Make sure the dctrl-tools package is installed. It provides useful commands for searching the apt and dpkg package lists. To get a full description of all packages from a particular section that are installable with apt, run
grep-aptavail -F Section hamradio
This will show the full package metadata for every package in the
hamradio section. If all you want to see are the package names, run
grep-aptavail -n -F Section -s Package hamradio
If your system is set up for multiarch, the same package may show up more than once in this listing if it is built for more than one architecture. So to refine this further, use either
grep-aptavail -n -F Section -s Package hamradio | sort | uniq
grep-aptavail -n -F Section -s Package hamradio | sort -u
to sort the package list and remove duplicate packages with the same name.
Note that you will have to use the actual name of the section, which is different from the "human-readable" name that Synaptic shows in its GUI. For example, the searches above use the section name
hamradio instead of the string "Amateur Radio" shown in Synaptic.
See the man page for grep-aptavail for a full description of all options and some examples.