FlightAware Discussions

Broken antenna on roof?

Hi,
I have an AirNav ADS-B antenna on my roof that was working fine until I fixed it with a proper iron clamp to the pole. Before it was fixed with plastic material. While I was at it I decided to move it up a bit, some 60cm more, so I pulled the cable coming out of the roof and I fixed the antenna.
I did those operations while the antenna was connected to a raspberry pi with PiAware running.
Then I started to receive only a tiny fraction of the airplaines I was receiving before moving the antenna.
I tried to disconnect the antenna from Raspberry PI and noticed that it was receiving even less airplanes.
The day after my operation on the antenna (I did it on Sat 22nd), PiAware resumed receiving the usual amount of signals, but after a few hours it dropped again.

I am not expert in electronics, radio, antennas, so I’m asking the community: what could went wrong with the antenna?

Thanks!

I am attaching a screenshot of the receiving history.

Could have broken the center conductor in the coax cable or the connection to the antenna.

Not sure how you used the clamp to clamp down the antenna or how hard you clamped it down, but that probably could also give a connection problem.

Then there is the much more unlikely possibility of a problem with the dongle.

For the miraculous temporary fix on Sunday: that could be thermal expansion closing the connection break in the cable.

Problem with the AirNav antenna is that you can’t replace the cable separately or can you?

Thanks for your reply.

Yes, a broken center conductor may be a good explanation on what’s going on. I can exclude the clamp, because it acts on the antenna itself, not on the cable.
Maybe it broke when I pulled the cable out of the roof tube, which has a narrow bend.
Could it make sense to cut the cable and replace it by adding connectors in between?

Thanks!

-Ermanno

You don’t know where it is bad, do you?

You’d have to replace most of the coax and hope the rest of the cable going to the antenna is good.
Finding proper replacement coax and installing connectors on coax isn’t quite so simple for 1090 MHz.
But i guess it will most likely still be an improvement.

The clamp could also be in the way of the reception, depending on where you clamped the antenna.
(clamp should be at the base, the upper part of the antenna mustn’t be obstructed)
But it shouldn’t cause such drastic reduction in performance.

It turns out it was the SMA connector. An electronics shop fixed it for me just by swapping the connector.
They told me that the cable unlikely breaks “inside” without a visible external damage.
So that’s a happy ending! :smiley: