shuisheng wrote:
I am new to antenna field. Anyboday can explain to me what is low
profile antenna? Many thanks.

An underground buried antenna would be an example of a
very low-profile antenna. Virtually invisible antennas
are another example. Disguised antennas (e.g. flagpoles)
are another example. Attic antennas are another example.
In general, low-profile antennas are inferior in performance
to high-profile (extremely visible) antennas.
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73, Cecil http://www.qsl.net/w5dxp