Twin X-Mount Dipole Idea

[W5LZ]

If the object is to see what various antennas will do then try all the ideas you can think of. But I think in the end you'll wind up with what most people do, a horizontal antenna and a vertical. There's a reason why that's so common...
- 'Doc

 

[Lil'Yeshua]

If the object is to see what various antennas will do then try all the ideas you can think of. But I think in the end you'll wind up with what most people do, a horizontal antenna and a vertical. There's a reason why that's so common...
- 'Doc

I'm wanting to do this. This link is where I bought the plans from. It's in the mail on it's way to me.
Circular-Polarized CB Beam Antenna Plans
And yes,I want to see if I can do variations of this.
I don't have home Internet to do EZNEC so I study up on what might work but work right.

 

[The DB]

Circular-Polarized CB Beam Antenna Plans

Interesting how the information on that page makes everything sound so positive. When I see all good an no bad like this red flags go off in my head. I'm not saying that there aren't good points to circular polarization, but there are some bad points as well. For example, the losses suffered off the top when talking to any non-circular polarized antenna, or for that matter two circular polarized antennas, but one is right handed and the other is left handed.

That being said, I hope it works for you.


The DB

 

[Lil'Yeshua]

I thought it would be neat to build. I have been doing research on turnstile and NVIS antennas. Just waiting on the plans before I purchase anymore aluminum from DX Engineering.

 

[Lil'Yeshua]

Link for home brew NVIS antenna

Here's a YouTube vid with link for a home brew NVIS antenna.
How To Make A NVIS HF Radio Antenna - YouTube

 

[Lil'Yeshua]

Homebrew Slinky Ham Radio Antenna - YouTube ????

 

[ghz24]

circular polarization

Lil'Yeshua
Ive seen that page you ordered from before.
Not trying to get his design for free but, I doubt he has an antenna that is a new design.
I am very curious which designs he includes.
When you get the plans could you share (in very general terms) the basic type of designs he included?
I'm working on an electrically steerable CP "beam" no rotor, gain of about 7 dBi I don't charge but I don't call the dimensions "plans" . I don't know if I can switch from right to left though ...Maybe
If you physically stagger the vertical and horizontal elements on the boom you can use an ordinary phasing harness the 90 degree phase delay would be accomplished by the distance along the boom from vertical to horizontal.
Velocity factor would be in air or ~1 I think.

Says you'll get 3 designs. CP yagis have some problems like this

shows a simple CP yagis gain pattern the V and H components are equal but if you look at

you'll see something is wrong with the axial ratio.
Each time a CP signal bounces it reverses direction right handed becomes left handed. The reflectors on a yagi reverse the signal they reflect, making it a combination of right and left. I haven't looked at what directors do to the quality (yet)
A helix would work very well but you can't electrically switch from right to left handed.

 

[Lil'Yeshua]

Sure! I'll share general dimensions and the other two plans. I was pondering today on what i could share. I don't have access to any modeling software but that's interesting what you posted. Yes I'm aware of placing the elements in the configuration you've described. The closest thing I can ascribe his plans to is the turnstile antenna set up in a beam configuration. The guy said he shipped the plans Tuesday(had to print more material)Hopefully it will be in the mail Saturday.

 

[Yankee]

Is this image generated from a program you own? Which one?

 

[ghz24]

Is this image generated from a program you own? Which one?

Yes the program is 4nec2, it is free and available at 4nec2 antenna modeler and optimizer
The free version is the only version so it's true free-ware not cripple-ware or expire-ware or even nag-ware.
IMHO it's the best free modeling program. (and not that hard to learn)

 

[Yankee]

Wonderful. Thanks for the link. I have a real interest in antenna geometry, but am just a piker at it, so this will really help. :

 

[Lil'Yeshua]

Thanks for the link as well. I may not have home Internet but I can use my iPhone 5 to download the program onto my PC

 

[ghz24]

modeling advice

Personally I learned a lot by dissecting/altering existing models posted by other people.
Even if you want to create a model from scratch it's nice to have a template to refer to. It's much easier to alter an existing model and save as newname.nec
The models are just text files renamed from .txt to .nec
Poke around in the menus and play with the settings you understand and don't sweat the ones you don't (if any) . If all else fails try the help resources.
If you want to dissect some models I have some posted here
I'm not an expert at it just an enthusiast/student/seeker but if you have a question I'll try my best not to misguide you.
Hope you like it half as much as me.

 

[Lil'Yeshua]

Okay. Just got the plans in the mail. I received a pack of 5 4.7 UH RF chokes for my 959 to make the clarifier slide more. A dynamic speech processor circuit board with a several page assembly instructions that include DSP definition,Theory of operation, references on the subject,assembly instructions,a list of parts suppliers, A parts list for the DSP,Schematic circuit diagram,A diagram showing where all the components go,A guide on how to figure out the resistor and capacitor values. Installation guide into a transceiver along with 4 different mic plug pin outs. How to figure a series dropping resistor for +250 VDC power sources. Adjustment and operation for those without a O-Scope but have a modulation meter. Power mics not required if set up right.
Remedy for RF Decoupling. Fixes for Cobra and uniden/uniden clones for squealing. What to do in case of excessive audio gain. I have a R/S circuit thingy that I can put a circuit together temporarily before actually putting everything on the supplied circuit board.
Last but not least,the construction plans for a Circular-Polarized CB Base Antenna. There's the introduction,theory of operation,Design considerations which include,1.Bandwidth,2.Impedance,3.Gain,4.Front to back ratio.
It shows two ways to create a circular wave. 1.Two perpendicular 1/2 wave dipoles crossed at the same point,each fed RF energy 90 degrees apart like I am thinking on doing. The second design is two perpendicular 1/2 wave dipoles on a 1/4 wave boom. For the CP Beam the first method is chosen. The plans show how to space the driven,director,and reflector elements. Figuring the wavelength for aluminum antennas,the equation for spacing and boom lenght. Element lenght.
How to figure coax lengths for a phasing harness. A picture diagram of the phasing harness showing coax lengths. This harness uses a T connector. To tune antenna you need a dummy load of suitable power rating and screw on to one PL-259 at a time where it connects to the antenna while the other is connected to the other dipole.
It then shows how to match the CP Antenna to the radio. The impedance of a dipole antenna is somewhere around 72 ohms therefore a gamma match is needed to achieve 50 ohms. A 50-75 pF air variable capacitor for each dipole.
Antenna construction details which materials needed including gamma match with measurements for them. BIG NOTE: the coax shield is connected to the exact center of the driven element with the gamma capacitor and matcher attached to where the impedance I'd 50 ohms between the coax shield connection point and the shorting strap connects.
The simpler way of building a CP Antenna with 1/4 wavelength separation of the elements. Note:!!!! Building it this way is not a beam. The energy is bi-directional like for any dipole antenna.
Summary:this is all I can say without copyright infringement so here's the contact links for the plans to make this antenna. Personal note:to make this antenna work for me,I can't use the 1/4 wave SS whips or the MFJ mini dipole mounts. Peace!
CBC International
Lou Franklin, K6NH
Tel/fax (520) 298-7980
Toll free (888) 434-9227
E-Mail: use links on Webb
P.O. Box 30655
Tucson AZ 85751 USA
CBC International - books plans kits modifications repairs for CB radios
P.S. I might could share in PM's
Sounds exciting!

 

[Lil'Yeshua]

This I'd no wimpy antenna. For CB band the boom lenght is around 12 feet. A considerable undertaking if I might add