SSB Antenna Options

[Ryban]

When I replaced our rigging and boomkin, I switched our boat from a dual backstay to a single backstay for a variety of reasons that aren't really relevant to this conversation. However, one of the old backstays was installed with an insulated length to use with an onboard SSB radio (with an antenna tuner inbetween the two).

I'd like to keep our SSB transmit capability, mostly for redunancy, and am wondering what options are avialble that don't require installing insulators on the backstay. I've seen this antenna featured in a few articles: https://defender.com/en_us/gam-elect...ngle-side-band which is basically a split lead antenna that fits over the the backstay -- but it's pretty pricey for what it is (in my opinion).

I'm assuming that just running an antenna along the length of the backstay with isolaters afixed to keep the two separated by some small distance isn't going to work well for me, otherwise I'd probably see products like that being sold too. Is this a non-starter because of attenuation/reflections from the grounded backstay being parallel and in close proximitiy to the transmitting antenna? How does the split antenna above get around that issue?

[alctel]

I used a length of nylon covered lifeline hauled up on the spare main halyard, connected to the antenna wire via nicopress sleeve

[davil]

one more for running a rigging wire isolated, my preference was not hoisting it using a spare halyard, instead ran a rigging stainless wire inside a PVC irrigation tube (about 20 ft) tied to the backstay with small nylon ties, it is there permanent.

It works for me, reception seems ok for the limited use of an SSB these days, but get Parker's weather reports.

[S/V Illusion]

Originally Posted by Ryban

I'm assuming that just running an antenna along the length of the backstay with isolaters afixed to keep the two separated by some small distance isn't going to work well for me, otherwise I'd probably see products like that being sold too. ?

Look up what a “fan dipole” is. Many sold (or built) every day.

The interaction between disparate wires in close proximity is a function of resonant length more than anything else. Dissimilar lengths are what fan dipoles are being they have multiple but different length conductors adjacent to each other with very little interaction.

As this applies to your question, a random length wire through a tuner operating on multiple marine frequencies can be co-located along a backstay as long as they are not electrically connected.

[team karst]

Originally Posted by S/V Illusion

….

Dissimilar lengths are what fan dipoles are being they have multiple but different length conductors adjacent to each other with very little interaction.



……connected.

Have you modeled that theory?

[S/V Illusion]

Originally Posted by team karst

Have you modeled that theory?

Multiple times.

And as a practical matter, I’ve built and used fan dipoles demonstrating the validity of the interaction effects being minimal.

[ka4wja]

Ryban,
1) The above info is mostly correct.
(and, while I do grasp what Illusion is trying to show through example, it's really not a "fan-dipole", whether driven or coupled....so, please don't go looking up "fan-dipole", as it might confuse you.)


2) So....What you propose will work....but...

a) But, be advised that having your antenna wire in close proximity to the backstay will effect its performance, as well as couple a good deal of RF into the backstay (and hence your entire rig). Now, while this isn't always bad, it CAN be an issue on some boats / in some installs...you just need to be aware, so that you don't spend $$$ on something that "someone" told you would work, and then you'd need to look at other options.

Worst case is you try and have issues....and then move on to another idea (such as a separate wire running up that you can use and your antenna....our old friend here abouts, Bill Trayfors, WA6CCA, coined this as an "alternative backstay antenna")

Also be aware that this RF coupled to your rigging and any other equipment attached to your mast, etc., can cause significant RFI issues on-board. (although some, particularly on simpler boats, report having no major issues at all....so, not saying "no"....rather I'm saying "be aware"...)


b) And, be advised that "coupled" antennas (such as the GAM-Split-Lead), "slant-fed", and "shunt-fed" antennas have been well understood since the 1920's and 30's....they are nothing new.
And, while the do serve a purpose (and in some cases do work fine), they are inherently difficult to operate (and match) over wide frequency ranges, hence in our applications are not usually a good choice.
(but, again....in some installs they do work fine....it's just that this is rare and unpredictable....so, nobody of any experience actually goes out and recommends them)


3) I understand that rigging insulators are pricey....but there are many BS stories about them that should be understood as false.
Fact is they are designed to be stronger than the rigging wire size they are installed into!

Anecdotally (like all the BS stories about them), in > 50 years I've seen my share of rigging wire failures (on other boats and remnants in boat yards), and seen some rigging insulators throw-away, but I've never seen one break, nor have I ever heard (from a reliable source) of one cause a dismasting, ever.

So, if you wish to keep costs down, I understand....
But, if "someone" told you that "they're not safe", please just smile and walk away.



4) Finally....
I have a question.
I spent a great deal of time / effort putting together vast resource of info on all of these "SSB" matters, answer some specific questions on clarity, and try to keep it fairly up-to-date....
So, does anyone actually go to those "Stickies" up top of the Marine Electronics page here? ('cuz just about all of these matters are covered there.)

Just saying, the info / explanations are there....as well as links to many "official sources"....and links to videos that explain most of the "operation", etc....
All for free....with no BS...and nobody asking for "likes" or "please subscribe", etc....nothing is monetized, just all there for my fellow sailors, for free.

You might want to have a look see?


Good luck and Fair winds.

John

[S/V Illusion]

Originally Posted by ka4wja

Ryban,
1) The above info is mostly correct.
(and, while I do grasp what Illusion is trying to show through example, it's really not a "fan-dipole", whether driven or coupled....so, please don't go looking up "fan-dipole", as it might confuse you.)


John

I used the fan dipole example to demonstrate how little interaction occurs between proximate but dissimilar lengths of wire.

[MicHughV]

Well, presumably the antenna is fed by an automatic tuner...

Here's what I did in a similar situation.

I mounted the tuner in the lazarette locker right up against the transom, under the deck. I got a small insulated (about 3" high) thru-deck fitting that was installed right on top of the tuner. From the tuner to the bottom of this fitting was a short length of GTO-15 cable, maybe 2-3" or so. The tuner, was off course fed from the radio.

Attached to the corner of the stern pulpit (so it would be out of the way) with some fancy string work, I had a 1.5" pvc pipe, such that the top was about 6' off the deck. I did this, so nobody would inadvertently touch the antenna while I was on it.
From the top of the pvc pole to the top of the mast, I ran a length of 1/8" galv. wire in a plastic sleeve. Each end was fitted with a small insulator. From the insulator on each end I used tarred twine to attach to the top of the mast and pvc pole, but you could really use any type of rope here, I allowed for about 18" clear distance on each end of the wire insulators.

From the aforementioned thru-deck fitting I ran another length of GTO-15 wire thru' the pvc pipe and attached to the galv. wire antenna with a bronze cable clamp which I taped over with electrical tape.

That's it.
Sounds more complicated than it is actually to install.
It worked like a champ. I never had a problem either sending or receiving a signal.

On occasion the heading of my boat, while I was on the radio seemed to make a difference. I would change course for a few minutes such that my stern was aimed at the source of the other radio. but most of the time, it worked fine.
i
Hope this provdes some idea.

[bdgWesternMass]

Originally Posted by ka4wja

Ryban,
..
So, does anyone actually go to those "Stickies" up top of the Marine Electronics page here? ('cuz just about all of these matters are covered there.)

John

Yes, thank you for doing it. I always check the sticky.

[Ryban]

Clearly I did not do a good job of looking at the forum before posting my question -- I read through your sticky in full, and it's a very good resource. Thank you!

It isn't so much the price of the insulators -- I actually still have the two I took off when the boat was rigged with a dual backstay. I just don't have any good way to inspect these, and I don't know how old they are. I do think the insulators themselves are probably plenty strong, but it also adds 4 additional wire termination points to the backstay, rather than the normal two. Though I've never had one fail, I do get the feeling that this necessarily makes the backstay slightly more compromised.

[ka4wja]

Ryban,
1) Okay on the new info...

Originally Posted by Ryban

It isn't so much the price of the insulators -- I actually still have the two I took off when the boat was rigged with a dual backstay. I just don't have any good way to inspect these, and I don't know how old they are. I do think the insulators themselves are probably plenty strong, but it also adds 4 additional wire termination points to the backstay, rather than the normal two. Though I've never had one fail, I do get the feeling that this necessarily makes the backstay slightly more compromised.

2) And, just for clarity (for everyone here), the "antenna" is not the insulated length between the insulators....rather the antenna is the whole thing from the remote tuner (including the remote tuner!), the GTO-15 wire leading from the tuner up to the backstay, and the backstay itself (between the insulators)...these are ALL the "antenna"....
...AND...
Further it is the lower end....the remote tuner and the first 5 - 15 feet of wire from the remote tuner (whether GTO-15 wire or SS rigging wire...or lower-half of a 23' whip)....that are the most important part of "the antenna"....just like the more important part of the antenna ground is the part closest to the start of the antenna, the remote tuner and the low-imp connection to the sea water, etc...
{I know some will want an explanation, and a few may even wish to argue....but, please can we all just accept some engineering/scientific facts?}


3) Looking specifically at your situation / application...

Originally Posted by Ryban

When I replaced our rigging and boomkin, I switched our boat from a dual backstay to a single backstay for a variety of reasons that aren't really relevant to this conversation. However, one of the old backstays was installed with an insulated length to use with an onboard SSB radio (with an antenna tuner inbetween the two).

Assume the remote tuner is already located near one of the old chainplates?

a) So, why not simply rig a wire (SS rigging wire, vinyl-coated SS life-line wire, or even some 14ga or 12ga insulated copper wire) from that chainplate --- up to your masthead (or close-to it)?
Giving you an ~ 30' - 45' long antenna length, just about what is typical.
This is what we'd refer to as an alternative "backstay-antenna"....(note this is not an "alternative-backstay" antenna....but an alternative "backstay-antenna"....meaning it's an alternative antenna that looks like a backstay, but is not part of your standing / structural rigging)
Tied off at both ends with some double-braided polyester line (like sta-set), I prefer with a couple insulators, but if you accept possible arcing/melting issues when transmitting with a wet antenna, you could get by without insulators....
Btw, I personally, experimenting with antennas on-board, I have personally had partially melted rope loops (the loop of a bowline) at the wire ends....and this was just from a few weeks of testing....so, after that, I ALWAYS recommend insulators, and not rely on the "non-conductive rope"! No BS here....you really need to insulate the antenna, or accept it as just a "fun" "temporary" antenna.
Just saying....there are real reasons that we use insulators, not just "because that's what everyone does".
[for an ocean-going boat, I'd recommend what Bill used-to recommend...vinyl-covered SS life-line wire, put the eye of the lifeline thru a ceramic (or plastic) insulator....and, it will last a long time....crimp/swage GTO-15 to the bottom end, and run that thru-deck to the tuner...]


b) If this wire would be in-the-way of your sail, boom, etc....or otherwise not fit properly, then MicHughV's idea of running your wire vertical / straight-up above the deck (using either some sort-of stand-off support, like his PVC pipe....or you could rig a piece of SS tubing, like a 6' high stanchion, with a cross-support, and use this as the bottom part of your antenna?), with a wire running up from the top of this pipe/tubing to your masthead....thereby giving you the typical 30' - 45' long alternative "backstay antenna"?



4) Of course, my overall recommend is still "use insulators" (new or used, depends on how-old and what condition).

Sure, going up the mast to "inspect" your rigging terminals is a pain, but in all honesty how often do you do this? Once-a-year is what I do....and, it takes me all of an extra minute to reach out an look at the terminals on my upper insulator.

As for the terminals on the lower insulator, I see them all the time (they're right by my helm, so a see 'em every day).




Ryban, I hope I pointed you to some ideas/options for you, that you're comfortable with? (as well as gave you my own personal recommends)

...AND...

Finally, just to be clear, I'm not a professional rigger....I hire that out...
I did take a materials science class in college (majored in Physics, tho), and I am a certified welder, and machine tool operator, as well as been sailing offshore on-off my whole life....so I know enough to know what I don't know.
Which is why I hire a professional rigger to re-rig my boat...
I mean, I KNOW I could do it myself, but it is a lot of work on a 47-footer with a 64' tall double-spreader mast, and I make my living in electronics....so, I paid my rigger (Colin Mack, of Mack Sails and rigging), wrote a check (a big f'ing check) and I'm a happy camper.


Fair winds.
John

[SY Harmony]

Originally Posted by Ryban

I'd like to keep our SSB transmit capability, mostly for redunancy, and am wondering what options are avialble that don't require installing insulators on the backstay.

Are you staying marine bands only or ham also?
Will this be a temporary use antenna or a more permanent install?
There are many compromise antenna options you could rig up.

[Brian.D]

I'll throw my 2¢ worth in the mix...

For all bands with tuner, 7.2 meter or 9.2 meter wire rope, like used on life lines. Raise this with a spare halyard (put one in if you don't have one).

For single band coverage (tuner or no tuner) a dipole will work tuned to the frequency of operation. Also raise with a spare halyard.

I have always been against cutting the backstay. Just because it is now compromised. Many will disagree and that is fine.

For info on the dipole, read this. The info can also pertain to a single wire as mentioned for all band operations with tuner.

JMHO

[Ryban]

Thanks for all the feedback -- this is super helpful and I learned a lot already.

I think I will start with what I have, and hoist up a length of 12 gauge insulated copper wire, crimp this to my GTO-15 cable I have coming out of the tuner from the previous install and start experimenting. If that goes well, I'll probably swap it out for insulated SS lifeline wire for longevity.

I don't think the system is currently grounded though, at least not from my inspections. Is there a reason why copper strapping is recommended as the ground connection instead of copper wire? Are there any concerns about providing a path for stray current corrosion (in a marina) by using a thru-hull as a ground in this way?

I've also been considering swapping all my old Groco seacocks for TruDesign composite ones, which might require me to re-think a grounding strategy long term.