FlightAware Discussions

ADS-B antenna close to 5GHz WiMax dishes

Hi guys,
After quite a while I finally decided to move my ADS FA antenna to the roof. It is standard FA 1090MHz antenna, with about 10m (32 feet) cable, marked as H155, 50 ohm cable. FA USB blue (plus) dongle, with Pi at the other end.
Unfortunately, FA stick is quite close to WiMax dishes, I’m not sure what are they, but they look like those: https://www.senetic.com/product-lbe-m5-23-us/
I have limited options with moving out my antenna far away, since cable shaft is common for many cables.
Now, my range dropped from 150nm to less than 50nm. I can suspect either cable being too long (and bad) or neighbourhood of those 5GHz antennas.
What do you think?
Chris

50 nmi can’t be due to 10m high quality cable.
You can either get the FA filter or an LNA.

With antennas so close i’d recommend the rtl-sdr LNA it seems very resistent to out of band transmissions.
https://rtl-sdr.com/new-product-rtl-sdr-blog-1090-mhz-ads-b-lna/
It requires a bias-t to be purchased separately.
Or you use the rtl-sdr v3 dongle which has a builtin bias-t.

There is also the uputronics LNA available:
https://store.uputronics.com/index.php?route=product/product&path=59&product_id=50

It’s powered by either USB or a bias-t.

You can’t by chance place your antenna above those 5 GHz antennas?
They look rather directional.

If the cable is of bad quality it could theoretically be also coupling over from the cable run, but i doubt it.
Or if the cable is damaged or has some defect, that could also be a reason.
Sharp bends or squishing the cable can also cause problems.

Anyway if you get an LNA, it would be best close to the antenna, but it’s absolutely fine to place it at the receiver end of the 10m just for filtering.
The results won’t be quite as perfect, but the difference will probably be limited.

Edit: Forgot one option:
The green radarbox dongle has the SAW filter before the LNA, so it should also work better in this case.
(it seems on the Flightaware sticks the internal LNA is easily overloaded because it’s first before the filter)

Thanks for the answer, but I was under impression that the blue USB dongle already has the filter built-in? LNA might be an option, I agree.

It indeed has a filter built in.
But the filter comes after the amplifier.

That amplifier (LNA) seems prone to overloading, this is most likely what is occuring.
In overload the 5GHz can produce other frequencies in the amplifier, for example 1090 MHz.
After that no filter can help you.

Possibly silly question - how is such LNA powered?

Hope I understood the question right.

The uputronics allows you to plug in a micro-usb cable to power it, or use bias-t, that means it is powered via the antenna cable, either by a small power inserter placed between dongle and lna or by a dongle that is able to supply bias-t Power by itself.

It’s powered via the coax cable.
https://www.everythingrf.com/community/what-is-a-bias-tee

The LNA splits out the power and the antenna is unpowered after the LNA.

Either the dongle can supply power (4-5V) via the coax cable (internal bias-t) or you need an external bias-t.
Such an external bias-t is placed between LNA and dongle. It needs to be supplied with 4-5 V.
You can for example connect it to the +5V GPIO pin on the Raspberry Pi.

The dongle bias-t needs to be activated in software.

The uputronics as mentioned is simpler, it’s connected between antenna and dongle, then power is supplied with an USB cable.