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Pardon my ignorance, but regarding morse coding I came across the following information:

The radio frequency of 500 kilohertz (500 kHz) has been an international calling and distress frequency for Morse code maritime communication.

Does that mean all morse signals sent with a carrier RF signal fixed at 500 kHz frequency?

Another information I know from the antenna theory states that the transmitter antenna length should be at least 1/8 of the propagated radio wave.

It seems the wavelength for 500kHz radio wave used once in wireless morse communication is 600m.

This requires an antenna length at least 75m.

Is my conclusion correct or did/do they have another workaround for a smaller antenna?

EDIT:

The electrical generators and radio equipment on board the Titanic were the best available at the time. The wireless equipment was built by the Marconi Company, the dominant provider of radio equipment and radio operators at the time. Powered by a 5 kilowatt motor generator, and backed up by an emergency generator and batteries, the ship's radio had a guaranteed range of 250 miles under any weather conditions, and could usually maintain communications over 400 miles. The antenna system for this radio equipment can be prominently seen in most of the clear photographs of the ship. It consisted of four wires strung between two masts, the forward one located about ¼ of the way back from the bow of the ship, and the other being near the stern. The height of the antenna was 205 feet above water level. The antenna was fed by four individual wire feed lines, which appear to emerge from the radio room in front of the first of the four large stacks, or "funnels" of the ship. The feed points appear to be located approximately 1/3 back from the leading end of the antenna.

source: http://www.avsia.com/djohnson/titanic.html

One of the first uses of T-aerials in the early 20th century was on ships, since they could be strung between masts. This is the antenna of the RMS Titanic, which broadcast the rescue call during her sinking in 1912. It was a multiwire T with a 50 m vertical wire and four 120 m horizontal wires.

enter image description here

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  • \$\begingroup\$ "It seems wavelength": Well, calculating wavelength from frequency has nothing speculative when you know the speed of light (which you hopefully do). Where do you take the "at least 1/8" from? That's an unbacked claim, and I think you're using it out of context. So, no, that's simply false. You can build much smaller antennas, the question is how efficient or broadband these are, but that's a different story. So, a) add references for all the things you "came across". \$\endgroup\$ – Marcus Müller Oct 15 '17 at 21:09
  • \$\begingroup\$ Any random antenna will radiate signals, the efficiency is defined by erp - effective radiated power, which is a function of transmitter output power and antenna gain at the frequency of interest. \$\endgroup\$ – Chu Oct 15 '17 at 21:36
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As your quote says "500KHz has been an international calling and distress frequency for Morse code maritime communication". This frequency was used by large ships, so antenna length was no problem. Morse code (on any frequency) has not been used for marine communications for many years.

Morse code can be used on any frequency - Amateur Radio operators still use it on many bands in the short wave spectrum - bands from 1.8 MHz (160 metres) to 28 MHz (10 metres).

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