Hi Derek
According to the history of the Eastern Province Command Signals Unit, the record of 130 miles was claimed by Captain Sadler of the Natal Carbineers in 1911, using a 5 inch mirror from Compassberg to the Cockscomb Mountains , to Major Home.
This article gives a summary of typical distances of various methods of communication used during the Boer War.
The Military History Journal
Vol 11 No 1 - June 1998
WIRE AT WAR -
Signals communication in the South African War 1899-1902
by Major J D Harris, sometime of the Queen's Dragoon Guards
BOER WAR COMMUNICATIONS EQUIPMENTS AND PERFORMANCES EQUIPMENT MARCHING DISTANCE(RANGE) SPEED(WORDS PER MINUTE) COMMENT
Electric telegraph Limited only by length of line 300 24 hours service
Telephone Limited only by length of line 200 24 hours service
Helio 12" reflector 83.5 miles (134 km) 8-16 Sunlight
Helio 10" reflector 83.5 miles (134 km)a 8-16 Sunlight
Helio 9" reflector 83.5 miles (134 km) 8-16 Sunlight
Helio 5" reflector 52.5 miles (84.5 km) 8-16 Sunlight
Helio (saddle) 3" reflector 37 miles (59.5 km) 8-16 Sunlight
Helio (limelight) 5" reflector 31 miles (50 km) 8-16
Helio (moonlight) 5" reflector 12 miles (19.3 km) 8-16 Strong moonlight
Lamp, trench pattern shutter Short and variable 4 Lamp, electric,
daylight signalling Not stated, estimated 30 miles (48.2 km) 8-16
Flags, Largeb Difficult over 5 miles (8 km) 2c Faster with silk flags and Morse code, slower using semaphore
Notes:
a. Using the 10-inch reflector in ideal conditions, marching distance of over miles (160km) were recorded in both India and China.
b. Pigeons were also used, as were searchlights in conjunction with shutters, as Admiral Sir Percy Scott records in his autobiography.
c. Highly skilled operators were capable of six words per minute.
Regards
Adrian