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View Poll Results: HAM, Marine SSB, Other?
HAM only 21 10.66%
Marine SSB only 57 28.93%
Both 88 44.67%
Other (sat phone, etc. please specify) 33 16.75%
No long range communication device 25 12.69%
Multiple Choice Poll. Voters: 197. You may not vote on this poll

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Old 10-12-2007, 13:35   #76
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Gosh, Bill, that's a lot of Radios!

Bill (btrayfors) I liked your setup, particularly the kewl retro stand off insulators you have.

One question though... If you're ever boarded by a foreign Navy - how are you going to convince them that you're not a re-do of the USS Pueblo?

And Steve - yes rigging all those antennas is a challenge to not have them interfere with the sails.

Bill - do you use different standing rigging lines as dipoles (with additional insulators)? How do you rig your boat? Do you have to manage your dipoles as some of us have to with running backstays (i.e. slack them before tacking)?

I think that most of us are fine making do with 1 antenna.

Cheers,
Bill
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Old 10-12-2007, 13:41   #77
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Dipoles can be vertical, sloped or horizontal, the former being the most practical for obvious reasons and the latter would be least practical albeit the most effective if mounted high enough.

The best compromise is therefore a combination or in this case an inverted V configuration with it's apex at the top of the mast with the aft segment in the configuration of a backstay. The fwd portion is problemmatic but of you have room, a baby stay configuration would not interfere with the jib.

the other practical alternative is the sloper configuration where, if your mast is high enough, you can run the entire dipole length sloping from the mast top to transom. The problem with this is, in theory, to avoid RF on the feedline, the coax should be at right angle to the antenna making it an awkward antenna to feed properly.

Any of them will work depending on your boat so try whichever makes sense based on how your boat is rigged.
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Old 10-12-2007, 13:47   #78
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Steve and Bill F...

The reason for rigging a vertical dipole is simple: there's no other seagoing antenna you can rig on a sailboat which will come even close to its performance. It is a killer DX antenna which will WAY outperform any backstay antenna.

The dipoles I use are "marinized", i.e., made from marine-grade materials designed to stand up to the harshest weather and seaway. Details can be found here: Gallery :: Constructing a Marine Dipole Antenna

Click twice on each pic for full resolution.

I rig my dipoles on the foredeck, about halfway between the forestay and the mast. They are hoisted with a spare halyard, with the lower ends tied off on the toerails. Vertical dipoles should be rigged as LOW as possible, not as high as possible.

I use short lengths of RG-8X coax to run back to a spinnaker track fitting on the leading edge of the mast, then down the mast to a little black box installed just under the gooseneck. This box is permanently connected to an antenna switch below near the radios.

The dipole or dipoles are deployed in this fashion when in a marina, at anchor, or on very long tacks offshore. To sail, it's only necessary to loosen the lower end(s) and pull them back into the shrouds. They will work there, but will some detuning. The process of setting up for sail takes less than 2 minutes, as does the process of setting them up again at anchor or in a marina.

I don't use running backstays, but if I did it wouldn't matter at all, since my dipoles are rigged on the foredeck not aft. When I first started using dipoles I'd rig them aft, with a long coax lead down the hatch to the radios. But, after awhile I hit on the little black box idea, and it has worked like a charm for 18 years now. Very simple. Very effective. Never a problem when underway.

Bill
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Old 10-12-2007, 13:52   #79
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s/v Illusion,

Sorry, your post came while I was composing mine.

No, it's NOT true that an inverted vee is the most effective. In fact, the opposite is true if we're talking about long-distance communications.

The reason is simple, and can be found in the ARRL or any antenna handbook:

1. a vertical dipole, rigged close to the ground, puts out nearly all its power VERY CLOSE TO THE HORIZON....it has a very low angle of radiation...and that's precisely where you want it for DX;

2. an inverted vee has a much higher angle of radiation, better for short hops but not for DX.

Over the past 40 years of use I've proven this over and over in actual use, not just theory. And, more recently, the big DX-peditions have discovered vertical dipole antennas, and often prefer them to yagis!

The limitation on a small sailboat, of course, is the amount of hoist. Usually, a 20meter dipole (about 32' long when trimmed) is about all you can handle vertically. So, for the lower bands you're left with some other configuration...an inverted vee or an "L" or traps or....

Bill
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Old 10-12-2007, 13:55   #80
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FB, Bill - those are beautiful! Thanks for the link... (and I bet if you opened an online store for completed dipoles, you'd sell quite a few).

I love mobile dipoles... I used to use a pair of Outbackers on my bicycle, rigged with a folding assembly that let them tuck around the mast when not in use. Nothing like avoiding the losses of a tuner... and it would operate either vertically or horizontally. I generally used the former mode, though occasionally the slight directivity of the horizontal lobes would be useful (less often than I would have thought, though).

73 de N4RVE
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Old 10-12-2007, 13:57   #81
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Tacking must be fun...

Quote:
Originally Posted by btrayfors View Post
I rig my dipoles on the foredeck, about halfway between the forestay and the mast.
What do you do when you tack?

This would be even harder on our cutter with a roller furling stay sail!

I think I'll stick with my backstay...

Cheers,
Bill

p.s. the running backstay comment was that I think you'd need to attend to the dipoles when tacking as you would if you had runners.
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Old 10-12-2007, 14:52   #82
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Quote:
Originally Posted by btrayfors View Post
s/v Illusion,

Sorry, your post came while I was composing mine.

No, it's NOT true that an inverted vee is the most effective. In fact, the opposite is true if we're talking about long-distance communications.

The reason is simple, and can be found in the ARRL or any antenna handbook:

1. a vertical dipole, rigged close to the ground, puts out nearly all its power VERY CLOSE TO THE HORIZON....it has a very low angle of radiation...and that's precisely where you want it for DX;

2. an inverted vee has a much higher angle of radiation, better for short hops but not for DX.

Over the past 40 years of use I've proven this over and over in actual use, not just theory. And, more recently, the big DX-peditions have discovered vertical dipole antennas, and often prefer them to yagis!

The limitation on a small sailboat, of course, is the amount of hoist. Usually, a 20meter dipole (about 32' long when trimmed) is about all you can handle vertically. So, for the lower bands you're left with some other configuration...an inverted vee or an "L" or traps or....

Bill
I don't think you'll find where I said an inverted V is the most effective...
What I said was in the post above - sorry if I wasn't clear.

If you've been a ham as long as me, I think you'll agree there is no such thing as a generalization about any one antenna which is always true - in this case, the vertical compared with a sloper for example in terms of low angle radiation over a good ground.

Not my intent to argue the minutia but with boat antennas, all benefit equally from the perfectly-conducting "ground" and it's hard to say any one is that much better. I've seen too numerous times the unfortunate result when someone tried to makeshift a specific design which really didn't "fit" their boat and in so doing, caused damage or created a dangerous situation.

What I try to suggest to people contemplating erecting an HF antenna is to make sure you have the best counterpoise practical, good cables, good connections and an antenna that doesn't interfere with access, movement or rigging and if possible, not capacitively coupled to anythign else although that too can often be ignored.

K1VSK
playing with antennas since 1960

p.s. never trade my monoband yagis for a vertical for any $$$
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Old 10-12-2007, 15:16   #83
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Hey, Don...

You've just been playing in the wrong sandbox all these years :-)

Just kidding. I think we've both been foolin' with antennas for a very long time.

What I was reacting to was your note about a horizontal dipole being best if rigged high enough. Clearly, that's not possible on a sailboat. More importantly, it just ain't so.

The vertical dipole is such a killer DX antenna because, when rigged LOW to the ground, it's vertical radiation is very low. It has a huge lobe just above the horizon, and all around....exactly what you want for DX.

While I agree I'd not trade monoband yagis on land for vertical dipoles...for lots of reasons....that's not to say they're not very effective. Some well-financed DX-peditions with more bucks than god actually prefer the vertical dipoles, and claim as much as 18-20db gain. Obviously, the gain doesn't come from the dipole itself, but from the skipped hops, i.e., fewer hops to the receiving station because of the extremely low takeoff angle.

I've used and written about these for years. There's nothing that can even come close on a sailboat that's a true seagoing antenna, i.e., one which can stand up to the marine environment and to a rough seaway.

About 8 years ago I decided to try them on land at the home QTH where I have tall oak trees. I have vertical dipoles here on 20m, 30m, and 40m. Have worked over 100 countries QRP with no trouble at all...they work very well over land, too!

Why even consider them? BECAUSE THEY PUT OUT A WHALE OF A SIGNAL compared to a backstay antenna. This morning I listened to a pathetic exchange where a boat in Culebra was trying to contact a K4 here on the East Coast. No go on 40m. They decided to try 20m. Also extremely difficult copy. If the boat had been using a vertical dipole on 20m they would have had solid communication. How do I know? Because I've been sailing the Virgins since 1969, had my present boat there for 11 years, and know very well what a vertical dipole will do on this path compared to a backstay antenna.

Is it worth it? That's for each sailor to decide :-)

Bill
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Old 10-12-2007, 18:20   #84
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I learned a long time ago, particularly with respect to boat antennas, that there are no certainties. Used to keep a sked with a friend in Auckland on 20M and would often find myself at the marina at sked time. There were times he couldn't tell the difference in sig strength between my 1500W Alpha/80 ft high wide-spaced yagi at home and the 100W to a sloper off my masthead on the boat. Unfortunately, his signal was barely above the rather high noise level on board but consistently armchair copy at home so gain works both ways - the shoper has none and the yagi obviously does. It's all in what you do with it...
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Old 10-12-2007, 20:19   #85
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Kingman Reef Lessons, inter alia

"Kenny, K2KW, is the DXpedition coordinator for Force 12, Inc. and wrote an overview comparing verticals and Yagis on DXpeditions (available at http://pages.prodigy.net/k2kw/dxcomp.htm). Kenny's letter communicated to the Kingman Team the excellent and unsurpassed performance properties of verticals at their destination. This, plus the history of Team Vertical convinced the Kingman Team that verticals were the correct selection.

Some team members remained skeptical, as verticals on salt water performance is something that needs to be experienced to comprehend. The Kingman Reef DXpedition was an excellent opportunity for others to share the experience. Comparing raw gain figures between two antennas (i.e. Yagi at 30' and 2 element vertical) is not the main issue, it is the energy from each antenna at low angles. Eliminating one hop is worth a good 10dB and the lower angle aspect (transmit and receive) might omit more than one hop. Add to that the difference in gain at the low angles. Having a single lobe with energy down to 1 is the key to DX performance. After 9days 14 hours 20 minutes and 81,000 QSO's later, the K5K team members were convinced!"

The verticals they're talking about were center-fed vertical dipoles.


Yeah, there are no guarantees. But we're not comparing yagis at 80' in a QRN/RFI quiet environment to vertical dipoles in noisy marinas. What we're comparing -- at least I am -- are antennas which are practical aboard small sailboats. And, most especially, the standard insulated backstay (end-fed random length wire fed thru a tuner) and 1/2 wave tuned monoband vertical dipoles fed directly (no tuner needed).


If you've never compared the performance of these two types of antennas aboard a sailboat, switching back and forth between them, and getting signal reports from far distant stations over time well, then, I understand the reluctance to believe that there really is a BIG difference.

Bill
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Old 10-12-2007, 20:57   #86
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The premise N2KW uses is based on lowering angle of radiation without regard to gain. A vertical is omni-directional and as such has no gain. If you can compensate for a slightly elevated radiation angle with a gain antenna, you can more than make up for any loss in radiation angle advantage of a vertical. Again, generalities are correct only sometimes. The reality is that on a sailboat with all that metal around, any vertical antenna field is inevitably distorted or degraded thereby effecting both it's radiation pattern and radiation angle to such an extent it can't even be modeled let alone make any broad statements.

On an island and on a boat are two very different places.

My only point, again, is that considering one single antenna option when installing or improving an HF radio onboard is a mistake.
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Old 11-12-2007, 04:21   #87
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A vertical is omni-directional and as such has no gain.
All omni-directional antenna's have gain, except for the theoretical isotropic antenna. Colinear vertical's can have LOTS of gain, but even a simple half-wave vertical dipole has gain.

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Old 11-12-2007, 07:36   #88
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This one stumps even some of the most advanced RF engineers, that is, the "gain" of an antenna. Even the law states that the "Effective Radiated Power (ERP) will not exceed..." and this is based on the input into the antenna multiplied by the antenna gain. There is this concept that, the moment they exhibit gain, antennas magically create power within themselves. Sadly, this is not the case. If one examines an antenna it will be noted it is constructed of basic materials, the best being gold, silver, copper, then aluminium following on. These materials in themselves cannot create power.

For this reason (no gain) it is often said that verticals radiate equally poorly in all directions

For a further explanation, see link
Marc's Technical Pages: Antenna Gain Explained
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Old 11-12-2007, 07:50   #89
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There is this concept that, the moment they exhibit gain, antennas magically create power within themselves.
Never heard of that concept. An antenna that has gain simply concentrates more of the input power in some directions over others. Antenna gain also has to have some reference, usually a 1/2 wave dipole in free space or the isotropic antenna. A vertical does not radiate equally in all directions. The radiation off the ends is considerably lower than broadside.

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Old 11-12-2007, 07:55   #90
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Yeah, I guess it's all an Illusion. All these years all these hams and all these engineers have been talking about and measuring antenna gain, only to find out that you can't create energy.

Jeez, whatta concept :-)

My friend, you really need to go back to the books. Or wherever you got all that misinformation.

Of course energy isn't "created" by antennas which exhibit gain (and they do).

As Eric says, gain is a function of concentration of energy in a given direction. And, over DX paths, it's also a function of the takeoff angle or the vertical angle of radiation.

Yagis, quads, rhombics, and other highly directional antennas concentrate energy in specific, predictable azimuthal directions. Their vertical radiation is often a function of height. You need to get yagis really high off the ground to get them to favor low vertical angles of radiation.

By contrast, half-wave vertical dipoles rigged LOW to the ground have a very low takeoff angle. They have one huge lobe located just above the horizon. In addition to the strength of this lobe, in comparison to other antennas at the same vertical takeoff angles, they derive gain from requiring fewer hops to the distant station. It is estimated that a single hop foregone may be worth about 10db (more than the average gain of, say, a 3 or 4-element monoband yagi). On very long paths, more than one hop may be saved, increasing the apparent "gain".

Bill
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