The "N2ITH" Dipole antenna system.....

[WX2MIG]

Even though this kinda started in the "Hoarding copper wire" thread, I figured I'd kick things off in a new thread.....

It could every well be that I may not be the original inventor of this contraption, after all, if a half wit like me could think this up, there's a damn good chance someone else thought of it long before I did. If someone else did infact engineer this prior to me doing it, then please let me know, other wise I'll take all due credit......

After discussing the basics of this concept on the other thread, Doc mentioned substituting the plastic coated guy wire for non conductive cord, and that's propbably not a bad idea, it will not only avoid interaction between the actual antenna and it's support structure, but may also help suppress contradicting movement between the two trees.....
Beyond that, my idea will work the same as described......

The free floating hanger device......

This first photo shows the basic conponents used.
! - 3/4" PVC "T" fitting
3 - 3/4" PVC end caps
1 - Stainless threaded eye bolt with fender washers and self locking nut.

This photo shows the eye bolt assembly attached to the one end cap, plus the short pieces of 3/4" PVC pipe used to couple everything together.

A view showing from inside the end cap......

This last photo shows the final assembled device. The black wire represents the cord that will run through the assembly, plus the swivel pulley from which I'll run another length of cord to hoist and support the actual dipole antenna. This will also allow me to raise, lower, and adjust the actual location of said antenna in relation to the trees and my garage.....

As this project progress' I'll post more photo's...
Now I have to shop around for some good quality braided cord...possibly some military surplus parachute cord in olive drab would be a good chice.....?

 

[WX2MIG]

One thing I forgot to include.....

I also secured the connections that will receive the downward force with a couple of #4 X 1/2" stainless screws as you will see in this next photo.

I gave the assembly a coat of olive drab paint to help camoflage it in with the trees......

 

[Robb]

I bought a roll of 100 ft - 3/16" Dacron rope from Ham Radio Outlet for $15. Supposed to be the best and weather/UV resistant. If you wanted to do it on the cheap(I can understand that) then you can buy clothesline polyester for half that price for the same length. Of course, I can't say that it will stand the test of time, but it should work OK for at least a couple of years.

Are you going to make your own balun too? There are a few web pages that show how. Or are you going to use ladder line? Cheaper than the cost of coax over that distance - that's for sure - and ladder line has good velocity factor specs as LMR-400 too. I have my reservations about ladder line -as common mode current could be a real problem. Unless you use enough ladder line to get within 35 ft and then use a balun and use 35 ft of coax into the shack.
Thinking out loud...

 

[WX2MIG]

Rob,

The Mil-Surp parachute cord is a kern mantle type cordage that is one of the most resistant to UV, low stretch, and strength to diameter ratio, plus since it's military surplus....it can usually be found quite cheap. The best part is it comes in olive drab, and that will allow it to blend in with the trees, and not stand out like a length of bright white cord would......

I'm going to call around tomorrow to see if any of the local Mil-Surp stores have it, if not I have well over a dozen Mil-Surp websites to choose from. I just might spring for a 1200 ft roll, that way I'll have more than enough for this project, and a bunch left over for other projects and uses.....

As for a balun....I do plan to use one, and if you got any good website with plans and spec's I sure would appreciate it if you'd post them here for me.....

I have access to a variety of schedule #40 PVC pipe & fittings, I've seen them built using PVC as the housing, so half the materials are already at my dissposal....

 

[BJ radionut]

Ladder Line vs. Coax

Rob/Tony: Good Morning fellows. Just a few thoughts on the project.
I have never had my best results using any coax on a multi-band wire antenna. When you add coax to an antenna not tuned for specific frequencies you can add a big loss factor on those frequencies where the antenna system is not resonant.
Coax use at high SWR does not retain the same loss figures as when used on a tuned system. The increase in loss of signal can be much greater the farther from resonance the antenna becomes.
I have, yes used a 40 meter dipole on 15 meters and performance is good...same for 80 meter dipole on 10 meters.
You should not expected coax to retain the same specs for loss when using either antenna I have used as an example above, when let's say operated 20 meters...the loss factor will be greater.
Then also if you are running high power(greater than 100wt's) on mismatched coax transmission line, you can run the risk of even greater problems.
I will not attempt to explain all the factors that occur when you use coax in a non-tuned system...there are others here can do a much better job and have a greater understanding than I. I am just speaking from good "old" experience.

The next thought is use of a Balun on the same coax feed dipole being used as a multi-band antenna system where it is not resonant...more problems can be experienced. The Balun on a resonant system not only helps with reducing the feed-line radiation, it will help reduce unwanted harmonic radiation. This may tend to reduce or suppress the exact frequency you are trying pass when using the coax feed dipole out of resonance?
The multi-band antenna feed with ladder line/twin-lead/or 600 ohm feeders will have much better performance in this type set-up...again my experience...
I wish I had the writing and skills explaining all the factors involved I speak, yet I do not... I just know from good "old" experience over 30+ years of "doing it"...
My time is short...off to work and a little 75 and 10 meter mobile time...
All the Best
BJ

 

[N9RZD]

Hey Tony ,
Good thinking,
seems like you guys are going in the right direction ,

dacron is indeed the best rope for this purpose
it wont stretch , and low resistance to uv are the big reasons

the other thing id point out
is using a spring or a bungie on the ends of the rope
if you are tying off to trees ,
it will absorb the spring , in a storm as the trees sway

good luck

 

[WX2MIG]

Hey Tony ,
Good thinking,
seems like you guys are going in the right direction ,

dacron is indeed the best rope for this purpose
it wont stretch , and low resistance to uv are the big reasons

the other thing id point out
is using a spring or a bungie on the ends of the rope
if you are tying off to trees ,
it will absorb the spring , in a storm as the trees sway

good luck

N9RZD....

I have a couple of old garage door springs laying around, and figured if I could find a way of using them for just that reason, I will.....

bjradionut.....

I have a few considerations to look at in any wire antenna I errect here, ladder line is better for perfomance, but it sticks out like a sore thumb, and in my opinion is less wind resistant than coax. Also the center feed point will most likely be directly above our swimming pool, so whatever I feed this dipole with, will have to be pulled toward the garage and kept high above the pool for obvious reasons. This is also why a G5RV would never work here, I doubt I'd be able to hang 35' of ladder line straight down without it coming in contact with something, or someone......

Still got a lot of time to kick these plans around, and I do appreciate any and all advice, some of it I may be able to use, and some I may not, but it's always good to have options.......

 

[hookedon6]

... Also the center feed point will most likely be directly above our swimming pool...

you may want to consider an OCF, fed @ approx 1/3 overall length

 

[Robb]

Yeah, a Windom Off Center Feed(OCF) would get it out of the way of the pool - that's for sure! I'm pretty sure that a balun is required for the mismatch it creates by using unequal wire length though. Measure a half-wavelength of the lowest frequency you want to build; then divide that number by by three. One side of the Windom will be 2/3 of this half wave, and the other side of the Windom will be the remaining third. If my memory serves me correct - anyway.

I don't know if using a garage spring would be a good idea though. It's metal; and as a general rule - you need to keep metal out of the ends as much as possible. The bunji - or a couple of them - may be the ticket/way to go. Big 'ol spring may act as a coil and detune your hard work here - just a guess. I bought as Windom 10-40 a week ago and can't put it up; as the tree I was going to put it on now has to come down for other reasons

So, either I will get a Hustler 6BTV or I will have to shell out even more moneyand get a 10-15-20 Yagi - just because of the thought that negative db loss by using a vertical really rubs me the wrong wayand is totally unacceptable.

Man, this hobby is anything but cheap! Or simple.
:headbang

 

[W5LZ]

Just a few thoughts.

If that dipole hangs over a pool, and if you can sort of pull the feed line sideways so that it'll clear things, it ought'a work. The closer to 90 degrees the feed line is from the dipole, the better, but it can certainly be off that 90 degrees thing a fair amount and not hurt anything.
If the antenna is balanced and the feed line isn't, a balun can certainly be useful. If the antenna is not balanced, such as an OCF antenna, and the feed line is coax, there's no need for a balun at all, neither are 'balanced'.
About the only benefit from using an OCF antenna is that it will typically produce a feed point impedance less than the 72-75 ohms of a typical center fed dipole. Since the feed point impedance of an antenna also depends on that antenna's height above ground, the 'sweet spot' isn't always 1/3 of the length from one end. It can vary by a sort of wide margin depending on that height and what's around the antenna.
I've seen quite a few OCF antennas called a 'Windom', but don't think I've ever seen a real 'Windom' except once. A Windom is an OCF antenna, but an OCF antenna is almost never a Windom. A Windom antenna uses a single wire as the feed line, period. The 'other side' of that feed line is a ground system. If there are two conductors making up that feed line, it ain't a Windom. Names do mean something. You can call your cat a dog, but it still ain't gonna bark, right? Mis-naming something only leads to confusion. (By the way, they are not the best antennas in the world by a long shot. And they are vertical antennas, believe it or not.)
'Nuff of all that...
- 'Doc

 

[WX2MIG]

I see I gotta clear up a few misconceptions here.....

The garage door springs are not for supporting the ends of the antenna, they would be used at the ends of the support structure, or the parachute cord to absorb the tension from the trees swaying in different directions. The actual antenna will be suspended below that support structure, and the ends will more than likely not come close to the trees or the metal springs. The ends of the dipole will most likely be attached at lower points where tree sway will not be as much a factor, but if I do find a need to add suspension to the ends of the antenna, I would deffinitely use non-conductive bungie cord, and not metal springs......

If I go with a center fed dipole, the feed point would in fact be over the swimming pool, but I will be able to pull the feed line back away from anyone's reach at a 90 degree angle to the antenna, and secure it to the back fence, if I do this with coax there is likely to be much less loss or interfearance to the system then if I did it with 300 ohm ladder line....

 

[BJ radionut]

Some other thoughts.

Tony: A couple of questions.
How far down from your apex or tie point is the swimming pool?
What is the approximate distance from the garage to your far point?
You may have other options.
Example: A small loop or Delta loop can be feed at a near corner or even on the side. The feed point need not be the highest elevation of the antenna.
A loop in rectangle shape can really be feed anywhere. Yes you may not be truly omni-directional or you may have an antenna with strange lopes greater than others in the radiation pattern...but so what...
I have used a loop that was a rectangle, I have used one that was even 5 sided just to get it in the space available. They were both neither vertical nor horizontal. They kinda laid "hora-vertical" or were they "verti-zonical" did not matter. I made many contacts and it was interesting to hear reports from all over where they were hot and not.

I think you may be surprised how much abuse Ladder Line or Twin Lead can handle. My array has made it through the ice and wind this Winter in fine shape. I use home-brew insulators from Lexan and tape the solder connections and it will survive more than you think.
Twin Lead 300 ohm foam type (even Radio Shack version) is very strong and forgiving and will handle a small amplifier and never know it, it is also light, flexible and easy to work with. I have to hold it from blowing around taped small UV resistant Ty-raps to the outer jacket and secure it with light Dacron string to other trees, gutters...what ever.
I think both of you are on the right track...keep thinking...soon you will have a system that will fit your "family" needs and yours.
I'll help if I can...been there done that...and still messing around...can not wait for Spring!
All the Best
BJ

 

[WX2MIG]

sorry....got a phone call from the wife and had to cut my last post off short.......

Although not the best, a G5RV might work if it weren't for the pool being where it is, and that's also assuming I can actually get it up the whole 35', I'm still not sure what the final height will be until I get the support line up and tied off. At this point I'm figuring my best approach will be a dipole cut to the longest wave length I can manage in the space I got,
Now the Windom, or off set feed point thing would infact add to my options, but don't they pretty much require a tuner to balance them out, or can that be done with a balun......????

 

[WX2MIG]

Thanks for your input Bj, it is greatly appreciated.....

I haven't taken any formal measurements, the over all distance will be the biggest factor since the support will be adjustable from one tree to the other, in other words the center point can be put when it best suits the antenna design, so at this point any formal measurements beyond that of total usable distance is of little concern.

I'm hoping to fit enough wire for the 160m band, but if that's not in the cards I'll have to settle on the 75/80m band, then tune for everything above that....(that's the plan anyway)........

 

[W5LZ]

Your options are about the same as everyone else's, not the best, but usable somewhere. The 160 meter band isn't exactly over crowded simply because it takes more room to get an antenna up for it, and most people just don't have the room (260 feet +/- a bit?), I don't.
There are 'work arounds' for almost anything. Those 'work arounds' are never as good as a 'real-live' antenna made for whatever band you're thinking about, but they do work, at least a little, which is almost always better than nothing, right?
No matter what antenna(s) you end up with, there are two things that always come in very handy. One is a good ground system (as in lots of radials in the dirt), and a sort of 'hefty' tuner. That combination can make for some really nice results from some really weird/odd/(dumb!)/different/'non-optimal' antennas.
Oh well. Nothing says you have to have just one antenna, or that it has to last for ever and ever. Got a 'brain storm' and just have to try something? Why not?
- 'Doc