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I have had a license since I was a kid, but have not touched anything ham radio related in years. I have been thinking about diving back in and combining it with my sailing. I'm looking for thoughts on an HF antenna that I can easily deploy when needed, which will mean at the dock or anchor and not while underway.

My sailboat is a 30 feet long and has a mast that stands 38 feet above the deck. The distance from the mast step to the aft most point is 18 feet, so if this is a right triangle, the length of the hypotenuse is 42 feet.

I am thinking that a half wave, end fed antenna that could be made to work on 20, 15 and 10 meters would be easy to hoist between the stern and the mast head when needed and would appreciate your thoughts. Also, are there end fed quarter wave antennas? If so I could have one for 40 meters as well. I would prefer to avoid a tuner just because it's one more thing on a small boat.

One other consideration is that, being a sail boat there are 1/4 inch stainless steel cables which hold the mast up. I'm really not interested in putting insulators in these cables or trying to load them as antennas, but I am wondering what interference or impact they might create.

UPDATE: The boat is used primarily for racing so this is the cause of my hesitance to modify the rig.

Also, the mast is "deck stepped" which means that it's bottom sits on the deck. On most sailboats, the mast actually does down through the deck and sits just above the keel.

At the top of the mast is an existing small VHF antenna for the marine VHF radio with a feedline inside the mast.

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    $\begingroup$ I don't have any immediate ideas, but one thing that may matter is if you sail fresh or salt water. Also you may think about submitting this question at a site like Sailing World. Since HF is something that the world traveling set is more likely to use $\endgroup$
    – Rowan Hawkins
    Commented May 18, 2017 at 19:36
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    $\begingroup$ Welcome to ham.stackexchange.com, Jim! We recommend that new users take the tour at ham.stackexchange.com/tour to get the most from the site. :-) $\endgroup$
    – Mike Waters
    Commented May 18, 2017 at 21:41
  • $\begingroup$ Could you post a photo of your sailboat here? I know you listed the dimensions, but a picture or two showing the guys, etc might help. $\endgroup$
    – Mike Waters
    Commented May 20, 2017 at 16:47
  • $\begingroup$ Also, is the mast conductive or not? What's it made from? $\endgroup$
    – Mike Waters
    Commented May 20, 2017 at 17:02
  • $\begingroup$ The mast is aluminum. I'll post some pics of the rig and the boat overall, thanks for the comments everyone! $\endgroup$
    – Jim Archer
    Commented May 21, 2017 at 4:09

3 Answers 3

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I'm really not interested in putting insulators in these cables or trying to load them as antennas

That's a shame, because the mast and the cables probably make an excellent antenna. In fact unless you go through some trouble to get the antenna far away from the mast, or oriented orthogonally, the mast and cables are going to end up being a significant part of the antenna whether you like it or not. Remember you don't need a DC connection: mutual inductance and capacitance will couple things together at RF.

You don't need to put insulators on the cables. Finding a good feed arrangement will take some experimentation, but there are plenty of ways to couple into the mast which don't involve any structural modifications, which I guess is your fear.

If the mast, cables, and hull make a closed loop anywhere, you can put a smaller loop within that and feed the small loop. The two loops effectively make a transformer.

Another method is to clamp a ferrite around one of the cables or the mast, and also run several turns of wire through the ferrite, and feed that. Again, a transformer feed. This works even if there's not a loop to feed. That is, you could clamp such a ferrite around a metal pole stuck in the ground (or the water) and make a fine antenna. A mast on a sailboat is not far from this. Might get tricky to find an appropriate ferrite at higher frequencies or higher power levels though, but might be great for QRP operation on 40 meters.

A gamma match is another option which not only solves the problem of coupling into the mast without structural modifications, but also gives a couple variables to provide a decent match.

If you run a wire up the top of the mast like SDsolar suggests, you've effectively made a crude gamma match. The mast and the wire together make a transmission line. By varying the length of that wire you change the length of that transmission line. You can also decide to connect the wire at the top to the mast or not, which will give you an open or shorted transmission line stub which functions as a kind of stub match.

These are just a few options. For further ideas you can research existing methods of coupling into loop antennas or shunt feeding towers, which are similar problems.

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  • $\begingroup$ Great comments Phil, thanks you! The mast is a 38 foot alumi spar and in addition to the forestay & backstay there are three shrouds on each said. All stays are 1/4 stranded stainless cable. Pretty standard. The shrouds use a single set of spreaders and "t-ball" connectors to secure to the mast. The rig is modified from original, and is my own design. I'll post some pics and dimensions. If I can actually get the mast and/or rig to act as an effective antenna without having to modify it that would be fine, but modifications would likely harm the boats racing performance. I'll check your links. $\endgroup$
    – Jim Archer
    Commented May 21, 2017 at 4:13
  • $\begingroup$ Oh, also the boat is fiberglass, including the hull and deck. So no loop as it is now, but nothing would stop me from making one. The shrouds (cables that hold the mast up side to side) are secured to the hull by metal "chain plates" so I could connect the left side and right side chain plates together with a cable, below the deck. $\endgroup$
    – Jim Archer
    Commented May 21, 2017 at 4:24
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I own an O-Day 272LE sloop and have been operating HF on it for the past several years, including serious Field Day operation from along Delaware Bay and Rehoboth Bay in Delaware.

The stainless-steel cockpit railing makes a good mount for vertical antennas on the stern and bow. This allows for maximum separation from the boat's rigging. For serious FD operation, I use a telescoping MFJ 33-foot mast for 40 meters and a 1/4-wave aluminum tubing 20-meter vertical. Also have used 1/4-wave verticals for 10 and 15 meters though found there wasn't enough activity there to warrant the trouble.

I also have used a gamma match on one of the shrouds to get on 80 meters and made a few QSOs with that. This could also be done for 40 meters. For casual operation I just mount a single-band mobile whip on the stern rail, such as the Hamstick or MFJ-1620T using a mount designed for putting an antenna on a truck mirror.

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  • $\begingroup$ Ooops when I said "side stays" I meant the shrouds were what I was gamma-matching. $\endgroup$
    – AA1K Jon Zaimes
    Commented May 22, 2017 at 11:15
  • $\begingroup$ Welcome, and thanks for your informed answer! I've edited your answer to incorporate your correction. In the future, please edit rather than leaving comments. $\endgroup$
    – Kevin Reid AG6YO ♦
    Commented May 22, 2017 at 14:03
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Welcome back to the hobby.

If you can run a wire up to the top of the mast, insulated from it, that is great. Then just run it to the furthest point on the boat.

From your post I presume you have an antenna tuner.

Your instincts are good about not wanting to use load-bearing cabling as part of the antenna.

The water will make a great ground. Saltwater is slightly better, but any water is better than any earth ground.

Enjoy!

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