Longwire and Diople optimal lengths.

[admin]

There are lots of sources for this info, but here are some that seem close to the mark:
Starting out simple:

End-fed longwire, 9:1 unun and recommended feedline lengths -good and to avoid.

LongWireLength.pdf

LongWireLength_Unun.pdf

Dipole lengths are given in this table:

dipole_wire_length.pdf

And that popular Windom:

windom_dipole_howto.pdf

For completeness, two commercial examples:

Bullet-End-Fed-Antenna-Notes.pdf

Buckmaster_ocfd.pdf

If you prefer to design your own antennas with a computer model, the grand-daddy of them all is EZNEC, available for free download at:
https://www.softpedia.com/get/Science-CAD/EZNEC.shtml
Be aware that this is a perfectly functional download, but if you want updates etc. (details at this link), you need to part with $99. -Or use a totally free older version.
Runs on all modern versions of Windows, and also Wine for Linux.