Transmitters, like any other 50/60 Hz AC power operated equipment,
should be grounded for safety reasons.

This is done automatically via the AC power cable regardless of what
floor level the transmitter is located.

If a balanced feedline is used to the antenna then no other grounding
is needed.

If the antenna is an endfed wire then, for good RF radiating
efficiency, there should be a low impedance connection between the
TUNER and ground. The transmitter can still be left to its own
devices.

If the transmitter and tuner are in the same box then the low
impedance ground connection and the AC power ground are in parallel
with each other. This results in an even lower impedance RF ground
connection.

On whatever floor the transmitter + tuner is located, to obtain a low
impedance ground, connect everything in sight together via the
shortest reasonably possible wires, including hot and cold metal water
pipes, the domestic plumbing system, central heating system, not
forgetting the incoming water and gas mains.

The more the merrier! But only 2 or 3 distributed wires can be very
effective.

Running a copper strip down an outside wall to a set of shallow buried
radial wires in your back yard will be useful provided the length of
the copper strip is NOT 1/4-wavelength at your favourite operating
frequency. A single ground rod is wasted time, money and labour.

But, in general, if you live several floors up in a block of flats, a
centre-fed dipole of random length, fed via a 450-ohm ladder-line,
plus a tuner plus ckoke-balun, will be the more convenient and RF
power-efficient option.

Any objections from the experts and Guru's?
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Reg, G4FGQ.