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Old 01-05-2012, 08:35   #1
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HF antenna Back Stay vs. Screwdriver antenna

Does anyone have any direct experience comparing HF antenna using the back stay vs. a screwdriver antenna. Since I have used a screwdriver mobile for years with great success, I was thinking the screwdriver should work as well or better on the boat. The install is a little easier since it eliminates the need for a tuner.

Thanks ahead for comments,
Jack
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Old 01-05-2012, 08:56   #2
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Re: HF antenna Back Stay vs. Screwdriver antenna

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Originally Posted by BocaIII View Post
Does anyone have any direct experience comparing HF antenna using the back stay vs. a screwdriver antenna. Since I have used a screwdriver mobile for years with great success, I was thinking the screwdriver should work as well or better on the boat. The install is a little easier since it eliminates the need for a tuner.

Thanks ahead for comments,
Jack
Jack,

A screwdriver antenna would work just fine, provided that it was built well enough and of materials to withstand the marine environment. Also, it would probably be necessary to support the antenna in a couple of places, not just at the base, because of the sometimes violent motion at sea.

You could expect the antenna to work as well as -- or maybe better -- than a traditional backstay antenna on the high bands (say, 10mHz and above) due primarily to its low vertical angle of radiation.

On the lower bands, however, a well-installed traditional backstay antenna might have the edge, especially on 7mHz and below. The greater length is important, no matter how good the center loading of a screwdriver antenna.

Here's a comparison of some options for marine antennas I did several years ago: MarineAntennaChoices2

Cheers,

Bill
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Old 01-05-2012, 09:06   #3
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Re: HF antenna Back Stay vs. Screwdriver antenna

Bill,

Thanks for your comments. Based on my knowledge, I agree with your comments. A little of my background, I am an electrical engineer by education and a ham radio operator. My high sierra screwdriver works exceptional well on MARS freqs below 3.3 Mhz.

Hi-Q makes a screwdriver for marine application. It was original built for the German navy for use on submarines. And yes, it requires major mounting supports which is just another simple engineering project.

I was hoping to hear from some one with actual experience using a screwdriver in this application.

Thanks again,
Jack
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Old 01-05-2012, 09:13   #4
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Re: HF antenna Back Stay vs. Screwdriver antenna

Jack,

Maybe you'll find someone who has used one and can compare to his/her backstay antenna. But, there are likely to be very, very few out there. I know sailors who have used them ashore, and those who have used them on their boats, but not together with a backstay antenna.

I'm glad your High Sierra works well on 3.3mHz. But, the question is, compared to what? I know for a fact that the length of the backstay is very important on the lower bands. One of my sailor friends whose boat was next to me one winter used to like to talk to his buddies in England (from Washington DC). He tried just about everything, because he's an avid ham and an experimenter. He had multiple antennas of all sorts. He found that when he increased the length of his end-fed antenna to over 55', it made a whale of a difference on 75 meters.

Whatever. The screwdriver will work very well, and unless you plan a lot of DXing on the low bands, I'd not be concerned about it.

73,

Bill
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Old 01-05-2012, 09:32   #5
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Re: HF antenna Back Stay vs. Screwdriver antenna

Bill,

I really appreciate your comments...they are reaffirming my thinking.
My High Sierra screwdriver performance is compared to my 102' G5RV base station.

Thanks again, 73's
Jack
W4GRJ / AFA4DG
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Old 01-05-2012, 10:49   #6
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Re: HF antenna Back Stay vs. Screwdriver antenna

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Originally Posted by BocaIII View Post
Bill,

I really appreciate your comments...they are reaffirming my thinking.
My High Sierra screwdriver performance is compared to my 102' G5RV base station.

Thanks again, 73's
Jack
W4GRJ / AFA4DG
Most welcome, Jack.

It's really hard to compare those two antennas, since the G5RV is almost certainly in some sort of a horizontal setup.

One thing I've found over the years in experimenting with many types of antennas on boats as well as on land is that vertical takeoff angle is extremely important, especially for DX. A simple single-band vertical dipole for, say, 20m....rigged low down to the deck and hoisted with a spare halyard....will outperform almost any antenna you can think of on a sailboat.

Vertical dipoles work extremely well over land as well. When I moved to this house some 14 years ago, I used some of the tall trees to hoist vertical dipoles on 20 meters and 15 meters. I also had a 120' long commercial folded dipole, rigged horizontally about 30' off the ground.

With an antenna switch, I could switch antennas easily. What I found over the years was that about 90-95% of the time the vertical dipoles WAY WAY outperformed the big horizontal antenna. You could hear the difference, and it was even more pronounced on transmit.

About 5-10% of the time, however, the horizontal dipole was close to...or even sometimes a tiny bit better than....the vertical dipoles. I judged this to be those relatively rare instances where incoming signals were at a relatively high angle.

The real DX-ers -- those who do extravagant DX-peditions to tiny islands around the world -- discovered vertical dipoles a few years back, and were astounded by their results. Some claimed as much as 18 or 20db "gain" as the result of the extremely low takeoff angle which reduced the number of ionospheric "hops" to the receiving station.

That sure parallels my experience, both afloat and ashore. I can work into Eastern Europe easily with 5 watts QRP, and get in on first call!

Sorry to wander off topic, but antennas -- especially on boats -- are my passion. At least one of them :-)

73,

Bill
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Old 01-05-2012, 20:51   #7
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Re: HF antenna Back Stay vs. Screwdriver antenna

As an vertical antenna gets shorter than 1/4 wavelength, its radiation resistance falls. That means for a given "ground" resistance, less of the power is radiated and more is dissipated in the ground resistance. So a really high quality, low resistance ground will pay greater dividends with shorter antennas than with longer ones. Fortunately, you can have a really low resistance ground system on a saltwater boat with a lot less wire than you need on land - that screwdriver antenna will probably work well.
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Old 29-03-2014, 15:56   #8
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Re: HF antenna Back Stay vs. Screwdriver antenna

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Originally Posted by btrayfors View Post
Most welcome, Jack.

It's really hard to compare those two antennas, since the G5RV is almost certainly in some sort of a horizontal setup.

One thing I've found over the years in experimenting with many types of antennas on boats as well as on land is that vertical takeoff angle is extremely important, especially for DX. A simple single-band vertical dipole for, say, 20m....rigged low down to the deck and hoisted with a spare halyard....will outperform almost any antenna you can think of on a sailboat.

Vertical dipoles work extremely well over land as well. When I moved to this house some 14 years ago, I used some of the tall trees to hoist vertical dipoles on 20 meters and 15 meters. I also had a 120' long commercial folded dipole, rigged horizontally about 30' off the ground.

With an antenna switch, I could switch antennas easily. What I found over the years was that about 90-95% of the time the vertical dipoles WAY WAY outperformed the big horizontal antenna. You could hear the difference, and it was even more pronounced on transmit.

About 5-10% of the time, however, the horizontal dipole was close to...or even sometimes a tiny bit better than....the vertical dipoles. I judged this to be those relatively rare instances where incoming signals were at a relatively high angle.

The real DX-ers -- those who do extravagant DX-peditions to tiny islands around the world -- discovered vertical dipoles a few years back, and were astounded by their results. Some claimed as much as 18 or 20db "gain" as the result of the extremely low takeoff angle which reduced the number of ionospheric "hops" to the receiving station.

That sure parallels my experience, both afloat and ashore. I can work into Eastern Europe easily with 5 watts QRP, and get in on first call!

Sorry to wander off topic, but antennas -- especially on boats -- are my passion. At least one of them :-)

73,

Bill
WA6CCA
How do you feed a vertical dipole without running the feed line parallel to the bottom leg?
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Old 29-03-2014, 19:54   #9
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Re: HF antenna Back Stay vs. Screwdriver antenna

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How do you feed a vertical dipole without running the feed line parallel to the bottom leg?
Easy peasy: haul the antenna aloft on a spare halyard and tie off the bottom end near the toerail about halfway between the forestay and the mast. Bring the feedline back to the mast, as high up as is practical and as near perpendicular to the dipole as possible. Don't need to be paranoid about this, just try to make it as perpendicular as you can easily do.

Here's a pic of two such dipoles on my boat, the 20-meter dipole is to port and an 8mHz dipole (for the marine band) is on the starbord side. You can see the center insulator and feedline on the 20-meter dipole.

Dipoles_0371

If you back up a page (numbers at the bottom) you'll see the details of how I built rugged marine versions of the vertical dipoles. These are strong enough to withstand a hurricane.

Bill
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Old 29-03-2014, 22:22   #10
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Re: HF antenna Back Stay vs. Screwdriver antenna

Check with Ross (GEMINI)
He has a High Sierra as well as other antennas
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Old 31-03-2014, 05:47   #11
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Re: HF antenna Back Stay vs. Screwdriver antenna

Why in heavens name would you want to use a contraption like a ham screwdriver on a yacht. You will probably install an antenna that will fail in less than 3 months. Even if it does work longer than 3 months the antenna will be a lossy mess of green goop in no time.

If simple autotune mobile antennas appeal to your sense consider one of these.

HF Mobile Antennas Stealth Telecom Stealth Telecom

These antennas are professionally built and are sealed and IP rated. They will certainly outlast any ham screwdriver. One of the HighQ submarine antennas would make more sense. There is not a single ham screwdriver antenna built that would last more than 1 month on a yacht.

Regardless of what mobile antenna solution you chose, you really making a choice thats very poor in terms of raw efficiency. Big screwdriver coils and short tapping the coil leads to very poor efficiency despite what hams think and say. In the end analysis a antenna like the stealth telecom which is a copy of the Codan 9350 used for decades by the red cross would be just as efficient as a screwdriver antenna over seawater. The Codan or the STealthTelecom would be a better overall choice. But for the life of me I cannot understand why anyone would not want to use a backstay and a marine automatic tuner. There efficiency and practicality is unequaled.

Quote:
Originally Posted by BocaIII View Post
Does anyone have any direct experience comparing HF antenna using the back stay vs. a screwdriver antenna. Since I have used a screwdriver mobile for years with great success, I was thinking the screwdriver should work as well or better on the boat. The install is a little easier since it eliminates the need for a tuner.

Thanks ahead for comments,
Jack
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Old 31-03-2014, 07:14   #12
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Re: HF antenna Back Stay vs. Screwdriver antenna

I have used a 20 metre long back stay with a SGC 230 ATU and a HiQ 5-80 mobile antenna for the last 8-9 years, two Atlantic crossings and probably 10,000 plus miles.

Some Comments...

the HiQ 5-80 was installed to give some redundancy in case of mast failure.. thankfully untested in that role. It is mounted on its own pole on the stern and shares both a ground plate and extensive internal grounding system with the SGC Tuner.

I have an A/B switch arrangement so it has been easy to make comparisons.

The HiQ has been 100% reliable and is still in excellent condition.. I am on my second set of Stalok rigging insulators.

The HiQ 5-80 is about 2 S points 12 db (send and receive) down on most bands below 30 metres irrespective of distance.

My back stay appears to strongly favor fore / aft on 40 metres and generally I prefer to work nets on 40 using the HiQ 5-80.

At 30 metres there is very little in it.

On 20 thru 10 metres the Hi Q 5-80 is a real DX performer and outperforms by about 3db on 20 metres and up to 3-4 S-points on 10 metres. When I add my THP 600 watt linear to the Hi Q 5-80 the results on higher bands are phenomenal. I can't run the linear with the SGC 230 for obvious reasons.

Both antennas are frequency agile and can be used on both marine and ham bands.

My backstay really is too long (one wave length at 14 mhz) for DX work on higher bands which reduces the validity of the comparison. But it is a brilliant performer on 160, 80 and the 4 mhz marine band.

Summary

The HiQ 5-80 has exceeded expectations but frankly I suspect most people today would achieve communications redundancy by buying a Sat phone and I would not criticize that decision. For winlink and general net use I rarely bother to use the HiQ 5-80 and unless you enjoy the occasional marine mobile DX work it is a little bit of a luxury. Life with an ATU is easy! But it was really nice to routinely be described as the strongest station out of North America into Europe on 14 mhz.

ps Bill gave me some excellent advice on using baluns and I found various lengths of long wire slopers that loaded up nicely with out an ATU and allowed the full power of the THP on 80 and 40... very nice results. Bills comments on vertical dipoles for 10 thru 20 metres are spot on but I got very poor results with a vertical / sloper dipole on 40, even tried a loaded vertical dipole for 80 metres but the results were also poor.
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Old 31-03-2014, 13:00   #13
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Re: HF antenna Back Stay vs. Screwdriver antenna

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
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Old 01-04-2014, 09:32   #14
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Re: HF antenna Back Stay vs. Screwdriver antenna

Strange things we think about as we are about to go to sleep...

I have thought further about my answers yesterday and suspect I got the balance wrong. The HiQ 5-80 antenna is clearly a great antenna for 20 metres and up.. Great DX and some really fast higher frequency PMBOs to access. If I was to start from scratch again I may have ditched the back stay and just gone with a centre loaded whip. Better and newer designs are available and when I went and looked at the HiQ web page it was easy to see my antenna is now a relative dinosaur.

Bill summed it up right when he said low angle of radiation and efficient. But not so good on the lower frequencies.

Mine on the stern also gave a much clearer pattern and probably had much less interaction with the rigging.

So why not get a centre loaded vertical that is simply longer and more efficient on the lower frequencies? The limiting factor on the design is not mechanical but road / legal issues which don't come into play at sea. The HiQ for example is so strong and water tight I could easily imagine it expanded to a full quarter wave on 20 metres. I understand some of the premium manufacturers support customization of antennas.

When I was using an Icom Txcver I used a Turbo tuner (N2VZ Enterprises Automatic Screwdriver Antenna Controller) which gave very good matches although a little slower than a conventional ATU. It simply used the centre loaded coil and attached motor to find a good match. Bullet proof and rated for full legal power..... Try to achieve the same thing with a conventional ATU and you looking at big $$$.

I would preface all my comments with the suggestion that if you buy junk and stick it on your stern rail its life expectancy and effectiveness is not going to be great.

But to answer the original question - yes I would be happy to skip the back stay and go for a stern mounted centre loaded vertical.

Ross
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Old 02-04-2014, 03:43   #15
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Re: HF antenna Back Stay vs. Screwdriver antenna

The ground quality is a more important determining factor than the length of the antenna. Granted that a 1/2 wave antenna will have a few degrees lower angle of radiation. Over seawater there is no practical advantage using a half wave length antenna. The lowest takeoff angle is determined by the quality of the ground. The best communications antenna is not one that radiates the lowest possible radiation angle at all times, but an antenna that covers the broadest range of radiation angles and has useful gain across all these angles. 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.
Quote:
Originally Posted by btrayfors View Post
Most welcome, Jack.

It's really hard to compare those two antennas, since the G5RV is almost certainly in some sort of a horizontal setup.

One thing I've found over the years in experimenting with many types of antennas on boats as well as on land is that vertical takeoff angle is extremely important, especially for DX. A simple single-band vertical dipole for, say, 20m....rigged low down to the deck and hoisted with a spare halyard....will outperform almost any antenna you can think of on a sailboat.

Vertical dipoles work extremely well over land as well. When I moved to this house some 14 years ago, I used some of the tall trees to hoist vertical dipoles on 20 meters and 15 meters. I also had a 120' long commercial folded dipole, rigged horizontally about 30' off the ground.

With an antenna switch, I could switch antennas easily. What I found over the years was that about 90-95% of the time the vertical dipoles WAY WAY outperformed the big horizontal antenna. You could hear the difference, and it was even more pronounced on transmit.

About 5-10% of the time, however, the horizontal dipole was close to...or even sometimes a tiny bit better than....the vertical dipoles. I judged this to be those relatively rare instances where incoming signals were at a relatively high angle.

The real DX-ers -- those who do extravagant DX-peditions to tiny islands around the world -- discovered vertical dipoles a few years back, and were astounded by their results. Some claimed as much as 18 or 20db "gain" as the result of the extremely low takeoff angle which reduced the number of ionospheric "hops" to the receiving station.

That sure parallels my experience, both afloat and ashore. I can work into Eastern Europe easily with 5 watts QRP, and get in on first call!

Sorry to wander off topic, but antennas -- especially on boats -- are my passion. At least one of them :-)

73,

Bill
WA6CCA
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