SSB

[Don S/V ILLusion]

If you are operating under a U.S. license, you must do so within the constraint of that authority, regardless of where you are located. Compliance with local requirements is also concurrently expected.

Also, I don't think anyone was implying an absolute restriction on length of transmission; quite the contrary - what he said was "discouraged because there are only a limited number of frequencies". This is more a matter of courtesy which is just as compelling and therefore just as relevant.

 

[Don S/V ILLusion]

Interesting, If lost the back stay and the primary antenna. I would pull out the rope antenna , lay it on the deck and make what calls I could.

The attenuation would be so great under those conditions as to make the exercise futile. In addition to all the wiring under the deck and what's left of the mast and rigging on deck under that circumstance, the interaction would severely attenuate any reasonable radiation pattern and when coupled with the fact the antenna is now horizontal and close to the water, the polarization would make it essentially useless. This is why I question some of the marketing although I do agree that conceptually, it's a great idea. It's being marketed as a backup which seems to me to be, in polite terms, imaginative.

 

[Chuckbear]

Bills question was this, "Are there lots of restrictions on length of communication and such?" and I answered his question. This is with courtesy aside, and the extent of FCC regulations are dependent upon the regulations of the visiting country, in which case that countries regulations apply.

 

[Franklin]

SSB is for sailors. So sailors should set the rules, not FCC. There really aren't that many feq if you consider it's for all sailors worldwide. All it takes is 10 sailors hogging the feq having hour long conversations with family back home to kill the feq. I would think 10-15 minutes is more reasonable. Anything more then that is abusive....but of course, if nobody else is on or wanting on, then by all means, talk until you are blue in the face.

 

[Bill Roosa]

Antennas

So the back stay half dipole is the de facto standard for sailboat HF antenna.

I know a little about the Ham side of things and the laws of physics being what they are (universal) it would appear that there are other configurations of wires and balins out there that could be used. I'm a little concerned about using a half dipole as it has probably the worst gain of any of them and it has the whole grounding problem. A simple long whip antenna provides better reception and is much easier to install. You can install them on a car if I understand the literature correctly.

I'm wondering what is driving this choice? I suspect it is a combination of safety and available length for the antenna.

Another way of asking this question is what frequencies are most using? If the lower frequencies are not being used then you could have a same length dipole and at least twice the gain.

 

[Don S/V ILLusion]

Bill
What you refer to as a "half dipole" and a whip are equivalent - they are other unbalanced antennas both needing a counterpoise to be effective. In both cases, they radiation pattern is vertical and follows ground path so there would be no discernable difference.

By contrast, a dipole is a balanced antenna, having two equivalent sides and is usable on only one frequency as it is a tuned antenna thereby making it impractical for marine use.
For ham bands however, a dipole does provide some advantages and is a popular antenna aboard boats but usually configured as an inverted V to accommodate the center feedpoint issue.

I think you know but another consideration is that a dipole (operated on it's designed freq) requires neither a tuner or counterpoise; a ship or any other unbalanced antenna requires both regardless of it's operating freq.

There is really no such thing as a gain antenna - antennas don't produce an increase in radiated signal. Rather, some configurations can distort the radiation pattern such that more signal is radiated in a specific direction or radiation angle so as to appear to increase radiated power in a specific area but obviously boats are not stationary so the whole issue of gain is dubious.

Stated differently, there is no such thing as the best antenna for a boat - it depends on how much effort one puts into a counterpoise, where you are trying to communicate and how wide a range of frequencies over which you intend to use the radio.

 

[windward54]

Bill, I think it is a combination of things that drives the choice. Safety is one as the long wire antenna can be mounted in such a way as to prevent injury. I think the biggest part is that it works very effectively, all things considered for the space it takes up.

As for the most used bands, hard to say on SSB. I find that most of my talking is on the ham side out, and use the 17 and 20 meter bands, with some on 40 meter.

 

[mutualfun]

The attenuation would be so great under those conditions as to make the exercise futile. In addition to all the wiring under the deck and what's left of the mast and rigging on deck under that circumstance, the interaction would severely attenuate any reasonable radiation pattern and when coupled with the fact the antenna is now horizontal and close to the water, the polarization would make it essentially useless. This is why I question some of the marketing although I do agree that conceptually, it's a great idea. It's being marketed as a backup which seems to me to be, in polite terms, imaginative.

Only reason I stated that I would lay it on the deck is a friend of mine has a rope antenna as mine and he tried it just to see if he could transmit and receive, I will do the same this summer so I know! I am curious when you contact Dr John Gregory what he will tell you about the questions you want to ask him.
Randy

 

[Don S/V ILLusion]

Randy
Just sent email with questions and will post his response
Don

 

[Don S/V ILLusion]

I asked the company to provide answers to two specific questions. The first reply was unresponsive and upon requesting clarification, received this:

Q. What is the advantage of ladder line compared with the conventional copper foil counterpoise?
A. "The reason for the ladder line is that is also comes in 470 ohms. The Impedance on the auto antenna tuners are 80 to 1200 ohms form 2 -22 MHz. This is a better match then just running a copper strip when is resonant only at one frequency."

Q. What reference is used for the gain figures quoted in your advertisement?

A. "Now as for the antenna , lowering the SWR increases the gain of the antenna . The antenna being completely matched to the tuner to maximize the output power also increases the gain. The antenna a recipe cal integer is far more efficient then long wire cut to some un receptacle number."

I hesitate to describe my reaction and will leave it to other ham radio operators and those with some understanding of basic antenna fundamentals to form their own opinion.

 

[windward54]

Now you know why I went with the Gam antenna. I talked to the guys there as I had a couple of questions and they were great. There were no claims that the antenna worked better or was superior to anything else on the market, just that they offered an antenna that was equal to a backstay antenna without having to cut up the stay. The antenna was reviewed by Gordon West, and I was lucky enough to have a chance to talk to him about the antenna. His opinion was the same as offered by the manufacturers. He did give me a couple of tips to make it work a little better though.

 

[Bill Roosa]

Antenna theory

Don
I believe they call it "antenna theory" not antenna fact for a reason. What you are asking is tantamount to asking a NASA scientist during the early 60s to predict the chemical composition of the moon.

caveat emptor says it all.

Windward; What the heck is a gam antenna?
A picture or diagram would be helpful. Could this be a Gama antenna? directional short wavelength (<3 m) loop antenna??

 

[Phantomsailor]

Installing a marine SSB or ham radio aboard your boat is not as difficult as some would lead you to believe. Gordon West's advice (backed up by on the air testing) is solid. I've installed SSBs aboard my own boat, a boat I raced to Hawaii on, and 3 other boats that participated in the '07 BaHa Ha Ha. All of these installs were installed the same way with outstanding results. On the way to Hawaii, I was able to send and receive e-mail, weather faxes, and grib files from the mainland all the way across (2,200 nm). On the Ha Ha, my installs were among the strongest signals. I was crewing on one of the boats with my SSB install, and could hear and compare the signals from the 2 other boats with my installations aboard.

To summarize these 5 installations:
* All used an insulated backstay.
* All had the antenna tuner mounted as close to the backstay as possible
* All had copper foil running from the ground lug on the antenna tuner to the nearest underwater metal. On 2 of the boats, this was the propeller strut mounting bolts, and the other 3 were the engine intake thru-hulls. None of the boats has experienced any corrosion issues after connecting the SSB RF ground foil to the underwater metal.
* All had copper foil running from the antenna tuner ground lug to the stern pushpit railing making the pushpit, lifelines, and bow pulpit an effective antenna counterpoise. 1 boat had metal toe rails. The toe rails were also connected via foil to the tuner's ground adding to the counterpoise. If you are wondering if it is dangerous to touch the pushpit or lifelines while transmitting, you should know that I personally tested for this by touching and grabbing the pushpit & lifelines while transmitting. No RF burns or other effects were experienced.
* None of the boats had foil run to the SSB tranceiver. This was done to avoid "ground loops".
* All had ferrite beads placed at the transceiver and antenna tuner ends of the tuner control cable. Ferrite beads were also placed at each end of all cables to and from the pactor modem. In the case of the M802 installs (4 boats), ferrite beads were installed at each end of the remote head cable
* All had T-4 Coax line isolators installed in the transceiver to tuner coax cable near the antenna tuner. http://www.radioworks.com/

If a thru-hull is used and the thru-hull is part of a bonding system (green wire connecting thru-hull to other thru-hulls and other underwater metal), the green wire should be disconnected from the thru-hull you plan to use for your SSB RF ground seawater connection. If worries about galvanic corrosion persist, you can isolate the thru-hull DC current wise but not RF by using the isolation technique described by Stan Honey's "Marine Grounding Systems" article. The article is here: http://www.sailmail.com/grounds.htm

The above descriptions of these installs doesn't mean that insulated backstays are the only way to go. A 23' whip will work, the GAM antenna will work, a simple piece of wire hoisted with a spare halyard and connected to the antenna tuner's output will work.

Hope that helps.
Rodney
S/V Sashay
K6YOT
WDB9686

 

[windward54]

Bill,, a Gam antenna is a 34' double-strand wire antenna that slides over your backstay, made by Gam Electronics. Works great and you don't have to cut up the backstay. Works like the isolated backstay in theory, but they use a better material then stainless steel wire to help get the signal out. Nice thing about this other then keeping the integrity of your backstay is you can install the antenna low; I anchored mine in the turnbuckle of the backstay. By keeping it low to the water, in theory I should get a little better angle. Or so I was promised by Gordon West. Because the wire is incapsulated in plastic, there is no danger of an RF burn. I keep people away from it anyway, just in case. Also, you can take it down and reuse it any time. As long as you don't have a split backstay, it installs in minutes by one person, without having to go up the mast. You just slide it up the backstay and use plastic wire ties about every 6 feet to secure it.

www.gamelectronicsinc.com

 

[windward54]

Hey Phantomsailor, are you finding more people on ham then on SSB like I have experienced???

 

[Don S/V ILLusion]

Don
I believe they call it "antenna theory" not antenna fact for a reason. What you are asking is tantamount to asking a NASA scientist during the early 60s to predict the chemical composition of the moon.

Bill
I take a very different view - that hams are almost fanatical when it comes to antennas and are notorious for experimentation, computer modeling and plain old trial-and-error work with all types of antennas and in my view, it is all about practical and measurable results - not theory.

I think a more accurate metaphor would be like asking a high school physics or chemistry student to predict the chemical composition of water - although the answers I received sound more like your analogy.

 

[Franklin]

So the antenna has to be balanced. I've learned that much in this thread and I thank you guys. I believe I also learned that either an antenna has to be exactly the right size, or it has to be able to "resize" via a tuner. True?

I assume that's the reason for the grounding to the sea...as the sea give it the ability to grow in size beyond the length of the wire.

Now a inverted V has been used without grouding. I assume that limits the frequencies it can use. I am kind of curious about this because I don't have a backstay, but I have two swept back stays. I was wondering if I ran an Inverted V wire to the top of a 60' mast in the same fashion as the swept back stays are (an end on each side of the boat), what frequences I could use with that antenna and a tuner leading to it?

 

[Don S/V ILLusion]

So the antenna has to be balanced. I've learned that much in this thread and I thank you guys. I believe I also learned that either an antenna has to be exactly the right size, or it has to be able to "resize" via a tuner. True?

Effectively, Yes. In reality, it's not that straight forward but for purpose of this discussion, that's all you need to know.

I assume that's the reason for the grounding to the sea...as the sea give it the ability to grow in size beyond the length of the wire.

good analogy

Now a inverted V has been used without grouding. I assume that limits the frequencies it can use. I am kind of curious about this because I don't have a backstay, but I have two swept back stays. I was wondering if I ran an Inverted V wire to the top of a 60' mast in the same fashion as the swept back stays are (an end on each side of the boat), what frequences I could use with that antenna and a tuner leading to it?

The freq on which an inverted V (dipole) works is a function of it's length (or wavelength) or is typically cut to resonate on a specific frequency and fed directly with coax. It can only be effectively used on a diverse range of frequencies if you feed it with twin lead and a tuner. Therefore, in answer to this question, you can use it effectively on any frequency only when:
1. it is fed with twin lead through a tuner, and
2. it's length is longer than the wavelength of the freq on which you intend to operate the radio.

Regarding Phantomsailior's comments, he is correct but I believe the discussion is not so much what can work but rather degrees of effectiveness.

 

[Phantomsailor]

Hey Phantomsailor, are you finding more people on ham then on SSB like I have experienced???

Yes, much more on people on ham frequencies. Though I do hear asian fishermen on the marine frequencies... and trust me, these guys don't care how long they talk Since we're just past the bottom of the 11 year sunspot cycle, propagation will continue to improve.

 

[Franklin]

1. it is fed with twin lead through a tuner, and
2. it's length is longer than the wavelength of the freq on which you intend to operate the radio.

1) What is a twin lead?

2) Is the length you refer to the length of one leg of the V or the entire length of the wire of the V?

3) If the deck to mast is 55' and the two ends are 12'6" apart, would that help you point me in the right direction to find out what percentage of SSB channels I could use? If it's like 70% or more, then I think this is the solution for me because it sounds a lot cheaper then a 23' whip antenna and easier.