Such an antenna will be huge, see ARRL Antenna Book (17th Edition).
Example: It states a 3.5 MHz to 28 MHz discone would be 75 feet high and
huge circular areas above and below as well.

But from 7 MHz to 28 MHz, an HF discone would be about 36 feet high and the
above circular portion about 26 feet.
Still a big fella.

Construction details are given in the ARRL Antenna Book - mine is 16th
edition
Photos included

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73 From The Signal In The Noise
Caveat Lector Ya All
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"Fumper" wrote in message
...
I am looking for an HF discone 0 to 30 MHZ antenna. Any Ideas?
Steve