"/* frank */" wrote in message
...
I can install only a dipole of about 10 meters
(as inverted V).

Is there any project, any commercial antenna
of such length, that allow me to work all band
7 - 14 - 21 - 28 MHz ?

A very good antenna is a half-sized G5RV (7.5m each side). Excellent
results 7 - 28 MHz. Use tuned feeders (any length) and ATU.

73, Peter