FlightAware Discussions

5dBI Magnetic Omni Antenna

I have two antennas in the same spot indoors in a window.

  1. The FlightAware Antenna 1090 MHz
    and
  2. A 5dBi Magnetic Base Omni
    https://www.telcoantennas.com.au/5dbi-magnetic-base-omni-antenna

I’m monitoring an aircraft doing a fixed circuit resembling a square. When I’m using the Flightaware antenna the signal drops out about 9nm away. When I’m using the Omni it barely drops out at all. The Omni will pick up something about 20nm away.

The flight aware antenna is connected directly to the blue USB stick using an adapter (no cable per se). https://www.telcoantennas.com.au/sma-male-to-n-male-adapter

So I dont know why the Flightaware antenna under performs. Could it be the connection or are these antennas designed in a way that would cause this? So for example, if I put the Flightaware antenna on the roof, all the issues would go away?

Your connector, according to the website, should be correct.
You may want to double check it as they are often mis-labelled.

Have you tried to optimise the gain settings? You may be picking up too much signal with the FA antenna and that is causing the Dongle to be overloaded.

75 OHM top(it has a smaller diameter centre pin). 50Ohm bottom. The FA antenna has a 50Ohm socket.
image
From https://en.wikipedia.org/wiki/N_connector

If you install wiedehopf’s graphs then you can get a better feel for the differences between the antennas and gain settings.

Such a difference should not occur The FA one should clearly outperform the other one.
There are several threads here in this forum which should help to isolate the issue.

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Signal overload from mobile phone signals most likely.
The better performing Flightaware antenna is also receiving more out of band signals and overloading the dongle. You will probably need a filter. See this recent thread:

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As I mentioned in another thread, don’t expect a mag base to live up to its claims. That said, your mag antenna is not designed for 1090MHz, but rather the Oz mobile phone bands.
image
In this case, it just exaggerates the point your FA antenna is under-performing.

As @jonhawkes2030 suggests, a reverse-sex SMA is high on the list of probable causes.

Your original RG223 cable - did you make that or buy it pre-made (if so, where from?)?

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Thanks for your suggestions. I think it’s ok per your chart.

The original cable (that I’m no longer using). I bought it from here: https://secomms.com.au/product/13-metre-rg223-rf-coaxial-cable-assembly-male-n-to-male-sma-rg223-telegartner/

I have three mobile phone sites / towers within 100m of the antenna.

Optus
3G 900MHz, 2100MHz
4G+ 700MHz, 1800MHz, 2300MHz, 2600MHz

  • Vodafone
    3G 900MHz, 2100MHz
    4G 850MHz, 1800MHz, 2100MHz

Telstra
3G 850MHz
4GX 700MHz, 1800MHz
4GX 900MHz, 2600MHz
5G 850MHz, 3500MHz

I’m running a blue Flightaware Pro stick, so I thought that filter would be enough. Maybe I should get this? https://www.amazon.com.au/ADS-B-1090MHz-Band-pass-SMA-Filter/dp/B010GBQXK8

What do you think ? Is it really going to hurt?

Thanks. I’ll do some reading.

That cable shows the correct connectors, so it’s looking like overload as a probability.
You could try backing off the gain and see if that helps, but a filter is probably your fix.

You have Mobile at 900 Mhz. Light blue FA filter you have linked may be OK, but dark blue FA filter will be better.

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No, don’t buy that filter. It’s very wide for the US market and unsuitable for everyone else.

Hmmm… ok, what about these two?


OR

Both good, but quite different.
The FA filter is ‘just a filter’ and will work simply by plugging it into your feed.
The RTL-SDR Blog box is both a filter and amp (multiple of each) and needs power to operate.
As the amps give you a lot of gain, it’s better suited to an un-amplified dongle. Additionally, because you need to feed it power, you’ll need either a separate Bias-T or a dongle with a Bias-T built in.
An ideal pairing is the RTL-SDR Blog V3 dongle

I might go with that dark blue filter and see what happens. Otherwise I’m going to end up with a crazy amount of parts for this project. :slight_smile: Which I suspect could be what happens when you start down this rabbit hole.Thanks again.

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No worries, you will get more stuff over time :). That’s where we all started from.
After one year of feeding i have changed antenna meanwhile four times :slight_smile:

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Didn’t he link the uputronics filtered amp?
That one has a Micro USB or Mini USB or something like that (strange cable) where you can supply it via USB cable.

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Ooops. Well spotted.

It does indeed.
This it the Filter/Amp I mistook it for.

Just out of curiosity:
Can it be powered via USB from Raspberry or does it require a seperate power supply unit?

Sure.
There will be a voltage drop if you use a long cable plus the drop across the isolation diode.
So long as the USB PSU can cope with the load, it won’t be any different to powering it direct.

For completeness - it can be powered via Bias-T as well.

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