FlightAware Discussions

Drastic performance drop

That’s one flavor of the typical TEN90 antennas. Works, but there are others which clearly outperform this one.

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Is one of them the original FA?

the TEN90?

No, the FA Antenna is a different type. There are some pictures of the inside here in this discussion board.
I do not believe their statement regarding “6dB gain”. The Jetvision or any Vinnant delivers much better performance with less gain. So either they have more (what i do not think) or the values for the TEN90 are wrong.

It looks like the AirNav one I have has a board on the inside of it instead of traditional wiring. It happened to open itself up when I was maneuvering it within the provided bracket and happen to notice a board :slight_smile:

So you are saying the blue FA antenna is not any better than what I currently have?

I don’t know about a “blue” FA Antenna. Normally the FA are dark green/black and at least 60cm long. In some countries they can be white as it’s a different provider

That one is another TEN90, seem to be the same as the light green provided by Airnav

image

A few thoughts on this:

  1. LNA amps tend to run at higher currents, it’s part of how they are optimized for noise performance and not gain. If you were to sweep one you would see that the frequency of internet is often about 3 dB below the peak gain point. As such, it’s not too surprising that the amp failed in a hot attic.
  2. Having been bit too many times, I always put a Band Pass Filter (BPF) in front of any amp in the signal chain. The old saying “All amplifiers are mixers and all mixers and amplifiers” rings true here. A strong signal at the wrong frequency would mix with another signal, which could be pretty weak, and end up on your desired frequency. A 1.3 dB hit or so on the gain of your system is worth not having to worry about strong near signals.

I’m just getting into this, but, here’s a sweep of the Flight Aware 1090 BPF. Markers 2 and 3 are in the 902-928 MHz ISM band, where I have some IoT things operating at +20 dBm with the antenna 2’ away from the 1090 receive. So that band is down about 40 dB. When combined with the SAW filter in the blue Flight Aware dongle, things just work.
I wish Flight Aware would show a block diagram of the RF chain in the dongle to help with these sort of system decisions.

So just be sure if you have the pre-amp in the attic to have a spare and good access. I would not put the PI and receiver dongle in the attic, it’s just too hot. The coax loss to get the signal to those devices is not a problem after you’ve got the gain of the pre-amp.

FWIW, I’m running the XRDS-RF on 10’ of LMR240 (well, sort of but it’s close enough) all from Amazon. Enclosed is the return loss sweep of that antenna. It really wants to be on a metal mast for at least about 2’, I did the sweep holding it and introduced the funny null you see in the sweep.

Just my $.02 as I get into this.


Unless you are always going to mount it under cover, you’ll want to put some effort into making sure it is waterproof.

Silly I thought that’s watertight out of the box. It’ll be in the attic until spring so we are good til then.

If it opens up by itself then it isn’t watertight :wink:

Thank you for informative explanation. I think the amp is dead, might have overheated in the July heat in the attic. I thought I had a spare to last me through the winter until I redesign the layout but can’t find it now. Oh well, have to live with what I have :slight_smile:

It is better but still about 50% less of what it was. I will need the LNA back :slight_smile: