Dream Antenna

[n3lrx]

OK, so my dream antenna if I was to move to Texas would be a full wave 240 ft loop of wire, 60 ft square. Would this work? It could also be a 1/2 160 m loop. Or I can trap it to make it a full wave at 160.

Would this work? Does length even count in wavelengths with a loop? I could wire up the entire 2.5 acres of property and use a 2.5 acre loop.

I've got a friend in Texas who's quite a welder and he'll weld me together 4, 40 ft tilt over poles for the support.  The railroad uses them for jacking up their control point antennas and a bit of wire won't be near as much wind load as a UHF yagi or VHF folded dipole array. I've studied how they do it and I'm sure my design will work as well. They would be easy to tilt over for maintenance just remove the bolt or pin and walk it down, and walk it back up and put the bolt through it.

I wouldn't need to worry about ice weight in the winter as a problem since San Antonio rarely sees ice.

Traps I don't know how to make. I'm sure Google probably knows but I haven't looked yet.

[flintstone mop]

40 foot high poles to elevate the loop?
You might want to "re-calculate"... Don, K4KYV has a couple of approaches to 160M. A full length dipole 90 feet in the air and a broadcast style tower, isolated from ground, and the radial field. I forget the height.
You can choose the Vertical for longer distance (DX) or the dipole for local.....500-600 miles.
If you have the space, you should go BIG and TALL.
Fred

[n3lrx]

I don't have the funds or resources to go to 90 ft. A 90 foot tower is way out of my affordability. New or used I doubt I could afford one. Unless I go into the tower removal business in the area and offer to take down and haul away towers free for those that have Dish and no longer need over the air antennas. I guess that's a cheap way to get some Rohn 25. If people will bite and just want their towers removed for free. Some may still want money for the hardware even if you take it down for them.

[KA2DZT]

The length of the loop is important.  I use full size loops here.  To find the length, divide the freq into 1005 and this is the length in feet.  My loops are in the vertical plane.  The top side in up at about 80-90 ft.  The lower side is only about 10-12 ft above the ground.  They are fed along the low side with a 1/4 wavelength of 75 ohm coax and then 50 ohm coax (any length) to the shack.  The exact shape is not critical, doesn't have to be an exact square.

Fred

[Steve - K4HX]

A full-wave horizontal loop at 40 feet would be a good local coverage antenna on 75 meters (out to 300-400 miles). If you feed it with open wire line, you can use it on several bands.

[wa3dsp]

My antenna at my vacation house is a rectangular loop of about 320 feet that essentially follows the property line of the yard. It is fed with open wire line at the midpoint of one long side to an air balun mounted in a waterproof box just outside of the shack. About 8 feet of RG214 coax couples the balun to my tuner. I also have an MFJ current balun in series for good measure. It works great on all bands. I primarily use it on 75. The only problem is it is more of an NVIS antenna as it is only about 25 feet above the ground. I use six poles to support it, one in each corner and one midpoint on the long sides. One in the front yard is also a flagpole.

In my studies of loop antennas I determined that a resonant length is not essential or maybe even desired. One paper I read actually showed better results for a non-resonant length. So just put something up and make it a long and as high as you can.

[K6JEK]

I wonder how many of you guys use loops and if you like them. I am about to put one up but my expectations are checked by my experience at the Monterey Bay Area Radio club. A few years ago I helped put up a beautiful 75m loop. Three of us did it. Horizontal,  up 55 - 60', relatively square.  Fed it with ladder line but not much of it. It was a chore. This is former Ft. Ord land, scrubby, thorny, rocky, rattlesnakes.

We never did have a QSO where it was better than the 75M inverted V dipole up about the same height. It really wasn't much quieter either. We could tune it for other bands but it sure seemed like a lot of work and wire for what we achieved. I guess we were expecting something dramatic and did not get it.

Nevertheless, I'm going to try one again.

Once upon a time, when we were awash in sunspots I had a vertical 20M delta loop fed 1/4λ from the apex. It was wonderful.

[n3lrx]

If and when I move down there it will most likely be a dipole or inverted-v to start with but I've always wanted a loop. I've heard a lot of good signals from loops.

[Pete, WA2CWA]

I had a 40 meter vertical loop for years and thought it worked well. After a number of years the wire insulation started to look grungy so
I decided to replace it with some better stuff so I took it down. Before getting the necessary wire, I threw up a dipole in the interim. Seems the dipole worked just as well as the loop. The loop never went back up.

[n3lrx]

Hmm, since the topic has changed in favor of a dipole, what if I took two dipoles or inverted V's and fed them out of phase to 'screw' the signal into the ether. Kinda like the Satellite guys use to talk to satellites. I'll have the real estate to do either. I've already been told he don't care how many antennas I put up or even if I need some of his property to do it. Does that work on HF? If so does it prove any advantage?

[Pete, WA2CWA]

Hmm, since the topic has changed in favor of a dipole, what if I took two dipoles or inverted V's and fed them out of phase to 'screw' the signal into the ether. Kinda like the Satellite guys use to talk to satellites. I'll have the real estate to do either. I've already been told he don't care how many antennas I put up or even if I need some of his property to do it. Does that work on HF? If so does it prove any advantage?

Sort of a HF turnstile antenna; makes a great omni directional antenna. Save money on feedline.

[steve_qix]

I hear you on the towers, however a tower to just hold up the center of a dipole could be done real cheap.  

Like you, a new 90 foot tower is out of the question, but I was able to land 2 used towers for super-cheap.  I bought 5/8 inch Dacron to guy the 90 foot tower, so it's non conductive and no insulators required.

One of the towers is a military unit 24 inches on a face.  The other is Rohn 45.  Built the tower on the ground and tipped it up in one piece and use 2 sets of guys, one at the top and one at about 50 feet.  

I've also put up that military telescoping mast at 90 feet.  You need more guys, but it definitely works.

I say this because a dipole with the center at 90 feet is a really, really good general purpose antenna.  Work Europe on 75 meter AM during the fall/winter months, and coast-to-coast is no problem at night, but the local signal is excellent also.  What I'm using now is a coax fed fan dipole for 160/75 with the center at 90 feet.  The ends come down to about 60 or so feet - held up by ropes in trees.

If there's any way to get up a single high center support, it's probably the biggest bang for the buck.

Anyway, just another idea.

[WA2ROC]

I have a 290 foot 80 meter loop hanging between 6 or 7 trees, mainly because that's where the wire could be hung easily.  It's sorta triangular in shape and is fed with about 50 feet of 450 ohm window line directly into a balanced tuner.

It out performs my 100 foot dipole, noise-wise, and just about anyone I hear I can talk too, using no more than 100 watts,. 

Monday nights I load it up on 20 maters for the Monday 20 Mater AM net and usually have no problems with mid westerners and west coasters. Locals, not so much.

I like my loop....

[n3lrx]

Cool, that's what I'll start with only one center support, and since I'll only be using one I'll be able to go higher than 40 ft. The satellites will most likely be trees to get started. The area is all low cedar so that will put the ends up at about 20 feet. I've got plenty of wire to string up thanks to W3JN, so a 75/160 fan is also possible. Now I just have to consider what I'll have to do to relocate.  In my current position I need to do a lot of research and I'll have to start some balls rolling before I leave.

[Steve - K4HX]

Don't waste your time on the two dipoles. A single dipole at 40 feet is already omnidirectional (or nearly so). Nothing to be gained but more complexity.

If you really want to put up two dipoles, put up two spaced about 40-50 feet apart and phase them. With switching and matching your can have three patterns: unidirectional in two selectable directions, bidirectional (lower take off angle) and nearly omni and mostly high take off angle.

[K1JJ]

If you really want to put up two dipoles, put up two spaced about 40-50 feet apart and phase them. With switching and matching your can have three patterns: unidirectional in two selectable directions, bidirectional (lower take off angle) and nearly omni and mostly high take off angle.

Agreed!  

There is less than a dB difference between a loop and single dipole when modeled.   A dipole is easier to support, takes up less precious "antenna field" interaction space and its "effective" height is higher than a loop due to less ground coupling, thus somewhat lower take-off angle.

The ultimate antenna for 75M - the poor man's ass kicking array:  As HuzMan said, a pair of coax-fed dipoles switched and fed  +90 or -90 or 0 degrees in-phase. This will give us unidirectional gain of 4-5dB  in either direction with a reasonable low angle and a 20dB front to back for better receiving - PLUS feed them in-phase and produce a strong high angle cloud burner local signal.

I'm not kidding - a pair of 75M phased dipoles at 60' is possibly the best free lunch in the 75M/ 40M world there is. To surpass this would require a 3el rotary Yagi at 90' on 75M.
Considering it's almost like quadrupling our output power in the favored direction, you'd think it would be a more popular antenna system.

T

[wa3dsp]

Loop antennas are known to have better signal to noise ratios and I would have to say that in my experience that holds true. My vacation location is near the coast where there is a higher power line noise level. The loop does much better than a previous dipole. A couple of other loop users I have spoken with give the same report.

Even on a smaller lot you can get a lot of wire up there with a loop. My shore lot is about 120x60. I run a loop around almost the entire perimeter, total length about 320 feet. It does not have to be a resonant length. Make it as long as you can.

[K1JJ]

Loop antennas are known to have better signal to noise ratios and I would have to say that in my experience that holds true. My vacation location is near the coast where there is a higher power line noise level. The loop does much better than a previous dipole. A couple of other loop users I have spoken with give the same report.

Interesting.  I've heard this often and respect these opinions.

I have often wondered why a loop would be quieter. After all, does it know when to discriminate noise from real radio signals?  I could see it happening if the pattern were altered compared to a dipole.

I have a pair of closed, parasitically coupled loops for 75M at 190' high, used for Europe and western USA.  In my own experience I've seen little difference in noise levels between the loops and other high 75M Yagis I use here. Go figure.


Here's a short discourse about noise and loops. It goes to show that this debate will probably go on for a long time... :-)




Posted on  a reflector:

"I have used a 75 meter loop antenna here where I live for the past 5
 years. It works very well. I live right in town on a lot surrounded by
 other homes. I started with a dipole but was advised that a loop would
 hear less noise. It turned out to be quite true. I am now a convert to
 the loop antenna. Have no idea of the physics of how it works, but it
 sure does work well on bands between 75 and 20 meters. It actually seems
 to work best on 40 meters."


[response]

"It is not true. Only in the cases of corona buildup, etc, on the
 elements would that be the case.
 If you hear less noise with the loop, vs the dipole, it's due to
 the change in pattern. Not due to any qualities of the loop itself.
 Noise is RF the same as any other signal, and follows all the same
 rules. It's no different than an actual signal.
 If what you/they say is true, and the loop received less noise, it would
 also receive less "desired" signals. Or in other words, everything
 would be down vs the dipole.
 The most likely explanation is the change in pattern less favored
 the direction the noise is coming from. Either that, or the noise is
 local to your shack, and for some reason the loop's feed line is better
 decoupled than the one feeding the dipole.
 If I had to bet, I'd say it's the change in pattern.
 There are no magical anti noise properties with loops."



[Photo courtesy the HuzMan]

[KA2DZT]

I agree with the corona discharge type static being reduced with a loop vs an antenna that has open ends.  So, this would be static that is being produced right on the antenna rather than noise that is being received on the antenna from some other source.

Fred

[K6JEK]

If you really want to put up two dipoles, put up two spaced about 40-50 feet apart and phase them. With switching and matching your can have three patterns: unidirectional in two selectable directions, bidirectional (lower take off angle) and nearly omni and mostly high take off angle.

Agreed!  

There is less than a dB difference between a loop and single dipole when modeled.   A dipole is easier to support, takes up less precious "antenna field" interaction space and its average height is higher than a loop due to less ground coupling.

The ultimate antenna for 75M - the poor man's ass kicking array:  As HuzMan said, a pair of coax-fed dipoles switched and fed  +90 or -90 or 0 degrees in-phase. This will give us unidirectional gain of 4-5dB  in either direction with a reasonable low angle and a 20dB front to back for better receiving - PLUS feed them in-phase and produce a strong high angle cloud burner local signal.

I'm not kidding - a pair of 75M phased dipoles at 60' is possibly the best free lunch in the 75M/ 40M world there is. To surpass this would require a 3el rotary Yagi at 90' on 75M.
Considering it's almost like quadrupling our output power in the favored direction, you'd think it would be a more popular antenna system.

T

Yes. Had em. Will have em again some day. Phed Phased Dipoles Phantastic.

[WBear2GCR]

Sterber Curtain?
Lazy H type stuff?

I had a friend here who put up a Sterber Curtain for 10m nominally and swore he could
load it on 160m just fine, it was pretty long, quite a few sections...

I personally like the phased dipole concept, the trick though is to put the thing up in the right orientation the first time, since there ain't no second time!

HLR has a very strong sig-a-nig-a-nal with his phased array, whatever it is.

          _-_-

[ka7niq]

If you really want to put up two dipoles, put up two spaced about 40-50 feet apart and phase them. With switching and matching your can have three patterns: unidirectional in two selectable directions, bidirectional (lower take off angle) and nearly omni and mostly high take off angle.

Agreed!  

There is less than a dB difference between a loop and single dipole when modeled.   A dipole is easier to support, takes up less precious "antenna field" interaction space and its "effective" height is higher than a loop due to less ground coupling, thus somewhat lower take-off angle.

The ultimate antenna for 75M - the poor man's ass kicking array:  As HuzMan said, a pair of coax-fed dipoles switched and fed  +90 or -90 or 0 degrees in-phase. This will give us unidirectional gain of 4-5dB  in either direction with a reasonable low angle and a 20dB front to back for better receiving - PLUS feed them in-phase and produce a strong high angle cloud burner local signal.

I'm not kidding - a pair of 75M phased dipoles at 60' is possibly the best free lunch in the 75M/ 40M world there is. To surpass this would require a 3el rotary Yagi at 90' on 75M.
Considering it's almost like quadrupling our output power in the favored direction, you'd think it would be a more popular antenna system.

T

How Cool!
Where can I learn more about doing these phased dipoles ?

As far as loops go, I am inclined to agree that for the low bands, loops are a total waste of time, unless you can get them up high!
Tom, W8JI, has shown that the more wire you have out at low heights (under a wavelength), the more loss you will have.
Perhaps this is why they are reported to be "quieter" ?

[ka7niq]

Sterber Curtain?
Lazy H type stuff?

I had a friend here who put up a Sterber Curtain for 10m nominally and swore he could
load it on 160m just fine, it was pretty long, quite a few sections...

I personally like the phased dipole concept, the trick though is to put the thing up in the right orientation the first time, since there ain't no second time!

HLR has a very strong sig-a-nig-a-nal with his phased array, whatever it is.

          _-_-

Hey Bro, I am an Audiophool too, you know, like direct driven electrostats by Tubes, B&W 801's, Krell, Threshold, Sumo Gold, stupid stuff like that.

[Steve - K4HX]

I wouldn't say that low (somewhat undefined) loops are a waste of time. On the fundamental frequency, they are great for high angle coverage on links 0-300 miles. Just depends what you want.

Some good info on phased dipoles at the link below.

http://www.eham.net/articles/27922

[n3lrx]

My mind has been changed on my dream antenna to a phased array, I had heard praise of loops but the information posted here has changed that. And running a diaper pole I can actually go higher since I only have one support to erect to start instead of 4, or however many it takes to construct a loop. And those supports would have to be a tower of some sort because as I said the area is all low cedar the majority of trees are 20 feet or less. There's just no way I can get a loop high enough to even be effective for local talk let alone 300 miles or more is impossible without constructing said towers.

Thanks guys for the info. Expertise is why I come here.