Cheap broadband planar elliptical dipole antenna

Useful information regarding antennas for SDR products.
Scannerz
Posts: 17
Joined: Tue Oct 20, 2015 1:19 am

Cheap broadband planar elliptical dipole antenna

Postby Scannerz » Fri May 11, 2018 11:14 pm

Cheap broadband planar elliptical dipole antenna.


The antenna consists of two ovals (Goldern Ratio) disks
Inner of the coax goes to the top disk,
Braid of the coax goes to the bottom disk.

Each of the ovals dimentions are 335mm x 207mm
Short length of RG58 or LMR195 would be ok for connection to the disks.
With a female type connector of your choice to the lower end of the coax.

Keep the distance between the disks close together 1mm to 3mm.

Run the coax down the lower section of the disk,
Could use glue/silicon/gaffer tape here, To keep the coax firm against the lower disk.
Silicon a plastic cover over the connections to keep water out.

Each disk could be made from Aluminium or Galvanised tin sheet.
You can solder directly to tin, Though the aluminium will require
two small brass plates one bolted to each disk.

The two ground plane radials should be bolted to the lower disk (see pics)
So the lower disk should be of slightly thicker gauge material for strength.

I mounted the two disks on a recycled plastic garden stake.
Do try to mount them on some sort of plastic as there is more moisture in wood,
And could impact performance.

You can transmit on 146mhz and anywhere between 250mhz to 2800mhz with an SWR of around 1.5:1 throughout the range.

Will receive 118mhz to 2800mhz or greater.
This based on a dipole so it has increasing gain in frequency and as such is some what Bi-directional.

It is neat because you can go any where in the ranges stated and not have to change antennas.

Uses..... VHF, VHF-UHF-TV, UHF low, UHF high, ADSB, 23cm Band....e.t.c.

My 9 element UHF antenna will out perform this antenna, Though not by much.
Also the 9 ele has a restricted bandwidth.

My 5/8 over 5/8 vhf antenna will beat this also (really digs out distant signals)
Though once again only works in the VHF region.

For ADSB I use the Antenna to LNA4ALL to 900mhz highpass filter (Or Bandpass filter) to SDRplay.


Easy to build and pretty cheap and works pretty well.
Any questions do ask...cheers Tony.
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Scannerz
Posts: 17
Joined: Tue Oct 20, 2015 1:19 am

Re: Cheap broadband planar elliptical dipole antenna

Postby Scannerz » Fri May 11, 2018 11:18 pm

SWR chart for the antenna using rigexpert 1400 overclocked to 2800mhz.
Readings from 1400 to 2800 are not realy supported though should be pretty close.
cheers Tony.
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Scannerz
Posts: 17
Joined: Tue Oct 20, 2015 1:19 am

Re: Cheap broadband planar elliptical dipole antenna

Postby Scannerz » Thu May 17, 2018 5:47 am

Forgot to add the links.... the goldern ratio oval

https://www.blocklayer.com/oval-templates.aspx

Also has lots of other interesting printable templates, rulers,star,cones =(thinking of discone base here)
Also the larger the oval/disk the lower the frequency transmission starting point.
.....................................................................
Original circular Disk type which got me started was this one...

www.wa5vjb.com/references/PlanarDiskAntennas.pdf

cheers.

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vk7jj
Posts: 126
Joined: Thu Mar 02, 2017 9:56 am

Re: Cheap broadband planar elliptical dipole antenna

Postby vk7jj » Thu May 17, 2018 8:21 am

Congratulations on your innovation and thanks very much for your efforts and in sharing, it's interesting and appreciated. Very nice SWR figures too :)

I might whip one up using stiff bronze fly-screen material with some sort of simple frame to assist with the radials and have a play.

Regards Phil VK7JJ

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Scannerz
Posts: 17
Joined: Tue Oct 20, 2015 1:19 am

Re: Cheap broadband planar elliptical dipole antenna

Postby Scannerz » Fri May 18, 2018 10:05 pm

Thanks Phil,
I have made some other small/simple improvements to other antennas.
One was adding an extra square plate Reflector to a 15 Element yagi for L-Band Aero signals.
Which in turn gave an extra 6dbi (One S point) increase in signal strength.

Picture included...

Tony from VK3.
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F1BJB
Posts: 112
Joined: Wed Jul 15, 2015 4:24 pm
Location: Beauvais France

Re: Cheap broadband planar elliptical dipole antenna

Postby F1BJB » Thu May 24, 2018 7:59 am

Scannerz wrote:Thanks Phil,
I have made some other small/simple improvements to other antennas.
One was adding an extra square plate Reflector to a 15 Element yagi for L-Band Aero signals.
Which in turn gave an extra 6dbi (One S point) increase in signal strength.

Hi
Most Yagi design have only a single reflector.
If adding anything behind it improves the gain by 6 dB the original design is very bad.
Here your reflector is quite big for the wavelength but anyway it is strange.

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Scannerz
Posts: 17
Joined: Tue Oct 20, 2015 1:19 am

Re: Cheap broadband planar elliptical dipole antenna

Postby Scannerz » Sun May 27, 2018 12:07 am

Maybe you are right though even without the extra reflector the yagi performs very well on L-Band.

Yagis can receive from the back end though obviously its going to be poor.
As I try to think outside the box i thought i`d give it a try.

The yagi designs where done with this free program from John Drew vk5dj,
Maybe you can find something wrong with its calculations...Let us know....

Yagi Calculator
http://www.vk5dj.com/yagi.html

Using his calculator i have built
2x 5 Element yagi for 260mhz Fleetsat...Works Well.
22 Element yagi for 1090 adsb....Works unbelievably well.
15 element for 1550mhz L-Band of course works well.

cheers and all the best Tony from VK3.

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Scannerz
Posts: 17
Joined: Tue Oct 20, 2015 1:19 am

Re: Cheap broadband planar elliptical dipole antenna

Postby Scannerz » Fri Jun 01, 2018 11:21 pm

In relation to F1BJB comments about the yagi are correct.

So after some thought I figured that the extra reflector for the yagi is helpful
for my use with a preamp (lna4all).

The amp is adding 16 to 18db extra gain for the yagi`s designed for 1000mhz to 1600mhz.
So I`m basically redirecting the added receive gain more forward than being wasted at the rear of the antenna.
At least for L-Band Aero signals in my case.

That being said for ADSB reception a yagi with the amp (lna4all)
Is also able to get good broad pickup performance without the extra Reflector.
Or more directed performance with the extra Reflector.

thanks Tony.

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