WHEN SEA GOING VESSELS HAD DIRECTIONAL SHORT WAVE AERIALS

Today [in the second decade of the 21st century] just about any vessels which goes far enough out to sea so as not to see a land mass has directional communication aerials. However one doesn't actual see them because they are enclosed in white [usually] multi-shaped radomes which protect the aerials within from the elements without whether natural or ship made. But they are not short wave aerials, far from it, for they operate in the GigaHertz band, in what is called the Microwave Band with 1 GHz acknowledged the first rung of the Microwave Band ladder. That's small beer as we run up the scale to millimeter waves used for all kinds of radars which are 30 to 300 GHz band. Note in the Royal Navy telecommunications world, little emphasis was placed on wavelengths, giving way to bands and frequencies measured in Hertz. However they were used in Radar Bands S, C, X for example etc and ECM work [Electronic Counter Measurers] always referred to in wavelength = lambda.

Below is a simple table having a 'use' column to show how each band was used in the service.

All shipborne W/T transmit aerials where omnidirectional aerials either broadband or tuned whips, with receiving whip aerials suitably transformer coupled at source to cover specific frequency bands. Invariably they were all for'ard in the ship's substructure with transmit aerials well aft so as to lessen mutual interference. In such a configuration the ships could be coned without affecting reception. Transmission used whip aerials, again omnidirectional with many parts of the superstructure including funnels rigged with wire aerials attached to the metal parts of the superstructure via glass insulators, giving the several strands forming the transmitting aerials a broadband characteristic. They are however omnidirectional, some parts emitting a horizontal polarisation whilst others a vertical polarisation.  Before the advent of Satcoms and satellite lock-on highly directional aerials, warships had no directional aerials of any sort, but whilst that mattered, it wasn't critical when all long haul communications were conducted over HF [short wave]. What is clear is that we had W/T communications from the very late 19th century in some form or other through most of the 20th century and we managed to communicate successfully because we mastered the means and ways of the ionosphere, and our operators were taught to ignore the noise and to listen only to the Morse Code even when coming at them at great speeds.  That's not to say that we didn't have directional short wave aerials, for we had many dotted around the country and around the world sending and receiving enormous amounts  of signal traffic, but note, all fixed terra firma sites feeding terra firma shore communications centres but not ships of course, which by ordinary manoeuvres would move in and out of the direction from whence the signal was coming, causing massive swings of signal strength from 'loud and clear' to 'faint and unreadable'.   

Therein lies the root of my story, namely a ship travelling in a straight line towards and away from a land mass on which is built a highly directional aerial array such that it could be connected to transmitters or to receivers to communicate with a distant vessel steering a steady course.

Do war ships do that? No! Do merchant ships of any type and use? Yes, very possibly!

We are talking about the mid 1930's when merchant ships were travelling in large numbers from the UK to the USA and back again, steering either westerly courses  or easterly courses at great speed, sailing the traditional great circle  route

 

BAND DESIG FREQUENCY NAVAL USE
ELF Extremely Low Frequency 3Hz-30Hz None
SLF Super Low Frequency 30Hz-300Hz None
ULF Ultra Low Frequency = AF = Audio Frequencies 300Hz-3000Hz Audio Frequency into a transmitter modulator and out of a receivers demodulator
VLF Very Low Frequency 3kHz-30kHz International time checks and submarine received Morse Code signals from shore.
LF Low Frequency 30kHz-300kHz Distress [eg 500 kHz CW]  and  local coastal communications
MF Medium Frequency 300kHz-3000kHz Distress [eg 2182 kHz DSB] and  local coastal communications
HF High Frequency or Shortwave 3MHz-30MHz Long distance communications via the ionosphere, one way, either ship to shore or quite separately,   shore to ship
VHF Very High Frequency 30MHz-300MHz Aircraft communications, radar, commercial shipping, and port working
UHF Ultra High Frequency 300MHz-3000MHz Submarine Satcoms, aircraft, radars and intership working
SHF Super High Frequency 3GHz-30GHz Ship Satcoms, radar and missile telemetry
EHF Extremely High Frequency 30GHz-300GHz Radar and telemetry

RMS QUEEN MARYs AERIAL RIG 1935.pdf



As long as the vessel stayed inside the imaginary tube [which had plenty of latitude for manoeuvres like zig zagging for example] shown by my black lines whilst sailing on her great circle route [in blue], which took her into New York via Newfoundland, passing Halifax Nova Scotia enroute, her transmissions were guaranteed with a change of frequency only if required to overcome the day/night affect of the ionosphere, whilst her reception was guaranteed by her one main dipole receiving aerial and two quadripole reception aerials covering the bands 17, 8 and 6 Mc/s situated in a position high up in the ship between the forward and central funnel stacks, each of the three aerials having a substantial sleeve uplink terminal to a connection on a mini reception main roof, giving the effect of a cluster of wide-band receiving aerials being fed to the four radio officers below in the manned W/T office for'ard. 

 Now of course, and for a long time gone, nobody needs directional areas for short wave for compared to many years ago now, few organisations use short wave operationally so its no longer of consequence?

As in all things maritime, the Queens were way ahead of all, had no peers and no real competitors.

Take care now.