Vertical wire aerial tests.
The perceived problem of omni-directional properties which, dare I say it, was considered as, and spoke of, as being "EVIL" !
Thickness [or gauge] of wire used at a TX and at a RX.

Marconi experimenting at Salisbury

Iron cables versus copper.
Best spark discharge to suit aerials under test.

Poor induction coil - great improvements necessary - present system "not filled for use by untechnical persons." {If words like unintelligent, unassuming etc etc are still in use, why today, do we say non-technical ?}

Note the interesting effects of resonance on tuning.

Coherer's - Marconi's  is the most sensitive, however not very stable and the tubes are likely to crack.  Maximum constraints are 1mA/1.5V otherwise the sensitivity is destroyed rapidly. Coherer's of moderate sensitivity are more stable assuming the constraints above are adhered to. Sensitivity is determined by the amount of Mercury used in the Coherer.

Experiments in 1892 over land and sea proved that the sea hindered the E/M waves less than the land.

Parabolic reflectors and Righi transmitters. λ/0.25 and λ/0.75 of the oscillations produced. Best achieved distance over which communications were possible was a mere three quarters of a mile.

Mr Marconi's experiments of 7th May 1898 carried out at the Needles and reported on by Commander Hornby R.N.
Success at 14½ miles using 10wpm.  Distance directly related to vertical height of aerial;  30' being allowed for 1 mile, 60' for 4 miles and 120' for 16 miles.  Height to be achieved using balloons and kites although good vertical heights could be achieved on ships. {To communicate with Hong Kong would have required a rocket launch but one still attached to earth}.

Limitations all round when only one frequency [waveband or Tune] was available.  Marconi to provide different Tunes so that two [or more] ships can communicate simultaneously with causing interference.

Sparks flying around everywhere, and operators receiving nasty shocks

HMS Defiance report on Telegraphy Without Wires. The reasons why a seagoing system is, as yet, difficult to manufacture.