Directional antennas

yes… but you’ll get only 1/4 of your mlat positions

Almost all dongles report 500mA on lsusb, but it’s not necessarily the actual consumption

Something wrong in the simulation below.
Logically it should have no side and back lobes, but this one has a BIG back lobe.
I will have to recheck the model.

Note: Only one dipole excited in simulation. It is located in quadrant formed by +X and +Y (top-right).

I’ve been looking for a .NEC fle for a corner reflector this afternoon. I guess you created it from scratch?

I have some results from my cubical quad. I’ll post a bit later

The cubical quad I built works :smiley: . Today is probably not a good day to test as we have freezing fog in the South of England so a lot of flights cancelled. The weather looks to be the same for the next couple of days :unamused:

Anyway, here is the quad.

This is how it compares to my latest CoCo. The quad is pointing SW. Rings are 50nm

This is my latest CoCo. I stripped the outer and braid from my coax just leaving the core and insulation. Then slipped a piece of copper tubing over the insulation which was carefully cut to 91mm ( my coax has VF 0.66). Then soldered core to tube/tube to core etc.

Note, the quad and the CoCo are in my loft, not outside.

@triggers @abcd567
There is a corner reflector model in the models/VHFbeams/

@obj Yeah 1 million sounds so much… never thought about that. Given that the relay is a € 25 surplus unit it will be even closer to retirement than that. Anyway it could spark a new project: building a solid state coax relay with PIN diodes… Let’s first find out if the theory works.

Many thanks, completely missed that!

Thanks a lot. Never noticed it. This will be a great help in debugging my 4-corner simulation.

I’ve made some changes to the cubical quad in the first post and got better distance from it.

It was just a matter of adjusting the reflector and director distances from the driven element. The cubical quad,whch is in my loft, is now giving the same distance as my FA antenna which is outside on a 2.5m pole :smiley:

I have changed the first post to reflect these changes.

Will try to make it this weekend.
Hope this is a “forgiving” design, and not like “intolerant” wire/coaxial collinears.

Hi abcd,
I’ve been messing around with 4NEC2 and I came to the conclusion that the squares can be ± 1mm as long as the reflector sides are 2mm bigger than the driven and the director sides are 2mm smaller than the driven, but the spacing of the director and the reflector have a greater influence on the antenna efficiency.

Looking forward to your conclusions especially as you now have something to measure it with :wink:

That is just insane :unamused: Let us know how you get on. I’ve bought shares in copper mines :laughing:

Hi Bob,

I’ve had a go at modelling a corner reflector antenna with 4NEC2. The model looks like it is possible to get >12db and as you say, no side lobes or back lobes.

The model suggests the reflector sides should be 0.5 meters long and 0.3 meters tall. If we intend to cover 360° then there will be a heavy load at the top of the pole especially in windy weather.

Note - I may well have my calculations wrong :unamused:

I can recommend to buy shares in aluminium too. :open_mouth:
The project is well underway. Apart from some WAF compensating jobs (bathroom renovation) no showstoppers yet.


I’d make the reflector elements from wire mesh – the important part is no opening larger than a quarter wavelength, which is easy to do.That will reduce the wind load somewhat.

…after watching my Flight Aware screen showing a local U2 doing leisurely circles over central California, I’m thinking about a higher gain reflector antenna, maybe a helix, for tracking just those kinds of birds…

bob k6rtm

Removed bug from 4-corner simulation model I made few days ago.

  1. The corner mesh was too small.
  2. The dipole was too close to corner.

New simulation:
Each of four meshes are 400mm x 400 mm
The dipole moved from X=50mm, Y=50mm to X=100mm, Y=100mm

Only one dipole is excited (the one in XY quadrant).
Good Radiation Pattern and Gain (13 dBi)
SWR is very high (3.1)

Further improvement.
Ran sweep of dipole location, found can get SWR = 1.3 when dipole is located at X=135mm, Y=135 mm.
However the radiation pattern shows some side & back lobes.

I used to have a 4 ele quad on 144MHz and miss that little antenna (it was a Jaybeam - long since departed manufacturer).
Around 10db gain and good performance from a relatively small antenna.

Online calculator


A bit off topic but I thought I’d discovered an easy way to straighten wire. I got inspiration from watching a series of videos called “Pasta Grannies” I love making pasta 8)

Anyway, I did a quick trawl of U-tube and someone else has already posted this

I’m in the process of straightening several meters of wire to build a corner antenna.

@abcd, I have a 4NEC2 model of a corner antenna for 1090 Mhz. I’ll email it to you to take a look.

Another method which might not work for spaghetti but surely does on longer ends of copperwire uses a hand drill to twist the wire:

Blogged about it on … -antennas/

I like the concept of the corner reflector but isn’t horizontal beamwidth going to be an issue if trying to cover 360. Those models indicate only about 30-35 degree horizontal beamwidths. Of course that is a single model run and maybe the spacing parameters can be tweaked to broaden the beam some.