingy is to have fun at it.
- 'Doc