Wheres RadOp when you need him?
If I understand the question properly, antennas typically come as part of a field deployable
radio kit. You can also build/attach suitable antennas to a deployable field radio kit.
There are alot of radio kits for varous applications so the answer to the question
is broad. For field deployability, the intention is to set up the system including the
antenna (usually supplied with the kit) as quickly as possible.
The 'net offers alot of MF, HF, VHF, UHF, and microwave antenna theory and product
information. It might be a good idea to start reading up on antenna theory basics,
transmission lines, and radio system block diagrams.
This is a good starter:
After that, various radio kits come with with own antennas. Sometimes, the antennas are
busted, damaged feed line, or defective connectors, or the radiation pattern isn't suitable
for the application. Then a best effort custom built punch in the face antenna has to be
constructed for the desired functionality; directional or omni-directional for the band,
frequency, and power output. Understanding the application, the characteristics of the
frequency band, the possible locations of stations (yours and enemy), output power
levels, and reception limitations lead to figuring out what type of antenna to build.
Having test equipment to measure the SWR and field strength is nice, but if you have
to eye-ball it, you may wish to have quick antenna design memorized and calculation
in your head. For instance, a 6.8 MHz HF quarter wave dipole has legs approximately 17.25'.
A higher frequency will have shorter legs, a lower frequency will be longer.
Radio work is fun. Enjoy the job.