Building antennas

[Superidgit]

Thanks Wav a page I never viewed before DESIGN THE CLOUD WARMER NVIS BEAM ANTENNA

I think I will try this one I do have a working 1/2 Pole and matched 1.1 with RF Chokes all I would need to do is add a reflector at 0.15A below + 5% longer then driven.

8.75Ft + 5%= 9.1875 for each leg 9.1875 x 2 =18.375 Total Size of Ref. Ele.
0.15A at 27.555 Spacing = aprox 140/freq mhz What is 0.15A Spacing?

Hey Unreal or anyone for that matter, that antenna does look pretty cool. But a couple of questions for you.

First you just hang your coax in the middle there? Or could you run your coax along one of the support poles and then along one side of your antenna.? Just to give it a cleaner look.

Also, If nothing is connected to the reflector, How does a small piece of wire actually reflect so much?


And so on a clear day this antennas capability would be reduced greatly, than on a cloudy day?

 

[RickC.]

Micheal,

First of all, congrats on becoming interested in building your own antennas-- the down side is, this stuff can eat your brain!

That said, the suggestion for the ARRL books are good ones, and don't be worried by any naysayers-- the posts were already deleted by the time I saw this thread, so I don't know what was said.

But you know, I am constantly surprised at the fear and trepidation expressed by some at building dipoles and such. It really is simple and they work well if attention is paid to mechanical and soldering details. Some people seem to be afraid they'll destroy their radios if they hook it up to something they built themselves or something that doesn't have a particular brand name. Nope...

The one suggestion I'd add is to find the highest wattage soldering iron (not gun) you can find because antenna wire makes an excellent heat sink and it can be hard to get up enough heat to make a proper joint with longer lengths of wire and the coax drawing heat away from the joint.

So, what's going to be your first project?


Rick

 

[BJ radionut]

S igit: Look at the design... A 2 element Yagi pointed straight up...
This antenna and several others designs like it take advantage of pointing maximum signal straight at the reflective parts of the the Earths atmospheric layers. I won't quote which ones as these layers(E,F etc.) can be frequency and or time of day and or seasonally(Winter,Fall etc.) dependent...
So for conversation will leave the other details alone for a moment...
So take your maximum signal...let's use a Flashlight for a signal, point that Flashlight directly at a mirror...maximum signal reflected straight back at you. Now think about the Flashlight Beam...the farther you get away from the mirror the wider that beam of light becomes...then once reflected... the wider that signal is "spread out"...Hope that makes sense?

These types of antennas are generally used for "short" or "in-close" communication on lower HF frequencies(several 100's miles)...
OK you'll can start the Flamer thrower...but that's how I'll explain it.

Now let me state this...Most antennas for HF below 20 meters will experience some of this effect...dipoles/doublets/long wires etc. due to their close proximity to the ground...

Now as to the topic ask by KB7PZI...WELCOME to a whole new world of Ham radio...And my Fav...building, experimenting with wire or home-brew antennas.
I for one Welcome your questions!

I do not claim to be an expert by any stretch but I have a "little" experience on the subject. Antennas do not have to be "perfect" nor does every one fall into "Must" rules of construction or design

That does not mean they won't friggin work!

Ask me one of these days "In the Air" You might be surprised what I am using.
Keep right on asking young jedi...
All the Best
BJ

 

[wavrider]

Micheal,


The one suggestion I'd add is to find the highest wattage soldering iron (not gun) you can find because antenna wire makes an excellent heat sink and it can be hard to get up enough heat to make a proper joint with longer lengths of wire and the coax drawing heat away from the joint.

Rick

I got tired of dragging an extension cord and that big fat soldering iron around the back field.

I gave an propane torch a try, man that thing works great, heats up those wires real fast and melts solder like it is a piece of butter:redface:

 

[Captain Kilowatt]

There is really no reason a standard Weller 100/140 watt gun can't be used to solder up to 10 gauge wire. I do it all the time. You do have to loosen and retighten the element tips now and then in order to maintain a good electrical connection for best heat. One of the most basic things about antenna building is the ability to solder well and most people don't know how to do it right. A little practice and a little advice works wonders. A BIG iron is fine but I just wanted to say that it is far from necessary for ordinary antenna wire. I have used a small 40 watt pencil iron on two pieces of 14 gauge wire. Clean wire and a clean iron with a bit of fresh molten solder on the tip to aid in transferring heat to the wire is all that is needed. Oh.....a steady hand helps too.

 

[wavrider]

Thanks Wav a page I never viewed before DESIGN THE CLOUD WARMER NVIS BEAM ANTENNA

I think I will try this one I do have a working 1/2 Pole and matched 1.1 with RF Chokes all I would need to do is add a reflector at 0.15A below + 5% longer then driven.

8.75Ft + 5%= 9.1875 for each leg 9.1875 x 2 =18.375 Total Size of Ref. Ele.
0.15A at 27.555 Spacing = aprox 140/freq mhz What is 0.15A Spacing?

BJ answered most of the questions with the flashlight explanation. Great comparison or at least I think so.

wavelength spacing
1005/freq then multiply by .15

I will guess you are working on a 10 meter NVIS antenna so lets center it up on the 28.400 mhz freq

1005/28.4= 35.38 for a wavelength in feet.

35.38X.15=5.3 feet So your reflector will be placed 5.3 feet under your driven dipole, Just like BJ said, it is a yagi antenna or some call it a beam with the reflector place under the driven element.

They work pretty good for daytime rag chew NVIS on the lower bands, say 40 meters and lower in freq.

For ten meters you may want to look at a lazy H, or a 3.2 dipole for a wire with some gain.

If you have an antenna coupler (tuner) and some ladder line laying around a lazy H would be a bi directional antenna made from wires with some decent gain, around 3dbd claimed from some EZNEC models I reviewed. Heck it is even been said it works decent on 6 meters also.

Google will be your friend here for looking up a lazy H antenna.

3/2 dipole is 702/freq
702/28.4=24.7 feet per side or about 50 feet total.
3/4 wave length long for each leg. It will give you a good impedance match at the feed point. Inverted V should give you around a 50 ohm match.

I would cut each leg about 26 1/2 feet long then start trimming it to resonance, it will give you a small amount of gain over a dipole, but it will not be a figure 8 pattern it will have major lobes at 45 degrees off the end of the legs and a small minor lobe at the feed point, so if you install the antenna at the right angle you can work DX into EU, S Africa, Japan and South Pacific, all off of a wire. Of course providing that propagation is there, Mother Nature does play a big roll in that.

Coax should be run straight down from the feed point, in theory the coax is shielded and thus it should not effect the antenna radiation pattern, but everything I have researched, yes ARRL handbooks, antenna handbooks amongst others says to run the feed line directly down from the feed point.

I am no expert, I have built plenty of antennas that radiated less than the Heath kit dummy load does. But I had fun building them and trying them and heck that is all that really matters.

If you start getting serious about building antennas an antenna analyzer is a must. It will be one of the most used piece of test equipment in your shack.

Who knows before long you may be building some forced current phased arrays

I think I touched on all the questions, and hopefully created some more.

 

[wavrider]

darn !
by by wire weasel :sad:
hopefully its just a temporary bann

Booty darn it I am laughing so hard I have tears, you just ain't right.

thanks for the laugh.

 

[Beetle]

Sorry, I am sure you still do all of your research in a library somewhere, most people though go directly to the sources, thus Social Networking. In todays age, asking these type of questions in a forum is the same as "cracking a book" or looking it up on Google.

>>And once you've asked the question and received an answer, what have you learned? Don't discount books; get some of your own for reference. Study them. Experiment and learn.

Thanks again for your input and all of the assistance you have given, I am sure months / years from now when others have the same question - they will simply shy away from asking due to your post. With answers like yours, you will guarantee the demise of this wonderful hobby.

>>IMO, the "demise" of amateur radio will be hastened by too much reliance on "social networking", with the result that everybody will know how to find the answer to a question rather than knowing how something works, why it works that way, and how to adjust it themselves.

I would prefer to spend my time more productively, so I won't respond to any more of your responses, but go ahead and feel free to flame me. If I am asked by the moderators of the site to leave due to my unreasonable question on antennas, then I will leave.

Hope you can still enjoy this hobby in your own way and I certainly enjoy it in my way.

>>If you're concerned about spending your time productively, then get some of the books mentioned and learn the subject - don't just memorize answers from a question pool.

>>You're right - there are literally hundreds of different kinds of antennas - but darn few that you can just attach to a modern transceiver without measuring its length pretty carefully and installing it correctly. And yes, you should learn how to solder; I'm assuming from your first post that you might not know at the moment.

>>"Social networking" can't replace individual capability.

 

[BJ radionut]

Wavrider: Smiles old friend...The Lazy H...fabulos!

Now take it and lay it Horizontal...
ex: each leg of the first doublet 126 ft long/center feed 450 ohm ladder line...
Ladder line continues to...
Second doublet(same size) spaced 58 ft behind first...then random length to HB "Double L" tuner in the shack...
My "Backfire Array" ...First antenna 45ft at center...second about 35ft at center...ends roughly 25 to 30ft above ground
Major lobes...from experience...not modeled(never figured that program out)
East/West...secondary majors off each corner NW/NE...SW/SE...
minors off ends N/S....
Works well 80/40/30/20...(17/15 are WOW) it hates 10m RF everywhere...with analyzer could fix that...still have not bought one!

Long band conditions...I have an 80m Delta Loop /450 feed...30ft at Apex...15 ft at corners...can make 6db difference sometimes when conditions are crummy "close-in" on 75 very early in the mornings...can hear difference out as far 500-1000 miles out...She is a killer into Euro land on 20m/17m...

I was using the "Backfire Array when we worked...
I had a 4 element version cut for 40m (2 Lazy H's)(34 ft spacing) Horizontal up a few years ago...Wind storm DAMN IT brought her down...put the longer 2 element version up been running it ever since...
Had reflectors laying on the ground last Winter under the Backfire...made a little difference on the major lobes...but damn the better half wanted the grass cut so they came up in the Spring
Getting Late Here
All the Best
BJ

 

[HomerBB]

.

So, what's going to be your first project?

I think I'll do a dipole. Oh, I did do a dipole, and again and again.
Antennas, don't get any better . . .

 

[wavrider]

Wavrider: Smiles old friend...The Lazy H...fabulos!

Now take it and lay it Horizontal...
ex: each leg of the first doublet 126 ft long/center feed 450 ohm ladder line...
Ladder line continues to...
Second doublet(same size) spaced 58 ft behind first...then random length to HB "Double L" tuner in the shack...
My "Backfire Array" ...First antenna 45ft at center...second about 35ft at center...ends roughly 25 to 30ft above ground
Major lobes...from experience...not modeled(never figured that program out)
East/West...secondary majors off each corner NW/NE...SW/SE...
minors off ends N/S....
Works well 80/40/30/20...(17/15 are WOW) it hates 10m RF everywhere...with analyzer could fix that...still have not bought one!

Long band conditions...I have an 80m Delta Loop /450 feed...30ft at Apex...15 ft at corners...can make 6db difference sometimes when conditions are crummy "close-in" on 75 very early in the mornings...can hear difference out as far 500-1000 miles out...She is a killer into Euro land on 20m/17m...

I was using the "Backfire Array when we worked...
I had a 4 element version cut for 40m (2 Lazy H's)(34 ft spacing) Horizontal up a few years ago...Wind storm DAMN IT brought her down...put the longer 2 element version up been running it ever since...
Had reflectors laying on the ground last Winter under the Backfire...made a little difference on the major lobes...but damn the better half wanted the grass cut so they came up in the Spring
Getting Late Here
All the Best
BJ

Got to love those wires. It is a lot of work making a simple wire have gain but it has been done before and the results speak for theirselves.

I understand about the reflector or radials laying on the ground, except it was not my wife wanting the grass cut, it was the stupid cows, using the guy wires to my towers and antennas to rub their necks and backs on.

 

[BOOTY MONSTER]

S igit: Look at the design... A 2 element Yagi pointed straight up...
This antenna and several others designs like it take advantage of pointing maximum signal straight at the reflective parts of the the Earths atmospheric layers. I won't quote which ones as these layers(E,F etc.) can be frequency and or time of day and or seasonally(Winter,Fall etc.) dependent...
So for conversation will leave the other details alone for a moment...
So take your maximum signal...let's use a Flashlight for a signal, point that Flashlight directly at a mirror...maximum signal reflected straight back at you. Now think about the Flashlight Beam...the farther you get away from the mirror the wider that beam of light becomes...then once reflected... the wider that signal is "spread out"...Hope that makes sense?

These types of antennas are generally used for "short" or "in-close" communication on lower HF frequencies(several 100's miles)...
OK you'll can start the Flamer thrower...but that's how I'll explain it.

Now let me state this...Most antennas for HF below 20 meters will experience some of this effect...dipoles/doublets/long wires etc. due to their close proximity to the ground...

Now as to the topic ask by KB7PZI...WELCOME to a whole new world of Ham radio...And my Fav...building, experimenting with wire or home-brew antennas.
I for one Welcome your questions!

I do not claim to be an expert by any stretch but I have a "little" experience on the subject. Antennas do not have to be "perfect" nor does every one fall into "Must" rules of construction or design

That does not mean they won't friggin work!

Ask me one of these days "In the Air" You might be surprised what I am using.
Keep right on asking young jedi...
All the Best
BJ

what if you used 2 driven elements out farther to the sides to direct the signal lower and reduce the driven elements effect on each other . keep the reflector where it is . could that work ?
if so build 2 at 90 degree angle to each other and have N E S W directions .

back to mary jane

 

[binrat]

I think I'll do a dipole. Oh, I did do a dipole, and again and again.
Antennas, don't get any better . . .

Homer,
Building antennas is your addiction.

 

[wavrider]

I think I'll do a dipole. Oh, I did do a dipole, and again and again.
Antennas, don't get any better . . .

WOW Homer your Dipoles reproduce like rabbits

 

[wavrider]

what if you used 2 driven elements out farther to the sides to direct the signal lower and reduce the driven elements effect on each other . keep the reflector where it is . could that work ?
if so build 2 at 90 degree angle to each other and have N E S W directions .

back to mary jane

I am not sure but moving the driven element to the side away from being right on top of the reflector may make it just a simple dipole.

The spacing between the driven element and the reflector would have to be maintained, So the further to the side the driven element is the closer to the ground it would have to be to keep the .15 wl spacing between the driven element and the reflector,

Just my guess, for what it is worth.