Optimal SSB Antenna(e)

[John Drake]

I personally would create the longest antenna you can out of your backstay.

[ka4wja]

Smokester,
An insulated backstay antenna length of 40' - 45' is good...
And, no need to worry about the AT-140 tuning it....it will be fine!

Bill (btrayfors) and Chip (soonersailor) gave you THE definitive (and best) answers...
Especially heed their advise here about installation being VERY important....


And ironically, on a PS 37 the total length of your backstay is going to be about 45' - 47', or so...
Once you place the top insulator a few feet from the top and add a couple feet of GTO-15 wire from the tuner output to the backstay, you'll end up with a 40' - 45' long backstay antenna!!



[note the word "most"]
Understand that most ship-to-ship and ship-to-shore maritime comms (SSB Voice, DSC, and data/PACTOR) these days are on freqs of 12/13mhz and below (with some on 16mhz)....with 12/13mhz and 8mhz being the most used...
Most long-distance maritime comms is on 12/13mhz and 16/17mhz, with most regional maritime comms on 8mhz and some 5/6mhz...and some local nets and rally nets on 4mhz and 6mhz...

Most daytime long range ham radio comms at sea these days is on 14mhz and 18mhz (and some on 21mhz)....most nighttime long range ham radio comms is on 10mhz, 7mhz, 3.6mhz...

And, as the sunspot cycle winds down during the coming 3 - 5 years, the higher frequencies will become less useful to useless....

And, as having a vertical antenna that is at least 1/8-wavelength long, and less than 0.64-wavelength, for both better efficiency and still keeping the lowest angle of radiation possible, this means any length from 30' to 45' is a workable / effective length....and 40' - 45' being better for most users....


There is much more to all of this, if designing antennas for specific applications / frequencies .... but the above (including Bill's and Chip's postings) makes up 99% of what you need to know about this for your application....
Go for a length of 40' to 45'!!!


I hope this helps...

Fair winds...

John

[The Smokester]

Thanks ka4wja.The discussion of useful bands, and the role of the sun, is just what I needed. I will use a long antenna, probably about 40ft.

What about the KISS counterpoise...Is there experience on here with that?

[SoonerSailor]

Opening can of worms.....


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[ka4wja]

You're quite welcome!

Originally Posted by The Smokester

Thanks ka4wja.The discussion of useful bands, and the role of the sun, is just what I needed. I will use a long antenna, probably about 40ft.

What about the KISS counterpoise...Is there experience on here with that?

As for vertical antenna RF Ground systems / counterpoises, entire chapters and books have been written about them over the past 90 some years!!
And, trust me physics hasn't changed much in that time!

In the real world, if you are end-feeding a vertical antenna (even one that is 1/2-wave or 5/8-wave), it needs a counterpoise or rf ground system of some sort to optimally allow the rf antenna ground currents to be returned to the feedpoint and re-radiated...as well as perform other tasks, especially on-board our boats...
But, in the real-world that word "optimally" often gets overlooked....'cause, fact is that a vertical without any ground system / counterpoise at all, will still work...just not as well as one with a ground system/counterpoise...
(and it is this fact that is most often misunderstood, and this leads to the further misunderstandings about rf ground systems / counterpoises....and this then leads to arguments about "what works" and "what doesn't", when in fact "anything works".....it is just all a matter of degree...i.e. "how well does it work, compared to something else"....)

And, another fact is that sea water is as close to a "perfect" RF ground as you can get in the real world, short of installing a symmetrical counterpoise of 120 ~1/2-wavelength long copper wire radials...and even then surrounding the vertical with sea water is still better....and if you look at radiation angles (and pseudo-Brewster angles), if you surround the vertical with sea water out well past the near-field, to the far-field, certainly >> 10 wavelengths, you end up getting within a couple tenths of a db of "perfect"....(this is why our verticals work so well for long range comms.....typically 10-20db better than those using verticals on land!)


So, it shouldn't be a surprise that if you can connect the antenna tuner's ground directly to the sea water, in as low-impedance way as possible (typically using a wide copper strap to an underwater metallic plate or thru-hull fitting), then you have an excellent, wide-band, rf antenna ground system / counterpoise....
If you do this, there is little need for much else...

However, if you cannot do this, then building an artificial ground / counterpoise is a good idea...
And, you can do this in many ways...
Using lifelines, toerails, pullpits, etc. as well as metal tanks, keels, etc....
And, if you desire to make your own radials, you can do so for FREE or for as little as $5, and have them outperform the KISS SSB Ground...

I gave up commenting on the KISS after doing the tests, etc., and if you desire to read ALL about it, it's right here for you....it's FREE and undisputed...
Have a look...

Re: KISS-SSB Counterpoise



Bottom line, if you cannot design/install a better rf ground system / counterpoise for some unusual reason, you can make your own "KISS" for free, or less than $5....



I hope this helps...

Fair winds..

John

[The Smokester]

Thanks agsin, ka4wja. I read the links and understood. Based on all this input I will be connecting to seawater and using a 40 ft backstay antenna.

Thanks again to all.

[Goudurix]

Smokester,

not wanting to confuse you, but to optimise your antenna system you need to take into account your target frequencies.

Your typical 40-45 ft isolated backstay antenna (backstay part + the GTO15 lead until the antenna tuner) is the optimal length (0.625 wavelength) for the HAM 20m band but also about the maximal frequency. For higher frequencies, you will surely be able to tne it with the correct ATU, but you start to develop mainly high angle radiation which is not suitable for long range communication.
For the 10m band the maximal length is about 6.3m antenna length
For the 15m band it is max. 8.4 m
For the 17m band it is max. 9.8m
(it is 0.625 x wavelength but I also apply about 0.95 as shortening factor)

Will you have no long range com at all? No, of course not, that depends also on the propagation (see above) but you will lose quite some efficency with too long an antenna wire.

On the other hand, a 43 ft antenna will still be 0.25 WL at 6 Mhz so still very good efficiency there.

I stick to a 9m sloping wire antenna since I want to favor Ham 40m -17m bands. With my antenna I'm only 1/8 WL on the 80m band.

Summary:
Not to confuse you, but if it's about optimising your antenna system in a "random end-fed sloping wire antenna" you can also take into account your target frequencies.

Jan

[Krakato]

An excellent discussion here!

I've been a ham for 20+ years, but since we are about a year away from buying our boat (waiting for the pension to kick in), I've really started looking at antennas for boats.

So one question: What is everyone doing for lightning protection? Just unplug? Short the antenna to ground? Polyphasers?

Cheers,
Mike
NW5M

[btrayfors]

Mike,

Just unplug. In practice, there's really nothing you can do which will fully protect your boat and equipment from a lightning strike. And, the worst ones in terms of destroying electronic equipment are often nearby strikes which enter thru the ground!

Unplug your antenna. Turn off sensitive electronics. And pray.

Bill

Originally Posted by mhward1337

An excellent discussion here!

I've been a ham for 20+ years, but since we are about a year away from buying our boat (waiting for the pension to kick in), I've really started looking at antennas for boats.

So one question: What is everyone doing for lightning protection? Just unplug? Short the antenna to ground? Polyphasers?

Cheers,
Mike
NW5M

[roberto11]

Interesting post!!

I use an homemade rope antenna of around 45 feet + 3 feet gto15 from the auto tuner to the antenna.

The connection gto15 / antenna is made with insulated Faston terminals making easy to connect/disconnect (if need it)
I'm always wondering if using antennas of different lengths for different frequencies will work better.
Maybe with a little patience and an antenna analyzer......
I don't have much experience and I'm waiting for the suggestions from CF members that no better....
Thanks!!!


P.S. From the rope antenna.com web site

The rope antennas come in 4 Standard size

35 Ft

45 Ft

48 Ft

54 Ft



The lengths are from the top loop to the bottom loop.

😉The best size is the largest one that you can fit on your boat.😉

[ka4wja]

Roberto,
An antenna analyzer will do you NO good at all for this....but all of the below will!!


There are three different things to consider....
--- The antenna's efficiency (how much of your power it radiates into the atmosphere)
--- How much loss is created in the tuner to match the antenna to your transmitter
--- The antenna's radiation angle / plot (how much power the antenna radiates at all the various angle above the horizon)



1) Dealing with the 3rd item first...the antenna's radiation pattern...
Jan gave you some good info above, regarding longer vertical antennas producing higher angles of radiation....and that is true...except...
Except for:
a) the actual length that this happens at is when the antenna is longer than 0.64-wavelengths, not 0.625-wavelengths....(a minor difference, and usually within most of ours "measuring errors"....and if using a large diameter conductor such as a rigging wire, the 95% K-factor would be a bit lower...93% ??....so in actual effect the physical length is shorter than the 0.64-wave on paper!!)


b) the real-world use of a backstay, rope-tenna, "vertical-dipole", etc. on-board our boats is that they are not actually "vertical" but rather are "slopers" (albeit a 15* - 25* angle sloper, but still a sloper), and as such do not have quite as low of an angle as we would hope (yes, it IS low, typically 10* or so at its peak....and without the really deep null overhead)...



2) Still dealing with the antenna's radiation pattern...take note of the following facts (and conundrums):

--- The radiation at these low angles (below 15* - 18*) is what is important for long-range comms (> 1000 miles) and the really low angles (< 8*) for really long-ranges of > 6000 miles....
(But, lest we forget that even simple horizontal dipoles at 1/4-wavelength high, which have their peak radiation straight up (90*), still make contacts worldwide!!)

[BTW, be aware that on frequencies above 10mhz (daytime), the "higher angles of radiation" (those above 30*-40*) are useless for HF communications....and this energy is just wasted (passes out into space or is absorbed by the ionosphere)....
But, on the lower freqs, this is very usable....
Problem is we don't have antennas long enough to for this to happen on the lower freqs... ]

--- Also, understand that on the LOWER frequency bands, below 10mhz, particularly the 4mhz, 6mhz, and 8mhz marine bands AND the 40m and 75m/80m ham bands, HIGHER angles of radiation (angles ABOVE 60*) are usually desired for regional communications out-to 500 miles or so....both daytime and nighttime....(but typically most important for daytime regional comms)
Unfortunately, our vertical antennas do not have much energy at these high angles on these lower freqs....but those that can rig a horizontal antenna at about 1/4-wave high on one or more of these lower bands, will find a BIG boost in their regional daytime signals...

--- Further understand that, when the higher bands (above 15/16mhz) are "open" the signals are usually so strong that the difference in antennas of 5db - 6 db of performance at a given radiation angle is usually never noticed..

--- Most daytime (and evening) long range HF maritime comms being on 12mhz and 16mhz....and most daytime/evening long range HF ham comms on 14mhz (20m) or 18mhz (17m)....with nighttime long range comms being on 8mhz marine (and some 4mhz), and 7mhz & 3.6mhz ham....


Taking ALL of these things above into consideration (but not yet even looking into the antenna's efficiency, nor losses in the tuner)....and you soon realize that there are good scientific reasons for recommending an antenna length in the 40' - 45' range...
As this length allows for a low angle of radiation thru 14mhz, and even on higher bands will still provide some good signals...

Here is an old photo of an old slide, showing the relative radiation angles (in theory, over a "perfect ground") of straight vertical antennas of 14/wave, 1/2-wave, 5/8-wave, 3/4-wave, 1-wave, and 3-wavelengths long...


While in the real world, there would be ground interactions that would of course raise the peak angle of radiation primarily for the patterns on the left, on-board our boats, over sea water, this increase is slight...





3) Now if you wish to discuss antenna efficiencies, with end-fed verticals, etc...
Facts are facts....the shorter the antenna becomes (below 1/4wavelength) the less efficient it is....the closer to a 1/2-wave it gets the more efficient it is...(although base-fed 1/4-wave antennas operated against an excellent ground system, such as sea water or LOTS of copper radials, are damn close in efficiency to a 1/2-wave!)

And, although the "5/8-wave" antenna holds some advantage in theory, in actual practice, its efficiency is NO better than a 1/2-wave...(and since it typically has some odd lobes, etc. this can make it slightly less desirable than a 1/2-wave...)

Anyone care to guess what the length is for a 1/2-wave antenna at 12.359mhz (or 12.2- 12.4mhz)??
Approx. 38'...

Or how about 5/8-wave on 14.2mhz??
Approx. 41'...

A 1/4-wave on 6.2mhz is approx. 37.75'

So...
So, a 35' - 45' long antenna is a good compromise choice here....
It still provides good efficiencies at freqs from 6mhz thru 14mhz-16mhz, and while is less efficient on 3.6mhz thru 4.1mhz, there are few who would find this detrimental to their operations....



4) Tuner losses are highest when the antennas are shorter (in terms of wavelength), AND on the lower freqs where significant inductance is needed in the tuner...
These two things combine to increase tuner losses for short antennas on the lower frequencies...

Now "short" is relative....'cause nobody here is advocating really short antennas, such as used on vehicles....where efficiencies on 3.6mhz can be as low as 1% - 2%!!!
No, we are talking about an antenna that is "half-sized" or greater, and this doesn't present too much loss in efficiency...typical efficiencies are 50% - 60%...
BUT...

But, tuner losses are surprisingly high when matching such a low impedance load on these lower freqs (6-12 ohms on 3.6mhz to 4.2mhz)....tuner losses can be as much as 6db...
But, here again we have some help from mother nature....as when you are using these low freqs for comms (unless for fun, like I do), you are NOT bound to stay on these low freqs and CAN use others (and using the highest freq possible for a given path always presents the highest signal levels and lowest noise)....
And, when needing to use these low freqs for some specific range, signals are typically good....so giving up a couple db usually isn't too much of a big deal...






5) As for what specific lengths to use for a specific freq??
Read all the above...
And I think you'll understand that while in theory we'd need an antenna that would efficiently and effectively work from 1.6mhz thru 26mhz (for maritime bands) and/or 1.8mhz thru 29mhz (for the ham bands), in actual real-world use it's more like 4mhz thru 16mhz (maritime) and/or 3.6mhz thru 18mhz (ham)....

And, if you boil-it-down even more, you'll see that:
--- MOST HF VOICE operating from boats is from 4.1mhz thru 12.359mhz (marine) and from 7.2mhz thru 14.3mhz (ham)....{and some 3.9mhz nets}
--- MOST HF-DSC comms is on 2.187mhz, 4.207.5mhz, 8.414.5mhz and 12.577mhz....
--- MOST HF PACTOR comms is from 5mhz thru 14mhz...

So, for most sailors/cruisers with HF radios, it is these bands/freqs that are the most commonly used....and antennas designed to be most efficient and most effective throughout these freqs is what is usually done...and compromises are accepted with operation on the less common freqs/bands...

[Note that those with 23' whips are a disadvantage on the lower bands/freqs (6mhz and below), when compared to those with a typical backstay antenna length of 40' - 45'...]



Specific to your query here about different lengths working better, read ALL of the above for the details...but in brief....
Not sure if these are really the whole antenna length or just the "rope-tenna" part.....
But, to answer your question, I'm going to assume these are the entire antenna lengths (GTO-15 plus the "rope-tenna")....
So, the longer length antennas will favor the lower freqs, at the detriment of the higher freqs having an antenna with higher angles of radiation...
So, using just these lengths that they have...the choices that will be best for most sailors/cruisers is "35 ft" or "45 ft"....
Again, I'm NOT clear whether this is the whole antenna's length (including the GTO-15), or simply the length of the "rope-tenna"....or even simply the length of the "rope", and the antenna is always the same length for all of their models???

Originally Posted by roberto11

Interesting post!!

I'm always wondering if using antennas of different lengths for different frequencies will work better.
Maybe with a little patience and an antenna analyzer......
I don't have much experience and I'm waiting for the suggestions from CF members that no better....

From the rope antenna.com web site

The rope antennas come in 4 Standard size

35 Ft

45 Ft

48 Ft

54 Ft

The lengths are from the top loop to the bottom loop.

��The best size is the largest one that you can fit on your boat.��

I think it might just be that these are just the lengths of the "rope", and the "antenna" itself (which is the wire inside the rope AND the GTO-15 wire) is always the same length???

This is a question for the guys that make the darn thing...

But, as I write above....there are real scientific reasons that "everyone says, use a total antenna length of 35' - 45' (including the GTO-15 wire), and you'll be fine"....

If you wish to optimize your antenna for a specific band/freq (as I did) that's up to you....but for most folks, a 40' total length is good...


I hope this helps, without getting bogged-down in theory much!

Fair winds..

John

[roberto11]

Thank you👍🏻👍🏻👍🏻👍🏻👍🏻


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[ka4wja]

Roberto,
You're very welcome!

Fair winds.
John

[micah719]

Given that my intended boat is to be junk rigged (freestanding steel masts), the antenna is a big problem for me. The only solutions I can think of are either using a spare halyard to hoist an antenna, or fly a balloon and hang it off that. Either way, it means no radio other than VHF when the weather is sporty.