Which one is the best antenna?

:+1: Looks like you got the ground side about nailed. No clue about the materials in use, the mill thickness, or about the substrate, but I assume there are PCB strip simulators somewhere out there?

If I missed any other measurements worth-while, please let me know and I’ll do my best to measure.

I may pop it up on the roof after running a quick baseline between my current setups and see what the percentage difference looks like as compared to the FA antenna. Maybe an hour or two test with VRS keyed up on both lines side by side. I think I can throw that much of a bone in the interim while I get setup for the full-blown shootout again. I’m more than curious myself…

YES, RF Engineers usually test an antenna in free space.

Here is an interesting article that describes how to simulate free space in an electromagnetic (henceforth EM) anechoic chamber

It shows what lengths RF Engineers go to.

I’m not suggesting that we need to go to that extreme or that we should understand the mathematics but it does suggest that indoor testing is not as good as free space.

Also look at how the first active element begins at the SMA connector. Any metal mast or clamp would clearly affect that part of the antenna.

S

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No idea about pcb strip simulators, never used these. As pcb material characteristics are unknown, I have decided to use a model with 3mm air gap between the two copper plates, and not a pcb.

You have given all the measurements I need to build a simulation model. Thanks.

It’s quite a while since I had to do any microstrip simulation but why have you decided on using a 3mm airgap?
The relative permittivity of FR4 PCB is about 4.4 and the thickness of the PCB is 1.5mm so would not 0.3mm (1.5/4.4) provide a closer simulation?


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It’s tough to say - I think the typical cheap 1oz PCB trace is .035mm (35um) thick, but that’s rated for copper. I have no clue what this stuff is…tin-something/nickel? The entire PCB is 1.5mm thick so far as I can tell, I didn’t actually mic it out

Thanks for the info.

The 3mm air gap was just a random figure as I had no idea about permitivity of pcb material.

Now that you have worked out that air gap should be 0.3mm rather than 3mm, I will shift the decimal one place to left, changing 3 to 0.3. Easy :wink:

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Good luck. I have no idea how 4nec2 will perform trying to simulate microstrip, Unfortunately I suspect not very well. Real microstrip simulators take into account lots of factors relating to the PCB tracks which I’m sure 4nec2 will not. Still, it will be interesting to see what you come up with. Just be prepared to treat the results with a pinch of salt :thinking:

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So do I believe, but something is better than nothing, even if not accurate.

It is fun to explore a new design, though it is very tedious to build both the copper strips using a huge number of very thin wires

You could look at ANTENNA MAGUS.
There is a student edition.
I had trouble getting it installed, with the simple interface crashing and gave up.
Someone with a bigger brain may have success?

I have tried it couple of years ago. Do not remember exactly what happened, but quit it due to some problem.

The second side strip of PCB is ready now
Next is to put pieces together and run the simulation.

Full View:

image

 

Closeup:

image

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Either the simulation is grossly wrong
OR
If Simulation is OK, then the PCB antenna is rubbish

Only the field test will reveal the truth

 

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As you’ve highlighted, the max gain is 3dB
As this is only fractionally better than a 1/4λ groundplane. Only a basic side-by-side test (of physical antennas) will show if the model has any validity.

Clearly, the 12dB claimed is outrageous, I’d expect the design (not necessarily this implementation) to approach 6dB.

IF the simulation model is valid, then the radiation pattern is horrible, totally unsuitable for ADS-B, where we need maximum gain in horizontal direction.

There seems to be something wrong in simulation, either the model itself, or the software 4nec2 is not capable to handle such designs.

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Side by side comparison of the Pimoroni 1.2m Antenna and the FA Antenna. Same location, same setup, same gain setting on a FA Pro Stick. Cable lenght, about 40cm of LMR195. everything in a metal box for RF shealding.
Let them run for two days. The Pimoroni antenna seem to pick up less messages but range is about the same.
If i increase the gain from 38.6 to 40.2 messages are about the same as FA but the -3db messages reach 8% and far far away planes are not that well tracked(many one message tracks). Unfortunatelly i was not that inspired to install Graphs1090 when i began testing, i was only interested in range. So basically the 8.5db gain is about 7db gain.
I like the FA antenna, its lighter and shorter.

For me the AirNav Antenna was crap, half the range of those other two.
I have a Vinnant antenna which im goint to test in the same setup.
My A3 Antenna is in another location, so no objective test possible.

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Be interesting to see the Vinnant antenna test i got 1 here on mobile test watching

I have a plot from another location, more horizon view and higher, beats them both(FA and Pimoroni). So altitude, and clear view are about 70% of a good reception, i would say.

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http://radar.go.ro:8080/
Vinnant testing until Sunday, probably.

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I had purchased one for testing even though I don’t like the molded-in cable. As I was taking it out of the sleeve, a piece of spring wire that was sticking out of the cable boot made a nice gash in my hand and it only took two seconds of testing to determine that the whole thing was completely shorted.

Well, i shortened the cable as much as i could and put an N-Female connector. I also took the cap off and is seems like it has the FA design but other than that i have no equipment to test it nor do i wish to cut it open…for now. Im testing it against the Vinnant Antenna right now.

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