Twin X-Mount Dipole Idea

[Lil'Yeshua]

Question:What tools would I need to adjust the gamma matchers on this antenna? My MFJ-207+ohm meter or a MFJ-259b?


On second thought,I wonder if I could get away with using my MFJ-347's and some aluminum tubing adapted to screw into the 3/8 by 24tpi holes?
Hmmmmmmm!?


On third thought after studying the instruction manual,gamma matchers are a necessity to adjust each antenna's impedance 100 ohm so that when coupled to the T connector the resulting impedance is 50 ohms.

 

[Lil'Yeshua]

The antenna plans calls for approximately 60' total for 1" O.D. or 7/8" 6061-T6 aluminum tubing,30' total 7/8" O.D. Or 3/4",24' total 3/4" or 5/8".
This is to make six elements(two three element yagis)
Boom:12'
Gamma match(2):24" aluminum rod 1/4" dia., 75pF air variable capacitor,plexiglass 6" by 2",plumber's helper type zinc strap for shorting sleeve.
Waterproof box to mount air variable capacitor.


I'm thinking that I can make the elements using six 6' by 7/8" dia. tubes, six 6' by 3/4" dia. tubes, six 6' by 5/8" dia. tubes for the elements.
For the CB band the elements only have to be 16.74',17.47',18.39'.


Formula for Element lengths: Director[455\freq in MHz
Driven Element[475/freq in MHz
Reflector [500/freq in MHz

 

[Lil'Yeshua]

I downloaded the 4NEC2 but iI don't know the first thing about it help! :headbang i found the instructions. More study!!!!!!!!!!!!!!!!!!!!!!!!! :O

 

[Lil'Yeshua]

A easier way to build this antenna would be to purchase two Maco M103C antennas and combine them but I would save about $200 buying the materials and using the plans. One difference between the CP and the Maco would be the element spacing. The CP antenna has the driven element more toward the reflector than the Maco does. The CP has the driven element .20 wavelength distance between the director and driven element while the driven/reflector distance is .15 wavelength.



I want to reinterate this:According to the plans a simpler way of building a CP Antenna with 1/4 wavelength separation of the elements and using two 75 ohm coax's but no 1/4 wave 50 coax jumper. Note:!!!! Building it this way is not a CP beam. The energy is bi-directional like for any dipole antenna.

 

[ghz24]

Retraction

Ok I went back to alter the model I used for post #112 this thread,
and found a remnant from the previous model was partly causing the strange pattern. It was phased for no physical separation.
The pattern is flawed but the axial ratio on the corrected model at the bore site is .44 (very close to the value of the greenish yellow in the posted picture) vs a good value of .98 but at least it's where the high gain is.
Collaborators would have caught that maybe. Here is the corrected model

CM 11 meter circular polarized yagi, by ghz24
CM crude model reflectors added variables striped 
CE
GW	1	9	0	0	-104.8784	0	0	104.8784	0.0404
GW	2	9	56.8	-104.8784	0	56.8	104.8784	0	0.0404
GW	3	9	-113.6	0	-104.8784	-113.6	0	104.8784	0.0404
GW	4	9	-56.8	-104.8784	0	-56.8	104.8784	0	0.0404
GS	0	0	0.0254
GE	0
GN	-1
EK
EX	0	1	5	0	1	0	0	0
EX	0	2	5	0	1	0	0	0
FR	0	0	0	0	27.18	0
EN

Here is what the pattern should look like

I striped out the variables to simplify the model. It shouldn't be to hard to change the X,Y,Z and radius values in the " GW" lines to match the plans you have.
You may find you can improve on the designs or customize them to your desires ( higher f/b vs higher gain for example).
I've not watched them ( and they aren't mine) but there are some video tutorialsVideo tutorials

 

[Lil'Yeshua]

Ok I went back to alter the model I used for post #112 this thread,
and found a remnant from the previous model was partly causing the strange pattern. It was phased for no physical separation.
The pattern is flawed but the axial ratio on the corrected model at the bore site is .44 (very close to the value of the greenish yellow in the posted picture) vs a good value of .98 but at least it's where the high gain is.
Collaborators would have caught that maybe. Here is the corrected model

CM 11 meter circular polarized yagi, by ghz24
CM crude model reflectors added variables striped 
CE
GW	1	9	0	0	-104.8784	0	0	104.8784	0.0404
GW	2	9	56.8	-104.8784	0	56.8	104.8784	0	0.0404
GW	3	9	-113.6	0	-104.8784	-113.6	0	104.8784	0.0404
GW	4	9	-56.8	-104.8784	0	-56.8	104.8784	0	0.0404
GS	0	0	0.0254
GE	0
GN	-1
EK
EX	0	1	5	0	1	0	0	0
EX	0	2	5	0	1	0	0	0
FR	0	0	0	0	27.18	0
EN

Here is what the pattern should look like

I striped out the variables to simplify the model. It shouldn't be to hard to change the X,Y,Z and radius values in the " GW" lines to match the plans you have.
You may find you can improve on the designs or customize them to your desires ( higher f/b vs higher gain for example).
I've not watched them ( and they aren't mine) but there are some video tutorialsVideo tutorials

Thanks for the video! I'm a noob at this but I'm learning.

 

[Lil'Yeshua]

The antenna plans calls for approximately 60' total for 1" O.D. or 7/8" 6061-T6 aluminum tubing,30' total 7/8" O.D. Or 3/4",24' total 3/4" or 5/8".
This is to make six elements(two three element yagis)
Boom:12'
Gamma match(2):24" aluminum rod 1/4" dia., 75pF air variable capacitor,plexiglass 6" by 2",plumber's helper type zinc strap for shorting sleeve.
Waterproof box to mount air variable capacitor.


I'm thinking that I can make the elements using six 6' by 7/8" dia. tubes, six 6' by 3/4" dia. tubes, six 6' by 5/8" dia. tubes for the elements.
For the CB band the elements only have to be 16.74',17.47',18.39'.


Formula for Element lengths: Director[455\freq in MHz
Driven Element[475/freq in MHz
Reflector [500/freq in MHz

As far as I know,DX Engineering offers only 3&6' lengths of tubing in these dimensions. Anybody know where I can get 10' lengths ?



I answered my own question
http://www.onlinemetals.com/merchant.cfm?pid=4342&step=4&showunits=inches&id=71&top_cat=60


Well,$100 for DX Engineering aluminum tubes vs. $259 for online metals even though they have 6061-T6

 

[Yankee]

Amazing. Just amazing.

 

[Lil'Yeshua]

Tubing for elements at DX Engineering







P.S. New York is coming in skip

 

[Yankee]

Anybody know where I can get 10' lengths ?

Cycle 24 Antenna Products

They have 6' and 12' lengths of 3/8" to 2". Maybe contact them, they will even build your antenna for you. Might be cheaper.

 

[Lil'Yeshua]

Note: anyone wanting to build this type of antenna and don't want to take the Circular Polarization route can modify their antenna to have just a vertical or horizontal or both set of beams or no beams at all. It could be just the driven elements in a vertical and horizontal configuration without the benefit of reflectors and directors. I wonder if a Starduster configuration would be possible with one vertical and three driven radials? Question:Has anyone else made a Circular Polarization antenna and could you share your results and experience?

 

[Lil'Yeshua]

Cycle 24 Antenna Products

They have 6' and 12' lengths of 3/8" to 2". Maybe contact them, they will even build your antenna for you. Might be cheaper.

Thanks! I think that I could still make this antenna by using six foot length sections from DX Engineering. They only charged me $10 shipping on my last order. The CP Antenna plans I have gives an approximate list of materials to procure. I think the elements can be made using six feet of 1" O.D. Tubing saddle clamped to the boom. That would leave three feet on either side of the boom. .875" O.D. Tubing can be mated to it on both sides along with the .750" O.D. Tubing inserted into those on both sides. The boom can be made using two six foot 1.50" O.D. .58 wall tubing with a 1.375" sleeve to couple them together. I wonder if .58 wall tubing would be too flimsy. They do offer .120" wall tubing for 1.50" O.D.

 

[Lil'Yeshua]

Stainless steel or galvanized?
U-Bolt Saddle Clamps for 1.5 Inch (1 1/2″) Tubing | Cycle 24 Antenna Products
I sent Cycle 24 an email just to see what they would charge to make an CP Antenna.

 

[W5LZ]

"Stainless steel or galvanized?"
Depends on what your weather is like. It also depends on how long you think you will be using that antenna, and naturally the cost.
- 'Doc

 

[Lil'Yeshua]

"Stainless steel or galvanized?"
Depends on what your weather is like. It also depends on how long you think you will be using that antenna, and naturally the cost.
- 'Doc

It would stay up until the coax needs replaced. Slightly higher cost for a higher quality more durable product is always a plus.
Blue Ridge Mountain weather
U-Bolt Saddle Clamps | Cycle 24 Antenna Products

http://www.antennapartsoutlet.com/Products.html
http://www.antennapartsoutlet.com/Pages/Products/Gammas.html
op:


http://www.cycle-24.com/u-bolt-saddle-clamps/u-bolt-saddle-clamp-special-orders/