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Old 05-11-2021, 13:51   #1
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Alternate backstay antenna

I'm planning an SSB installation on my 41" ketch next Spring and while mining the forum for ideas and advice, I was quite intrigued by this post advocating the use of a sloper antenna (top fed) for HF.

Isolate the backstay right at the masthead, connect it to the central of the coax cable, connect the braid of the coax to a SS strap linking the mast and all other rigging, then feed it to a manual tuner down below. No counterpoise needed.

Could that really work? The discussion was among knowledgeable and experimented authors, so there must be some credit to it. Seems so simple.

Anyone having real experience with this alternate backstay antenna ?

It also seems like it would be fairly easy to test. Just have to borrow a manual tuner and use a proper length of coax. Undo the backstay up and down but maintain it in place with rope (it will be isolated) and give it a go so you can estimate the efficiency of the setup before committing to it.
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Old 07-11-2021, 00:17   #2
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Re: Alternate backstay antenna

Bazz,
1) Let me preface this with the short answer (considering a 53' mast height Out Island 41 ketch [58' mast height on a 416, I think??], with backstay chainplates about ~ 13' - 15' aft of main mast, i think??) is: [for a great low-band (3.6 - 8mhz) groundwave (50 - 300 miles over sea water, using vertical antennas, which is not possible on land), and acceptable NVIS performance due to the slight slope of the backstay, and excellent daytime 12 - 22mhz long-range (~ 2000 - 5000 miles+), and nighttime 3.6 - 14mhz long-range antenna]:
You're much better off with an auto-tuner-fed backstay, and a direct sea water counterpoise connection...(no matter how knowledgeable or experienced the authors of other antenna ideas, for most of our applications, the above is a fact)

Of course, if you have other applications / desires, there are other options and ideas....but...but that's a loooonngg answer.

And, Bazz, I'm fully aware that you'll get many comments / advice here, and I don't have the time, nor patience, for endless online arguments (which usually are just some folks flexing their egos, rather than trying to learn from each other), so please understand that I'm trying to keep ego out of my answers here....just my desire to help point you in the right direction.


2) Rule #1 in antenna system design is (and since the 1920's, always has been): anything metallic can radiate and be used as an antenna to some extent, it's all a matter of degree how well one thing works, versus another.

Rule #2 is (and always has been): what antenna will work best / most effectively depends on many factors....the 4 or 5 most important / most relevant to most HF communications users are:
a) "where" do you desire to communicate (what distances)
b) what time of day, time of year, etc.
c) what frequency bands are most needed, at whichever times and various distances
d) how much space / room do you have for antenna(s)
e) what is your budget

Rule #3 is that understanding the basics of radiowave propagation (and on-air experience) is such a vital part of HF comms success, it needs to closely follow the antenna choice decisions, or all else is moot!

Rule #4 is actually a rather new player (coming onto the scene mainly in the last 15 - 20 years, and especially problematic in just the past 10 years), as the received RFI (Radio-Frequency-Interference or "radio noise") is now such a large part of HF comms success, that in some applications where antenna choice / space for antennas is limited, it is the number 1 factor in HF comms success! {yes, in some applications it is more important that the antenna!)


3) Using the above, you can see that your question (regarding a "half-sloper" antenna) is both easy-to-answer AND impossible-to-answer.

a) Easy-to-answer: sure, it will work....'cuz anything will work (but, there are much better antennas for most of us)

b) Impossible-to-answer: we have no idea what bands / freqs, nor what distances / times of day / etc., budget, etc.

c) But, an educated / learned answer is: getting the "high-current point" up high is good for horizontal antennas and good for vertical antennas surrounded by obstructions (buildings, tall hills, etc.), but is all-but-irrelevant in the applications of a vertical in-the-clear over sea-water [yes, it IS in the clear]...as the mast/rigging is in its near-field (extreme near field), and some coupling does occur, but whether base-fed or top-fed, no difference in "gain"...well, no differences from being "top-fed", although the "top-fed-half-sloper" will actually be a worse performing antenna for wide-band / multi-band use, as well as being that you'd be using your entire rig / mast as the other half of your antenna (a very unbalanced situation).

Of course, you'd also have significant losses in the coax feeding the "half-sloper" (the VSWR of that antenna on any freq it is not a 1/4-wavelength long will be very high!!)....
As a weird, real world example, years ago communicating with a friend 15 miles away, on 80m, at night, when my signal (using an 80m antenna) is usually so strong (more than a thousand watts of power, with both transmit and receive antennas in the clear) that he can hear me with his antenna completely disconnected...well, when using a 20m dipole with vswr of > 10:1 (probably close to 20:1) he couldn't detect my signal above the noise....of course on-board a boat, at sea, it would work better, but then so does ANY antenna....(go back and reread rule #1)

Oh, and you'll also have very high tuner losses, much much higher than you'd have if using the tuner to feed the antenna directly.

Oh, and of course, most "coax-based" tuners don't have near the tuning range / capacity needed to properly match the transmitter to this antenna over the wide range of frequencies we use....(and, the losses in these "coax-based" tuners are even higher than those designed for this application)

{please note that this "looking for a better antenna" and finding a "solution [sic] to a non-problem" is getting to be common as more and more folks think that they find performance advantages in some situations and assume these apply to all situations....hint: they usually do not....}

[On an aside note: I started studying antennas and radios as a kid in the late 1960's, and got serious as a young teen in the 1970's, where I taught seminars on antenna system design and radiowave propagation, continuing education in college (a Physics major) and professionally (running my own communications firm for almost 40 years) and non-professionally (been studying/teaching/experimenting with antenna systems, both on-board and on-shore, in amateur radio and maritime radio comms, for > 45 years!) and continuing onto the present (where I still try to learn something new about antennas and radiowave propagation every week! And, the more I learn, the more I find that "Rule #1" and "Rule #2", are even more true today that I thought 45+ years ago!!]

Oh, and we haven't started discussing one of the biggest overall determiners of HF comms success these days: your on-board RFI....and, why would anyone desire to cause more RFI issues, by trying to use a coax-fed-half-sloper and their mast/rig?


4) Please understand that while experimenting with antennas is a great pastime and something that I (and many of my fellow hams) enjoy, there are many, many reasons that on our off-shore / ocean-crossing sailboats we use remote auto-tuners feeding backstays or whips.

And, while there are other applications where other antennas may perform better, there is no argument that for 95%+ of applications discussed here, the ole' venerable backstay antenna (or 23', 28', or 35' whips on trawlers or cats) is the "best overall antenna" choice.

You can find alternatives discussed on-line, etc....and some have merit for some minority of applications....but....
But, "facts is facts"....the physics of both RF and antenna systems, and that of radiowave propagation, haven't changed in 100 years....and, surprising to many laypersons [even those that are considered "experts" in their on-line communities], the research / studies / experiments done in the 1920's thru 1950's is damned good, and compares favorably [almost perfectly] with modern 21st Century computer models / analysis.

Hmmm, kinda' gives you a warm feeling doesn't it....knowing that the engineers at RCA, Westinghouse, Bell Labs, Motorola, GE, etc. etc. etc. etc, who, 70 to 100 years ago, did much of the work we base all of our designs on, were as good or better than 21st Century computer models.



5) I could ramble on and on, but without knowing your application, etc., there is no point, yet.

Also, since we don't know what your application is, there is little to be gained discussing the perceived benefits [sic] of other antenna systems, as this is more likely to spawn internet BS than to enlighten you or anyone else.

So, in that vein, I'll just add my usual recommend to have a look at the stickies at the top of the Marine Electronics page, where you'll find the answers to most of the important questions on marine (ham or maritime) HF comms (including antenna designs, alternatives, etc.....it's all there for free, along with many links to the reference material / official sources...)



If you let us know some more details, we can help more.

Fair winds.
John

P.S. Bazz, I'm not quite sure what the purpose / idea is here that you are asking about? As, it is clear that there are many alternative antenna ideas (some will work better than others), but for most of us and most of our applications, none do as well as the venerable remote-tuner-fed-backstay-antenna (no matter what is posted online, by whomever is considered learned/knowledgeable at that moment)
So...

So, I assume this about saving $150 or so?
As a brand-new, top-of-the-line Icom AT-140 tuner is ~ $450....used they're about $200....and, it'll last you decades, and work perfectly for most of our applications....a new iPhone (or high end laptop) costs 3 times that!
A decent "manual tuner" and the coax will cost you about ~ $250 - $300, so if you must save $150 - $200 on something, perhaps look elsewhere on-board, 'cuz I just cannot see why anyone would want to use a poorer antenna, and have more RFI, just to save $150!
But, that's just me.
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Old 08-11-2021, 09:01   #3
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Re: Alternate backstay antenna

Hi John,

Good to hear directly from you! I've been reading many of your posts lately, as well as watching your videos on YouTube. Very, very helpful – Thank you so much for doing those.

I bought my second sailboat two years ago, a 1984 Morgan Out Island 416 (tall rig). I've been sailing for 10 years now; my wife and I like it a lot and I think we're rather good at it. Retirement is in two years and we're planning to be cruising full-time by then. So, slowly but surely, I'm acquainting myself more and more with this boat and doing what must be done to make this happen.

The only electronics she currently has as means of communication is an old VHF, probably as old as the boat (I already have a new one in the box at home). Otherwise, the nav station is bare! It's a clean slate and I'll be planning as much as possible before installing things.

I've considered many scenarios for long range communications (we'll have cell phone, WIFI and VHF, so I will not talk about those) and I've settled for both satellite (with a minimum subscription) and HF-Pactor setup. I already have my maritime radiotelephone license (you have to take a course for it in Canada) and I'm studying now for the ham license. Ham: lots of options, immense range and, well, I like this stuff more and more. Could even keep doing it after my cruising years.

I just received a brand-new IC-M803. Prices were going up and the model is rather new. No point in waiting. Pactor, well, you never know, the P4 has some years on it now and Farallon might come up with something new or updated.

Antennas: ain't that a blast! Tiny EMWs, feeble, almost infinitesimal but still capable of inducing tiny, feeble currents detectable and usable thousands of km away, to me that is a few orders of magnitude more astounding than fiber optic. Natural magic, I would say. Of course, the basic setup, tried and true: the isolated backstay with an AT, is to be considered.

You asked me the purpose/idea I was asking about. Well, my criteria could be summed up by: efficiency, simplicity, price. In that order. I'll gladly pay more for something simpler with less chance of hiccups – for sanity's sake. A recurring irritant happening during an activity bringing pleasure is how experimental neurosis are induced in animals. Happens quite quickly too: a week in cats. I try to level those as much as I can. The alternative isolated top-fed backstay setup (at first glance) seems efficient, simpler and cheaper, that's why it sparked my interest and led me to post my (still unanswered) only question : Have you done it or do you know someone that did? I would like to talk with them.

Now, I understand from your comment that a manual tuner doesn't have the same range as an automatic one and that it could be cumbersome to use. Very good to know! I'm rather new to this and this is exactly the kind of knowledge I'm after. So, thank you again.

Fair winds,

Denis
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Old 08-11-2021, 13:40   #4
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Re: Alternate backstay antenna

Bazz,
More later....need to be brief at the moment...

So, in short...
Yes, I have used a "half-sloper", and they are "decent" single-band antennas (NOT multiband antennas)....but it's false to assume that your mast/rigging will be a good part of your antenna / your antenna's counterpoise, as the extremely small/narrow angle between your backstay and mast/rigging is detrimental to that...(note this is not the case, if feeding the backstay "against" a sea water antenna ground, nor some other counterpoise....where the mast can actually contribute some in a positive way, or at worst just effect the pattern slightly)

Gosh, there is a LOT more....but I have to go now.

Just remember that a "half-sloper" on a boat is a non-solution [sic] to a non-problem....
As I wrote "anything" will work, but why go looking for an antenna that is LESS efficient? (I assumed it was cost? But, I guess not?)

So, I'm afraid, I still don't grasp what you are after? You say you want: Efficiency, simplicity, and cheap?
Fact is [for the application I stated] you cannot get much more efficient of an antenna on a sailboat than a backstay fed against the sea water antenna ground.
Fact is [for the application I stated] you cannot get simpler than a decades-long-reliable remote auto-tuner, feeding the backstay against the sea water ground.
Fact is "cheap" is relative....yes, this will cost you ~ $150 more that the "half-sloper" fed with coax and a (likely unusable / or in-efficient) manual tuner, but if you went so far as buying a PACTOR 4 modem (~ $1600?), then I don't see $150 as being an issue?


On a side note: Why the PACTOR modem?
Unless you feel the need (business reasons) to be in constant email contact with persons on shore, there is no need to a PACTOR modem at all!
No need for distress, no need for safety, no need for weather, no need for ship-to-ship comms, no need for social nets, etc, etc....
The only thing the PACTOR does is allow email connectivity when on passage and/or in far remote locales (away from cellular, wi-fi, etc.)....but, you'll also have sat comm gear, too, so there's really no need for a PACTOR modem at all...
(unfortunately, the guys selling them don't tell you that, do they?)


Gotta' go.
John
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Old 08-11-2021, 15:07   #5
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Re: Alternate backstay antenna

Quick clarification...when I wrote "decent" in regards to a "half-sloper", that's not a big compliment.

Fact is, if it's all you can do ---- then that's all you can do ---- and it works (assuming you have decent angles and a decent counterpoise)....but...
But, remember a coax-fed "half-sloper" (like "slopers", dipoles, etc.) is a single-band antenna, not a multi-band antenna....and feeding it with coax, driven with a manual tuner does not make it a multiband antenna!

Please remember that much of what you read online is well-intentioned but unfortunately poorly engineered, and/or poorly understood by the very folks propagating the idea / design to begin with.

Please also understand that what our usual antenna application is, is rather odd compared to what is generally taught / what is typically published....we have darn rare (almost unique) criteria in our application...

We need an efficient antenna, that is efficient over multiple octaves (not just a couple bands), and can assist our communications effectiveness for ranges from just past our horizon (20 miles) out to many thousands of miles, nighttime and daytime, rain or shine, heavy weather or calm seas....
[note there is a difference between efficiency and effectiveness]
AND, it has to be 100% reliable...
AND, it needs to survive in difficult environs / conditions...
AND, it must fit into our vessel's rigging, structures, etc., without getting in the way of sail-handling, navigation, docking/mooring/anchoring, etc...


As I wrote before, there are applications where other antennas can work better, and if you have such an application, we can discuss antenna system design choices...
But, until someone grasps the basic rules of HF antenna system design (particularly fill-out the answers to Rule #2 above), there is little to be gained by online antenna ideas....
I mean, it's great to learn and discuss, but until all have a grasp of what they're discussing (I have no idea what your answers to the questions I wrote above in Rule #2 are), I don't see how to further assist?


I'm fairly certain this sounds a bit arrogant, but that's not my intention at all.
My intention is to politely say "other than if you already had the manual tuner and coax, and needed to save some dollars, why would anyone want a poorer performing antenna?"

I'm not sure what else to say.
I gave you the answers, based on our usual application, but I'm still not sure why anyone would want a poorer-performing antenna?

John


P.S. In case few of my fellow sailors wish not to take the above as fact, perhaps they can simply ask themselves two questions:

a) do you think electrons move / travel differently today than they did 20 years ago, or 50 years ago, or 100?
b) do you think engineers are ignoring "revolutionary" [sic] antenna ideas out of ignorance or ego, etc.?

No need to write your answers out here, keep 'em to yourself.

If their answers are no and no, then they should grasp what I'm saying is true.
If their answers are yes, I wish them all the best....but, since there is probably nothing from outside their bubble which will they will accept, there is nothing more for me to do.
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Old 10-11-2021, 17:03   #6
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Re: Alternate backstay antenna

Although I haven't used an alternative backstay on my boat, I have tested one here at my home. The intent was to eventually install it on the boat, but situations changed.

The concept of theory was to install a 35' length of wire and GTO15 cable. The cable and the antenna wire were going to be a total length of 35'. The GTO wire would be connected to an MFJ autotuner located in a weather sealed container. The radio was an ICOM IC707 SSB rig which is a ham radio.

Testing at the house comprised of a 35' length length of vinyl coated wire rope, 1/8" diameter, connected to a 4:1 balun. The balun was then fed with RG8X coax to my antenna tuner. The radio was then connected to the tuner with a SWR meter in between.

The other side of the balun was a home made KISS counterpoise. This counterpoise was thrown haphazardly for testing. Initial results show a usable SWR. After adjusting the counterpoise, the SWR was <1.2:1 on all ham bands.

I used WINLINK Express to connect to different stations along the West Coast (I am north of San Diego), upper central US, and Texas using 25 watts. I was able to connect to several stations on SSB using the Maritime Mobile Network on 14300kHz with 50~75 watts. Signal reports were good.

Now, this was when the band was still good and active. During times of diminished bands I was still able to connect on WINLINK with Texas on 7000kHz and San Francisco on 3000kHz.

Over all I think the performance on the boat would have been similar, or better if using seawater grounding.

Now, this was my experience with the concept of using either 35' or 23' antenna lengths. These lengths have been tested to work well with auto antenna tuners while providing usable SWR on all ham bands. Marine bands are very close to ham bands so I trust that they will also work well. But that is JMHO.

Good luck.
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Old 10-11-2021, 18:39   #7
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Re: Alternate backstay antenna

There are several reasons why an insulated backstay is almost ubiquitous as an HF antenna on a sailing yacht. Not the least of them are that it works as well as anything else, and is cheaper and more reliable than any alternative. (After all, the additional cost is only a pair of insulators.)

You must use a good earth plate on the hull (the earth connection to the sea forms the other half of the antenna), and you must keep the connection to the earth plate from the tuner (using copper foil) as short as possible, with a high-voltage non-inductive capacitor to let the RF through to the sea while blocking the negative side of the boat's DC system.

In my experience a manual tuner on a boat is a pain to use, though it will usually tame a fiercer VSWR than an auto-tuner (not a narrower one, as you seem to have gathered). Remember that any wire from the output of the tuner to the backstay will form part of the antenna. An auto-tuner will therefore usually be situated some distance from the radio, at the bottom of the antenna, which is the right place for it. So unless you want to operate your radio from the lazarette, get an auto-tuner.
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Old 11-11-2021, 10:20   #8
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Re: Alternate backstay antenna

Brian: Seems like a decent setup. Haven't thought of neon cable – promising idea. It could be used for a vertical dipole, couldn't it ?

I have found this cable, which combines SS cable and stranded tinned copper:

I know the consensus is around isolated backstay + autotuner. But I'm a tinkerer and I do want to test this idea of a top-fed backstay half-sloper on my ketch (which has a lot of standing rigging). Any info on those welcome


Mike: Could you point me in a direction where I could instruct myself as to the use of this capacitor you mention?

"[…] keep the connection to the earth plate from the tuner (using copper foil) as short as possible, with a high-voltage non-inductive capacitor to let the RF through to the sea while blocking the negative side of the boat's DC system."
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Old 11-11-2021, 18:39   #9
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Re: Alternate backstay antenna

Bazz, it's considered a good idea to keep the boat's electrical system isolated from the sea to reduce the likelihood of stray current corrosion. The transceiver and the tuner both have "negative earth", meaning that the negative side of the 12v DC supply is connected to the case. And you must connect the case of the tuner to earth (i.e., to the sea) in order for it to do its job properly. Therefore you need to put something in the cable between the tuner's earth terminal and the earth plate under the hull which will allow the RF through but block the DC.

That something is a capacitor. And as quite high voltages can arise across it (to the order of a few hundred volts from a 100 watt transmitter), it must be a high-voltage capacitor. Most high-voltage caps are electrolytics, but unfortunately these tend to have quite high impedance to RF). Therefore you need some other kind of cap.

There are caps made specifically for this purpose, but they tend to cost serious money. The cheapest way to source a cap for this purpose is actually from your local appliance repairman—ask him for the high-voltage capacitor from a dead microwave oven that he would otherwise throw away.

Connect one terminal of the cap to the earth terminal of the tuner, using a few inches of copper wire. Connect the other terminal of the cap to the earth plate using the shortest possible length of broad copper foil.

Why foil? Because RF travels only on the surface of a conductor ("surface effect"), and foil has a far greater surface area than round wire for the same amount of copper.

Why short? A conductor that is a quarter of a wavelength long acts as an impedance transformer, so a low impedance at one end becomes a high impedance at the other. Since the earth plate will always be a low impedance point, the other end of the foil will present a high impedance to the tuner if it's a quarter wavelength long, which is exactly what you don't want. In fact, this will happen if the length of the conductor is any odd multiple (1x, 3x, 5x, etc) of a quarter wave. At 15MHz, for example, a quarter wavelength is only five metres. At 30MHz it's only 2.5m.

The copper-over-stainless wire in your link will have less resistance than straight-out stainless (copper conducts electricity 44 times better than stainless), but the effect in any real-world antenna will be undetectable. And I certainly would not use anything with a tensile strength of only 100Kg as standing rigging.

Tinkering about with antennas is one of the chief joys of amateur radio, and I salute your attitude—but when you get to the stage of being bored with failures, it's no disgrace to adopt the tried and true.

It's perhaps worth my pointing out that the lower end of any vertical-ish antenna may (and if it is top fed like a sloper, will) have high RF voltages present. So make sure the lower insulator is sufficiently far off the deck that no hand can grab the wire while you're transmitting. RF burns are horrible—unlike ordinary burns, they start from the inside, so by the time the burn reaches the nerves in the skin which alert you, the damage has been done. RF burns hurt like hell and take forever to heal.

The backstays on both the main and mizzen on my old ketch were both split, which made using either of them as an antenna impractical. I used a main cap shroud instead, insulating it it from the aluminium spreader with a short bit of Tufnol tube. It worked fine.

By the way, don't connect the radio itself to the earth plate (a common mistake). The braid of the coaxial cable between the radio and the tuner is connected to the cases of both devices, so it will earth the radio via the capacitor.
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Old 11-11-2021, 19:25   #10
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Re: Alternate backstay antenna

Bazz, Mike, Brian, et al,

Please remember that answers to all of your queries are in the "stickies" at the top of the Marine Electronics page here on Cruiser's Forum....whether it be antenna choices, alternative backstay antennas, "rope-tenna's", antenna lengths, tuner losses, antenna ground systems, antenna recommends and efficiencies, RF and DC isolation, etc. etc....antenna pattern concerns, the myths of the "issues with ketches", etc. etc....

And, actually, the biggest recommend I can give here is:

Don't sweat these small issues! These are all mostly red herrings, that are usually a waste of most sailors' time!


{Just install the radio, tuner, ground strapping, etc. properly, and you'll be good-to-go!!!....wiring the DC power connections directly to the main battery bank, not thru a distribution panel / breaker panel / buss bars....use quality coax, with properly assembled connectors, and a line isolator....use a quality remote-auto-tuner....and, use wide copper strapping to an underwater antenna ground connection [Dynaplate or bronze thru-hull]....keep the GTO wire away from everything as best as possible, never run it parallel to other wiring...do NOT connect any other "ground"/"earth" wire / strap to the radio (no matter what the manuals tell you!), the only "ground"/"earth" connections are the copper strapping (antenna ground) and the negative power wire (DC ground)....}


1) Brian and I originally interpreted an "alternative backstay antenna" as an alternative "backstay antenna", meaning it's a base-fed (remote-tuner-fed) sloping wire vertical antenna, run from aft deck / gunwhale / pushpit / transom --- up towards the masthead, just as a rigging backstay does, but not acting as a backstay / not a part of the structure of the rigging, rather just used as an antenna...

And, this is usually as good as an insulated backstay antenna....although on some boats (usually those with other rigging nearby) it can be perform a bit worse. But, usually a great choice for those with rod-rigging, or synthetic rigging....and those without backstays (catamarans and "BR" rigged monohulls)....and, there are some on budgets who need to save the $$ on rigging insulators, that have also used this design...

My late friend Bill Trayfors was a proponent of using vinyl-coated SS lifeline wire for either an "alternative backstay antenna" or for a 20m vertical dipole (a "sloper", from the masthead)...and, no question is works fine and lasts a long time!

My own recommend here is to use 3/16" (+/-) double-braided polyester line (like Sta-Set), with a 35' - 40' length of decent marine-grade insulated copper wire (14 ga is fine, or even smaller works fine!) run up inside the line (between inner core and outer-braid).....and a length of GTO-15 from the end, down to the tuner [fyi, this simple-to-construct antenna will cost you the amount that the piece of line and piece of wire costs you, typically < $50 - $75....this is what a "Rope-Tenna" is, but they charge > $350 - $500 for it, ouch!!].....

Some use GTO-15 the whole way, and this certainly works great, just a bit pricey, but a great choice!


2) But, what I see Bazz asking about is an alternative TO a remote-tuner-fed antenna? (an alternative antenna that does not use a remote auto-tuner, whether the antenna is part of the rigging or not) And, this where I asked what is the application? What is the reason for this? And, the answer was not forthcoming (I wrongly assumed it was to save money)....But...

But, now I see that this is for "tinkering"? Not for long-range marine HF comms (whether maritime or ham)? Okay, that's cool!

Duh...I'm sorry I didn't grasp that earlier.

So....Go for it!
Have fun, enjoy antenna experimenting! And, chances are you'll have success in using just about ANY antenna on-board! (as I have said for decades, "anything metallic will work")

And, fyi, I've made many contacts, 1000's of miles away, with a scrap piece of wire stuck in the center of the antenna jack on the back of a 10 watt radio (sitting in my lap in the cockpit), with the other end of the wire clipped to a flag halyard with a clothes pin. I've also made many contacts with just a plan piece of wire, wrapped around a shroud, and stuck into the back of a radio. (heck, decades ago I made many contacts of > 2000 miles, using a VHF/UHF scanner antenna on the 10m / 15m ham radio bands!!) But, I'd not recommend any of these as a reliable way to communicate, even in benign weather, and certainly if you're looking for excellent long-range comms / sourcing decent long-range weather forecasts, well then you're going to want a remote-auto-tuner-fed antenna of ~ 25' - 65' long, whether is is part of your rigging or not!


3) Mike, I like your comment about trying to operate the radio from the lazarette! LOL

But, please forgive me, 'cuz some of your other words, I'd like to correct...as using words like "must" is disingenuous, because these things you mention in that vein, are not absolutes.

And, when trying to assist those new to HF comms (who are understandably vulnerable to influence, especially to "absolute statements" as they imply a significant amount of authority), it's best to give good recommendations and guide them, rather than tell them "this works, use this" or "you must do this"...

So, please allow me to clarify a few things.


a) While an "earth plate" / "grounding plate" (such as the brand name Dynaplate) is a great way to make a good low impedance connection to the sea water, and is highly recommended (and, I use two of them, each 18" x 6" x 1/2" thick....each connected to my remote tuner with short lengths of 6" wide copper strap)....but, to be clear, they are not a necessity (not a "must")...

Although we've "known" for many years that as long as the connection from the "earth" to the antenna is low-loss / low-impedance it's the losses in the "earth" (whether it be dirt, wire radials, screen, or sea water) that determine the overall efficiency of the "second-half-of-the-antenna"....and, since sea water is a great RF conductor (1000's of times better than even moist, nutrient-rich dirt), this connection to the sea water has always been considered important, and it is...but....but it doesn't need to be a gold-plated, solid copper, hull! LOL

Just about any decent low-loss / low-impedance connection will work fine....even a 1.5" dia bronze thru-hull (as long as it is clean) works well...

To be more direct, good 'ole Gordon West did real-world tests years ago, that proved (to many old so-called "experts" dismay) that while Dynaplates do work (and do work very well), they are not necessary....he found that just a clean underwater bronze thru-hull provided a good connection to the sea water! (please see the stickies above, for links to Gordo's test details and results!)



b) Secondly, yes....use of wide copper strapping (NOT foil) is usually recommended, in order to maintain a low-impedance antenna ground connection....and, the advice to keep this length as short as possible is good....but...

But, how short is a moving-point of contention.....the usual "keep it less than a 1/4-wave long at highest frequency" (typically < 8' - 10', shorter is better), is a good rule-of-thumb (and is what I always recommend to others)....but, it's not an "absolute".....(fyi, there are some who have long strapping, and they work well, too)

BUT....but, remember that we also want the tuner to be close to the backstay (or whip, etc.), 'cuz we want as much of the "antenna" out-in-the-clear (and away from RFI issues, etc.) as possible....

SO....so, the exact length of this "short" piece of copper strapping many times is longer than we'd want....

Hmm? you say....what is the best way? Well, every boat and every install is different (another big reason we shouldn't use absolutes like "must"), so I usually recommend placing the tuner as close to the backstay as possible, while still keeping the copper ground strapping less than 8' - 10' long....but, as I write, every boat and every installation is different, so....so, do the best that you can, and you'll be good-to-go!


c) The old (1970's) recommend of DC-isolating the antenna ground has been long since debunked as unnecessary in 99.9% of cases....as with most boats being wired to ABYC standards, etc....and as the tuner DC negative power wire is already RF isolated, DC-isolating the tuner's antenna ground connection is not necessary (not a "must").....and with and since we always (for > 40 years now, myself, Gordo, Bill T., Dave, Nick, Scott, etc. etc., as well as Sailmail, Jim Corenman, etc., SGC, etc. etc.) have recommended using a "line isolator" (RF Choke) on the coax line (whether DC isolated or not), it's not even a recommendation (and hasn't been in decades)...

And, fyi, if you do desire to "add a cap", simply put a .01uf to .1uf (500 volt to 1000 volt) silver mica or ceramic disc cap inside the tuner (you can buy them retail on-line or in most electronics stores across the USA, for < $5, usually about $0.89!)....just solder one in series with the tuner antenna ground wire, that runs from the tuner's circuit board to the antenna ground lug....(this is the original remote-auto-tuner design from the late 1970's / early 1980's from SGC and then SEA....Icom, Furuno, JRC, Sailor, Thrane, etc., elected to not put a DC-isolation cap in their modern tuners from 1980's to present)



4) Bazz, there is a lot more to all of this....but, to be blunt, until you take care of the basics (installing things correctly, ridding your boat of RFI, and learning the basics of radiowave propagation), worrying about most of this here is a waste of your time....and, spending time trying different antenna designs is also waste of time (until you have the basics done!)....



And, all of this here IS covered in the stickies....but the "basics" are always covered first and I continue to highlight them, 'cuz they make up 95%+ of success in HF comms (in actuality, even radio choice is a rather moot point, if you haven't taken care of the basics first!).

I do hope this helps? (I REALLY DO!)

Fair winds.
John

EDIT:
Just saw Mike's next post....and, I'm afraid he will not like much of what I just wrote...sorry about that!
But, fyi...all of this has been discussed in great detail (until everyone was exhausted!) many, many times....and all of this is well covered, in detail, in the stickies above....but..
But, most importantly, the reference materials are linked there as well....so, everyone can get the straight scoop directly from official sources.

And, finally, an fyi....I might not be able to get back here for few days (dealing with family health issues), but please have a look at the stickies, 'cuz all you need to know is there and/or the links to what you need to know are there!

Fair winds!
John
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Old 12-11-2021, 09:17   #11
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Re: Alternate backstay antenna

Some links:

Bill Trayfor's Vertical Dipole
DC Block for RF Antenna in Yachts
Using Seawater Ground for HF Radio
John's KISS Analysis and Homebrew KISS Ground Plane
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Old 15-11-2021, 15:18   #12
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Re: Alternate backstay antenna

This is great guys, lots of info - thanks!

John – Yes, I've seen and read the stickies, and I'm coming back often to them. It compliments my actual studying for the ham exam. Thank you for managing them.

Mike – Very thorough. It reminded me of another post, maybe not on this forum, where the thick copper foil was laid out (in the bilge, etc.) in segments each separated by a few capacitors (or resistors ?). Didn't know what to think of it at the time and didn't harvest the URL for it. However, it does look something like one of Brian's link (DC Block for RF Antenna in Yachts). Also, you said "I used a main cap shroud instead, insulating it it from the aluminum spreader with a short bit of Tufnol tube. It worked fine." Now that's interesting. At least I know there can be another solution involving shrouds.

Brian – Thanks for the links. Only one I didn't get was the "Using seawater…" Seems like the URL is not HTTP but pointing to folders on your drive. If it is about Gordon West's paper, I do have it. In fact, I talked to him over the phone a few weeks ago.

To all, there are still some parts of your comments and suggestion that are a bit arcane to me, but I'll get there. With what you've given me, I have plenty to be busy at the moment and will try to come back in a while, after I have studied a bit more, passed my license and made a few tests and experiments.

Thanks again and fair winds,

Denis
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Old 15-11-2021, 15:47   #13
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Re: Alternate backstay antenna

Bazz, you mention "thick" copper foil. Since the RF current travels only on the surface, the foil can be as thin as you like—wide and thin is best. Thickness only adds cost and lowers flexibility.

The idea of breaking up the foil into short lengths connected by capacitors (not resistors) is simply to change its resonance so that it does not appear to be a quarter wave at any frequency it will be used at.

I'm afraid I can't agree that braided strapping is better than foil at conducting RF. Mind you, the difference is negligible over the modest lengths we are talking about.
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Old 15-11-2021, 15:53   #14
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Re: Alternate backstay antenna

FWIW

Bazz (or Denis), I am nowhere near the guru that KA4WJA is, but I do have experience with practical ham radio efforts on a full time cruising yacht. I offer the two following experiences for your consideration:

1. I read perhaps the same posts re the top-fed sloper and was impressed enough to actually construct one on our boat. In short, it did not work well at all, and I abandoned it after a series of unsuccessful experiments and reverted to my previous system.

2. That previous system (if you can call something this simple a "system") is a MFJ manual tuner with a short GTO lead to the chain plate for the port shrouds. This leads the RF to excite the whole rig... shrouds to alloy mast to other shrouds and forestays. Our hull is cedar/epoxy composite and is the only insulator involved. The mast is not ordinarily grounded to the keel, but I have tried it grounded and it made little difference in performance, just minor changes to the tuner settings. The counterpoise is copper strapping to a keel bolt, and the keel is a steel shell in contact with the sea.

I have made comparisons in signal strength to neighboring vessels with insulated backstay antennae on many occasions, and the results are very similar. I've used it on 80, 40, 20 and 15 meter bands over the years and it gives useful results on all of them.
,,
In the past John has commented that while my system can and does work it is far from optimal, and no doubt this is true. However, it is supremely simple, inexpensive and easy to set up and I've never felt that it was inadequate for my usage. It might suffice for you as well.

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Old 16-11-2021, 09:44   #15
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Re: Alternate backstay antenna

Thanks for letting me about the broken link. Yes, it is to Gordon West's paper on using seawater as a means for ground. I'll fix it.
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