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Old 14-10-2010, 23:43   #1
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SSB Whip Antenna Versus Isolated Backstay

I am going for two years of circumnavigation from next summer. SSB radio is one of the key tools, but I would like to avoid the reconstructing of one of my two backstays to use it as antenna. Such a construction process stands to me as a huge intervention to the originally standing rig. If possible, I would prefer to use a whip antenna, but this preference is based on no experience. I really do not know what to plan for, so if anyone out there do have experiences of solving this matter to the best for the boat and the sending/receiving strength - please share with me.

Fair winds,
Gunnar
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Old 15-10-2010, 01:09   #2
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An other option is using braided copper wire that runs the length of the mast held away from the mast by insulated stand-offs. This may only work for wood masts, but am not sure. It is a sound method and I am going that route.
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Old 15-10-2010, 01:48   #3
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The only downsides to the separate whip antenna is it's weight and windage. Cool thing the riggers do these days is a synthetic backstay with a simple wire run up with it. Both enclosed in a sort of heat shrink cover. If you replace your backstays you should go this route as the non-antenna one would be synthetic and not absorb power.

Twin backstays, and the other idea of a wire on insulators do not sound like a good idea from a radiation standpoint. Any nearby conductive object is essentially part of the antenna. The mast and a second backstay are presumably grounded which, in theory, would greatly attenuate the signal. But one may not know for sure until one tries it.
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Old 15-10-2010, 06:21   #4
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OK guys go easy on me with this one. I believe a main differece between a whip and an insulated backstay for a antenna is transmitting distance. The insulated backstay all things being equal, can bounce its signal off the ionosphere sometimes thousands of miles, don't think whips typically duplicate this range.

Backstay insulators have been utilized on sailing vessels fo a very long time and my guess would be that correctly installed they are no more prone to failure than any of the other fittings on your boat.
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Old 15-10-2010, 06:28   #5
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Having done my own research for my own journey, I'd add a vote for the whip antenna, although they can get quite expensive compared to the usual backstay options. I've heard mixed reviews regarding the GAM Split Lead SSB antenna for a backstay, but this is another option.

My next decision has to do with grounding. I'm not sure dynaplate is something I want to add.

Disagree with post above regarding E, F1, and F2 bounce and antenna. Depends on the antenna and tuning art.
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Old 15-10-2010, 06:35   #6
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OK guys go easy on me with this one. I believe a main differece between a whip and an insulated backstay for a antenna is transmitting distance. The insulated backstay all things being equal, can bounce its signal off the ionosphere sometimes thousands of miles, don't think whips typically duplicate this range.


Not quite. Both (backstay and whip) are essentially vertically polarized and therefore radiate ground wave signals with only a small component of the signal radiated up. Also, signal "skip" is a function of frequency with only the higher freq marine channels having sufficient wavelength to bounce - most marine channels are too low although generalities all have exceptions and strange things happen after sunset sometimes. Any Not quite. Both (backstay and whip) are essentially vertically polarized and therefore radiate ground wave signals with only a small component of the signal radiated up. Also, signal "skip" is a function of frequency with only the higher freq marine channels having sufficient wavelength to bounce - most marine channels are too low although generalities all have exceptions and strange things happen after sunset sometimes. Any vertical antenna will generate predominantly a ground wave signal and therefore all are essentially equivalent in terms of effective distance. The only variable in the efficacy is the RF ground to which the antenna is attached.
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Old 15-10-2010, 06:37   #7
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Don't bother with the Dynaplate. Capacitive coupling thru the hull works great. Plus the keel. And the lifeline/toerail should be grounded near the tuner too, both for radiation and you don't really need an induced surprise voltage in them, no?

The recommended whip is quite a tall item..17 feet or something?? Going to need a serious mount to keep that up during rough times.
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Old 15-10-2010, 06:49   #8
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The marine channels use the skywave (skip) just fine. Nearly all the HF/SSB channels used for Sailmail and Nets are above 3kHz and rely entirely on the skywave to communicate as the ground wave is ineffective above 3kHz...no?

Anyway, the whip will work fine, and a 15.5m boat can carry it just fine without looking silly. I've one stored down below next to the spare rudder in case I lose the rig.
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Old 15-10-2010, 06:54   #9
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Lotsa mixed signals in the above posts :-)

Vertical polarization has little to do with long-distance contacts (horizontally polarized beams do just fine in this regard). Rather, the controlling factor is vertical angle of radiation, i.e., how far above the horizon the major radiating lobes of the antenna are. For long-distance contacts, you want to radiate signals as close to the horizon as you can. Vertical antennas are pretty good in this regard so long as they're located down low. Raise them up and their vertical angle of radiation increases.

While vertical whip antennas and backstay antennas are both more-or-less vertical, I wouldn't call them equal in most cases. They're both -- effectively -- random-length end-fed radiators. They are both capable of putting out decent signals over long distances, but the backstay has the edge on the lower bands because it is typically longer. Longer end-fed wires favor the lower bands (say, below about 10mHz), while shorter ones favor the higher bands. The difference can be dramatic.

The typical SSB whip antenna is 23' long. That's a lot of antenna to have bouncing around in a seaway. Clearly, some additional support above the mount is required.

What to do in the OP's case depends on his backstay configuration. If it's a true 2-backstay rig (independent backstays led all the way to the truck of the mast), then one good solution is to put a single insulator near the top of one of the backstays, and feed it from the chainplate belowdecks, with the tuner located closeby. I agree with the sentiment of not wanting to break up a perfectly good backstay, but I also have never heard of an insulator failure. I'd use one of the Haydn insulators...pricey, but fail-safe.

I agree with the sentiment of avoiding a ground plate. It's not really necessary to couple to the seawater, either directly or capacitatively. Some of the strongest signals on the bands from boats are those which are using radials of some sort which have no contact with seawater. I install lots of these, and have used them on my own boats for many years. Just this morning Rick, W4GE, served as Waterway Net Control from his 25' boat, using a random wire antenna and radials inside his hull. He had a strong signal from Charleston, SC south to Honduras and north to New York.

In this regard, I've had good success using the new KISS-SSB ground system on several client boats. Small, very easy to install, and very effective. Other types of radials work well, too. See my post "RF Grounds in the Marine Environment" on the SSCA board.

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Old 15-10-2010, 07:05   #10
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Quote:
Originally Posted by Camelot View Post
I am going for two years of circumnavigation from next summer. SSB radio is one of the key tools, but I would like to avoid the reconstructing of one of my two backstays to use it as antenna. Such a construction process stands to me as a huge intervention to the originally standing rig. If possible, I would prefer to use a whip antenna, but this preference is based on no experience. I really do not know what to plan for, so if anyone out there do have experiences of solving this matter to the best for the boat and the sending/receiving strength - please share with me.

Fair winds,
Gunnar
I've seen plenty of twin backstay rigs working fine using three insulators. One at the bottom of the active stay, one on single top stay just above split & one at top of second stay to isolate this.

I understand you may wish to avoid this, but its still the neatest solution.
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Old 15-10-2010, 07:08   #11
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Richard,

The OP's boat is a Beneteau Idylle 15.50 which as two full backstays, not the type of split backstay you're referring to.

B.
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Old 15-10-2010, 07:13   #12
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The typical SSB whip antenna is 23' long. That's a lot of antenna to have bouncing around in a seaway. Clearly, some additional support above the mount is required.
Yes 17-23 feet depending on the model. Additional mount a few inches higher should be sufficient. Also, mounting in tripod similar to how you mount a wind generator.

Flex isn't an issue for me. Whips are used in commercial settings and some are made for sailboats - just fine.

Biggest issue for me is cost$$$$$

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Old 15-10-2010, 07:52   #13
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Richard,

The OP's boat is a Beneteau Idylle 15.50 which as two full backstays, not the type of split backstay you're referring to.

B.
Even easier then you only need two insulators. I don't see why Gunnar is so averse to using them. I don't see too many broken backstays.

Only issue would be to keep the active part of the backstay as low & therefore as far from second backstay as possible, commensurate with having adequate length. On a 15.5m boat I don't think this would be a problem though.
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Old 15-10-2010, 07:54   #14
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If cost is a big issue, avoid both options you mention (insulating a backstay & installing a whip). Instead, go with a random wire, held up by mast or rigging. Ideally, your wire antenna should go vertical as soon as possible after leaving the tuner. Note that all 3 options will require a random wire tuner (~$50 for a manual tuner, $400 for automatic).

We've used random wires for all 15+ years of our cruising, & we're told we put out an excellent signal. (See our Yacht Rescue for a good story here)

You want your antenna to be as far as practical from your standing rigging or you'll get coupling & strange radiation effects. The top of your antenna does not have to go to the top of your mast - we use several feet of nylon cord as our upper insulator, tied to the end of an upper spreader. We also use bungees at the bottom to maintain tension, as the antennas do get hit by things.

Ocelot has no backstay & our main has too much roach to put an antenna behind the mast, so both of our random wire antennas (1 on a manual MFJ tuner, 1 on an Icom auto-tuner) go up just forward of our cap-shrouds, & tie to our top spreader. These antennas ARE a bit directional, as they're affected by the rest of our rig, but you'll get that with just about any antenna.

We also don't have a problem with Dyna-plates as grounds. We have 1 under each tuner. They're simpler than radials for a newbie, as radials should really be cut to length for each band you intend to use. You want wide copper strap going to whatever grounding system you use.

Hope this helps...
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Old 15-10-2010, 09:04   #15
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I have two Haydn insulators sitting next to me right now, to install on our single backstay. I got them from rigging only, great guys, know their stuff really well. THe price was less then other online retailers I checked.

Brian is right, they are fail safe. If the plastic that insulates the wire fails, then the metal makes contact, but the rig stays pointy end up.

Chris
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