Polymath wrote:

Radio Hams
are qualified to design, build and then
operate their own pieces of equipment.

However,

[ ] In the UK, no repeat no licence of any kind is necessary to
specify, design, construct, modify, repair, own, or (under some
circumstances) test an Amateur transmitter.

[ ] A pass in a current examination for a UK Amateur Licence qualifies
the successful candidate for the issue of a UK Licence. Holders of the
appropriate levels of licence are permitted to operate transmitting
equipment that is not subject to a formal approvals procedure, and to
carry out technical investigations. A qualification for a Licence, or
the Licence itself, is not, repeat not, a qualification to specify,
design, construct, modify, repair, or own transmitting equipment.

from
Aero Spike