I am sorry, but I misstated one thing. Double-conversion
receivers may tend to be somewhat more selective than a
single-conversion receiver due to the combined selectivity of
the first and second IF's, but the big advantage is that you get
rid of images more easily with the first mixer and a high IF and
most of the selectivity comes from the low IF of the second
mixer. Sorry for the confusion. Nothing like reading one's own
post after putting it on the list.

Martin