FlightAware Discussions

New Antenna and nothing... HELP

The LNA would be the Flightaware Dongle right?

Makes sense. That graph just looks extra scary compared to most of the others people post.

LNA means Low Noise Amplifier.
The blue dongle has this signal chain:

Input --> LNA --> SAW filter --> regular rtl dongle layout

So it is basically a “normal” rtl-sdr dvbt dongle with additional circuitry.

Got the filter today and just connected it up… Now I’m seeing all kinds of planes!!! Later I’ll run that scan and post the after image.

Thanks for all your help guys!!!


Still doesn’t look optimal, but i guess it works :wink:

Which filter did you order?

If you want some local statistics, consider https://github.com/wiedehopf/graphs1090#graphs1090
Or if you don’t feel comfortable manually adjusting gain, this should get you in the right ballpark: https://github.com/wiedehopf/adsb-scripts/wiki/Automatic-gain-optimization-for-dump1090-fa

ADS-B Dual 978 MHz + 1090 MHz Band-Pass SMA Filter https://www.amazon.com/dp/B010GBQXK8/ref=cm_sw_r_cp_apa_i_jmZNDb858ERCK

First, you need to gash your antenna wire and start over. Communications antennae that use coax are 50 ohms not 75. You stated that you were using a good piece of RG 6, thats 75 ohm cable. If you want good cable get RG-8 or its equivalent, put a type N connector on each end and get a type N female to SMA and then a short flexible pig tail SMA to SMA. this is to give you some flex between your receiver and heavy coax. You would otherwise break the receiver SMA connector. This will insure you get a good signal. From your description, I’m not confident your antenna is working. Good Luck.

Generally good advice, but many of the SDR’s used here “do” have 75Ω connectors.

Like all coax cables, not all are created equal. That said, RG8 would not be my choice above UHF (~500MHz).
Even Pasternack don’t recommend theirs above 1GHz (and who can afford Pasternack?!!)

If you want to throw money at it, there are vastly better cables than RG8, but a good quality quad RG6 is not a bad choice.


RG-6 seems to be working just fine.

I’ve worked in the residential cable industry for a long time and RG-6 was just easy to get. It’s only about 30 feet of cable so it’s doing great so far.

1 Like

You actually have less loss at 75Ω vs 50Ω (all else being equal), you are RX only and the RTL2832U is expecting 75Ω TV signals anyhow. If you are building a RX/TX system, impedance will be a much larger issue because 75Ω cant handle the same amount of power. Spending $200 on fat 50Ω cable will provide you very little bang for the buck as opposed to decent RG-6 with it comes to ADSB.

1 Like

Thanks for the education on coax and SDRs.

Mail](https://go.microsoft.com/fwlink/?LinkId=550986) for Windows 10

The mismatch is minimal between 75 ohm and 50 ohm. I run 75 ohm on both my feeders and have just about the same loss differences between LMR400 and RG-11 at 20 feet.