FlightAware Discussions

Bad FA 1090 26" antenna from Amazon?

I am wondering if something came loose internally on my two day old FA 26" 1090 antenna from Amazon.

I mounted it temporarily to the top of my bedroom metal TV mount bracket with the U-bolt clamp (hand tightened). Coverage went up over 50% in distance and messages. For two days, I had excellent performance with no other changes.

Today, I decided to move it higher on the bedroom wall with Velcro attached to the mounting bracket it comes with.

If I keep my hand on the metal portion of the U bolt clamp holder, coverage and messages go back to what I had two days ago. As soon as I remove my hand, messages go to 10-20/s. It’s behaving like old analog TV rabbit ears. Moving it back to top of the TV didn’t fix the problem.

I experimented with gain only after this problem occurred today. 40, 45, 50 gains do nothing to make it work. I also tried a jumper clip between the base of the antenna and the TV metal bracket frame, only my body capacitance seems to work.

I’m guessing I should return this for an exchange to Amazon?

Maybe some sort of power supply noise issue?
Would be my best guess.

You could try grounding the RPi (via the shield on a USB cable for example).

Have you checked if the cable / adapter connected to the antenna has the right pin diameter?
Some people had problems with that.

I can’t imagine a way the anntenna itself could break that would be fixed by body capacitance to be honest. But i’m no signal expert :slight_smile:

I order an expensive Proxicast cable from Amazon:

  • N Male to SMA Male Jumper Cable
  • Connect from SMA Equipment to N-Style Antennas
  • 15 ft Low-Loss LMR240 Size Coax
  • Gold Plated Signal Pins - Heat Shrink on Both Ends

As far as the USB, I tried an extra FA orange USB stick with separate filter and a Murray 1090 antenna, then I compared it to the cheap magnetic antenna I have. They both appear to work fine without any extra grounding of the USB. I’m not using USB extension cables, just the adapter directly plugged into the Pi.

Would a bad cable cause the capacitance issue?

The main USB I use is the FA Pro orange stick with built in filter

I’m not exactly sure how touching would help with a pin of the N connector that is too small.
But it’s worth checking i think.

Here is a picture of the too small and correct connector:
https://en.wikipedia.org/wiki/N_connector#/media/File:PICT7394_trimmed_N.jpg

Could you link the N to SMA cable you bought?

Wow, those pictures show quite a difference! Here is the Amazon link, I thought I was buying premium low loss coax with appropriate to that quality connectors.

https://www.amazon.com/Low-Loss-Coax-Extension-Cable-Ohm/dp/B071DFQGXY/

image

I’m not saying that’s your problem, you should just check the one you bought.
Unscrew it from the antenna and have a look.

If it looks right then it is probably right and i have no idea where the problem is :slight_smile:

Maybe you have a loose cable somewhere else?

By the way the orange stick has no builtin filter, the blue one has one.

At this point, I either have a bad antenna or bad cable.

Maybe I will order an additional cable for testing since I did receive a 978 antenna today too and I will need a cable anyway.

I really hate to return items unnecessarily, I was hoping to figure out whether it’s the cable or antenna.

The RPi is working fine with the magnetic antenna and orange amp. Maybe I will try plugging in the 978 antenna with my existing cable and see what happens.

I removed the Proxicast cable, nothing appears mechanically wrong with it, but the connectors seem to be not premium.

It should still be better than 10-20 messages even with the 978 MHz antenna, seems it receives 1090 MHz okay according to a picture on another thread.

Anyway no matter the quality in such cases it is good to disassemble the whole coax run and reassemble it just to make sure no connection is lose or somehow otherwise impaired.

I did inspect the cable, the 978 received a bad number of messages too. At this point, I am going to order another cable from the same manufacturer because they seem like they have decent quality. Anyone can have a manufacturing defect.

I’m not sure what picture of my signals you would be looking at, but here is a before and after from a magnetic base 1 week ago, to today’s with the FA antenna before I started moving things. It’s only after I move the location that something must have come loose.


1 week ago with magnetic antenna

Today before move with FA antenna (something must have gotten loose now):

I believe that the FA antennas are 50 Ohm impedance. SMA connectors are ONLY 50 ohm, so any cable connecting the two should have 50 Ohm “N” connectors with the larger diameter center pin. Connecting a 75Ohm female “N” connector onto a 50Ohm male “N” connector may permanently bend the fingers. (I think the connector pictured top left has been damaged. The fingers should all rest almost touching each other.) I know someone that their attic has Space Blanket type insulation on the underside of the roof, raising the antenna into a close proximity to the insulation had similar results to what’s been posted.

That shouldn’t happen with the FA antennas as the female N with 50 Ohm is on the antenna.
So the worst that can happen is a bad connection, nothing gets damaged.

But yes you are correct N to SMA should always have a 50 Ohm N connector that fits.

While we’re talking about cables and connectors. SMA connectors have pretty small torque specification or they can be damaged. 9"/Lb. is really easy to achieve even with a small wrench.