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AD7TO
05-15-2008, 09:27 PM
I would like to know any of you had the experence working with a curtian type antenna? I'm interested in the Sturba curtian and Bobtail curtain.
Here is a link to build a Sturba Curtian http://www.hamuniverse.com/sturba.html

I'm just wondering how effective these Sturba curtians are. Also I know the Bobtail curtain is a different antenna. From what information I can find they bolth sound like the work good. I know the Sturba curtian is bi directional buy I'm not sure about the Bobtail curtian.

I would apperate any information about these antennas. I would really like to know what your thoughts are when on the air with these antennas. And any tips on building a Sturba or Bobtail curtain.

Thanks

AI4IJ
05-15-2008, 10:27 PM
I would like to know any of you had the experence working with a curtian type antenna? I'm interested in the Sturba curtian and Bobtail curtain.
Here is a link to build a Sturba Curtian http://www.hamuniverse.com/sturba.html

I'm just wondering how effective these Sturba curtians are. Also I know the Bobtail curtain is a different antenna. From what information I can find they bolth sound like the work good. I know the Sturba curtian is bi directional buy I'm not sure about the Bobtail curtian.

I would apperate any information about these antennas. I would really like to know what your thoughts are when on the air with these antennas. And any tips on building a Sturba or Bobtail curtain.

Thanks

The antennas you mention are primarily for use on the lower HF bands; although, the principles involved are scalable even up to VHF/UHF. The reason why they are popular on the lower, rather than upper HF bands, is because there are smaller antennas that can provide the same or superior performance on the upper HF bands - like Yagis. But, on the lower bands, where Yagis tend to be prohibitively large, these antennas provide an alternative with gain and side rejection, without having to have great height, like would be required with a Yagi.

Both the Sterba array and the Bobtail Curtain array are vertically polarized antennas, despite their general horizontal orientation. The horizontal elements are used to effect phasing between the vertical elements.

Neither antenna requires any kind of ground or counterpoise system, as they are considered to be "self-contained," like a dipole is self-contained. But, their performance is tied to the ground quality, both in the near and far field of the antenna. Near the ocean, these antennas are very effective performers. And, strangely enough, they will tend to perform better over poor soil than over average soil - even if they perform best over high quality ground.

And, both antennas depend on their relatively close proximity to ground for their low angle performance - distinctly different than most other HF antennas.

These are DX antennas. That is to say, they are better suited for DX than local contacts.

A Bobtail Curtain antenna is basically two Half-Square antennas fed in phase. Whereas the Half-Square antenna is fed in a corner (for current feed with coax), the Bobtail Curtain is fed about two thirds up the center element (for current feed) or at the bottom of the center element (for voltage feed). The top one wavelength element provides phasing so that the outside vertical elements and the center vertical element are all fed in phase with a pattern that is bidirectional to the broadside of the array.

The Bobtail Curtain has a high-gain, low angle signal that is great for DX; but, its beamwidth is very narrow. The narrow beamwidth and the inability to rotate the array makes it particularly well-suited for point to point contacts - but, not so good for general amateur operation, unless you have a set of them oriented to cover more of the horizon.

While the Bobtail Curtain is a bidirectional antenna, it can also be modified to function as a unidirectional beam antenna with the addition of another Bobtail Curtain spaced about 1/8 wavelength from the first and a switch that makes either one the director or the reflector.

These antennas take up a LOT of space. If you don't have much real estate, or if you don't have the required inline supports of sufficient height to support the array, you might be better off choosing another design. Even though they do not require great height, they do require supports that are greater than 1/4 wave high at the design frequency. On 80M, that means your supports need to be at least 70 to 80 feet high (high enough that the ends of the vertical elements are out of reach of people and animals).

These antennas are only bidirectional (or unidirectional) on the band for which they were designed. On the other HF bands, they tend to perform very much like a regular horizontal doublet - because, the phasing is designed for only one band.

If you have a buddy somewhere else in the world with whom you would like to establish regular contact on the low bands, these are good candidates. But, if you are interested in general DXing, you might want to choose something else, or build several of them and switch between them for operation in other directions.

The Sterba array is going to have an even more narrow beamwidth than the Bobtail Curtain - and, it is much larger and more complex to build.

73
Richard
AI4IJ

G0GQK
05-15-2008, 10:30 PM
Well, if you have plenty of land, a few big masts lying around and about six miles of copper wire, as well as about 12 months to construct yourself a broadcasting station antenna, they work well, in two directions.

I remember listening to a US ham chatting to a another who was the owner of a big sterba curtain antenna and he asked him what he could hear "well, I can hear most anything, I can listen in to most folks in Europe, even when they is havin' a chat among themselves. When I call in to say howdy they tear off their headsets with their ears ringin' and say things like, "mein liebers Gott, vot in Himmel vos dat Heinrich ? I just smile and have fun blowin' out their eardrums, real friendly like "

G0GQK

NA0AA
05-16-2008, 12:01 AM
Do not believe the all band stuff in that first link, Sterba's are resonant antenna, mostly. - but you can tune almost anything if you work hard enough.

I built one for 6 meter but I don't have suitable supports - someday it might get used for field day.

KA4DPO
05-16-2008, 12:15 AM
I would like to know any of you had the experence working with a curtian type antenna? I'm interested in the Sturba curtian and Bobtail curtain.
Here is a link to build a Sturba Curtian http://www.hamuniverse.com/sturba.html

I'm just wondering how effective these Sturba curtians are. Also I know the Bobtail curtain is a different antenna. From what information I can find they bolth sound like the work good. I know the Sturba curtian is bi directional buy I'm not sure about the Bobtail curtian.

I would apperate any information about these antennas. I would really like to know what your thoughts are when on the air with these antennas. And any tips on building a Sturba or Bobtail curtain.

Thanks


A bobtail curtain is a horizontaly polarized antenna consisting of 1/2 wave sections matched by 1/4 wave closed stubs. Check the ARRL antenna handbook for the details. This is a good antenna with bi-directional properties and definetly has a horizontal pattern. Gain is a function of the number of 1/2 wave elements but it gets big in a hurry at 40 meters and below.

AI4IJ
05-16-2008, 12:50 AM
A bobtail curtain is a horizontaly polarized antenna consisting of 1/2 wave sections matched by 1/4 wave closed stubs. Check the ARRL antenna handbook for the details. This is a good antenna with bi-directional properties and definetly has a horizontal pattern. Gain is a function of the number of 1/2 wave elements but it gets big in a hurry at 40 meters and below.

No, the Bobtail Curtain is absolutely not a horizontally polarized antenna. You seem to be describing a collinear array.

A Bobtail Curtain has a one wavelength top wire that provides phasing for the 1/4 wave vertical elements at the ends and in the center of the antenna. This makes it the functional equivalent of three 1/4 wave verticals phased together - because, that is what it is. The radiation is primarily from the vertical elements and the horizontally polarized energy is largely self-cancelled.

73
Richard
AI4IJ

W8JI
05-16-2008, 02:06 AM
I would like to know any of you had the experence working with a curtian type antenna? I'm interested in the Sturba curtian and Bobtail curtain.
Here is a link to build a Sturba Curtian http://www.hamuniverse.com/sturba.html

I'm just wondering how effective these Sturba curtians are.

Well, I wouldn't trust a site that does not even know how to spell "Sterba".

In fact the Sterba Curtain is a narrow bandwidth modest gain antenna. It consists of broadside and collinear elements. The more sections you add the narrower the gain/pattern bandwidth becomes.

Sterba Antenna (http://www.w8ji.com/curtain%20sterba%20USIA%20array.htm)

It is nothing like Ham Universe describes.



Also I know the Bobtail curtain is a different antenna. From what information I can find they bolth sound like the work good. I know the Sturba curtian is bi directional buy I'm not sure about the Bobtail curtian.

It is bi-direction too, unless you add reflectors or end-fire phasing of a second array


I would apperate any information about these antennas. I would really like to know what your thoughts are when on the air with these antennas. And any tips on building a Sturba or Bobtail curtain.

Well, I've had Bruce and Sterba arrays in the past. They are OK for gain but are single band antennas. I did have a very large Bruce Array for 80 meters and it only had a decent pattern over about 100kHz of the band. There certainly are much better choices, like a Lazy H. The Lazy H will have broadside gain over almost a 3:1 frequency range if it employs distributed feed.

I'd recommend you look at a Lazy H antenna or a W8JK array if you want 2 or 3 band antenna with reasonable gain.

73 Tom

M0DSZ
05-16-2008, 07:06 AM
Short wave broadcasters were fond of Sterba arrays, the BBC used them with identical reflectors and the entire was hung between two tall towers. The reflector and antenna could be swapped to reverse the direction of radiation.
The Sterba "curtains" were generally limited to one band and fed with open-wire feeder, the array could be electrically slewed by variations in the feeder arrangments. A few pictures are on the internet from teh BBC and other stations.

N9XV
05-16-2008, 09:59 AM
The Sterba depicted on the link is "cut" for 10-meters. It may "load-up" on other bands, but its only a Sterba on 10-meters. On the very lower bands, I cant imagine that it would act much different than a ball of chicken wire!

AD7TO
05-16-2008, 10:11 AM
Thanks for all the information. I'm planing on building one a Bobtail or Sterba I just have decided which one yet. I'm thinking of building one for 40 meters or maybe 20 meters. But it sounds like from some of these posts that these curtains really work best on the lower HF bands. I'm just trying to gather as much information as I can about these antennas.

Does anyone know of some place where I can get good plansto build one of these antennas? Also I would doubt this but is there any commercial antenna manufactures that make and sell these antennas?

N9XV
05-16-2008, 10:23 AM
BTW, Nice detail on fig. 21-18 Tom! How high up in frequency could you expect to go with that design using tubing etc?

Kevin

W8JI
05-16-2008, 01:10 PM
Short wave broadcasters were fond of Sterba arrays, the BBC used them with identical reflectors and the entire was hung between two tall towers. The reflector and antenna could be swapped to reverse the direction of radiation.
The Sterba "curtains" were generally limited to one band and fed with open-wire feeder, the array could be electrically slewed by variations in the feeder arrangments. A few pictures are on the internet from teh BBC and other stations.

SW BC stations virtually never used a Sterba Curtain. They used USIA or Distributed FEED Curtains, virtually never a Sterba.

The Sterba also CANNOT be slewed because it has a single point feed.

The only application for a Sterba is a single band single frequency single direction non-slewed antenna, yet it costs nearly as much to build as a broad band distributed feed curtain.

The problem is Hams and SWL's generally don't know the difference between a USIA array or Distributed Feed Curtain and wrong call it a Sterba. But that is a mistake in the name people use, not the antennas problem.

W8JI
05-16-2008, 01:30 PM
BTW, Nice detail on fig. 21-18 Tom! How high up in frequency could you expect to go with that design using tubing etc?

Kevin


First, a curtain is effective on ANY band. They are often used on UHF or VHF. Some of the highest gain TV aerials ever used were actually distributed feed curtains with screen reflectors. Those little stacks of bowties with a screen behind them for UHF, sometimes four high and sometimes four high and two wide, were all forms of the curtain antenna. CushCraft even made a two meter curtain array, although at VHF and higher they are sometimes called mattress array or bedspring arrays. The first RADAR antennas were distributed feed curtains scaled for VHF.

Broadcast antennas use a group of wires to simulate a thick element.
The thick element reduces SWR variations with frequency and keeps the corona discharge problems at high power to a minimum.

It doesn't matter for amateur service what wire or tubing you use as long as the conductor is a reasonable size. It matters a great deal if you run 50kW or more of AM (200KW PEP) .

The lower frequency limit is where the dipole elements are 1/2 wave long or slightly less. The upper frequency limit is where the dipole elements are about 1.3 wavelengths long. This means the frequency limit for a good pattern and gain is just under 3:1. So a 30 meter curtain of minimum size would be at the limits on 30 meters and near ten meters.

Do not confuse the distributed feed curtain with the Bobtail (which is NOT a curtain at all, it is three phased verticals with a single wire feed) or the Sterba (which is a single band non-slewed lower gain antenna).

Again I would strongly recommend you start with a Lazy H antenna using center feed (distributed feed) rather than the Lazy H that has a transposed feedline. The Lazy H with center distributed feed can cover a 3:1 frequency range, the Lazy H with transposed 1/2 wave feed is like a Sterba. It is a single band antenna with limited maximum gain.

Read my web page carefully. It details how these antennas actually work and shows the non-Sterba distributed feed antennas actually used by the vast majority of SW BC stations.

Curtain Arrays (http://www.w8ji.com/curtain%20sterba%20USIA%20array.htm)

73 Tom

WA8RTI
05-16-2008, 01:39 PM
Direct experience no, but I talked to someone who had. While in Germany I talked with guy who was the engineer for a Christian shortwave broadcast station in Africa. He said they were running 100 kW into a 10 dB gain sterba curtain aimed at the USA. In other words an erp of 1 megawatt. If you've got the space and can live with a fixed direction antenna, go for it. What a signal you could have on 80 or 40 meters!!!

N9XV
05-16-2008, 03:39 PM
I've seen pictures of radar applications but just never really got any good design criteria etc. I'd like to model/build some for experimentation on 70-cm etc. Anyway, back to reading/researching!

"RTI" I always thought a corner reflector on 20 would be cool! Just erect a dipole near a baseball diamond backdrop fence I suppose???:D

Dare to dream - and hopefully some day build!

Kevin

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