best antenna

[abcd567]

@bezeefly:
From Point B in your Camera Photo.

Spider 2 r.png

[1090 MHz]

Ground_Plane_05.jpg
This is correct.

[Kato]

Thinner the wire used, easier it is to bend with narrow gaps, but antenna is mechanically weaker with thinner wire.

Thicker wire gives mechanically stronger antenna, but thicker wires are difficult to bend in narrow gaps.

It's my understanding that the thinner the wire, the narrower the bandwidth; so a thin wire antenna will not only be mechanically weak, but will also require higher precision in measurement - the advantage being better rejection of out-of-band interference.

On the other hand, thicker wire receives over a larger bandwidth; so has greater tolerance of (small) measurement errors, although perhaps slightly more at risk from interference.

Is the gap in the stub wires a constant, or is it proportional to the wire diameter?

Given that rf currents flow on the outside of the wire, I would have thought the latter and if that's the case, for an antenna intended for outdoor use, would it be preferable to opt for something like copper welding rod or even half-inch copper pipe and thus have a greater margin for measurement and construction inaccuracies?

[STR_EDDS]

ok, the diameter is 2.25mm, calculated from 4mm², got it now
i need that thickness, because i will install the antenna outdoors.
do you have calculations for 2,25mm dia?

[Rooster]

Its not the thickness that relates to bandwidth... it the ratio between length and diameter, unless you use - say a coke can as the radiator you wont see much difference !

[abcd567]

.......Is the gap in the stub wires a constant, or is it proportional to the wire diameter?.......

ok, the diameter is 2.25mm, calculated from 4mm², got it now
i need that thickness, because i will install the antenna outdoors.
do you have calculations for 2,25mm dia?

The gap between wires of IMPEDANCE MATCHING stub (the middle one) depends on dia of stub wire:

diameter of stub wires d	1mm	2mm	2.25mm	3mm
center to center distance of stub wires S	3mm	6mm	6.5mm	9mm
surface to surface gap between stub wires (S-d)	2mm	4mm	4.25	6mm

See calculations below (if you are not allergic to maths )

The 4 vertical element Franklin antenna with thin wire (3mm - 1 mm dia) has a typical impedance of 415-j430 ohms (obtained by simulation)
Zant = 415-j430 = √(415²+435²) = 600 ohms
Zcoax = 75 ohms
Required impedance of Stub to get impedance match Zstb = √(Zant x Zcoax) = √(600 x 75) = 212 ohms


From geometry of stub, Zstb = 276 log (2S/d)
which can be rearranged as S = (d/2) x 10 to power (Zstb/276)

The Zstb required for impedance matching of 75 ohm coax with 600 ohm antenna is 212 ohms (see calculations above). Using this value of Zstb, and various wire diameters d, the wire spacing S works out to be:

if d=1mm, S = (1/2) x 10 to power (212/276) = 2.9 mm say 3 mm
if d=2mm, S = (2/2) x 10 to power (212/276) = 5.9 mm say 6 mm
if d=2.25mm, S = (2.25/2) x 10 to power (212/276) = 6.6 mm say 6.5 mm
if d=3mm, S = (3/2) x 10 to power (212/276) = 8.8 mm say 9 mm


stub wire spacing 1.PNG.png

[abcd567]

Metric Electrical Wire Sizes: Area mm² & corresponding diameter mm

Wire Size mm2	1	1.5	2.5	4	6	10	16	25
Wire Dia mm	1.128	1.382	1.784	2.257	2.764	3.568	4.514	5.642

American Electrical Wire Sizes: AWG & corresponding diameter mm

Wire Size AWG	18	16	14	12	10	8	6	4
Wire Dia mm	1.024	1.291	1.628	2.053	2.588	3.264	4.115	5.19

[abcd567]

It's my understanding that the thinner the wire, the narrower the bandwidth; so a thin wire antenna will not only be mechanically weak, but will also require higher precision in measurement - the advantage being better rejection of out-of-band interference.

On the other hand, thicker wire receives over a larger bandwidth; so has greater tolerance of (small) measurement errors, although perhaps slightly more at risk from interference.

Is the gap in the stub wires a constant, or is it proportional to the wire diameter?

Given that rf currents flow on the outside of the wire, I would have thought the latter and if that's the case, for an antenna intended for outdoor use, would it be preferable to opt for something like copper welding rod or even half-inch copper pipe and thus have a greater margin for measurement and construction inaccuracies?

Its not the thickness that relates to bandwidth... it the ratio between length and diameter, unless you use - say a coke can as the radiator you wont see much difference !

Regarding bandwidth, I fully agree with rooster.

Regarding making Franklin with a pipe, it is practically not feasable to use more than 5 or 6 mm dia wire/pipe because of very tiny stub & radiator lengths (frequency is high, 1090 mhz). The technique to use water copper pipes for making antennas at VHF is very successful due to low frequency & hence much bigger dimensions of stubs & radiators running in meters, allowing use of 3/4" (20mm) pipes.

[bezeefly]

Here're the results of my 8-element coco and spider antennas. Both antennas were connected to an amplifier, placed indoor beside East facing window. It seemed the coco antenna had better coverage and range.

vf0.86-8ele-whip-amp-nm-19012015.jpgspider-amp-nm-21012015.jpg

[gquejada]

Hi I have designed and built successfully an 8 element beam for ADSB. It has the same range as my 9 element wire collinear.
I have built 2 of these both with identical range - 270nm

[ATTACH=CONFIG]5184[/ATTACH]


The MMANA files are also attached




Mike
remove the .txt from this file before using in MMANA

Hi, YWYY!

What are the specs to build this 8-element beam? Am still on my steep learning curve about antennas, but if I have clear instructions I can "blindly" follow, I can learn more easily.

Thanks!

[trigger]

Hi, YWYY!

What are the specs to build this 8-element beam? Am still on my steep learning curve about antennas, but if I have clear instructions I can "blindly" follow, I can learn more easily.

Thanks!

The spec is included in this post http://forum.flightradar24.com/threa...ll=1#post60390

[YWYY]

Also here for 2 x 8 element co-phased

http://forum.flightradar24.com/threa...ntenna/page200

http://forum.flightradar24.com/threa...ntenna/page201

Mike

[SpaxmoidJAm]

Cant remember if i posted this already so i'll post it any way

Its for working out the SWR but it will effectively show your tuning.

I'm not sure what software he is using but you get the idea of how to do it..

[STR_EDDS]

Today i tested my new 2,25mm dia franklin antenna.
I took the best spot in the nearby region.
Weather was cold and windy, after 15min i left

Here are the results:

-400km peak
-~100 Planes at the same time.


09 - YEUZj3z.jpg07 - SPruhbQ.jpg10 - XFOQlSq.jpg08 - 1EQFbOo.jpg06 - 2Qq8O1d.jpg

link to image albums (higher resolution)

http://imgur.com/a/3W9yd
http://imgur.com/a/JmhLO/

[toString]

Looks beautiful! ...The antenna and the scenery!