3-Element 5/8 Collinear Antenna 1090Mhz.

[Tony7]

3-Element 5/8 Collinear Antenna 1090Mhz.
........................................


The design for this antenna came from

(  http://www.tigereye.net.au/vk4ion/docs/VHF_UHF_antennas.pdf  )

...See concept from Page32...fig 16.77 (Its a PDF extract from "The Radio Communication Handbook")


The 2-Element version has an quoted expected gain of around
6 to 7dbd../8 to 9 dbi.

The 3-Element version 8 to 9dbd ??

Built a couple 2-Element versions for VHF and its performance is impressive.
I had to lower the height of the VHF antenna as it gave my AR5000
to much gain to handle.

As for 1090Mhz I tryed/built 2 3 and 5  Element versions.
The 3 Element gave best results.
Even better distance than a basic 12 Element 1/2wave Collinear.

Height is the key of course for any antenna, and good quaility coax.

My setup consists of RTL(gain set to max) with fan cooling and metal case then a home built High pass filter then a 20db preamp (ZX60-P162N+) then long run of LMR400 coax to the 3 Element Collinear.

Will post the details (How too) of High Pass filter soon.

The RTL averages around 50 to 200 messg sec/3000 to 12000 messg a Min.

cheers Tony.

[Tony7]

*************UPDATE**************

Built a 4 Element version of the above and this has been terrific.
Further increase in distant  aircraft pickups just by adding another Element.

With this 4 Element version I`m getting near or over 210nm consistently in clear directions.
The improvement is approx 3 to 20nm over the 3 Element version.

Recently picked up a Helium Balloon (HBAL) at 64000ft and a new distance record for me at 296nm / 548km.
The antenna is up 15 to 20 meters above ground which helps a lot,with LMR400 coax/preamp and home
made 900mhz HPass filter.

Highly recommended.

Need info or pics just ask...
thanks Tony.

[wcostrino]

Hello, Tony7
Did you made any progress on this antenna?
Can you post some information about range (graphical) and how did you connect the top of the antenna, if you did?
Did you test variations of it?
Thanks

[Tony7]

Hi,
Sorry for the late reply, Have not made any changes to the 5/8 over 5/8 antenna.
It works well enough for me. Here are some recent range test captures.
Comparing a 9 element collinear antenna and a 5/8 over 5/8 x4 antenna. (Both homemade)

Current setup is SDRPLAY v1, Dump1090, 2x900mhz Highpass filers, LNA4ALL to 5/8 Antenna.

As for connection to the top of the antenna, I use whipper sniper line (nylon line,cable ties) wound around the top
section of the antenna and the slung over a tree. (So i can hoist the antenna up high)

...
Also just for interest, I finally found a Windows version of Dump1090 for my Hackrf that works,
To which i had been looking for for a while......Check link below if anybody is interested.
     
https://twitter.com/jocover/status/616576727230234624?lang=en

[Platinum77]

Hi Tony,

I made this antenna following your data and I can confirm that it is working perfect
I trust this antenna so I decided to made same type of antenna for FLARM frequencies (868.3MHz)
I have calculated new lenghts but I don't understand where you have got number of coil turns...
Maybe you can help with that?

Saso

[mrschultz2]

I'd also like to know how the numbers were calculated.

Why 160mm and 55mm?  And why 5 1/2 turns? 

For 1090MHz the numbers I get for 5/8ths and 1/4 wavelength are 172 and 69 mm.

Was thinking of making one with brass tubing and 3D printed spacers for the coils.

[Truetrack]

Well some information in the antenna sketch above is misleading .
As widely known for our 1090 Mhz uncorrected values are:
1 WaveLength = 275 mm, 5/8WL = 172mm, 1/2WL = 138mm, 1/4WL =69mm.
Now for the necessary corrections:
WL vs. Braid Dia of ~8mm, (ratio of 34) with a V/F ~ 0.93 will reduce the 175 to a 162 .
Close enough to 160.
WL vs. Wire Dia of ~2mm, (ratio of abt140) thus a V/F ~ 0.96 will reduce the 1/2WL 138 to 132.
Close enough to 130 .
Now forget the 5 1/2 turns or the 55 mm.
you have to spread the 130 over the 6mm rod in turns to a stacking dist of 1/4 = 69mm,
you will achieve that with less than 5 turns.
As for the bottom Coil can only assume to have the Ant DC-grounded,
but acting as a RF-Choke and being tapped to reach a 50 Ohm feedpoint.

Sorry I only had a coarse Graph Table to read off the velocity factor
so cannot be more precise
regards

[mrschultz2]

Thanks, I looked at the PDF but must have missed the part that the coil wire has a length of 1/2 WL.

Didn't think the velocity factor for braid would be that much lower than solid, that explains the lower numbers than I was thinking.

[mrschultz2]

 I was a Lowe's and noticed they had aluminum tubing, so bought a piece.

Didn't make a ground plane, just went straight from the coax to the first element.

Didn't try too hard to get my coils very symmetrical, but even with that it does do very well, hung it in the same spot in the attic as my 10 segment collinear and it worked almost as well, messages per second dropped a little and range dropped a little.

Probably with some more work it might be slightly better that the one I have now but I doubt it would be worth it to spend the time on it.

[Caption Obvious]

mrschultz2 - I'd be interested to here what results you would get if you used a fiberglass driveway marker instead of aluminum tubing.  Lowes or Home Depot should have those also.  I picked up one at Home Depot yesterday to try.  The one I got was 7.5 mm diameter and a little over a meter long.


I would think that velocity factor would come into play for braid as there's not dielectric involved in it's construction.

Tony - I'd also like to better understand where you got your number from.  I'm not questioning your results however want to be able to design antennas for other frequencies.

[Ranjeeh]

I built the three element version in accordance with the description. Unfortunately I didn't have an antenna analyzer available at the time and when I installed it I lost all signals bar some very close aircraft. Thus I assumed I'd built another 'dud' and it went back into the shed.

Subsequently, on installing a Flightaware 66cm antenna and getting a similar problem, I discovered that that the increased signals of the Flightaware antenna were severely overloading the Flightaware dongle due to strong cell interference, which also caused the loss of most aircraft. A SAW bandpass filter fixed that problem, then I moved up to a Mode-S Beast.

When I got my antenna analyzer back some time later, I checked the colinear and found a VSWR of about 1.5 and an impedance close to 50 Ohm. I have just checked again and can confirm those figures. Although I haven't installed it on the mast again, I have no doubt that it is a very effective antenna.