HF antenna Back Stay vs. Screwdriver antenna

[plebian99]

You have been lucky with the HighQ 80. The HyQ antennas or infamous for sucking in water and self destructing from moisture damage. Even if there wire was silver plated unless you take precautions like coating the coil with something like silicone grease its not going to last. It would not be my choice for a backup antenna. A 7 meter standard marine fibreglass whip fed with any automatic antenna tuner has sufficient efficiency for long range and coastal communications. As a expert hf user you can maintain such contraptions. For the average sailor they are best advised to avoid such contraption antennas like screwdrivers. You anecdotal antenna comparisons between backstays and other short verticals are not really a surprise. Backstay is merely a random piece of wire that would only have a favorable radiation pattern from medium to low frequencies. On the higher frequencies it would be a cloud warmer. Since the typical short screwdriver would have radiation efficiencies anywhere from 80% to 100% Combine this with a favorable major lobe that favors the most popular takeoff angles its no surprise that it beats the average backstay. Ultimately sailing communications is not a ham radio contest and the standard backstay despite all its warts is sufficient for most sailors needs. Sailors are not chasing 300 pieces of cardboard to stick on the wall!

Originally Posted by btrayfors

Hey, Ross...

Great to hear from you from across the Pond!

Thanks for the comments and insight re: antennas during your transAtlantics and other wanderings.

What I gather from the above is:

1. a center-loaded remotely adjustable vertical antenna can, indeed, stand up well to the marine environment, as has your Hi-Q 5-80;

2. on the higher bands (10mHz and above) it has excellent performance on a boat due to the lower angle of radiation, higher transmit efficiency, and the excellent seawater ground;

3. a traditional backstay antenna, while a good overall performer, doesn't outshine the vertical except on the low bands (8mHz and below); at these frequencies, the longer length of the backstay antenna really matters.

That's pretty much what I/we expected, but it's good to have practical confirmation based on your extensive experience.

On my own boat, my "emergency HF antenna" is a simple Hustler mobile antenna with interchangeable resonators for the various bands. While this antenna doesn't have as much radiation efficiency as the Hi-Q (or most any "screwdriver-type" antenna, it nevertheless does work pretty well. I've used it in most places from Maine to the lower Caribbean, and in comparisons to my backstay antenna it follows pretty much the pattern described herein above. Normally, I keep the foldover mast and resonators disassembled belowdecks, ready to screw onto the base mount on my pushpit whenever needed. Much less expensive solution than a high quality screwdriver, but less capable, too!

Re: monoband vertical dipoles, you know very well that I've been using them and writing about them for several decades. These are unbeatable on 20 meters and above, either on a sailboat or ashore. Great DX antennas. But my experience using them on 7mHz and 8mHz has been disappointing, too. Not that they're bad antennas, just that on the lower bands they don't exhibit anywhere near the fantastic boost you get on the higher bands as a result of very low vertical angle of radiation and, presumably, fewer energy-dissipating "hops".

Take care. Hope to catch you on the bands this summer, maybe from Maine :-)

Bill
WA6CCA

[yachtgemini]

Plebian said ...

Hence if you compare a vertical 1/4 vs 1/2 vs a 5/8 antenna between the angles of 1 and 20 degrees there might be practically no difference in a saltwater environment at lower angles below 5 degrees. However shorter antennas will have a more useful radiation pattern for all possible propagation paths. I examine antennas more from a perspective of where there are nulls and lack of gain than being anal about low takeoff angle. Run a 1/4 vertical versus a 1/2 vertical through VOACAP area coverage maps and you will soon see what I mean. Sailors are not chasing DX nor do they need to work long path or through polar regions. The need for ultra low angle antennas is highly questionable for the needs for sailing HF communications.

Gemini replies....

I am not comparing a 1/4 or 5/8th... my existing whip is a 1/64 th on 2 meg channels... doubling it must give a significant improvement.

Why would I want a 1/4 wave on 20 metres (5 metre length)instead of a 2.5 metre length? Simple - it gives a workable antenna on 10 metres (half wave) and a better but still very small (1/16th) on 80m.

The only reason that screw driver antenna makers settled on the existing lengths was to satisfy road use regulations. Providing you stay shorter than 5/8ths on your highest frequency of interest performance should be good on the higher frequencies.

If I want to talk to a boat fairly close I am going to use a 2 meg or 4 meg frequency and at 1/64 th or 1/32nd wavelength there is going to be more than enough high angle radiation.

Sailors are not chasing DX ? If you use winlink mid ocean or want to get away from the congestion on the European PMBOs you need low angle take off. If you don't have good low angle performance and sail out side of the east coast/ Florida / Bahamas triangle your number of hours of winlink availability starts to reduce quickly.

Sailing the western Atlantic coast of Europe I can get 24/7 winlink access with some of my best speeds and access coming from Continental USA and Canada stations. For example I can hit VE1YZ Nova Scotia and get great speeds for at least 12 hours per day. This is single skip propagation and works very well. (btw I have never had any luck with long path winlink... not an issue of signal strength but probably latency.. irrespective of signal strength it seems to default back to P1)

If you want to talk about nulls and complex interactions look no further than the conventional backstay arrangement. I have had a go at modelling my boat and ran out of segments and patience. The results looked more like a porcupine than any recognizable antenna plot I have ever seen.

Vertical antennas (dipoles or straight verticals) work brilliantly and have a place on any cruising boat wanting reliable communications away from the east coast milk run.

Plebian said ... You have been lucky with the HighQ 80. The HyQ antennas or infamous for sucking in water and self destructing from moisture damage.

Ross said ... lucky? antenna was stock and had no special preparation and zero maintenance and has survived, 8 years, 12000 ocean miles, English winters, force 9/10 on Biscay, dust storm in west Africa, 2 Atlantic crossings, Heat in Trinidad, snowmageddon in Washington DC and 600 watts of RF.... I can't think of many other bits of complex marine gear that are so lucky!

Ross

[ka4wja]

I usually steer clear of the "this is the best antenna" discussions, as they sometimes (usually??) turn into more argument than discussion....
And, while I'm not making an exception here, I would like to add a few clarifications that may shed some light on things (without involving myself in a pissing match...



1) When teaching seminars about radiowave propagation, proper antenna choice, and antenna design, I am invariably asked many times, "what is the 'best' antenna?"....
And, my answer is always: "It depends."....

And, then I elaborate that YOU need to specify a few things first...
a) WHERE do you wish to communicate??
b) What TIME OF DAY and TIME OF YEAR??
c) What Frequency / Band??
d) What mode (CW, SSB, etc.)??

And, then of course the BIG determiners:
e) How much MONEY can you afford to spend??
f) How much room to you have to install/erect antennas??
g) Do you aesthetic restrictions???
h) Do you have "practical" restrictions?? (can't climb, etc.)
i) Are there structural considerations, or other "needs" that will have higher priority?? (such as "my antenna can't get in the way of my sails", etc.)

Now, once they hear all of the above some just give up and decide that whatever they throw up in the air is better than no antenna at all....
And, they are RIGHT!!!
But, you're not likely to see their calls listed in the top 10 in radiosport contests, nor on a DXCC Honor Roll, etc....

And further, the folks that actually spend the time to figure out the answers to the above questions (something that THEY must do THEMSELVES, as everyones' applications/answers are different), find the wonderful joy of what a great antenna can bring to radio operating!!!





2) Now I could go on about horizontal antennas having a 6db "gain" (ground reflection gain), compared to vertical antennas (which is true, when comparing their max gains)...
But, this would probably just start an argument, or at best add to the confusion...

Although, what this CAN do is show us the importance of the suitability of a particular antenna, for its intended purpose....the actual performance (or "gain") of the antenna AT the desired angles of radiation....
{Please note that I'm not talking about efficiencies, but yes...low-efficiency antennas WILL have lower "gain", less power radiated....but if they're the same/similar design, etc. they will have the same/similar radiation patterns, just with less gain...}



And, while I agree that vertical antennas over sea water work VERY well....there are a few misconceptions that I'd like to clear up....
(but, please understand I'm NOT picking on you Bill....it's just that you were the one to mention this.....so 'ya sorta' opened the can of worms...

Originally Posted by btrayfors

Re: monoband vertical dipoles, you know very well that I've been using them and writing about them for several decades. These are unbeatable on 20 meters and above, either on a sailboat or ashore. Great DX antennas. But my experience using them on 7mHz and 8mHz has been disappointing, too. Not that they're bad antennas, just that on the lower bands they don't exhibit anywhere near the fantastic boost you get on the higher bands as a result of very low vertical angle of radiation and, presumably, fewer energy-dissipating "hops".

The PRIMARY reason the vertical antenna (monopole or dipole) performs so well over sea water is that its main lobe of radiation is VERY low (due to the extremely low pseudo-Brewster angle over sea water, of less than 1*), and hence produces a fairly strong signal ("gain") at these VERY low angles (< 10 degrees), which corresponds to the overwhelming majority of angles that the ionosphere actually reflects....
(for most communication paths out to 8000 miles, or more, it is actually NOT due to the reduced "number of hops", but rather due to the antenna actually producing significant output ("gain") at these VERY low angles...as the "number of hops", is almost always controlled by the ionosphere itself, NOT our antenna radiation angle....)

A couple years ago, over on the SSCA discussion board, I wrote the following....

Let's start with the ionosphere....(F-layer)
What reflection angles / radiation angles it supports for a particular path (at a particular freq and time), is just that...what IT supports.....and has nothing to do with your antenna....
Mother Nature makes this decision and there is NOTHING that we can do about it....no matter what antenna, no matter how much salt water we have around us, the ionosphere controls what angle waves are reflected at......

Meaning that when the ionosphere supports a path, from say the US to EU (a common HF path to work, whether ham or maritime freqs are used), it is supporting that path at a specific reflection/radiation angle, of say 5* or so, at 12 or 14mhz, for a triple hop connection......and at different times (different layer heights) may support a double hop for this path as well....(and sometimes at the same time of the double-hop, it may support a triple hop path at a higher angle, but usually not...)

The only part the ionosphere plays regarding antennas, is how much signal output ("gain") your antenna has at this specific angle....

And, if we look at the range of angles we typically have supported over common paths, we see surprisingly low angles, which is why using an antenna which has as much gain as possible at very low angles, provides for better signal strengths....
Statistical analyses have been done over long periods of time, so we do have factual data that we can use to determine what angles are supported over many different paths....
As an example, for the US East Coast to EU on 14mhz (over the entire 11-yr solar cycle), although the range of possible angles is broad (from 1* to 20*), typical angles are 3* - 12* (making up >75% of all paths, whether double or triple hop), with the statistically most prevalent angles being 5* and 4* (making up about >25% of all paths)

So, here you can see why vertical antennas over sea water can really play well!!!

What I did not mention is that caution needs to be used when taking the above data to heart....
As in many years of the sunspot cycle, the "triple-hop" mode from the US to Europe IS the most prevalent, and with the minor exception of the few hours of the greyline and evening times, the "triple-hop" mode/path from the US to Europe produces greater signal levels, than a double-hop mode/path....
Yes, this seems counter-intuitive, but is backed-up with real-world data....sorry it is in some of my books, so I can't post a copy here...but I can tell you that it is almost exclusively when the ionization is building or falling off (such as early in the day and then late in the day/evening) does the triple-hop mode all but disappears, and the double-hop mode takes precedence, but with quite variable signals (hence the deep fading that we experience at these times), and then typically only when well after dark (such as spring/autumn 0200z to 0300z for a path between US and EU), the double-hop mode is typically the only mode supported by the ionosphere for this US to EU path....BUT...
But, the signals are lower than they were earlier, as there is less ionization....


What I'm trying to impress upon you all here is this:
Having an antenna with a substantial amount of energy radiated at VERY low angles (4* - 10*) will give excellent results on typical HF communications paths.....(although on the those shorter paths, such as US to Caribbean, or UK to Europe, etc. the angles can be higher, up to 25* is supported at times...)

EDIT:
I've found one chart on-line that shows some examples of this (from UK to Oceania and UK to Europe...but at the moment I can't find anything online showing from US to EU, US to Caribbean, etc...so please just take my word for the facts I presented above...although you can see here that from UK to Oceania, fully 30% of the time the ionosphere is reflecting signals at only 1*....and never any higher than 9*.....and the short-haul paths can be from 5* up to 25*....)
Hopefully I can get it to show up here....






3) To give you some comparisons....
A typical vertical (1/4 - 5/8 wave monopole or 1/2 wave dipole) over sea water will have as much "gain" at 4* to 5* elevation angles as a horizontal dipole at 1 to 1.5 wavelengths high (67' - 100' high at 14mhz/20m), and even more impressively this same vertical over sea water will have 2db more "gain" than even a 3-element monoband yagi at 50' high....and typically as much as 4 - 6db of gain over the "typical 3-element tri-band yagi", at 50'....
So, when someone comments on-the-air that your signal from your boat is "very strong for a 'mobile station'", you'll know why....

But, please understand that at the "higher angles" of say 10* or slightly above, the differences are less....and, of course at the lower angles used for the really long communications paths, such the US east coast to VK (Australia), the differences are greater!!
And, as we move up in frequency the most prominent angles also get a bit lower...and while on the lower freqs the most prominent angles are a bit higher, even at 80m from US to EU, the angles are still between 5* and 20*, with 7*-14* being the most prominent....and an eastern US to VK path on 80m having prominent angles all <10*....(heck even along the US to EU path, on 80m, 1* angles make up 4% of the times...)

So, all-in-all, having an antenna with sufficient LOW-ANGLE gain can make a significant difference in HF communication paths past 1500 miles....

Although one caveat....typically when the "higher bands" (> 16 - 18mhz) are "open", the signals are so strong that not having an antenna with lots of "gain" down low, is usually NOT a detriment to almost all comms....(but those looking to bust pile-ups, etc. will find this "fact" humorous....as they are always looking for every extra db they can find..)





4) I'm hesitant to post this part, as I don't wish to add any confusion....but hopefully this will be taken as just a side note, and not cause argument...
-- Typical radiation patterns for vertical antennas over land vary a great deal, depending on the type of land (soil conductivity) in BOTH the near-field (within 5-10 wavelengths) AND the far-field (out 10's of miles)....as well as on the frequency, etc...
But, using "average" to "good" soil conductivity, you have a maximum radiation significantly higher than you'd think...typically in the 20 - 25 degree range....and almost always above 15* - 16* even with 120 1/2-wavelenhgth radials in a coastal area....
This is WHY horizontally polarized antennas are almost always used for all land-based HF skywave communications....(since the vertical antennas do not present the extremely low radiation angles that they do over "perfect ground" / "sea water", and since a horizontal antenna has a 6db advantage over the vertical....)
A horizontal antenna at 5/8-wavelngth to 3/4-wavelength high (approx. 40' - 50' on 14mhz), will present a similar radiation pattern as your typical full-size vertical dipole (or vertical monopole with lots of radials), BUT...
But, the horizontal antenna / simple horizontal dipole will have 6db of gain over the vertical.....and if you add in the gain of a yagi, you quickly see that on-land, even a small/simple yagi at 50' will outperform verticals on 14mhz....(and this becomes even more significant as you move up in frequency...)

On the lower bands, such as 80m and 160m....verticals on land do have their place, especially on 160m!!! Where getting a horizontal antenna up high enough is very problematic and expensive!!

On 40m....it depends on how much money and how much room you have....as a simple dipole at 60' high will beat a vertical....and 2-element yagi at 80' or higher will be a "killer" antenna on 40m....

Also, remember when making antenna generalities / comparisons, we are comparing our antenna to other hams' antennas.....so, while a small and "simple" antenna might not seem like a good choice, IN COMPARISON to others' antennas for that particular band/freq, it may actually be a great antenna....
{an example here is a simple 1/2-wave horizontal dipole.....my college ham club station (W1YK) had an 80m dipole, fed with Times FM-8 (and some hardline), strung up above the middle of a courtyard, from the top of a 70' tower on top of a narrow 7-strory building, across the grass courtyard/quad, to the top of another 70'+ tower on top of another 6-story building, all up on-top of the tallest hill in Worcester, MA, one of the tallest hills in 100 miles, overlooking, the rolling valleys to the SW and down to the NE towards the Atlantic Ocean some 30-40 miles away....it was situated to "beam" NE/SW, and was approx. 160' - 175' high, with our shack on the roof of one of the buildings....and with our homebrewed amp, we had one of the strongest signals on 80m into Europe, all over the US, as well as well down-under....all with just "a simple dipole"...
When comparing this to the typical low-mounted inverted-v, our "simple dipole" was at least 10-15db better, and at times as much as 20-30db better than other stations in nearby towns, etc....
So, that's just one example of why some "simple" antennas in comparison perform so well!!!}


Some other references that some may find interesting...
http://www.cebik.com/content/gp/pba.pdf
http://www.cebik.com/content/a10/wire/sloper.html
http://www.cebik.com/content/gp/58-1.html


And, for those who have lots of idle time, a nice (50 minute long) video discussing HF contest antenna systems....with a great, easy-to-understand explanation of the "whys" of antenna stacking for HF comms....(something that I started discussing about 20 years ago, and is now coming into the main stream!!)

http://www.youtube.com/watch?v=gbwyQC099oM

Gosh, I can't believe I rambled on-and-on here....all I wanted to do was make sure that everyone knew that it's the ionosphere that sets the angle that our signals are reflected at, NOT our antennas....
I sorta' got on-a-roll....sorry about that...



Fair winds to all...


John
s/v Annie Laurie

[btrayfors]

John,

As usual, there's a lot of wisdom and experience in your verbal ramblings :-)

While I agree with much of what you say, I cannot agree with the conclusion as stated, i.e., "....all I wanted to do was make sure that everyone knew that it's the ionosphere that sets the angle that our signals are reflected at, NOT our antennas...."

That statement, and the rhetoric which precedes it, seems to downplay the importance of vertical takeoff angle in making medium and long-distance communications. It also suggests that the all-important ionosphere can only accept useful signals (i.e., those which can be refracted back to earth) at a single angle of incidence. This is patently not so.

NO, NO, NO. This conclusion runs contrary to most authoritative texts on DX communications circuits and, most important for me, it runs contrary to my own experience with thousands of QSO's I've had over the years comparing horizontal dipoles and yagis with 1/2 wave vertical dipoles rigged as they should be with the lower insulator close to the deck or ground.

Vertical takeoff angle is not only important, it is often the determining factor in making a successful 2-way communication...or not.

And, the gain realized from very low angle vertical takeoff with vertical dipoles is a function of both the huge lobe they make at 15 degrees or less above the horizon (including the pseudo-Brewster angle right down to the horizon) AND the reduced number of hops.

Key to this is the understanding that often there are several paths to the same DX station, some involving only one or two hops AND those involving more hops. To the same station!! Each hop which can be eliminated gains you about 10dbi. This works with both radiated signals and with incoming signals.

I won't run on about this, as many, many learned authors and antenna design specialists have already done so at length.

However, I'd invite you to carefully read just the following two references from reliable sources:

DXpedition Antennas for Salt Water Locations: A focus on 20m antennas

http://www.arrl.org/files/file/antplnr.pdf

Respectfully,

Bill
WA6CCA

[ka4wja]

Bill,
Actually we agree on this...
(my poor choice of words above notwithstanding...

Yes, the ability of the antenna (such as a vertical) to have a broad pattern below 15*, all the way down to darn near the horizon, IS very important!!!

That final paragraph was just me trying to be funny....by saying that I wasn't trying to comment on "what was the best antenna", but rather just impart the fact that whatever antenna we have, we can do nothing about the angles that the ionosphere reflects our signals at....
Of course all of what I wrote above that paragraph, states the facts that having an antenna that does place a significant amount of our power down low is very important....

It was just that I didn't intend to ramble on about antennas at all...just inform some about the ionosphere....


So, in summary we do agree.....my "humor" about unintentionally rambling on about antenna, just didn't make it...

Oh, and yes I'm very familiar with the K2KW / "Team Vertical DXpeditions" and all their wonderful (eye-opening) research and real-world use data, from the past 15 years...(I actually used some of the 6Y2A info in a seminar quite some time back...late 90's, I think???)



Fair winds..

John
s/v Annie Laurie

[btrayfors]

Glad we agree, John. I guess all's well in the Firmament after all :-)

Except that I'm watching the Evening World News and is most certainly isn't outside the HF world :-(

73,

Bill
WA6CCA

[yachtgemini]

and can I get collective agreement that 'for yachts operating outside the east coast USA requiring connections to winlink and other stations at ranges often beyond 1500 miles that vertical antenna are likely be a better performer than a simple backstay'

better means - stronger signals and faster data rates and maximum hours of operation.

Ross

ps a yes / no and one paragraph please

[Scott Berg]

Yes yes (needs to be at least 5 characters)

[btrayfors]

Yes. Very likely :-)

Bill

[ka4wja]

My short answer is:
Comparing a "typical" backstay to a screwdriver, etc. on freqs above 16 - 18 MHz, the answer is probably a YES...on freqs below 12 - 14mhz, the answer is probably a NO....


My long answer:
If the backstay was long enough to produce less low-angle radiation on the particular frequency of interest (the main lobe was at a high angle), AND the shorter vertical was long enough / efficient enough at the particular frequency of interest...
An example here would be at freqs above 20mhz, the answers is almost certainly a Yes...
But, certainly a No, on freqs of 8-10mhz and below....
In the middle HF region, it depends on the antennas in question....
And, considering BOTH the low angle of radiation from the antennas (assuming we desire angles of less than 10*), AND the relative efficiencies (or inefficiencies) of the antennas, using "typical" backstay antenna lengths (40' or so), compared to a screwdriver-type antenna or the "Hustler" mobile antennas, the answer on paper is that a backstay is still going to be good thru 14mhz, with the smaller mobile antennas beginning to outperform the backstay on frequencies above 16-18mhz...



Sorry that's two paragraphs...



Fair winds...

John
s/v Annie Laurie



P.S. at least I did not even go into the azimuthal directivity....which can have as much effect than anything else when comparing various antenna on-board...nor how the "sloping" of the backstay or vertical dipole, effects its pattern / radiation angle...

[yachtgemini]

I am beginning to think that John also trained as an economist ... on one hand .... but on the other hand ..... Remarkable considering both Bill T(?) and I did graduate studies in economics and we can keep it simple.... But as always thanks to Scott, Bill and John...

Now my next assertion.

For most sloop rigged cruising yachts using their HF radios along the popular 'coastal' routes including the east coast USA , Bahamas and the Caribbean for a mix of nets and winlink contacts and frequencies at or below 14 mhz the performance and frequency agility of a backstay antenna with a good quality ATU such as the Icom or SGC offering represents an excellent platform in terms of performance and convenience. The logical first / main antenna for a cruising boat.

Yes / No or for John 2 paragraphs .

[btrayfors]

Yes. Absolutely.

Bill

[El Pinguino]

I've never done any comparative testing however....

When I was in VP8land a few years ago I occupied myself working mainly digital low power for an hour or two each day.... on 14 megs and up logged everything from Argentina thru S Africa to Japan and across Asia.....

Icom 706Mk2G... Icom 140 tuner and a (tasmanian) Moonraker whip about 4 metres long ( was a bit longer but snapped at the taffrail in a blow so a few feet shorter now).

Factoring in the cost of setting up a backstay ant with insulators etc ( which I also have) I would go with the whip any time.

And when your mast falls down ( been there... done that ) your backstay isn't going to work real well.

Sorry.. not quite a yes/no but they are short paras....

[btrayfors]

Originally Posted by El Pinguino

......Factoring in the cost of setting up a backstay ant with insulators etc ( which I also have) I would go with the whip any time........

The 'backstay with insulators' is not your only option. A robust "alternate backstay" can be constructed at very low cost, and it's every bit as good as a traditional backstay. Lots of posts about these.

Bill

[El Pinguino]

Originally Posted by btrayfors

The 'backstay with insulators' is not your only option. A robust "alternate backstay" can be constructed at very low cost, and it's every bit as good as a traditional backstay. Lots of posts about these.

Bill

Agreed... when I replace my backstay in a few months that is my plan.