15 thoughts on “Antennas

  1. The Salvita was I recall, supposed to be capable of being dropped 30 feet and still float.

    At Colwyn Bay we were taught about different types of simple transmission antennae, but not much about receiving. Nothing at all about splicing, shackles, etc. I once related to Kipper Whale that I had seen disks along the aerials of some BP tankers in Falmouth and he exlained that they were capacity spreaders. I think he also told us about safety loops to prevent the aerials breaking if the masts ‘sprung’ on going aground.

    On the North Atlantic the fog and mist off Newfoundland would frequently cause the transmitter to trip due to shorting across the downlead insulators on the monkey island. I used to keep a dry cloth in the Radio Room and go up and wipe them off if it was foggy or there was a sea fret.

  2. Interested to know if any other RO’s have had er, mishaps with those wretched ”Salvita”[ God help us and mind yer back!] life boat thingamegigs? During a boat drill in Port Said back in ’67 I slung one over the side on its lanyard which promptly broke and I guess it still down there someplace. Were we supposed to go fly a kite for an aerial? To bad if no wind. Amazing.

  3. Apart from safety links, as far as I can recall at college, the subject of aerials was just left hanging…

    Thru deck insulators were the worse offenders for being good loads to earth though.
    So much so, that I ended up, as a techie/surveyor, taking my own Megger with me. Lost count of the number of insulators just painted over…

    And eventually designed a horiz dipole array for reception (a) low noise, (b) directional when faced with installing a fleet with telex. The upgrade to s/n was really noticeable

  4. What about a loading coil?. On my last little ship, [ and it was rather little, like 50 ft overall, ”Coos Bay”/EINX], a serious coil mounted up on the wheelhouse sorta fooled the MF Tx into thinking it was working into a decent antenna and EJK, GLD even GNI were worked ok with a 50 Watt Salvor from the SW Cork coast.

    • I guess the best part of any ship’s MF/HF antenna system is the ground plane. All that salt water and usually a steel hull in contact with it! It’s no wonder that even relatively inefficient antennas would radiate a respectable signal. Given clean insulators of course, and paint-free feed throughs… yes I’ve been there with a wire brush cleaning up after a dozy A/B ๐Ÿ™‚

      I note with interest that some Amateur stations are now experimenting with transmissions at around 500kHz. Enormous loading coils seem to be the order of the day. Even with relatively low ERP they’re getting some impressive results.

      • Thanks for that Bernard. Yeah, borrowing heavily from days of yore, I bolted a decent copper plate to the hull and the loading coil was a tapped 200 turn 12” dia former, resin glassed and on insulated mounts. Then up to a quad wire horizontal from main to mizzen masts, then up a 7mtr whip!. Worked fine, presumably resonating around 500khz. Loaded up nicely. Fascinated to hear of ”Ham” experiments in this area, you never know if in some future crisis it could come in handy…..

  5. Hey Tony. I’d clean the insulators weekly, sometimes more often if we’d been through any kind of weather. As to antenna length, I didn’t measure it but I’m talking about the Shell “A” and “P” class tankers, built in 1958/59 and around the 20,000 ton mark.

    My first trip solo was on Acavus/GXQQ – don’t know if this will work but here’s a link – with a Redifon G341/R408 setup and that antenna arrangement. It worked very well indeed, but I wasn’t impressed with the callsign! Wrong end of the traffic list, a handful on the key and *!@?* awful on R/T ๐Ÿ™‚ I invested in an electronic keyer after that one.

    http://www.helderline.nl/tanker/416/acavus+%282%29/

    Happy days indeed.

  6. I sailed on a couple of tankers with midships accommodation, with the main transmitting aerial strung from the monkey island back to the funnel. Still well short of a quarter wave on MF, but you could work GLD from way down off the Portuguese coast if you timed it right. One night I made an RT call via GNI on 1.8MHz from the Brazilian coast; couldn’t get Portishead on any band but Niton was romping in. The only trouble with those antennas was the insulators – you had to get them down once a week and clean the salt off them.

    You never worried about resonance – you just tuned for maximum smoke and hoped for the best! Good old valve PA’s – just about bomb proof.

    To answer the original question, no there was very little antenna theory or practice taught while I was doing my MRGC. I learned it all subsequently, mainly through my amateur activities. I should have got my amateur ticket while I was at the college of knowledge, it would have helped enormously.

    • Bernard, a run from the monkey island to the funnel on a midships tanker is one hell of a run. I sailed on a couple of ships where the main aerial ran from the monkey island to the fore mast but never one running aft. You would need a couple of chunky AB’s to haul up an aerial stretching aft, if you ever took the whole thing down on a tanker. That would probably be about as close as you could get to a quarter wave length on M/F on a tanker or cargo ship I would think. 500KHz is 600 metres so a quarter wavelength is 150 metres, which is about 500 feet in old money. Dependant on the size of tanker of course but I would think an aerial running aft on, say, a 20,000dwt clean oil tanker would be in the region of 350 to 400 feet. With clean insulators you should be able to load up nicely on M/F. How often did you have clean insulators though?
      Oh happy days.

  7. I do believe that the reason for the safety link was first brought into use in the First
    World War, [I may be wrong] in that when a ship was torpedoed the hull would flex
    and the transmitting aerial would snap, with the use of the safety link this remedied
    the problem. Going back to the inefficiency of ships aerials in general, there was
    one positive, in that the earth available was the best one could have!!

  8. As far as I can remember we did not specifically cover aerials or antennas during my PMG years between 1961 and 1963. I can recall some discussion on matching the length of a wire aerial to a quarter, or half (but that was a long way), wavelength on 500KHz if you could. This was theoretically possible on the older design of midships accommodation ships where aerials were strung from the monkey island to the foremast but for obvious reasons became more difficult on all aft ships and the general design of ships changed. I learnt a great deal about aerial maintenance from the Senior R/O on my second trip as a Junior including as Geoff says, splicing, thimbles, safety loops etc. On my last trip with Brocklebank Line it was an all aft ship that used all whip aerials of differing lengths. These were next to useless on M/F but were pretty good on H/F, particularly on higher frequencies where their length must have been closer to a fraction of a wavelength. The inefficiencies of pumping 1400 watts into a whip aerial on M/F must have been staggering. I sailed on one ship with big whip aerials attached to the funnel which was fine in theory but the funnel gases played hell with the insulators and you nearly choked to death on the all too regular trips to go up and clean them.
    I didn’t ever sail with Diekman and Klapper anetennas but they seemed to be as close as you could get to an acceptable compromise solution.
    Certainly the ability to match to a quarter wavelength as John describes above never even entered into the equation.

  9. The usual receiver antenna was an end fed bit of wire strung to something high up, usually the funnel etc. this was used to take info from 15kcs to 22 mcs. impossible. when I use my antenna at home the element length is automatically mechanically adjusted every 5kcs, and every band is mechanically altered to a quarter wave vertical dipole. you can hear the signal strength go up by 8 points as you near resonance.

  10. I attended radio college in the 1970’s, transmitting aerial’s and how and where to erect them was not really covered. However, the Marconi splice was practised on many occasion, and the use of thimbles and bulldog grips. It was only when at sea, and especially on aft accommodation vessels you realised the lack of thought that went into the positioning of the most important aerial. Wire aerials were directional, but on the MV Lincolnshire I was fortunate to sail with a Dickman-Klapper mast radiator, a vertical antenna made up of 8 vertical copper wires attached to two circular rings,one at the top, and the other at the bottom, with an MF mast radiator on top, this aerial was omni-directional and extremely effective, it also did not suffer from salt and funnel gas coatings. On another point, who remembers putting a neon tube onto the copper tubing going up to the aerial connection, looked good when they lit up, gave you a good feeling of putting out a good signal……. however it reduced your power output quite considerably!!!

    • Ooops!. Now I know the glowing wee thing what ”soaked up all that gravy’. Also, grand fun trying the Marconi Splice at minus 15dgs up in Oxalisund on the good old MV Pennyworth…..

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