Dual Source GPS/DCF77 NTP-Server with AIS and ADS-B receivers: Unterschied zwischen den Versionen

Version vom 10. Dezember 2016, 14:16 Uhr

1 Scope

This project is a continuation of my stream of experiments with the NTP protocol and GPS-disciplined clock models. I need to reference the past projects before we go into details:

• NTP-Server with Raspberry Pi and Trimble Resolution SMT
• NTP-Server with Raspberry Pi and Sure Electronics GPS Eval board

These past projects raised the question, how precise a DCF-77 clock would be. And this project here also needs to be seen in the context of an April 1st joke of Rainer DF2NU, who proposed that DCF-77 can be switched off now because the GPS system is there and it is much more precise. So I started to collect ideas to investigate how less precise a DCF-77 disciplined clock model would be compared to the GPS Pulse Per Second. The reason for the reduced precision is because the 77,5 kHz signals are reflected randomly in the ionosphere and the exact reflection point cannot be predicted, resulting in a varying signal runtime.

In addition to the clock question I was thinking of setting up a pair of receivers for the AIS frames broadcasted around Regensburg by the shipd on the danube and I wanted to receove ADS-B frames. Even though slowly navigating ships allow for some frame processing delay, and in case the delay is a couple of seconds, one would still consider such an application a real time application. A jet plane however travels quite distance in a couple of seconds, so a positioning application would need to add some timestamping logic in order to allow for a realistic position information, particularly if received by multiple receivers.

For this reason it makes perfect sense to add a precise clock to a position frame receiver setup.

2 List of components

• The chassis: http://shop.meconet.de/Gehaeuse/Outdoor/Chassis-Outdoor-CA-OTU-RB-433-RB-435-RB-493-RB-800-3-LAN-4-N-Type-large::111356.html - 72 €
• A Raspberry Pi 3: https://www.amazon.de/Raspberry-Pi-3-Model-B/dp/B01CEFWQFA - 35 €
• SanDisk 32GB MicroSD Card: https://www.amazon.de/SanDisk-Android-microSDHC-Speicherkarte-SD-Adapter/dp/B013UDL5RU/ref=sr_1_1 - 10 €
• GUDE Expert Mouse Clock 0107: https://www.amazon.de/VALUE-Funkuhr-Expert-mouseCLOCK-Kabel/dp/B0049K3ZI6 116 €
• FlightAware Pro Stick USB ADS-B Receiver: https://www.amazon.de/FlightAware-Pro-Stick-ADS-B-Empf%C3%A4nger/dp/B01D1ZAP3C/ref=sr_1_cc_2 - 17 €
• FlightAware ADS-B 1090MHz Band-pass SMA Filter: https://www.amazon.de/ADS-B-1090MHz-Band-pass-SMA-Filter/dp/B010GBQXK8/ref=sr_1_1 20 €
• FlightAware 1090MHz ADS-B Antenne - 66cm / 26in: https://www.amazon.de/1090MHz-ADS-B-Antenne-66cm-26in/dp/B00WZL6WPO/ref=sr_1_cc_1 - 45 €
• Pigtail N - SMA - 3 €
• USB A Extension Male/Female - 3 €
• Passive POE Injector: https://www.amazon.de/PoE-Passiv-Injector-PowerOverEthernet-Spannungsversorgung-WRAP-Boards/dp/B00FXOH4C0/ref=sr_1_24 - 3 €
• DC/DC converter: 3 €
• Ferrite cores: 2 €
• diverse standoff headers, screws: 5 €
• Sparkfun USB2serial 3,3V: https://www.sparkfun.com/products/9873 - 10 €
• Adafruit Ultimate GPS Breakout (66 channel w/10 Hz): http://www.watterott.com/de/Adafruit-Ultimate-GPS-Breakout-66-channel - 45 €
• BMP180 temperature and air pressure sensor: http://www.ebay.de/itm/BMP180-Temperatur-Druck-Modul-/291751659851?hash=item43edc1094b:g:TWoAAOSwc1FXZJQU - 5 €
• MMCX 10cm: 10 €
• FL Pigtail 25cm: 10 €
• AISspotter USB stick: http://busse-yachtshop.de/s/AIS-Empfaenger-im-USB-Stick-Gehaeuse - 99 €
• 2x N/N cable 2m with H155: 10 €
• Marineband radio antenna: 35 €
• diverse PCBs and pin headers: 2 €

~ 560 Euro

The prices are partly a bit over the market, roundet up, so that there are no surprises.

3 Configuration

4 Results

5 Integration

6 Images

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