|Topic Review (Newest First)|
|06-29-2009 09:42 PM|
|Freesail99||I have the Kaito KA1103. I have used the antenna that came with it and it works ok not great, and I also made one from wire and a dipole which also worked.|
|06-29-2009 09:34 PM|
Originally Posted by Freesail99 View Post
Could you tell me which SSB receiver do you have?
And which antenna?
|03-19-2008 12:21 PM|
Of course, antennas on a ship are different from those on a sailboat, because you have a lot more room to play with AND you have a wonderful RF ground in the form of a steel hull and decks!
It is true, of course, that all the standing rigging on a sailboat will affect both the azimuthal and the elevation radiation pattern, so that a perfect omnidirectional pattern at HF frequencies is highly unlikely (though the VHF antenna atop the mast is pretty much omnidirectional).
Whip antennas on sailboats work well, and some experienced hams prefer them. You have to have a good RF ground system to work them against, of course, and if you're going to go to sea you need to be mindful of the whipping action of a long antenna. Mostly, these are attached on the transom, with some support at the level of the pushpit. Still, they can be a real bear in a seaway :-)
I actually carry three types of HF antennas aboard...have done so for years.
The first type is the "alternative backstay", similar to the traditional insulated backstay, but rigged separately with a good autocoupler at it's base. This antenna is very versatile and can tune any marine, ham, or other HF frequency. As I've said before, it's a good antenna, but not a great antenna!
The second type is the monoband vertical dipole: I carry several for different bands, and can rig up to two simultaneously on the foredeck. These dipoles give me a great advantage over the backstay antenna on long DX paths but, of course, they're only for the high bands (8 mHz and above) since I only have a 64' mast!
The third type is a mobile whip...the popular Hustler center-loaded mobile antenna, with changeable resonators for different bands. This is rigged on the pushpit and is really there as a backup, e.g., in the event of a dismasting. A full-size vertical would do better, of course, but the Hustler does a credible job when called upon. I had a friend on a Valiant 40 who used the Hustler as his only HF antenna, and we remained in contact during his voyages in the Caribbean, Bermuda, and the entire East Coast of the U.S.
|03-19-2008 12:05 PM|
Lets see!? The vessels that I have worked on have had Long wire and whip antennas. But they still needed the antenna coupler/tuner for the SSB to work properly. I found that the long wire can be directional, especially if you are in the Bering Sea and trying to get the High Seas Operator at Pt Reyes Calif. The whip antenna wasn't quite so directional. But still the position it had on the pilot house top played into the directionality often. But wasn't as bad as the long wire.
Haven't worked with the back stay antenna yet. But am sure that it will have its own foibles with directionality also.
So far I prefer the whip antenna. But where to plant it on a sailboat is another question. (off a mast spreader?)
No antenna that I have worked with is truely omni-directional. Placement always plays into this.
|03-19-2008 11:44 AM|
Sorry, I certainly didn't mean to be condescending or to denegrate your experience. Truth is, we all have different life experiences which affect our outlook and belief system.
You, sir, made the declarative statement: "A vertical dipole has been around for ever and is nothing special in terms of it's radiation effectiveness or it's practical use aboard a boat."
My point is, respectfully, that this statement is erroneous, both in theory and in practice. Indeed, there is something special about vertical dipoles on boats. If you don't believe this, I suggest -- respectfully -- that you build a simple one for 20m, rig it on the foredeck with the lower insulator near the deck or lifelines, and give it a real try over a few weeks. I'll wager if you do that you'll be impressed with the signal reports you get and, if you switch rapidly between the backstay antenna and the vertical dipole, you'll get reports at the other end which will be as much as 2-3 S-units in favor of the dipole.
Again, my apologies if I sounded condescending. It wasn't my intention...just trying to inject a bit of humor.
|03-19-2008 11:20 AM|
I don't smoke cigars Bill but I do have decades of experience in working with virtually all types of antennas, both ashore and on boats from 26 ft to 409 ft so I'd appreciate a little less of a condescending response.
I have no problem with folks who have strong opinions but when they voice them in such declarative ways so as to dismiss the experience and expertise of others, it doesn't foster constructive debate.
My expereince is that here is no such thing as one single best antenna for a boat and if there is, it has yet to be invented. There are far too many parasitically influenced metallic objects in the field of a dipole on a boat to not cause significant pattern degredation far worse than other type antennas.
|03-19-2008 09:21 AM|
Just about every antenna imaginable has been tried on boats and ships. While in Morocco many years ago, I used to talk regularly with the radio op on a ship who had brought his own 5-element monoband yagis aboard for 15m and 20m. After the captain made him take them down, they ended up atop my house in Rabat...but that's a long story :-)
At dockside or in an anchorage it is possible, of course, to mount just about anything. I've even talked to sailboats which had yagi's atop the mainmast. But, clearly they weren't sailing with those in place!
To me, a practical marine antenna has to be one which will be suitable for real ocean sailing, not just one you can rig while dockside. Thus it has to be very strong and built of materials which will withstand the rigors of the marine environment, including storm-force winds and high seas. That's why I favor marinized vertical dipoles -- in addition to the traditional backstay, of course -- and have posted details of their construction here:
Gallery :: Constructing a Marine Dipole Antenna
(click twice on each pic for full resolution)
and details on how to tune a marine dipole here:
SSCA Discussion Board :: View topic - How to Tune a Marine Dipole Antenna
The major limitation of these dipoles is that they are single-band only. That's fine if you mainly use one band, e.g., 20 meters, for long-distance communication.
I've explored the many ways of building multi-band vertical dipoles, but none of them meet my criteria of being truly seagoing. At dockside, of course, you could build such an antenna and it might outperform the backstay on several bands.
|03-19-2008 12:42 AM|
I've seen dipole antennas strung up the backstay (not terribly vertical, I'll admit) and they didn't work so well there for most of the reasons aforementioned. Perhaps that's why people gave up.
Do you know if anyone has come up with a reasonable Yagi for marine SSB - or is the world still stuck on long-line backstay antennas??
|03-19-2008 12:03 AM|
Nice try, again, but no cigar. There really IS something about vertical dipoles which sets them apart from most other antennas you can rig on a sailboat. It's not academic; it's well proven both in theory and practice.
Yes, vertical dipoles have been around a long time. Most folks don't use them ashore because they don't have the means to hoist them high enough. And, a sloping end-fed antenna "played against a tower" is not the same thing at all. Nor is an inverted-vee dipole, which has a much higher average vertical angle of radiation.
A sloper, i.e., a sloping dipole is/can be a very effective antenna, too. I have one at my house on 40 meters and if you want to hear it just tune into the WaterWay Net any morning on 7268 at 0800.
As previously stated, DX-ers have discovered vertical dipoles and often prefer them over even yagis for DX-peditions. They like the all-round pattern of radiation and, especially, the very low vertical takeoff angles obtainable.
I certainly agree that any antenna you can rig on a boat is a compromise, and there's enough variation in floating platforms that, as the car manufacturers say, "your mileage will vary".
Still, after playing with antennas on sailboats for the past 35 years or so and after trying just about any type and combination of antenna systems imaginable, and after talking to literally hundreds of vessels on the high seas there's no doubt in my mind whatsoever that a vertical dipole will outperform most any practical antenna you can rig on a seagoing vessel.
|03-18-2008 11:51 PM|
Mast height is 64' plus. Forestay length is about 55'.
Re: insulated s/s lifeline, I use it because it's very easy to handle and, possibly, the insulation helps reduce noise during precipitation events. Can't swear to that, but many have found it so. Thus all my vertical dipoles -- on the boat and at home -- use insulated wire.
Size is relatively unimportant, though larger diameters may have a slight edge. Stainless steel doesn't conduct as well as copper, and RF travels almost exclusively on the surface, so the more the merrier. However, everything's a compromise.
Yes, just form the ends into loops. I've written and posted pix extensively on the SSCA website and others on dipole construction and tuning.
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