best antenna

[abcd567]

A FAILED EXPERIMENT - ADDING SLEEVE BALUN TO COCO
I have just now finished 8 hour trial runs of my old CoCo (3.5 element, 11cm element length) with & without Sleeve. The screenshots of VRS are given below. To me it looks that adding sleeve has improved near-range slightly, while removing Sleeve has improved far-range slightly, but the differences are marginal.

Note: The range rings are 50 kms apart. The outermost blue range ring is 450 kms from receiver.

Screenshot 1 of 2 : No Sleeve Balun
coco 11cm 3.5elem NO balun-R.png


Screenshot 2 of 2 : With Sleeve Balun
coco 11cm 3.5elem with sleeve balun-R.png

[abcd567]

Sleeve Balun Costruction Details
..... And here are the construction details of the Sleeve....
The length of Sleeve (i.e. cut length of Pepsi tin) is 6.9 cm (λ/4 in air VF=1)

picture 1 of 5
DSC03167.jpg

picture 2 of 5
DSC03168.jpg

picture 3 of 5
DSC03170.jpg

picture 4 of 5
DSC03171.jpg

picture 5 of 5 - Fully Assembled
DSC03172.jpg

[abcd567]

Any opinions as to why adding/removing Sleeve Balun to my CoCo did not make any significant difference?

[1090 MHz]

I think your can is just way too big in diameter. From what I've seen the sleeve baluns are typically twice the size of the cable... so a 1/4 inch hardline will have a 1/2 inch sleeve that's a 1/4 wave in length.

http://www.antenna-theory.com/definitions/bazooka.php

I'm actually working on my new antenna and it's sleeve balun is the last thing I need to do tonight. I have everything ready including N connectors for the 1/4 inch helix.

[abcd567]

I think your can is just way too big in diameter. From what I've seen the sleeve baluns are typically twice the size of the cable... so a 1/4 inch hardline will have a 1/2 inch sleeve that's a 1/4 wave in length.

http://www.antenna-theory.com/definitions/bazooka.php

I'm actually working on my new antenna and it's sleeve balun is the last thing I need to do tonight. I have everything ready including N connectors for the 1/4 inch helix.

Thanks for your advise about too large dia of sleeve. Actually I did not mind big dia sleeve due to the following quote from ARRL Antenna Book:
"The diameter of the coaxial detuning sleeve should be fairly large compared with the diameter of the cable it surrounds. A diameter of two inches or so is satisfactory with half-inch cable."

The above quote discourages small diameters, but does not put an upper limit on dia of sleeve.

As far as I know, the smaller dia is discouraged because of outer jacket of coax. if a sleeve is tight fitting to the cable, the entire space between sleeve & cable shield is filled with cable jacket. This will require that the length of sleeve is calculated using Velocity Factor of cable Jacket. Also, jacket material being much more lossy than the core insulating material, antenna efficiency will go down. For this reason it is preferred to have a large dia sleeve, so that almost entire insulation between sleeve & braid is air.

I used Pepsi can as it is very handy. It is made of soft aluminum, and hence easy to cut and drill hole in center. Since my coaxial braid is non-solderable type, using Pepsi can with F-Male to F-Male adapter was the easy solution.

Anyway, I will make another sleeve with a smaller dia can. I don't want to use cans made of iron sheets as it is a magnetic material. I cannot use aluminum tube either as I cannot solder an aluminum disk to the the aluminum tube. My only option is to find an aluminum can of smaller diameter. Till then the project is on hold....

[abcd567]

@1090 Mhz

Please visit http://www.w8ji.com/sleeve_baluns.htm

The conclusion is at bottom of above page. I am copying below these paragraphs.

From the above, we observe the following characteristics in a sleeve balun:
1.) The highest possible choke sleeve impedance (largest ratio of balun sleeve diameter to outside of transmission line) is desired. We won’t have a good balun if the choking Zo (ratio of sleeve inner diameter to coaxial shield outer diameter) is small.

2.) The balun requires the lowest possible loss over the length of the sleeve. It forms a transmission line from the inside of the sleeve to the outside of the coax. The coax jacket is a dielectric, so we need to keep a lot of air inside of the choking sleeve or the coax jacket will increase loss and reduce impedance, both being very undesirable.

3.) The velocity factor of the sleeve, based on the dielectric between the sleeve and the shield of the coaxial cable we are trying to balance or choke, is very important to length of the sleeve.

The following construction guidelines apply:
The cable should have a good low-loss jacket or a very large air or low loss dielectric gap between the shield and the sleeve. Since energy is normally confined to the inside of a coaxial cable manufacturers are not concerned about jacket losses. They use outer materials with long life, not low RF loss. It is advisable to use a filler material with a high volume of air to maximize sleeve impedance and minimize sleeve losses.

It is also advisable to use the largest practical diameter sleeve with the smallest diameter coaxial cable inside to maximize choking impedance.

The sleeve length has to account for velocity factor of the sleeve, since the sleeve forms a coaxial transmission line with the outer conductor of the coaxial cable it is intended to choke or decouple.

[F-EGLF1]

@1090 Mhz

Please visit http://www.w8ji.com/sleeve_baluns.htm

The conclusion is at bottom of above page. I am copying below these paragraphs.

From the above, we observe the following characteristics in a sleeve balun:
1.) The highest possible choke sleeve impedance (largest ratio of balun sleeve diameter to outside of transmission line) is desired. We won’t have a good balun if the choking Zo (ratio of sleeve inner diameter to coaxial shield outer diameter) is small.
.

I would agree, this is the type of advice I have been seeing in books etc, also it is important to keep the sleeve as concentric as possible to avoid uneven current flow.
If you take the diameter to the extreme then you end up with something resembling the alternative design that has either 4 quarter wave stubs at right angles to the co-ax or a quarter wave disk, electrically these serve the same purpose, just visualise folding the stubs or disk up into a cylinder.
Just out of interest I wonder what the result would be of a sleeve with a radius of 1/4 wave and hight the same, then you would have both the sleeve and effectively the quarter wave stubs.
Ben.

[abcd567]

......Just out of interest I wonder what the result would be of a sleeve with a radius of 1/4 wave and hight the same, then you would have both the sleeve and effectively the quarter wave stubs.
Ben.

Have you seen my sleeve's photos in my post # 1230? The Pepsi can I used as sleeve was cut to a length of 69 mm & has dia of 65 mm, so radius is very close to 1/8 λ. We need a can of double the dia of Pepsi can to get a radius of 69 mm i.e. 1/4 λ.

[abcd567]

Another Experiment: A 1/2 λ sleeve dipole
After Failed experiment of Sleeved CoCo, I decided to utilize the Pepsi sleeve for another experiment: A 1/2 λ sleeve dipole. The Pepsi can is the down 1/4 λ limb of the dipole, and upper limb is a whip made out of core of coaxial cable 69 mm long (with insulation) + 20 mm bare conductor for insertion into the connector.

The Pepsi can serves dual purpose:
(1) Lower limb of the dipole &
(2) Decoupling Sleeve

Please see below:
(1) Three hrs trial run VRS coverage screenshot.
(2) 4 photos, showing construction details.

Image 1 of 6 : VRS Coverage
The range rings are 50 kms apart, the outermost blue ring is 450 kms from the receiver.



Image 2 of 6 : Construction Details 1



Image 3 of 6 : Construction Details 2



Image 4 of 6 : Construction Details 3


Image 5 of 6 : Fully Assembled


Image 6 of 6: Sketch of Pepsi Can Dimensions


Edited on Sept 01, 2015 to restore broken link to image 2 of 6

[abcd567]

.
Test Setup for 1/2 λ Sleeve Dipole

Picture 1 of 2



Picture 2 of 2

[abcd567]

Have you ever seen what is inside a rubber ducky antenna? A Sleeve Dipole

http://martybugs.net/wireless/rubberducky.cgi

[1090 MHz]

As you know I'm modding a high gain WiFi omni antenna. It incorporated an internal 1/2 inch sleeve balun and 1/4 inch brass elements. Here are 2 WiFi antennas.. the bottom one is the one that is getting modded to become a high gain 8.5 element 1090MHz antenna. http://ads-b.ca/wifi/img_9602.htm

Take also into consideration the possibility that the aluminum pipe that is part of the antennas mount might also act as a sleeve balun too: http://ads-b.ca/antenna-build/img_9610.htm

The new antenna coco is made from 1/4 inch LDF1-50 hard line which is very close to the 1/4 brass tubing the WiFi antenna used. http://ads-b.ca/LDF1-50/coco/
The 1/2 inch brass sleeve balun was extended using copper water pipe. The brass and copper soldered together very nicely. It's a tight fit in the fiberglass tubing.

The new antenna will also be wired with LDF1-50 from antenna, down the tower, to the radio. I'm thinking of also installing a ferrite choke on the LDF1-50 just below the N connector. This will be inside the aluminum mounting pipe where it's kept dry.

[abcd567]

As you know I'm modding a high gain WiFi omni antenna. It incorporated an internal 1/2 inch sleeve balun and 1/4 inch brass elements. Here are 2 WiFi antennas.. the bottom one is the one that is getting modded to become a high gain 8.5 element 1090MHz antenna. http://ads-b.ca/wifi/img_9602.htm

Take also into consideration the possibility that the aluminum pipe that is part of the antennas mount might also act as a sleeve balun too: http://ads-b.ca/antenna-build/img_9610.htm

The new antenna coco is made from 1/4 inch LDF1-50 hard line which is very close to the 1/4 brass tubing the WiFi antenna used. http://ads-b.ca/LDF1-50/coco/
The 1/2 inch brass sleeve balun was extended using copper water pipe. The brass and copper soldered together very nicely. It's a tight fit in the fiberglass tubing.

The new antenna will also be wired with LDF1-50 from antenna, down the tower, to the radio. I'm thinking of also installing a ferrite choke on the LDF1-50 just below the N connector. This will be inside the aluminum mounting pipe where it's kept dry.

Thanks for the update. The new LDF1-50 antenna looks sturdier than the old brass tube one. Adding ferrite choke is a good idea.

[F-EGLF1]

Thanks for the update. The new LDF1-50 antenna looks sturdier than the old brass tube one. Adding ferrite choke is a good idea.

According to the ARRL handbook ferrite chokes are only of any use at frequencies below 144MHz (Section 15.1.4) this is due to the ferrite material responding differently at higher frequencies.
Ben.

[1090 MHz]

Ferrite chokes are actually good for frequencies up to around 1000 MHz. It all depends of what type of material the ferrite bead is made from.

Ferrite beads are used for RF decoupling and parasitic suppression. When placed over a coaxial cable they prevent RF from flowing on the outside of the shield but do not affect the signal inside the cable.

For RFI use,
Mix 31 is effective from 1-500 Mhz,
Mix 43 works from 20-250 Mhz,
Mix 61 is for 200-1000 Mhz
Mix 77 favors .5-20 MHz.

http://palomar-engineers.com/ferrite.../ferrite-beads