Author Topic: KAUS (#1) feeds setup  (Read 1397 times)

Offline flunkat

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KAUS (#1) feeds setup
« on: January 18, 2022, 04:29:26 PM »
My setup for KAUS #1 feeds. Mix of SDRs and Bearcat BC355N radios.



Offline flunkat

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Re: KAUS (#1) feeds setup
« Reply #1 on: January 21, 2022, 12:13:27 AM »
I just wanted to describe my setup (KAUS #1 feeds) in more detail since I got a couple of questions privately. Hopefully this info is useful to others trying to work through setup issues. If we get a discussion going it might help with my own setup issues. I’d love to learn more about everyone else’s setups. I’ve been reading the forums for new ideas. Just to introduce myself, I’m a commercially-rated pilot and an engineer, and I fly GA out of KAUS.

My site location:
-2.4 Nm from the official GPS coordinates for the field (KAUS).
-2.2 Nm from Tower and Tracon facility (has Tx antennas)
-1.6 Nm from closest facility antenna.
-Airfield elevation is on average about 500 feet MSL and my site at 430 ft MSL. I am lower than average field elevation and this has always been an issue in regards to catching ground level transmissions. I still catch like the majority (95%+) of the ground level transmissions with good quality though. I can catch all airplanes, but the ARF and Maintenance guys in their pickup trucks are a challenge.

The Frequency Environment:
   -   5 approach/departure frequencies:
      -   118.15 (Southeast) rarely heard.
      -   119.0 (North and west) heavily used.
      -   120.875 (South) not used often.
      -   127.225 (East) heavily used.
      -   125.325 (Final approach) heavily used.

   -   Tower - 121.000
   -   Ground - 121.900
   -   Clearance Delivery - 125.500

   -   ATIS - 124.400
   -    FBOs - 130.225, 130.375, 130.6

My Antenna:
1/2 wave J-pole (centered on 123.0 MHz) that I constructed out of 3/4” copper tubing. Mounted on roof peak at 33 ft AGL or 463 ft MSL. Still lower than field elevation. I also built a 5-element Yagi but I’m currently not using it since its too conspicuous and I don’t want to run afoul of my community HOA rules.

Feedline and upstream setup:
- Gas tube lightning protector about 5 ft from antenna. Connected directly to ground rod with 8 gage copper. Antenna mast is also directly grounded. The two other antennas in the picture on either side of the J-pole are for ADSB. I feed Flightaware and FlightRadar24. They were interested in my location since I can provide ground level traffic data (Austin-Bergstrom currently does not have ASDE-X ground radar).
- 2 FM radio band filters in series. One from GPIO labs and a Flamingo (thanks to Dave). There are a couple of very powerful FM transmitters near my site, so these help a lot.
- Filtered low noise airband preamp from GPIO labs.
- I use just RG6Q for the feed lines (impedance is mismatched but I haven’t noticed it affecting VHF Rx). I have not measured SWRs, which probably doesn’t matter anyway since its only Rx.
- 2-way passive splitter and sent to two different setups in my house.

Demod setup #1:
- Antronix 8-way lossless splitter/amp.
- 4 x Nesdr Smart SDRs (supplied by Dave)
- Powered USB hub (supplied by Dave)
- Raspberry Pi running rtl_airband (supplied by Dave)
- Details about rtl_airband configuration available on request. I worked a lot on this including looking at the source code to understand some parameters.

Demod setup #2:
   - Antronix 8-way lossless splitter/amp. Grounded to power supply to remove ground loops.
   - 4 x RTL-SDR Blog V3 SDRs, attached via powered USB hub to a Linux machine
   - rtl_airband on Linux machine  (details of config/settings available on request)
   - 4 x Uniden Bearcat BC355N radios

Uniden Bearcat hardware radios setup:
   - 4 x Line-to-mic level attenuation cables for audio out (-35dB)
   - 4 x ground loop isolators
   - 4 x Roccat Juke USB sound cards
   - These are plugged into the Linux machine running darkice (details of config/settings available on request)
   - 4 hardware radios cover the following frequencies
      (1) Scan mode, all approach frequencies (118.15, 119.0, 120.875, 125.325, 127.225)
      (2) Ground control (121.9)
      (3) Tower (121.0)
      (4) Clearance Delivery (125.5)

I do also have an SDRPlay RSPDuo which I normally play around with, but its been a hassle trying to get it to work consistently on Linux with SoapySDR. The 10Mhz sample rate is amazing though.

Would love to hear from others with ideas. FYI, I’m not proficient in radio stuff. I’m not a HAM operator nor am I an electrical engineer. I’m an Aerospace and Software engineer. I’m also a commercially-rated pilot with a passion for anything aviation.
« Last Edit: January 21, 2022, 04:30:36 AM by flunkat »