From Dave G3YMC

ON7YD wrote:

The result is that in most cases (and for dimensions that are
practical for hams) the efficiency of a short vertical will be a lot better
than from a loop with similar dimensions. Only those who suffer from
extreme environemental losses might be better off with a loop.

There is always the exception to this rule.  I have recently done extensive 
tests
with a vertical against my loop (see
http://www.dsergeant.btinternet.co.uk/vertical.htm. In my case performance of a
vertical is in most cases inferior to the loop. A transmitting loop is a very 
viable
antenna for many amateurs, but it must be done properly - no 1m square things 
with
thin wire.  The thing which has slowed down its use is this sort of negative
reaction.  Someone with more real estate could construct a loop working far 
better
than the one I have - same policy as with verticals, make it big, make it of 
thick
wire etc.  I shall probably take down my vertical shortly and restore it to an 
hf
Butternut, it certainly doesn't work at this QTH and the current level of 
activity on
the band hardly justifies it.

73s Dave G3YMC
[email protected]
[email protected]
http://www.dsergeant.btinternet.co.uk