FlightAware Discussions

Almost no data for UAT 978?

Running FA sdcard, updated to 4.0. Two dongles and two FA antennas. 978 has the 978/1090 bandpass filter. My 1090 seems to be working fine…

Mid-day (on 1090), 90-100 flights out to 200nm (Rochester, MN) antennas are 20ft AGL. My UAT 978 didn’t seem to be working at all, but I finally saw a couple flights show up.

I have at least a half-dozen small airports within 100nm (in addition to KRST and KMSP). Do I have something set up incorrectly, or is nobody using UAT 978??

Both receivers have gain set to “max”. Other than serializing the dongles to allow for both 1090/978 on the same Pi, nothing tweaked.

In this forum, I’m having a hard time deciphering current (Dec 2020) advice from obsolete topics that have since been corrected with code updates, etc.

Recent UAT 978 hit:
A2C4CB N278GA 1362 38,000 413 71.1 306° 2 -17.8

Notice the horrid RSSI at 71nm. Why is aircraft on UAT978 at 38,000ft?

Try turning down the gain on the 978 dongle. The 978 decoder does not work so well with over-amplification. Also try removing the filter (if you don’t need a filter for 1090 reception, you probably don’t need one for 978 either)

It is normal for 978 range to be much lower than 1090 range (lower power transponders, lower altitudes, modulation is a bit trickier to handle)

What’s horrid about it?

Dual 1090- and 978-out.

Thanks-- I’ll try adjusting the gain.

I have the FA Blue dongle for 1090 and Orange for 978 (why I was thinking the external filter was needed. I’ll remove and see if things change.)

The RSSI for 1090 is across the board better for flights much farther away. That’s why I was concerned about a -17 for something that close on 978. As you suggest, it may mean nothing…

Thank you for the quick reply.

https://github.com/wiedehopf/tar1090#heywhatsthatcom-range-outline

See the heywhatsthat page, range is greatly affected by aircraft altitude.
Now you can guess yourself which altitudes the 978 GA planes are gonna be at.

And as stated it’s much more likely you have the gain set too high.
With the FA orange for 978 i’d generally recommend a gain of 36 as a starting point.
Haven’t experimented with 978 directly but the light blue FA filter isn’t that much attenuation so it shouldn’t hurt.

With 978 it’s just the terrain that’s limiting your reception.
Or it’s overamplified and you only get far away planes and nothing 20 miles around you.