Marshall Amplification Field Marshall 100 Owner's Manual page 31

The key to getting the best range from your receiver is altitude.
High spots are least likely to be in a shadow. If you're not
getting a good signal, the first thing to do is get higher. Driving
to the top of a hill or climbing a water tower can dramatically
increase your transmitter's range.
Ow ner's Manual
Hint:
When tracking a
weak signal, hold your
antenna as high as you
can reach instead of
keeping it at eye level.
Standing on your
vehicle will also boost
the signal significantly.
Page 31